1 Scope This recommended practice provides standard procedures for determining the following characteristics of based drilling fluids: oil-a drilling fluid density mud weight; b viscosit
Symbols
This document defines several key symbols: \( DF \) represents the chemical potential or reaction availability of drilling fluid, \( W \) denotes the chemical potential or reaction availability of water solutions of standard salts, and \( C \) indicates the chemical potential or reaction availability of drilled cuttings Additionally, \( b \) refers to the slope of the annular velocity and shear stress at the wall in laminar flow, as specified in section N.7.2.8.
B VSST amount of weight-material sag, expressed in pounds-mass per gallon 1
C correction value to add to thermometer reading
Ca ,DF +2 c whole-drilling-fluid calcium concentration, expressed in milligrams per liter
Ca ,H O c aqueous-phase calcium concentration per volume of pure water, expressed in milligrams per liter c CaCl 2 ,AQ aqueous-phase calcium chloride concentration, expressed in milligrams per liter c CaCl
2 ,DF,A whole-drilling-fluid calcium chloride concentration, expressed in milligrams per liter c CaCl 2 ,DF,B whole-drilling-fluid calcium chloride concentration, expressed in pounds per barrel c CaCl
2 ,DF,C whole-drilling-fluid calcium chloride concentration, expressed in kilograms per cubic meter c Ca(OH)
2 ,% lime assay value, expressed as a weight-percent c Ca(OH)
2 ,DF,B whole-drilling-fluid total lime concentration, expressed in pounds per barrel c Ca(OH)
2 ,DF,C whole-drilling-fluid total lime concentration, expressed in kilograms per cubic meter c Ca(OH)
2 ,F lime concentration of field lime based on the lime assay, expressed in kilograms per cubic meter or pounds per barrel
Cl ,DF c − whole-drilling-fluid chloride concentration, expressed in milligrams per liter
Cl CaCl ,DF c − whole-drilling-fluid chloride concentration as calcium chloride, expressed in milligrams per liter
1 Gallon as used throughout this standard refers to the U.S gallon of 3.7854 liters
The article discusses various concentrations related to drilling fluids, specifically focusing on sodium chloride (NaCl) and low-gravity solids It defines the whole-drilling-fluid chloride concentration from sodium chloride, expressed in milligrams per liter, as well as in pounds per barrel and kilograms per cubic meter Additionally, it addresses the concentrations of insoluble and soluble sodium chloride in similar units The article also mentions the concentration of active sulfides and weighting materials, providing their measurements in both pounds per barrel and kilograms per cubic meter Lastly, it includes the distance from the outer wall, measured in inches.
D diameter of outer pipe, expressed in inches d diameter of inner pipe, expressed in inches
D TVD true vertical depth, expressed in feet
E pump efficiency, expressed as percentage f tube factor, taken from Table I.2
G′ storage modulus, expressed in newtons per square meter
G″ loss modulus, expressed in newtons per square meter k C consistency factor, expressed in pounds-force second per hundred square feet
L length of the hydraulic section, expressed in feet
The submerged length of the shear tube is measured in both centimeters and inches The Dräger tube's darkened length, or stained length, is indicated in units on the tube Various masses are defined, including the mass of the empty retort assembly (cup, lid, and body packed with steel wool) in grams, the mass of the filled retort assembly with the sample, and the mass of the empty, dry liquid receiver Additionally, the mass of the cooled liquid receiver containing condensed liquids and the cooled retort assembly is specified The mass of the dried retort cuttings and the initial mass of 10 mL of drilling fluid are also noted The mass of drilling fluid taken from the Sag Shoe after specific shear times at different speeds is recorded, along with the mass of the condensed liquid (oil and water) and the mass of the liquid drilling fluid sample Finally, the total shear mass, which includes the platform and weights, and the mass of wet cuttings and water are detailed, along with the heating back pressure expressed in kilopascals or pounds-gauge per square inch.
P measured pressure, expressed in pounds-gauge per square inch ΔP anticipated pressure increase, expressed in pounds-gauge per square inch
P L Δ Δ pressure gradient, expressed in pounds-gauge per square inch per foot
Q pump rate, expressed in gallons per minute
R 1 average reading for the standard thermometer, expressed in degrees
R 2 average reading for the working thermometer, expressed in degrees
R 600 dial reading at 600 revolutions per minute, expressed in degrees deflection
R 300 dial reading at 300 revolutions per minute, expressed in degrees deflection
R BPU calculated bed pickup measurement ratio, expressed as a percentage
R O ratio of the volume fraction of oil to the sum of the volume fractions of oil and pure water from the retort analysis, expressed as a percentage
R B ratio of the volume fraction of brine to the sum of the volume fractions of oil and brine, expressed as a percentage
R W ratio of the volume fraction of water to the sum of the volume fractions of oil and pure water from the retort analysis, expressed as a percentage
S Sag register t time, expressed in minutes
V 1 spurt loss, expressed in milliliters
V 7.5 filtrate volume after 7.5 min, expressed in milliliters
V 30 filtrate volume after 30 min, expressed in milliliters
V A annular volume, expressed in barrels
3 volume of 0.282 mol/l (0.282 N) silver nitrate reagent, expressed in milliliters
V EDTA volume of 0.1 mol/l EDTA solution, expressed in milliliters
2 SO 4 volume of 0.05 mol/l (0.1 N) sulfuric acid, expressed in milliliters
V K if positive, whole-drilling-fluid alkalinity, expressed in ml of 0.05 mol/l (0.1 N) sulfuric acid; if negative, whole-drilling-fluid acidity, expressed in ml of 0.1 mol/l (0.1 N) sodium hydroxide
V M receiver volume at specific mark, expressed in milliliters
V NaOH volume of 0.1 mol/l (0.1 N) NaOH, expressed in milliliters
V O volume of oil, expressed in milliliters
V PPT volume of filtrate from PPT, expressed in milliliters
V R total volume of condensed liquids (oil and water), expressed in milliliters
V RC volume of retort cup, expressed in milliliters
V S drilling fluid sample volume, expressed in milliliters;
V W water volume expressed in milliliters or water mass expressed in grams (1 ml = 1 g)
The change in annular velocity, denoted as Δv, is measured in feet per minute, while the annular velocity itself is represented by v, also in feet per minute Additionally, the static filtration rate, referred to as v sf, indicates the volume rate of flow in milliliters per minute, and w represents calcium chloride (CaCl).
The aqueous-phase mass fraction of calcium chloride (\$w_{CaCl_2}\$) is expressed as a percentage of the total aqueous-phase mass In a super-saturated fluid, the aqueous-phase mass fraction of calcium chloride (\$w_{CaCl_2,SAT}\$) is also represented as a percentage of the total aqueous-phase mass Additionally, the aqueous-phase mass fraction of sodium chloride (\$w_{NaCl}\$) is defined as a percentage of the total aqueous-phase mass The maximum aqueous-phase mass fraction of soluble sodium chloride (\$w_{NaCl,MAX}\$) indicates the highest percentage of sodium chloride that can coexist with a specific mass fraction of calcium chloride Furthermore, the recalculated maximum aqueous-phase mass fraction of soluble sodium chloride (\$w_{NaCl,MAX-C}\$) is provided as a percentage of the total aqueous-phase mass for a given mass fraction of calcium chloride.
