ISO 10426 consists of the following parts, under the general title Petroleum and natural gas industries — Cements and materials for well cementing: ⎯ Part 1: Specification ⎯ Part 2:Te
Specification, chemical and physical requirements
Well cement shall be specified using classes A, B, C, D, G and H and the grades: ordinary (O), moderate sulfate- resistant (MSR) and high sulfate-resistant (HSR)
A properly manufactured cement that adheres to ISO 10426 can be mixed and applied in the field with water ratios or additives chosen by the user However, compliance with ISO 10426 should not be determined based on these field conditions.
Processing additives, set modifying agents or chemical additives used to reduce chromium (VI) shall not prevent a well cement from performing its intended functions
This product is produced by grinding clinker, which primarily consists of hydraulic calcium silicates and often includes one or more forms of calcium sulfate as an additive Manufacturers may incorporate processing additives in the production of class A cement, as long as these materials comply with the requirements outlined in ASTM C465.
This product is intended for use when special properties are not required and is available only in O grade, similar to ASTM C150, type I
This product is produced by grinding clinker, which primarily consists of hydraulic calcium silicates and typically includes one or more forms of calcium sulfate as an additive Manufacturers may incorporate processing additives in the production of class B cement, as long as these materials comply with the requirements outlined in ASTM C465.
This product is intended for use when conditions require moderate or high sulfate resistance and is available in both MSR and HSR grades, similar to ASTM C150, type II
This product is produced by grinding clinker, which primarily consists of hydraulic calcium silicates and typically includes one or more forms of calcium sulfate as an additive Manufacturers may also incorporate processing additives in the production of class C cement, as long as these materials comply with the requirements outlined in ASTM C465.
This product is intended for use when conditions require high, early strength and is available in O, MSR and HSR grades, similar to ASTM C150, type III
This product is produced by grinding clinker, primarily made up of hydraulic calcium silicates, and typically includes calcium sulfate as an additive Manufacturers may incorporate processing additives in class D cement, ensuring compliance with ASTM C465 standards Additionally, suitable set-modifying agents can be blended or interground during the manufacturing process.
This product is intended for use under conditions of moderately high temperatures and pressures and is available in MSR and HSR grades
Class G well cement is produced by grinding clinker, primarily made up of hydraulic calcium silicates, with the addition of calcium sulfate as an interground additive During the manufacturing process, no other additives besides calcium sulfate or water are allowed to be blended with the clinker However, chemical additives for chromium(VI) reduction are permitted, as long as they do not hinder the cement's intended functionality.
This product is intended for use as a basic well cement and is available in MSR and HSR grades
Class H well cement is produced by grinding clinker, primarily made up of hydraulic calcium silicates, with the addition of calcium sulfate as an interground additive During its manufacture, no other additives besides calcium sulfate or water are allowed to be blended with the clinker However, chemical additives for chromium(VI) reduction are permitted, as long as they do not hinder the cement's intended functionality.
This product is intended for use as a basic well cement and is available in MSR and HSR grades
Well cements shall conform to the respective chemical requirements of classes and grades referenced in Table 1
Manufacturing compliance outlined in ISO 10426 does not apply to field conditions and is specifically not relevant for cements that fail to meet the chemical requirements of the specified classes and grades in Table 1.