Y PA yield point, expressed in pascals
The yield point (YP) of drilling fluid is measured in pounds-force per one hundred square feet, with specific values for gel strength at 10 minutes (β 10m) and 10 seconds (β 10s) The drilling fluid depth gradient (Γ DFG) is expressed in kilopascals per meter and pounds per square inch per foot Shear strength is indicated as γ A in pounds-force per one hundred square feet and γ B in pascals, while the fluid shear rate (γ i) is measured in reciprocal seconds Drill-pipe rotation (η) is quantified in revolutions per minute, and apparent viscosity (η AV) and plastic viscosity (η PV) are expressed in millipascal-seconds (centipoises) Various volume fractions of components in the drilling fluid, such as brine (ϕ B), solids (ϕ D), dried retort solids (ϕ d), low-gravity solids (ϕ LG), oil (ϕ O), pure water (ϕ W), and weighting-material solids (ϕ WM), are represented as percentages Drilling fluid density is detailed in multiple units, including pounds per gallon (ρ), grams per milliliter (ρ B), and kilograms per cubic meter (ρ C) Additionally, the average density of suspended solids (ρ d) and the effects of drilled cuttings on pressure drop (ρ ECD-hyd) are noted, along with the total predicted equivalent circulating density (ρ ECD-tot) and changes in wellbore pressure due to pipe rotation (Δρ ECD-rot) The maximum recorded drilling fluid density (ρ max), nominal density (ρ nom), and the density of the oil used (ρ O) are also specified, alongside water density (ρ w) at the test temperature.
The density of the weighting material solids, denoted as ρ WM, is measured in grams per milliliter The wall shear stress, represented by τ W, is quantified in pounds-force per one hundred square feet Additionally, the yield stress of the drilling fluid, indicated as τ Y, is also expressed in pounds-force per one hundred square feet.
Abbreviations
For the purposes of this document, the following abbreviations apply
ACS American Chemical Society ASTM American Society of Testing Materials
AV apparent viscosity refers to the measure of a fluid's resistance to flow BAD, or base alkalinity demand, indicates the amount of acid required to neutralize a base CAS stands for Chemical Abstracting Services, which provides a comprehensive database of chemical information ECD, or equivalent circulating density, is expressed in kilograms per cubic meter or pounds per gallon, and is crucial in various engineering applications EDTA is the sodium salt of ethylenediaminetetraacetic acid dihydrate, commonly used in chelation therapy and various industrial processes.
ES electrical stability ESD equivalent static density [expressed in kilograms per cubic meter (pounds per gallon)] HTHP high temperature, high pressure
OCMA Oil Company Materials Association (now-defunct organization but an OCMA grade bentonite specification is included in API 13A) OBR oil-to-brine ratio
OWR oil-to-water ratio PNP propylene glycol normal-propyl ether PPA permeability plugging apparatus PPT permeability plugging test PTFE polytetrafluoroethylene (e.g Teflon ® )
PV plastic viscosity PVT pressure, volume and temperature relationship ROC retained oil on cuttings, (either wet or dry)
SI International System of Units
TVD true vertical depth [expressed in meters (feet)]
USC United States customary units VSST Viscometer Sag Shoe Test
5 Determination of Drilling Fluid Density (Mud Weight)
Principle
To determine the mass of a specific volume of liquid, the density of drilling fluid is measured This density is typically expressed in grams per milliliter or kilograms per cubic meter, as well as in pounds per gallon or pounds per cubic foot.
Apparatus
5.2.1 Any density-measuring instrument having an accuracy of ±0.01 g/ml or ±10 kg/m 3 (0.1 lb/gal or 0.5 lb/ft 3 )
The mud balance is a key instrument for determining the density of drilling fluids It features a design where a cup holding the drilling fluid is balanced by a fixed counterweight, while a sliding-weight rider moves along a graduated scale for precise measurements To ensure accuracy, a bubble level is incorporated into the beam, and additional attachments can be used to extend the balance's range when needed.
Frequent calibration of the instrument with fresh water, ideally every one to two weeks, is essential to ensure accurate readings of 1.00 g/ml or 1000 kg/m³ (8.345 lb/gal or 62.4 lb/ft³) at 21 °C (70 °F) If the readings deviate from this standard, adjustments should be made using the balancing screw or by modifying the amount of lead shot in the graduated arm's well Additionally, the upper density calibration should be conducted according to the manufacturer's specifications, typically on an annual basis.
5.2.2 Thermometer, with a range of 0 °C to 105 °C (32 °F to 220 °F) and an accuracy of ±1 °C (±2 °F).
Procedure
5.3.1 The mud balance instrument should be set on a flat, level surface
5.3.2 Measure the temperature of the drilling fluid and record
To test the drilling fluid, fill a clean, dry cup with the sample and securely attach the cap by rotating it until it is firmly in place Make sure to expel some fluid through the cap's hole to release any trapped air or gas.
5.3.4 Holding the cap firmly on the filled sample cup (with cap hole covered by a finger), wash or wipe the outside of the cup clean and dry
5.3.5 Place the beam on the base support and balance it by moving the rider along the graduated scale Balance is achieved when the bubble is under the centerline
To determine the drilling fluid density, refer to one of the four calibrated scales located on the arrow side of the sliding weight Given that the water density is established at 1 g/ml, the density can be directly read in grams per milliliter using the specific gravity scale, as well as in pounds per gallon and pounds per cubic foot Additionally, it can be expressed as a drilling fluid gradient in pounds per square inch per 1000 ft.
Calculation
5.4.1 Report the drilling fluid density to the nearest 0.01 g/ml or 10 kg/m 3 (0.1 lb/gal or 0.5 lb/ft 3 )
5.4.2 To convert the reading, ρ, to other units, use Equations (1) to (7) and Table 1 and Table 2
Equations (1) to (3) are used to convert the density, ρ S , expressed in grams per milliliter, to other units:
The density of drilling fluid, denoted as \$\rho_C\$, is calculated using the formula \$\rho_C = C \times \rho\$ (1), where \$\rho\$ is measured in kilograms per cubic meter Additionally, the density in pounds per gallon is given by \$\rho_{B1} = 8.345 \times \rho_S\$ (2), while the density in pounds per cubic foot is represented as \$\rho_{B2} = b.43 \times \rho_S\$ (3).
Table 1 provides the multiplication factor for conversion from one density unit to another
Table 1—Conversion of Density Units
Measured in Multiply to Get g/ml kg/m 3 lb/gal lb/ft 3 g/ml 1 1000 8.345 62.43 kg/m 3 0.001 1 0.0083 0.06243 lb/gal 0.120 120 1 7.4805 lb/ft 3 0.0160 16.02 0.1337 1
Equations (4) to (7) facilitate the conversion of density into the drilling fluid depth gradient, denoted as Γ DFG Specifically, Γ DFG,A is calculated in kilopascals per meter using the formula Γ DFG,A = 9.81 × ρ S Additionally, the relationship between Γ DFG,A and Γ DFG,B is given by Γ DFG,A = 22.6 × Γ DFG,B, where Γ DFG,B is expressed in pounds per square inch per foot The equations also define Γ DFG,B as Γ DFG,B = 0.0520 × ρ B1 and Γ DFG,B = 0.00694 × ρ B2, linking the depth gradient to the respective densities.