Chemical analyses of hydraulic cements shall be carried out as specified in EN 196-2
NOTE For the purposes of this provision, ASTM C114 is equivalent to EN 196-2
Magnesium oxide (MgO), maximum, percent 6,0 NA a 6,0 NA NA NA Sulfur trioxide (SO 3 ), maximum, percent b 3,5 NA 4,5 NA NA NA Loss on ignition, maximum, percent 3,0 NA 3,0 NA NA NA
Insoluble residue, maximum, percent 0,75 NA 0,75 NA NA NA
Tricalcium aluminate (C 3 A), maximum, percent d NR c NA 15 NA NA NA
Moderate sulfate-resistant grade (MSR)
Magnesium oxide (MgO), maximum, percent NA 6,0 6,0 6,0 6,0 6,0 Sulfur trioxide (SO 3 ), maximum, percent b NA 3,0 3,5 3,0 3,0 3,0
Loss on ignition, maximum, percent NA 3,0 3,0 3,0 3,0 3,0
Insoluble residue, maximum, percent NA 0,75 0,75 0,75 0,75 0,75 Tricalcium silicate (C 3 S) maximum, percent d NA NR NR NR 58 58 minimum, percent d NA NR NR NR 48 48
Tricalcium aluminate (C 3 A), maximum percent d NA 8 8 8 8 8
Total alkali content, expressed as sodium oxide (Na 2 O) equivalent, maximum, percent e NA NR NR NR 0,75 0,75
High sulfate-resistant grade (HSR)
Magnesium oxide (MgO), maximum, percent NA 6,0 6,0 6,0 6,0 6,0 Sulfur trioxide (SO 3 ), maximum, percent b NA 3,0 3,5 3,0 3,0 3,0
Loss on ignition, maximum, percent NA 3,0 3,0 3,0 3,0 3,0
Insoluble residue, maximum, percent NA 0,75 0,75 0,75 0,75 0,75 Tricalcium silicate (C 3 S) maximum, percent d NA NR NR NR 65 65 minimum, percent d NA NR NR NR 48 48
Tricalcium aluminate (C₃A) has a maximum percentage limit, while tetracalcium aluminoferrite (C₄AF) combined with twice the tricalcium aluminate (C₃A) also has a specified maximum percentage The total alkali content, expressed as sodium oxide (Na₂O) equivalent, is capped at a maximum of 0.75% If the tricalcium aluminate content is 8% or less, the maximum SO₃ content is limited to 3%, or 3.5% for class C cement It is important to note that the expression of chemical limitations through calculated assumed compounds does not guarantee that the oxides are present entirely as such compounds; these compounds are determined based on the mass percentages of Al₂O₃ to Fe₂O₃.
2 O 3 is greater than 0,64, the compounds shall be calculated as follows:
2 O 3 is 0,64 or less, the C 3 A content is zero
— The C 3 S and C 4 AF shall be calculated as follows:
2 O 3 e The sodium oxide equivalent, expressed as Na 2 O equivalent, shall be calculated by the formula:
Na 2 O equivalent is equal to 0,658w K
Well cement shall conform to the respective physical and performance requirements specified in Table 2 and in Clauses 6 through 10
Table 2 — Summary of physical and performance requirements
Mix water, % mass fraction of cement (Table 5) 46 46 56 38 44 38
Fineness tests (alternative methods) (Clause 6)
Turbidimeter (specific surface, minimum, m 2 /kg) 150 160 220 NR a NR NR
Air permeability (specific surface, minimum, m 2 /kg) 280 280 400 NR NR NR
Free-fluid content, maximum, percent (Clause 8) NR NR NR NR 5,9 5,9
(Clause 9) NA 60 (140) atm NR NR NR NR 10,3
Specifi- cation test schedule number
(15 min to 30 min stirring period) B c c
Thickening time (minimum/maximum) min
(Clause 10) 5 30 NR NR NR NR 90 d 90 d
(Clause 10) 5 30 NR NR NR NR 120 e 120 e
Clause 10 outlines the specifications for Bearden units of consistency (B c), which are measured using a pressurized consistometer and calibrated according to the same clause It also defines the minimum and maximum thickening times, with "NR" indicating "no requirement" and "NA" indicating "not applicable."
Sampling frequency, timing of tests, and equipment
4.2.1.1 For well cement classes C, D, G, and H, a sample for testing shall be taken by either of the following methods: a) over an interval of 24 h; b) on a 1 000 ton (maximum) production run
4.2.1.2 For well cement classes A and B, a sample for testing shall be taken by either of the following methods: a) over a 14-day interval; b) on a 25 000 ton (maximum) production run
4.2.1.3 These samples shall represent the product as produced At the choice of the manufacturer, either sampling method may be used
4.2.2 Time from sampling to testing
Each sample shall be tested for conformance to this part of ISO 10426 All tests shall be completed within seven working days after sampling
Equipment used for testing well cements shall comply with Table 3 Dimensions shown in Figures 5 through 7 and
Figures 10 through 12 are for the purposes of manufacturing the cement-specification test equipment
Dimensional recertification is not required
Equipment calibrated in accordance with the requirements of this part of ISO 10426 is considered accurate if the calibration is within the specified limits
Table 3 — Specification test equipment for well-cement manufacturers
Test or preparation Well cement classes
Sampling All 5 Apparatus as specified in EN 196-7
NOTE For the purposes of this provision, ASTM C183 is equivalent to
Fineness A, B, C 6 Turbidimeter and auxiliary equipment as specified in ASTM C115 or air permeability apparatus and auxiliary equipment as specified in
NOTE For the purposes of this provision, ASTM C204 is equivalent to
Slurry preparation All 7 Apparatus as specified in 7.1 Free fluid G, H 8 Apparatus as specified in 8.1
D 9 Apparatus as specified in 9.1, except pressurized curing bath of
9.1.3.3 Thickening time All 10 Pressurized consistometer specified in 10.1
One or more of the procedures in accordance with EN 196-7 shall be used to secure a sample of well cement for specification testing purposes
NOTE For the purposes of this provision, ASTM C183 is equivalent to EN 196-7
Procedure
Fineness tests for well cement must be conducted following ASTM C115 for the turbidimeter test or EN 196-6 using air permeability apparatus for the air permeability test It is important to note that ASTM C204 is considered equivalent to EN 196-6 for this purpose.