A list of density conversions is given in Table 2
Pounds per Cubic Foot g/ml kg/m 3 (lb/gal) (lb/ft 3 )
2.90 2900 24.2 181.0 a Same value as relative density as specific gravity in grams per cubic centimeter or kilogram per liter b Accurate conversion factor
6 Alternative Method for Determination of Drilling Fluid Density
Principle
The pressurized mud balance offers a more precise technique for measuring the density of drilling fluids that contain entrained air or gas, surpassing the accuracy of traditional mud balances While it operates similarly to the conventional mud balance, the key distinction lies in the use of a fixed-volume sample cup that maintains pressure during the measurement process.
The primary goal of applying pressure to the sample is to reduce the influence of entrained air or gas on the measurements of drilling fluid density By pressurizing the sample cup, the volume of any entrained air or gas is significantly minimized, leading to more precise density measurements of the drilling fluid.
Apparatus
6.2.1 Any density-measuring instrument having an accuracy of ±0.01 g/ml or ±10 kg/m 3 (0.1 lb/gal or 0.5 lb/ft 3 )
The pressurized mud balance features a sample cup and screw-on lid balanced by a fixed counterweight on one end of the beam, while a sliding-weight rider moves along a graduated scale To ensure precise balancing, a bubble-level is integrated into the beam.
To ensure accurate measurements, the instrument should be calibrated regularly with fresh water, ideally every one to two weeks At a temperature of 21 °C (70 °F), fresh water should yield a density reading of 1.00 g/ml or 1000 kg/m³ (8.345 lb/gal or 62.4 lb/ft³) If the reading deviates from this standard, adjustments can be made using the balancing screw or by modifying the amount of lead shot in the graduated arm's well Additionally, the calibration for upper density should follow the manufacturer's guidelines and be conducted less frequently, approximately once a year.
Procedure
6.3.1 Measure the temperature of the drilling fluid and record
6.3.2 Fill the sample cup of the pressurized mud balance to a level approximately 6.5 mm (0.25 in.) below the upper edge of the cup
To properly seal the cup, position the lid with the check-valve facing down and press it into the cup until it makes contact with the outer skirt This action will allow any excess drilling fluid to escape through the check-valve Once the lid is securely in place, lift the check-valve to the closed position, rinse the cup and threads with water, and then screw on the threaded cap.
The pressurizing plunger operates like a syringe; to fill it, submerge its end in drilling fluid while the piston rod is fully depressed Then, pull the piston rod upward to fill the cylinder with drilling fluid It is essential to expel this volume with the plunger action and refill it with a fresh drilling fluid sample to prevent dilution from any residual liquid left over from the previous cleanup of the plunger mechanism.
To properly pressurize the sample cup, apply a downward force of at least 225 N (50 lb-force) on the cylinder housing, which will keep the check-valve open while simultaneously pushing the piston rod down onto the O-ring surface of the cap valve.
The pressure-actuated check-valve in the lid closes when the cup is pressurized, pushing the valve upward To close the valve, gradually reduce pressure on the cylinder housing while keeping pressure on the piston rod Once the check-valve is closed, release the pressure on the piston rod before disconnecting the plunger.
To weigh the pressurized drilling fluid sample, first rinse and dry the exterior of the cup Position the instrument on the knife edge and adjust the sliding weight until the beam is balanced, indicated by the bubble centering between the two black marks The density can then be read from one of the four calibrated scales on the arrow side of the sliding weight Given that the density of water is 1 g/ml, the density of the fluid can be directly measured in grams per milliliter, pounds per gallon, pounds per cubic foot, or as a drilling fluid gradient in pounds per square inch per 1000 ft.
6.3.8 To release the pressure inside the cup, reconnect the empty plunger assembly and push downward on the cylinder housing
6.3.9 Clean the cup, lid, and plunger assembly
Calculation
Report the drilling fluid density to the nearest 0.01 g/ml or 10 kg/m 3 (0.1 lb/gal or 0.5 lb/ft 3 )
For conversions, use the equations given in 5.4.2
Principle
7.1.1 Viscosity and gel strength are measurements that relate to the flow or rheological properties of drilling fluids
Instruments used to measure the viscosity and gel strength of drilling fluids at temperatures ranging from 4°C to 65°C (40°F to 150°F) include the Marsh funnel, which provides a routine indication of viscosity, and a direct-indicating viscometer, a mechanical device that measures viscosity at different shear rates Lower temperature rheology is expected in the riser annulus during deepwater drilling under elevated pressures.
NOTE Information on the rheology of drilling fluids can be found in API 13D.
Determination of Viscosity Using the Marsh Funnel
7.2.1.1 Marsh funnel, calibrated to deliver 946 ml (1 quart) of fresh water at a temperature of 21 °C ± 3 °C
(70 °F ± 5 °F) in 26 seconds ± 0.5 seconds, with a graduated cup as a receiver
The Marsh funnel shall have the following characteristics: a) funnel cone, length 305 mm (12.0 in.), diameter 152 mm (6.0 in.) and a capacity to bottom of screen of
1500 ml (1.6 quarts); b) orifice, length 50.8 mm (2.0 in.) and inside diameter 4.7 mm (0.185 in = 3 /16 in.); c) screen, with 1.6 mm (0.063 in = 1 /16 in.) openings (12 mesh); fixed at 19.0 mm (0.75 in.) below top of funnel
7.2.1.2 Graduated cup, with a capacity of at least 946 ml (1 quart)
7.2.1.4 Thermometer, with a range of 0 °C to 105 °C (32 °F to 220 °F) and an accuracy of ±1 °C (±2 °F)
7.2.2.1 Cover the funnel orifice with a finger and pour freshly sampled drilling fluid through the screen into the clean, upright funnel Fill until fluid reaches the bottom of the screen
7.2.2.2 Remove finger and start the stopwatch simultaneously Measure the time for drilling fluid to fill to the 946 ml (1 quart) mark of the cup
7.2.2.3 Measure the temperature of the fluid, in degrees Celsius (degrees Fahrenheit)
7.2.2.4 Report the time (7.2.2.2) to the nearest second as the Marsh funnel viscosity Report the temperature (7.2.2.3) of the fluid to the nearest degree Celsius (degree Fahrenheit).
Determination of Viscosity and Gel Strengths Using a Direct-reading Viscometer
7.3.1.1 Direct-indicating viscometer, powered by an electric motor or a hand crank
Drilling fluid is situated in the annular space between two concentric cylinders, where the outer rotor sleeve rotates at a constant speed, generating torque on the inner bob A torsion spring limits the bob's movement, and a dial attached to it displays its displacement To accurately determine plastic viscosity and yield point, instrument constants must be calibrated using rotor sleeve speeds of 300 r/min and 600 r/min The rotor sleeve must adhere to specific specifications, including an inside diameter of 36.83 mm (1.450 in.), a total length of 87.0 mm (3.425 in.), and a scribed line positioned 58.4 mm (2.30 in.) above the sleeve's bottom, featuring two rows of 3.18 mm.
The rotor sleeve features holes measuring 0.125 inches, spaced 120° (2.09 rad) apart, located just below the scribed line on the sleeve surface, which has an average surface roughness of 16 to 32 and is cross-hatch honed The Bob—B1 component is closed, with a flat base and tapered top, having a diameter of 34.49 mm (1.358 in.) and a cylinder length of 38.0 mm (1.496 in.), also exhibiting an average surface roughness of 16 to 32 and cross-hatch honed Additionally, the torsion spring constant—F1.0 has a torsional stiffness of 10.54 N⋅m/rad (386 dyne-cm/degree deflection) and a shear stress constant of 29.3 pascals per radian of deflection (0.511 pascals per degree of deflection).
(1.067 lbf/100ãft 2 per degree of deflection) d) Rotor sleeve speeds: high speed: 600 r/min low speed: 300 r/min
NOTE Other rotor speeds are available in viscometers from various manufacturers
The thermostatically controlled viscometer cup, or thermocup, operates under two conditions: when the temperature is greater than room temperature, it utilizes a direct-heated design, while for temperatures below room temperature, it employs a double-walled structure linked to a refrigerated circulating bath.
7.3.1.4 Thermometer, with a range of 0 °C to 105 °C (32 °F to 220 °F) and an accuracy of ±1 °C (±2 °F)
To ensure accurate measurements of drilling fluid viscosity, place a sample in a thermostatically controlled viscometer cup, leaving approximately 50 ml to 100 ml of empty volume for fluid displacement Immerse the rotor sleeve precisely to the scribed line, and conduct field measurements promptly after sampling to maintain the integrity of the results.
50 °C ± 1 °C (120 °F ± 2 °F) or 65 °C ± 1 °C (150 °F ± 2 °F) for reference comparisons to historical data Testing at a lower temperature, such as 4 °C ± 1 °C (40 °F ± 2 °F), is recommended for low temperature effects The place of sampling should be stated in the report
When testing fluids at temperatures exceeding 90 °C (190 °F), it is crucial to use a solid metal bob to prevent hazards Using a hollow bob can lead to vaporization of the liquid inside when submerged in high-temperature fluids, potentially resulting in an explosion.
7.3.2.2 Heat (or cool) the sample to the selected temperature Use intermittent or constant shear at
Stir the sample at 600 r/min while heating or cooling to achieve a uniform temperature Once the cup temperature reaches the desired level, insert the thermometer into the sample and continue stirring until the sample attains the selected temperature Finally, record the sample's temperature.
At a sleeve rotation speed of 600 r/min, allow the viscometer dial to stabilize, which varies based on the characteristics of the drilling fluid Once steady, record the dial reading as R 600.
7.3.2.4 Reduce the rotor speed to 300 r/min and wait for the dial reading to reach steady value Record the dial reading R 300
NOTE Additional dial reading values are often measured and reported, typically R 200 , R 100 , R 6 , and R 3 Improved modeling accuracy can be achieved by also measuring the R 60 and R 30 dial readings
7.3.2.5 Stir the drilling fluid sample for 10 seconds at 600 r/min
To determine the initial gel strength of the drilling fluid, stop the rotor and let the sample sit undisturbed for 10 seconds For hand-crank viscometers, gradually turn the hand-wheel to achieve a positive dial reading, recording the highest value as the initial gel strength or 10-second gel strength For instruments operating at 3 r/min, the maximum reading after starting at this speed is noted as the initial gel strength Document the initial gel strength, denoted as β 10s, in pounds-force per one hundred square feet (lbf/100 ft²).
The gel strength value obtained from the dial reading is an approximation measured in lbf/100•ft² The dial reading reflects degrees of deflection, where 1 degree corresponds to 0.511 Pa in SI units and 1.067 lbf/100•ft² in USC units For ease of reporting, these precise unit conversions are frequently overlooked, and a common practice in the field is to simplify the reporting of pascals by dividing the dial units by 2.
Re-stir the drilling fluid sample at 600 r/min for 10 seconds, then stop the motor and let the fluid stand undisturbed for 10 minutes After this period, repeat the measurements as outlined in section 7.3.2.6 and report the maximum reading as β 10m, which represents the 10-minute gel strength in pounds-force per one hundred square feet (lbf/100 ft²).
The gel strength value obtained from the dial reading is an approximation measured in lbf/100•ft² The dial reading reflects degrees of deflection, where 1 degree corresponds to 0.511 Pa in SI units and 1.067 lbf/100•ft² in USC units For ease of reporting, these precise unit conversions are frequently overlooked, and a common practice in the field is to simplify the reporting of pascals by dividing the dial units by 2.
7.3.3.1 The dimensions for the rotor, bob and spring constant, as described in 7.3.1.1, determine the following:
⎯ 1° deflection of the bob equals a shear stress of approximately 1 lbf/100ãft 2 , or more exactly 1 degree of deflection = 1.067 lbf/100ãft 2 = 0.511 Pa;
⎯ 1 r/min of the rotor equals a shear rate of 1.7023 s −1
Viscosity, measured in millipascal-seconds (equivalent to centipoises), is defined as the shear stress in millipascal divided by the shear rate in reciprocal seconds At a shear rate of 511 s\(^{-1}\) corresponding to 300 r/min, the degrees of deflection will also be expressed in millipascal-seconds (or centipoises).
7.3.3.2 The calculation for the plastic viscosity, η PV , expressed in millipascal-seconds (centipoises), is given in Equation (8):
PV R 600 R 300 η = − (8) where η PV is the plastic viscosity, expressed in millipascal-seconds (centipoises);
R 600 is the dial reading at 600 revolutions per minute, expressed in degrees deflection;
R 300 is the dial reading at 300 revolutions per minute, expressed in degrees deflection
NOTE 1 Plastic viscosity is commonly known in the industry by the abbreviation PV
7.3.3.3 The calculation for yield point, Y PA , expressed in pascals, is given in Equation (9):
Y PA is the yield point, expressed in pascals
To convert lbf/100•ft² to pascals, multiply by 0.479 Each degree of deflection corresponds to 0.511 Pa in SI units, allowing equation (9) to convert dial unit values to pascals For ease of reporting, common field practice involves dividing dial units by 2, as shown in equation (10).
7.3.3.4 When calculating values in USC units, the yield point in pounds-force per one hundred square feet is calculated as follows:
Y PB is the yield point, expressed in pounds-force per one hundred square feet
The yield point, abbreviated as YP, is expressed in lbf/100•ft² and is a key measurement in the industry It is calculated using Equation (10) based on dial readings, which are measured in degrees.
```,,`,,```,`,,`,,,,```````,,,-`-`,,`,,`,`,,` - deflection (1⁄360 of 1 full rotation) Each 1 degree of deflection is equal to 0.511 Pa in SI units and to 1.067 lbf/100•ft 2 in
USC units In equation (10) the exact units correction is neglected for simplicity in reporting
7.3.3.5 The calculation for apparent viscosity, ηAV, expressed in millipascal-seconds (centipoises), is given in Equation (11):
R 600 is the dial reading at 600 r/min, expressed in degrees of deflection; η AV is the apparent viscosity, expressed in millipascal-seconds (centipoises)
NOTE Apparent viscosity is commonly known in the industry by the abbreviation AV
Report the plastic viscosity, yield point, 10-second gel strength, 10-min gel strength, and apparent viscosity
Principle
Measuring the filtration behavior and filter cake characteristics of oil-based drilling fluids is essential for effective treatment and control Additionally, understanding the properties of the filtrate, including concentrations of oil, aqueous phase, or emulsion, is crucial for optimizing drilling fluid performance.
The filtration characteristics of oil-based drilling fluids are influenced by the quantity, type, and size of solid particles, as well as the emulsified aqueous phase present in the fluid Additionally, the properties of the liquid phase play a significant role in these characteristics.