Requirements
Acceptance requirements for the fineness test are a minimum specific surface area (expressed in square metres per kilogram) as given in Table 2 Classes D, G and H cements have no fineness requirement
At the discretion of the manufacturer, either of the two fineness test methods (turbidimeter or air permeability test) shall be used to determine the fineness.
Apparatus
The indicated load on scales must be accurate to within 0.1% of the actual load, except for measurements between 0.1g and 10g, where the accuracy should be within 0.01g Annual calibration is mandatory to ensure precision.
The reference weights must have a mass accuracy within the tolerances specified in Table 4 For beam-type scales with reference weights located on the beam, the indicated masses must meet the requirements outlined in section 7.1.1.
Table 4 — Permissible variation in mass of reference weights
A No 20 wire cloth sieve (openings 850 àm), in accordance with the requirements given in ISO 3310-1, shall be used for sieving cement prior to slurry preparation
NOTE For the purposes of this provision, ASTM E11 is equivalent to ISO 3310-1
The mixing device for the preparation of well cement slurries shall be a 1 l (1 qt) size, bottom-drive, blade-type mixer
A commonly used mixing device features a durable, corrosion-resistant mixing-blade assembly and container The design allows for easy removal of the mixing blade for weighing and replacement It is essential to weigh the blade initially and periodically, replacing it with a new one before a 10% mass loss occurs or if any visible deformation is detected In the event of a leak during the mixing process, the contents must be discarded, the leak repaired, and the procedure restarted.
The mixing device shall be calibrated annually to a tolerance of ± 200 r/min (± 3,3 r/s) at 4 000 r/min (66,7 r/s) rotational speed, and ± 500 r/min (± 8,3 r/s) at 12 000 r/min (200 r/s) rotational speed
Figure 1 — Example of a typical cement-mixing device
Procedure
Before mixing, cement must be sieved according to the method outlined in EN 196-7, utilizing the sieve specified in section 7.1.3 It is important to note that ASTM C183 is considered equivalent to EN 196-7 for this requirement.
7.2.2 Temperature of water and cement
The temperature of the mix water in the container within 60 s prior to mixing shall be 23 °C ± 1 °C (73 °F ± 2 °F) and the temperature of the cement within 60 s prior to mixing shall be 23 °C ± 1 °C (73 °F ± 2 °F)
For testing purposes, it is essential to use distilled or de-ionized water The mixing water must be accurately weighed and added directly into a clean, dry mixing container, without any adjustments for evaporation or wetting.
The quantities of slurry components specified in Table 5 will be utilized for testing, ensuring that the mix-water percentages, calculated based on the mass of dry cement, align with the water percentages presented in Table 2.
To prepare the mix, place the mixing container with the specified mass of mix water on the mixer base and turn on the motor, maintaining a speed of 4,000 r/min ± 200 r/min (66.7 r/s ± 3.3 r/s) Add the cement sample uniformly within 15 seconds After this initial mixing period, cover the container and increase the speed to 12,000 r/min ± 500 r/min (200 r/s ± 8.3 r/s) for an additional 35 seconds ± 1 second.
8 Free-fluid test (formerly free water)
Apparatus
The atmospheric pressure consistometer, also known as the pressurized consistometer, is utilized for stirring and conditioning cement slurry to assess free-fluid content, as outlined in section 10.1.
The atmospheric consistometer features a rotating cylindrical slurry container and a stationary paddle assembly, all housed in a temperature-controlled liquid bath It is designed to maintain the bath temperature at 27 °C ± 2 °C (80 °F ± 3 °F) while rotating the slurry container at a specified speed.