Interactions of these various components can be influenced by temperature and pressure
8.1.3 Filtration tests are performed at high-temperature conditions and under static conditions Two filtration procedures are given: one for testing up to 175 °C (350 °F) and one for testing from 175 °C (350 °F) to 230 °C
(450 °F) Use only the filtration equipment and procedure specified for the temperature required
The article notes that while there is no specified low-temperature filtration test procedure for oil-based drilling fluids, it can be conducted similarly to the water-based drilling fluid test outlined in API 13B-1.
8.1.4 The 175 ml, 250 ml, or 500 ml unit may be used for static filtration testing up to and including 175 °C
For testing temperatures exceeding 175 °C (350 °F), only the 500 ml unit is permitted This unit must include a thermocouple that is in direct contact with the fluid inside the cell to ensure precise temperature measurements, and it should utilize a porous stainless-steel filter media.
High-temperature/High-pressure Test up to 175 °C (350 °F)
The high-temperature/high-pressure filter press is designed to withstand working pressures of up to 9000 kPa (1300 psi) and elevated temperatures It includes a filter cell for containment and a pressurized gas source, such as carbon dioxide or nitrogen, equipped with regulators.
The heating system is equipped with a temperature controller or thermostat to maintain a temperature of 175 °C (350 °F) It includes a high-pressure filtrate collection vessel that is kept at the appropriate back-pressure to prevent flashing or evaporation of the filtrate Additionally, the filter cell features a thermometer well, a removable end, a filter-media support, and oil-resistant seals.
NOTE Valve stems on each end of the cell can be opened or closed during the test
CAUTION—Strict adherence to manufacturer's recommendations as to sample volumes, equipment temperatures and pressures is essential Failure to do so could result in serious injury
Avoid using nitrous oxide cartridges as pressure sources for HTHP filtration, as they can detonate under temperature and pressure when in contact with grease, oil, or carbonaceous materials These cartridges should only be utilized for Garrett gas train carbonate analysis, following the guidelines set by API 13B-1.
Table 3—Recommended Minimum Back-pressure
Test Temperature Vapor Pressure Minimum Back- pressure °C °F kPa psi kPa psi
For effective filtration, use hardened, low-ash grade filter paper for temperatures up to 200 °C (400 °F), ensuring a new paper is utilized for each test For temperatures exceeding 200 °C (400 °F), employ a porous disc, specifically Dynalloy X-5, and replace it with a new disc for every test conducted.
8.2.1.3 Mechanical or electronic timer, with at least a 30 min interval
8.2.1.4 Thermometer, with a range up to 260 °C (500 °F), and with a 12.5 cm (5 in.) or longer stem, or a thermocouple with a range up to 260 °C (500 °F), preferred
8.2.1.5 Graduated cylinder (TC), long, slender glass tube, with a capacity of 10 ml or 20 ml.
8.2.1.6 Graduated cylinder (TC), optional, with a capacity of 25 ml
8.2.1.7 Field mixer, cup type, to operate at 10,000 r/min to 15,000 r/min.
8.2.1.8 Ruler, graduated in millimeters (inches), to measure filter cake thickness
This calendered, hardened qualitative filter paper, crafted from cotton linters, features a low ash content of 0.015% by weight It has a slow filtration rate of 2685 Herzbergs and retains particles in liquid ranging from 2 to 5 μm The filter paper has a basis weight of 92 g/m², a diameter of 2.5 inches (63.5 mm), and a thickness of 0.137 mm.
8.2.2.1 Place the thermometer in the well of the heating jacket Preheat the jacket to approximately
6 °C (10 °F) above the desired test temperature Adjust the thermostat to the desired test temperature
When a filtration unit includes a thermocouple that directly measures the drilling fluid temperature within the cell, it is essential to monitor and report this test temperature during the filtration test The filtration results obtained at this measured temperature may vary from those based on the cell wall temperature It is important to note in the “Comments” section whether the results were derived from the fluid temperature measured with a direct contact thermocouple.
Stir the drilling fluid sample for 10 minutes with a field mixer operating at 10,000 r/min Then, pour the fluid sample into the filter cell, ensuring to leave a minimum of 2.5 cm (1 inch) of space in the cell for fluid expansion.
Install the porous disk [or the filter paper if the test temperature is below 200 °C (400 °F)] in the cell
To complete the assembly of the filter cell, ensure that both the top and bottom valves are closed before placing it in the heating jacket Next, transfer the thermometer from the heating jacket into the well of the filter cell.
8.2.2.4 Connect the high-pressure filtrate collection vessel onto the lower valve stem and lock it in place
Ensure that the collection vessel is completely free of water or oil.
8.2.2.5 Connect the regulated pressure source to the upper valve Connect a similar regulated pressure source to the filtrate collection vessel and lock these connections in place
8.2.2.6 Keeping the two valve stems closed, adjust the pressure on the upper pressure regulator to
To ensure accurate testing, adjust the upper pressure regulator to maintain a pressure of 690 kPa (100 psi) above the minimum back-pressure specified in Table 3 Open the upper valve stem and keep the pressure steady until the test temperature is achieved.
NOTE If the time required to reach the test temperature exceeds 1 h, the heater might be defective and the validity of the test is questionable
When the sample attains the designated test temperature, as measured by the thermocouple, adjust the lower pressure regulator to the specified "minimum back-pressure" corresponding to that temperature.
Table 3 Open the lower valve stem and immediately increase the pressure on the upper regulator to
3450 kPa (500 psi) higher than the back-pressure This will start the filtration process Start the timer
To ensure accurate testing, maintain the temperature within ±3 °C (±5 °F) as shown by the thermometer in the filter cell If back-pressure exceeds the predetermined level during the test, carefully draw off and collect some filtrate to lower the back-pressure.
Collect the filtrate in a long, slender graduated cylinder and record the total volume of the filtrate, which includes both water and oil, after 30 minutes Additionally, note the volumes of any solid and aqueous phases, if they are present.
The long, slender glass cylinder enhances the accuracy of detecting and measuring volumes of oil, water, and solids in the filtrate Additionally, heating the cylinder near the emulsion interface can facilitate better separation of water, solids, and oil within the filtrate.
After collecting the 30-minute filtrate, promptly turn off the heating and unplug the heating jacket Close both the upper and lower valve stems to maintain pressure, then carefully bleed off the pressure from the regulators and hoses according to the manufacturer's instructions Disconnect the pressurization system and remove the cell from the heating jacket, allowing it to cool to below 50 °C (125 °F).
Keep the cell upright during cooling, depressurization and disassembly
Caution: The filter cell can maintain a pressure of 6200 kPa (950 psi) even after cooling To prevent serious injury, ensure the cell is kept upright and allowed to cool to room temperature before bleeding off the pressure prior to disassembly.
High-temperature/High-pressure Test 175 °C (350 °F) up to and Including 230 °C (450 °F)
8.3.1.1 High-temperature/high-pressure filter press, consisting of the following components: a) 500 ml volume cell, only;
NOTE For safety reasons, it is advisable that only the 500 ml cell be used for testing up to and above 230 °C
The filter cell is designed to withstand working pressures of up to 15,500 kPa (2250 psi) at a temperature of 230 °C (450 °F) It utilizes a preferred nitrogen gas source with regulators and features a heating system equipped with a temperature controller to reach 260 °C (500 °F) Additionally, a high-pressure filtrate collection vessel is maintained at the appropriate back-pressure to prevent flashing or evaporation of the filtrate The filter cell also includes an internal thermocouple for monitoring the temperature of the drilling fluid sample at its center, and it has a removable end fitted with oil-resistant seals.