During the stirring and conditioning period for the slurry, a speed of 150 r/min ±15 r/min (2.5 r/s ± 0.25 r/s) is required It is essential that the paddle and all components of the slurry container that come into contact with the slurry are made from corrosion-resistant materials.
Figure 3 — Typical container assembly for an atmospheric pressure consistometer
2 centre lock reverse jam nut
Figure 4 — Typical lid and mechanism for an atmospheric pressure consistometer
Dimensions in millimetres (inches) unless otherwise indicated
Figure 5 — Typical container for an atmospheric pressure consistometer
The paddle is made from 300 series stainless steel, measuring 1.0 mm by 7.9 mm (0.04 in by 0.311 in), while the shaft is constructed from 400 series steel, with dimensions of 6.4 mm by 211.1 mm (0.25 in by 8.311 in), and is both annealed and ground.
Figure 6 — Typical paddle for an atmospheric pressure consistometer
Scales shall meet the requirements set in 7.1.1
A 500 ml conical flask, in accordance with ASTM E1404-94(2008), type I, class 2, or with ISO 24450 shall be used See Figure 7
Dimensions in millimetres a Wall thickness b Outside diameter (at widest point)
Figure 7 — The ASTM conical flask for free-fluid measurement
Calibration
Temperature-measuring and -controlling devices must undergo calibration at least once every three months This requirement applies to various instruments, including thermometers, thermocouples, and temperature controllers found in consistometers, curing chambers, and ultrasonic devices, as well as those used independently from the main equipment.
Measurements must be conducted at a minimum of three temperatures within the defined operating range of the equipment The lowest calibrated temperature should not exceed 5 °C (10 °F) above the minimum limit, while the highest calibrated temperature should also remain within 5 °C of the maximum limit.
Thermometers and thermocouples must be calibrated using a certified temperature source, ensuring accuracy within 2 °C (3 °F) of the user-defined operating range, which should not exceed 10 °F below the maximum limit If the device fails to meet this accuracy, it must be replaced Notably, thermocouples installed in the cylinder wall of a consistometer are exempt from calibration if they are not used for temperature control For further details, refer to Annex A.
The rotational speed of the slurry container must be maintained at 150 r/min ± 15 r/min (2.5 r/s ± 0.25 r/s) and should be monitored at least quarterly Any deviations from this specified range should be promptly corrected.
The timer must maintain an accuracy of ± 30 seconds per hour and should undergo accuracy checks at least once a year If it is determined to be inaccurate, it must be corrected or replaced.
Procedure
8.3.1 Prepare the slurry in accordance with the procedure in Clause 7
8.3.2 Fill a clean and dry consistometer slurry container to the fill groove
To initiate the testing process, assemble the slurry container and its associated parts, then carefully place them in the consistometer Next, start the motor in accordance with the manufacturer's operating instructions, ensuring that the interval between completing the mixing process and starting the consistometer does not exceed 1 minute.
8.3.4 Stir the slurry in the consistometer for a period of 20 min ± 30 s Maintain the temperature of the slurry at
27 °C ± 2 °C (80°F ± 3 °F) and atmospheric pressure throughout the stirring period
Transfer 790 g ± 5 g of class H slurry or 760 g ± 5 g of class G slurry into a clean, dry 500 ml conical flask within 1 minute after stirring Ensure to record the actual mass transferred and seal the flask to prevent evaporation.
To ensure accurate measurements, place the slurry-filled flask on a stable, level surface free from vibrations The surrounding air temperature should be maintained at 23 °C ± 3 °C (73 °F ± 6 °F), with a temperature sensor that complies with the specifications outlined in section 8.2.1 Allow the flask to remain undisturbed for a duration of 2 hours ± 5 minutes.
After a period of approximately 2 hours and 5 minutes, carefully remove the supernatant fluid using a pipette or syringe Accurately measure the volume of the supernatant to within ± 0.1 ml and document this measurement as "millilitres free fluid."
8.3.8 Convert the millilitres free fluid to a percentage of starting slurry volume (∼400 ml depending on the recorded initial mass) and express that value as percent free fluid.
Calculation of percent free fluid
The volume fraction, ϕ, of free fluid in the slurry, expressed as a percentage, is then calculated using Equation (1):
The volume of free fluid (supernatant fluid) collected, denoted as V FF, is measured in millilitres The specific gravity of the slurry, represented by ρ, is 1.98 for class H with 38% water and 1.91 for class G with 44% water If the specific gravity of the base cement deviates from the standard value of 3.18 ± 0.04, the actual specific gravity of the slurry must be calculated and utilized Additionally, m S refers to the initially recorded mass of the slurry, expressed in grams.