NOTE Valve stems on each end of the cell can be opened or closed during a test
It is crucial to be aware that not all manufacturers' equipment is suitable for use above 150 °C (300 °F), as ignorance of the pressure/temperature ratings can lead to serious injuries When conducting tests at elevated temperatures and pressures, additional safety measures are necessary Specifically, the 175 ml and 250 ml filtration cells are not advised for use under these extreme conditions.
Caution is advised against using nitrous oxide cartridges as pressure sources for HTHP filtration, as they can detonate when exposed to grease, oil, or carbonaceous materials under temperature and pressure These cartridges should only be utilized for Garrett gas train carbonate analysis, following the guidelines set by API 13B-1.
8.3.1.2 Filter medium, Dynalloy X-5 porous disc, for temperatures above 200 °C (400 °F) A new disc is required for each test
8.3.1.3 Mechanical or electronic timer, with at least a 30 min interval
8.3.1.4 Thermometer, with a range up to 260 °C (500 °F), and with a 12.5 cm (5 in.) or longer stem, or a thermocouple with a range up to 260 °C (500 °F), preferred.
8.3.1.5 Graduated cylinder (TC), long, slender with a volume of 10 ml or 20 ml.
8.3.1.6 Graduated cylinder (TC), optional, with a volume of 25 ml.
8.3.1.7 Field mixer, cup type, to operate at 10,000 r/min to 15,000 r/min.
8.3.1.8 Ruler, graduated in millimeters (inches), to measure filter cake thickness
8.3.2.1 Place the thermometer in the well of the heating jacket Preheat the jacket to approximately
6 °C (10 °F) above the desired test temperature Adjust the thermostat to the test temperature
When a filtration unit includes a thermocouple that directly measures the drilling fluid temperature within the cell, it is essential to monitor and report this test temperature during the filtration test The filtration results obtained at this measured temperature may vary from those based on the cell wall temperature It is important to note in the “Comments” section whether the results were derived from the fluid temperature measured with a direct contact thermocouple.
Stir the drilling fluid sample for 10 minutes with a field mixer operating at 10,000 r/min Pour the fluid into the filter cell, ensuring to leave a minimum of 5.0 cm (2 in.) of space for fluid expansion, and then install the filter medium in the cell.
To complete the assembly of the filter cell, install the thermocouple to monitor the fluid temperature at the cell's center Ensure the upper and lower valve stems are closed before placing the cell in the heating jacket Finally, connect the thermocouple to the temperature-readout instrument and verify its accuracy.
To begin, securely attach the high-pressure filtrate collection vessel to the lower valve stem and lock it in position It is essential to ensure that the collection vessel is completely free of any residual water or oil.
8.3.2.5 Connect the pressurized gas source to the upper valve Connect a similar pressurized gas source to the lower collection vessel and lock these connections in place
8.3.2.6 Keeping the two valve stems closed, adjust the pressure on the upper pressure regulator to
To ensure accurate testing, maintain a pressure of 690 kPa (100 psi) above the minimum back-pressure specified in Table 3 Open the upper valve stem and, if necessary, readjust the upper pressure regulator to sustain this pressure level until the test temperature is achieved Keep both pressures stable throughout the process.
NOTE If the time required to reach the test temperature exceeds 1 h, the heater might be defective and the validity of the test is questionable
Once the sample attains the designated test temperature, as measured by the thermocouple, adjust the lower pressure regulator to the specified "minimum back-pressure" for that temperature, as outlined in Table 3 Subsequently, open the lower valve stem and promptly raise the pressure on the upper regulator.
To initiate the filtration process, apply a pressure of 3450 kPa (500 psi) above the back-pressure and start the timer It is crucial to maintain the test temperature within ±3 °C (±5 °F) as monitored by the thermometer in the filter cell If the back-pressure exceeds the predetermined level during the test, carefully draw off and collect some filtrate to alleviate the back-pressure.
Collect the filtrate in a long, slender graduated cylinder and record the total volume after 30 minutes, including both water and oil Additionally, note the volumes of any solid and water phases present.
After collecting the 30-minute filtrate, promptly turn off the heat and unplug the heating jacket Close both the upper and lower valve stems to maintain pressure, then carefully bleed off pressure from the regulators and hoses according to the manufacturer's instructions before disconnecting the pressurization system Finally, remove the cell from the heating jacket and let it cool to below 50 °C.
(125 °F) Keep the cell upright during cooling, depressurization and disassembly
CAUTION: The filter cell can maintain a pressure of 6200 kPa (950 psi) even after cooling To prevent serious injury, ensure the cell is kept upright and allowed to cool to room temperature before bleeding off the pressure prior to disassembly.
To safely bleed pressure from the filter cell, gradually open the upper valve stem while preventing any spraying of drilling fluid as gas is released Ensure that all pressure is completely released before removing the cap, and then proceed to carefully disassemble the cell.
8.3.2.11 Pour the liquid from the cell
8.3.2.12 Remove the filter cake on the filter disc or paper Measure the filter cake thickness, at its center, to the nearest millimeter ( 1 /32 in.)
During the test, settling of solids onto the filter cake may have occurred, indicated by an unusually thick cake or a coarse texture It is essential to document these characteristics To reduce settling, minimize the heat-up and cool-down times, and ensure the cake is promptly recovered and examined.
Principle
A retort test evaluates the amount of water and oil extracted from an oil-based drilling fluid sample when subjected to heat in a calibrated retort instrument This section outlines the procedures for conducting a retort analysis using either volumetric or gravimetric methods.
NOTE The gravimetric procedure will provide more accurate values than the standard volumetric approach
Understanding the concentrations of water, oil, and solids is essential for effectively managing drilling fluid properties, including the oil-to-water ratio, rheology, density, filtration, and salinity of the aqueous phase.
Given that knowledge of solids in an oil-based drilling fluid is essential to the evaluation of solids control equipment, reference shall be made to API 13C
In a retort test, a specific volume or mass of oil-based drilling fluid is heated in a retort instrument to vaporize its liquid components, with the resulting vapors being condensed and collected in a precision-graduated liquid receiver.
The volumetric method calculates the volume fractions of oil, water, and solids as percentages based on the total initial volume of oil-based drilling fluid, along with the condensed liquid volumes of water and oil collected in a precision-graduated liquid receiver.
The gravimetric method calculates the volume fractions of oil, water, and solids as percentages based on the mass of retorted oil-based drilling fluid, the mass of dry solids post-retorting, and the densities of water, oil, and the drilling fluid, along with the volume of condensed water collected in a precision graduated receiver If the oil's density is unknown, alternative procedures are available to either calculate it from mass measurements or utilize handheld density-measuring devices.
The gravimetric method measures mass loss during retorting, contrasting with the volumetric method that relies on recovered volume Consequently, the volume fraction of solids may be lower in the gravimetric approach, particularly when dealing with oil-based drilling fluids or when volatile components are not completely condensed in the volumetric method.