EXAMPLE Calculation of percent free fluid: m S = 791,7 g
V FF = 15,1 ml ρ= 1,98 g/cm 3 (class H) ϕ= 15,1 × (1,98) × 100/791,7 ϕ= 3,78 NOTE Millilitres and cubic centimetres are assumed to be equal for purposes of calculation.
Acceptance requirements
The free fluid for classes G and H well cements shall not exceed 5,9 %
Apparatus
9.1.1 Cube moulds and compressive strength-testing machine
Moulds and testing machine for compressive strength tests shall conform to the requirements in
ASTM C109/C109M or EN 196-1, except for a) the bearing block surface dimension requirement; b) the bearing block Rockwell hardness requirement; c) the moulds, which may be separable into more than two parts
Moulds must be inspected for tolerances at least every two years, while the load frame for measuring the break force of cement specimens requires annual calibration The indicated force should not vary by more than 2% of the applied load or one minimum instrument scale division, whichever is greater, at a force of 9.0 kN.
The load cell or load indicator must be tested with a load of 2,000 lbf at minimum levels of 25%, 50%, and 75% of its capacity For units featuring multiple indicators for various ranges, each indicator must be calibrated in accordance with these specified criteria.
9.1.2 Cube mould base and cover plates
Generally, plate glass, brass or stainless steel plates having a minimum thickness of 6 mm (1/4in) are used
Cover plates may be grooved on the surface that contacts the top of the cement
A curing bath or tank must be used that allows for the full immersion of compressive strength molds in water while maintaining the required test temperatures within ± 2 °C (± 3 °F) There are two types of water curing baths detailed in sections 9.1.3.2 and 9.1.3.3.
An atmospheric pressure curing bath is a vessel for curing specimens at atmospheric pressure and temperatures of 66 °C (150 °F) or less, having an agitator or circulating system
A pressurized curing bath is designed to cure specimens at temperatures reaching 110 °C (230 °F) and can maintain a controlled pressure of 20.7 MPa ± 3.45 MPa (3,000 psi ± 500 psi) This vessel must meet the specifications outlined in Table 6.
The cooling bath dimensions shall be such that the specimens being cooled from the curing temperature can be completely submerged in water maintained at 27 °C ± 3 °C (80 °F ± 6 °F)
The temperature-measuring system must be calibrated to an accuracy of ± 2 °C (± 3 °F) at least every three months The calibration procedure outlined in Annex A is widely utilized Additionally, two frequently used temperature-measuring systems are detailed in sections 9.1.5.2 and 9.1.5.3.
A thermometer with a range from 21 °C to 82 °C (70 °F to 180 °F), with minimum scale divisions not exceeding
A thermocouple system with the appropriate range may be used
A corrosion-resistant puddling rod of nominal diameter 6 mm (1/4 in) is typically used
A sealant with an easy-to-use consistency, excellent sealing capabilities to prevent leakage, water resistance, and inertness to cement is typically employed to seal the exterior contact points of the specimen mold Additionally, it is non-corrosive under the curing temperatures and pressures outlined in Table 7.
Procedure
The assembled moulds must be watertight, with clean and dry interior faces and contact surfaces of the plates A light coating of release agent may be applied to facilitate easy removal.
9.2.2 Preparation and placement of slurry
Prepare the cement slurry in accordance with Clause 7
To prepare the specimens, fill the moulds with slurry to half their depth and evenly puddle it 27 times per specimen Ensure all compartments are filled before starting the puddling process After puddling the first layer, stir the remaining slurry to reduce segregation, then fill the moulds to the brim and puddle again Use a straight-edge to level the excess slurry with the top of the mould, and discard any moulds that leak Finally, cover the moulds with a clean, dry plate, ensuring at least three specimens are used for each test.
For classes A, B, C, G and H cements, place the specimens in the water bath preheated to the final curing temperature for tests at atmospheric pressure, within 5 min after mixing (see Table 2)
For class D cement, place the specimens in the pressure vessel in water at 27 °C ± 3 °C (80 °F ± 6 °F), and within
5 min after mixing, apply temperature and pressure according to Table 6
Table 6 — Specification schedules for pressurized curing of specimens
Elapsed time from first application of heat and pressure h: min (± 2 min) 0:00 0:30 0:45 1:00 1:15 1:30 2:00 2:30 3:00 3:30 4:00
The test pressure of 20.7 MPa ± 3.4 MPa (3,000 psi ± 500 psi) must be applied immediately after placing the specimens in the pressure vessel and maintained throughout the curing period Additionally, the temperature during the 4-hour period should remain within ± 2 °C (± 3 °F) for the entire duration of the curing and testing process.