Apparatus
9.2.1 Retort instrument, as specified below. a) Retort assembly, including a retort body, cup and lid constructed of 303 stainless steel, or equivalent
Standard cup sizes include 10 ml (precision ±0.05 ml), 20 ml (precision ±0.1 ml), and 50 ml (precision ±0.25 ml) The volumetric procedure requires the verification of the retort cup volume with lid through gravimetric methods as outlined in Annex J (J.4) Additionally, a condenser must be used to cool oil and water vapors below their vaporization temperature, while a heating jacket with a nominal power of 350 W and a temperature controller that limits the retort temperature to 500 °C ± 40 °C are also essential components.
9.2.2 Liquid receiver (TC), specially designed cylindrical glassware with a rounded bottom to facilitate cleaning and a funnel-shaped top to catch falling drops, meeting the following specifications:
⎯ scale: milliliter or volume fraction (as a percentage);
⎯ material: transparent and inert to oil, water, and salt solutions at temperatures up to 32 °C (90 °F)
⎯ When using the volumetric procedure, the receiver volume shall be verified gravimetrically in accordance with the procedure and calculations in Annex J (J.3)
Table 4—Precision of Liquid Receiver
10 ml 20 ml 50 ml 50 ml tapered
Precision (0 % to 100 %) ±0.05 ml ±0.10 ml ±0.25 ml —
9.2.3 Fine steel wool, oil-free
Liquid steel wool or coated steel wool substitutes should not be used for this application
9.2.4 High-temperature-resistant silicone grease, to be used as a thread seal and lubricant
9.2.5 Pipe cleaners and/or T-drill
9.2.6 Putty knife or spatula, with blade shaped to fit the inside dimensions of the sample cup of the retort
9.2.8 Syringe, of capacity 10 ml, 20 ml, or 50 ml, to fill retort cup
9.2.10 Top-loading balance, capable of weighing 2000 g with an accuracy of ±0.01 g
Procedure-Volumetric Method
To ensure accurate test results and maintain safety, it is essential to keep the retort sample cup, condenser passage, and liquid receiver clean, dry, and cooled from previous use Before each test, thoroughly clean the sample cup and lid with a putty knife or spatula, and periodically polish the interior with steel wool Additionally, clean and dry the condenser passage using pipe cleaners to prevent material build-up, which can reduce condensation efficiency and lead to erroneous liquid readings.
CAUTION—A moist or partially clogged condenser passage may be a safety hazard
9.3.2 The heating jacket should be cooled to less than 93 °C (200 °F)
9.3.3 Pack the retort body with steel wool
9.3.4 Collect a representative sample of oil-based drilling fluid and allow it to cool to approximately 27 °C
(80 °F) Screen the test sample through the 1.68 mm (0.066 in or 12-mesh) screen of the Marsh funnel to remove lost circulation material, large cuttings or debris
To ensure a homogeneous drilling fluid sample, mix it thoroughly while avoiding air entrapment and ensuring that no solids settle at the bottom of the container.
NOTE Air or gas entrapment in the retort sample will result in erroneously high retort solids, due to a reduced volume of drilling fluid sample
To prevent air entrapment, fill the retort sample cup slowly and lightly tap its side to release any trapped air After placing the lid on the cup, rotate it to ensure a proper fit, allowing a small amount of drilling fluid to flow out of the hole in the lid Finally, wipe away any excess sample from the lid, taking care not to wick out the drilling fluid through the hole.
9.3.7 Apply lubricant/sealant sparingly to the threads of the retort sample cup With lid in place, hand tighten the retort sample cup onto the body
Apply lubricant or sealant carefully to the threads of the condenser passage stem before attaching it to the condenser body Next, position the retort assembly within the heating jacket and secure the insulating lid.
9.3.9 Place the clean, dry liquid receiver below the condenser passage outlet
To enhance the accuracy of oil and water volume readings, pre-wetting the interior of the glass liquid receiver with propylene glycol normal-propyl ether (PNP) is recommended PNP is utilized to break the oil-based mud emulsion during the chemical titration of oil-based drilling fluid The procedure involves adding approximately 0.5 ml of PNP to the liquid receiver, tilting and rolling it to ensure the solvent coats the interior, and then inverting the receiver to remove any excess solvent.
PNP is highly degradable and should only be used when fresh and within its expiration date Proper disposal must adhere to local, state, and federal regulations, ensuring environmental safety.
PNP in liquid or vapor form can lead to moderate eye irritation and corneal injury While prolonged skin contact may cause slight irritation and redness, significant absorption of harmful amounts is unlikely Repeated exposure can result in skin drying, flaking, irritation, or burns Brief inhalation of PNP is generally safe, but excessive inhalation may irritate the nose and throat and cause lethargy PNP has low toxicity when swallowed, though large amounts can lead to injury, and repeated exposure may affect the liver, kidneys, and eyes Laboratory studies did not indicate any birth defects in animals.
To accurately weigh the liquid receiver, consider placing it in a 100 ml graduated cylinder, as its rounded bottom may make it unstable on a top-loading balance.
NOTE 5 The length of the liquid receiver might require that it be angled out from the retort condenser passage and perhaps supported off the edge of the worktable
To ensure accurate results, activate the heating jacket and let the retort assembly operate for at least one hour Collect the condensate in the glass liquid receiver If the drilling fluid overflows into the receiver, cool and clean the equipment, then repeat the test with a greater quantity of steel wool packed into the retort body.
9.3.11 Remove the liquid receiver and allow it to cool
CAUTION—The retort body is still extremely hot and will cause severe burns if contacted
Heating the emulsion interface between oil and water can break the emulsion To do this safely, remove the retort assembly from the heating jacket by holding the condenser Gently heat the glass liquid receiver along the emulsion band by briefly touching it with the hot retort assembly, ensuring not to boil the liquid Once the emulsion interface is disrupted, allow the liquid receiver to cool.
Record the total liquid volume, V R , and water volume, V W , collected in the liquid receiver
Accurate reading of the meniscus is crucial for precision Always ensure that your eye is level with the interface when taking measurements For air-to-liquid meniscus readings, note the volume at the lowest point of the meniscus, located at the center of the liquid receiver In cases of opaque liquids, you may need to estimate the liquid's height in the middle of the cylinder Additionally, when measuring the water-to-oil meniscus, always read the water volume at its lowest point.
9.3.12 Turn off the heating jacket Remove the retort assembly and condenser from the heating jacket and allow them to cool Remove the condenser Clean the retort assembly and condenser.
Calculation-Volumetric Method
To determine the volume fractions of water, oil, and total solids in the drilling fluid, use the measured volumes of oil and water along with the original whole drilling fluid sample volume, which can be 10 ml, 20 ml, or 50 ml Calculate these fractions as percentages to obtain the final results.
9.4.2 Calculate the volume of oil in the condensed sample
V O is the volume of oil, expressed in milliliters;
V R is the total volume of condensed liquids (oil and water), expressed in milliliters;
V W is the water volume expressed in milliliters or water mass expressed in grams (1 ml = 1 g) (see 3.2)
9.4.3 Calculate the volume fraction of oil in the total sample
100 V S ϕ = ×V (13) where ϕ O is the volume fraction of oil, expressed as a percentage of the total sample volume;
V O is the volume of oil, expressed in milliliters;
V S is the drilling fluid sample volume, expressed in milliliters
9.4.4 Calculate the volume fraction of water
100 V S ϕ = × V (14) where ϕ W is the volume fraction of water, expressed as a percentage;
V W is the water volume expressed in milliliters or water mass expressed in grams (1 ml = 1 g) (see 3.2);
V S is the drilling fluid sample volume, expressed in milliliters
9.4.5 Calculate the volume fraction of solids remaining in the retort d 100 W O ϕ = −ϕ −ϕ (15) where ϕ d is the volume fraction of dried retort solids, expressed as a percentage of the total sample volume;
```,,`,,```,`,,`,,,,```````,,,-`-`,,`,,`,`,,` - ϕ W is the volume fraction of water, expressed as a percentage; ϕ O is the volume fraction of oil, expressed as a percentage of the total sample volume
The calculated volume of suspended solids may be overestimated due to the presence of dissolved salts To address this, a volumetric correction for salinity can be applied using established volume factors for salt solutions, as detailed in Section 12 Additionally, Section 12 provides calculations for determining the oil-to-water ratio, as well as the corrected concentration and density of solids.
Procedure-Gravimetric Method
To ensure accurate test results and maintain safety, it is essential to keep the retort sample cup, condenser passage, and liquid receiver clean, dry, and cooled from previous use Before each test, thoroughly clean the sample cup and lid with a putty knife or spatula, and periodically polish the interior with steel wool Additionally, clean and dry the condenser passage using pipe cleaners to prevent material build-up, which can reduce condensation efficiency and lead to erroneous liquid readings.
CAUTION—A moist or partially clogged condenser passage may be a safety hazard
9.5.2 The heating jacket should be cooled to less than 93 °C (200 °F)
9.5.3 Pack the retort body with steel wool
9.5.4 Apply lubricant/sealant sparingly to the threads of the retort cup With lid in place, hand-tighten the retort cup onto the body
9.5.5 Apply lubricant/sealant sparingly to the threads on the condenser passage stem and attach to the condenser body
9.5.6 Weigh and record the total mass of the empty retort sample cup, lid, and retort body packed with steel wool Record this as m 1 , expressed in grams
NOTE All weights are recorded to the nearest 0.01 g
9.5.7 Collect a representative sample of oil-based drilling fluid and allow it to cool to approximately 27 °C
(80 °F) Screen the test sample through the 1.68 mm (0.066 in or 12-mesh) screen of the Marsh funnel to remove lost circulation material, large cuttings or debris
Thoroughly mix the drilling fluid sample to achieve homogeneity, taking care to avoid air entrapment and ensuring that no solids settle at the bottom of the container.
NOTE Air or gas entrapment in the retort sample will result in erroneously high retort solids, due to a reduced volume of drilling fluid sample
9.5.9 Measure and record the density of the oil-based drilling fluid using a mud balance as described in
Section 5 or Section 6 (more accurate) Alternative gravimetric methods, such as a volumetric flask or cup, are also acceptable
Record the drilling fluid density as ρ S , to the nearest 0.01 g/ml, 10 kg/m 3 (0.1 lb/gal or 0.5 lb/ft 3 )
Alternatively, there are several small-volume portable handheld density-measuring devices that can be used to accurately measure the density of the drilling fluid
To determine the density of an unknown oil, utilize a mud balance as outlined in Section 5 or Section 6 for greater accuracy Alternatively, gravimetric methods like using a volumetric flask or cup can also be employed to measure the density of the base oil.
Record the oil density as ρ O , to the nearest 0.01 g/ml, 10 kg/m 3 (0.1 lb/gal or 0.5 lb/ft 3 )
Alternatively, there are several small-volume portable handheld density-measuring devices that can be used to accurately measure the density of the condensed oil
To prepare the retort sample, carefully remove the retort cup from the retort body and fill it slowly to prevent air entrapment Gently tap the cup's side to release any trapped air, then securely place and rotate the lid for a proper fit Ensure a slight excess of drilling fluid flows from the hole in the lid, and wipe away any excess sample to prevent wicking of the drilling fluid.
To begin the process, securely attach the retort sample cup with lid to the retort body Next, weigh the entire assembly, which includes the retort sample cup filled with drilling fluid, the lid, and the retort body packed with steel wool This total weight should be recorded as \( m_2 \) in grams.
NOTE All weights are recorded to the nearest 0.01 g
9.5.13 Attach the condenser Place the retort assembly into the heating jacket Close the insulating lid
9.5.14 Weigh an empty, clean, dry liquid receiver Record this as m 3 , expressed in grams Place the receiver below the condenser passage outlet
To enhance the accuracy of oil and water volume readings, pre-wetting the interior of the glass liquid receiver with propylene glycol normal-propyl ether (PNP) is recommended PNP is utilized to break the oil-based mud emulsion during the chemical titration of oil-based drilling fluid The procedure involves adding approximately 0.5 ml of PNP to the liquid receiver, tilting and rolling it to ensure the solvent coats the interior, and then inverting the receiver to remove any excess solvent.
PNP is highly degradable and should only be used when fresh and within its expiration date Proper disposal must adhere to local, state, and federal regulations, ensuring environmental safety.
PNP, whether in liquid or vapor form, can lead to moderate eye irritation and corneal injury While prolonged skin contact may cause slight irritation and local redness, significant absorption of harmful amounts is unlikely Repeated exposure may result in skin drying, flaking, irritation, or burns Brief inhalation of PNP is generally safe, but excessive inhalation can irritate the nose and throat and may lead to lethargy PNP is of low toxicity when swallowed, though large quantities can cause injury, and repeated exposure may affect the liver, kidneys, and eyes Notably, laboratory studies have not shown any birth defects associated with PNP.
To accurately weigh the liquid receiver, consider placing it in a 100 ml graduated cylinder, as its rounded bottom may make it unstable on a top-loading balance.
NOTE 5 The length of the liquid receiver might require that it be angled out from the retort condenser passage and perhaps supported off the edge of the worktable
To begin the test, activate the heating jacket and let the retort assembly operate for at least one hour Collect the resulting condensate in the glass liquid receiver In the event of drilling fluid overflowing into the receiver, ensure to cool and clean the equipment before repeating the test with a greater quantity of steel wool packed into the retort body.
9.5.16 Remove the liquid receiver and allow it to cool
CAUTION—The retort body is still extremely hot and will cause severe burns if contacted
Heating the emulsion interface between oil and water can break the emulsion To do this safely, remove the retort assembly from the heating jacket by holding the condenser Gently heat the glass liquid receiver along the emulsion band by briefly touching it with the hot retort assembly, ensuring not to boil the liquid Once the emulsion interface is disrupted, allow the liquid receiver to cool.
Record the total condensed liquid volume, V R , and water volume, V W , collected in the liquid receiver These are converted to mass, expressed in grams, as described in 9.6
Accurate reading of the meniscus is crucial for precise measurements Always ensure that your eye is level with the meniscus when taking a reading For air-to-liquid measurements, identify the volume at the lowest point of the meniscus, which is located at the center of the liquid receiver In cases involving opaque liquids, you may need to estimate the liquid's height in the middle of the cylinder Additionally, when measuring the water-to-oil meniscus, always read the water volume at its lowest point.
9.5.17 Weigh the glass liquid receiver and its liquid content (oil and water) Record as m 4 , expressed in grams
9.5.18 Turn off the heating jacket Remove the retort assembly and condenser from the heating jacket and allow them to cool Remove the condenser
On September 5, 2019, remove the condenser and passage stem from the retort assembly Weigh the cooled retort assembly, which includes the retort sample cup, lid, and retort body with steel wool packing, excluding the condenser Record this weight as \( m_5 \), expressed in grams.
9.5.20 Clean the retort assembly and condenser.