The curing period refers to the duration from when specimens are exposed to the designated temperature in the curing vessel until they are tested for strength It is essential to conduct strength tests at the specified times outlined in Table 7.
For specimens cured at atmospheric pressure, the curing period starts when specimens are initially placed in the curing bath preheated to the test temperature
For specimens cured at pressures above atmospheric, the curing period starts with the initial application of pressure and temperature
Specimens cured at 60 °C (140 °F) or lower must be removed from the curing bath 45 minutes ± 5 minutes before testing After removal, they should be taken out of their moulds and cooled in a water bath at 27 °C ± 3 °C (80 °F ± 6 °F) for 40 minutes, ensuring they are not left out of water for more than 5 minutes to prevent dehydration For specimens cured at temperatures of 77 °C (170 °F) or higher, maintain the specified maximum temperature and pressure until 1 hour and 45 minutes ± 5 minutes before testing, after which heating should be discontinued.
After 60 minutes, reduce the temperature to 77 °C (170 °F) or lower, ensuring that the pressure remains unchanged except for the decrease caused by the temperature drop At 45 minutes before testing the specimens, release the remaining pressure and remove the specimens from the molds Cool the specimens by placing them in a water bath set at 27 °C ± 3 °C (80 °F ± 6 °F) for 40 minutes.
Damaged cube-test specimens must be discarded before testing If there are fewer than two specimens available for assessing compressive strength at any time, a retest is required.
Test procedure (after ASTM C109/C109M)
9.3.1 Remove specimens from the water bath or the cooling bath that has been maintained at 27 °C ± 3°C
(80 °F ± 6 °F) Wipe each specimen to remove any loose material from the faces that will be in contact with the bearing blocks of the testing machine
The test faces' dimensions must be measured to an accuracy of ± 1.0 mm (± 1/16 in) for calculating the cross-sectional area The load should be applied to the specimen faces that were in contact with the vertical surfaces of the mold, avoiding contact with the base or cover plates Ensure the specimen is centered below the upper bearing block in the testing machine, and verify that the spherically seated block can tilt freely before testing each cube No cushioning or bedding materials should be used.
CAUTION — Employ appropriate safety and handling procedures in testing the specimen
The loading rate for specimens anticipated to exceed a strength of 3.4 MPa (500 psi) should be set at 72 kN/min ± 7 kN/min (16,000 lbf/min ± 1,600 lbf/min) Conversely, for specimens expected to have a strength below 3.4 MPa, a different loading rate should be applied.
For compressive strength testing, a load rate of 18 kN/min ± 2 kN/min (4,000 lbf/min ± 400 lbf/min) at 500 psi should be utilized The specific compressive strength test machine may necessitate additional time for the load frame to achieve the desired load rate following the initial contact with the cement sample.
9.3.4 Calculate the compressive strength expressed in megapascals (pounds force per square inch).
Compressive strength acceptance criteria
The compressive strength of all acceptance-test specimens from the same sample, tested at the same time, must be recorded and averaged to the nearest 50 kPa (10 psi) To meet the requirements, at least two-thirds of the original individual specimens, along with the overall average, should meet or exceed the minimum compressive strength outlined in Table 7 If fewer than two strength values remain for calculating the compressive strength at any given time, a retest is necessary.
Table 7 — Compressive strength specification requirements
Minimum compressive strength at indicated curing period
The curing temperature must be kept within ± 2 °C (± 3 °F) of the specified value Test pressure should be applied immediately after placing specimens in the pressure vessel and maintained within ± 3.4 MPa (± 500 psi) for schedules 4S and 6S The notation "NR" signifies "no requirement."
Apparatus
A pressurized consistometer (see Figures 8 and 9) shall consist of a rotating cylindrical slurry container (see
Figures 10 and 11) equipped with a stationary paddle assembly (see Figure 12) enclosed in a pressure vessel capable of withstanding the pressures and temperatures described in Tables 9 through 11
The space between the slurry container and the walls of the pressure vessel shall be completely filled with a hydrocarbon oil The selected oil shall have the following physical properties:
⎯ viscosity range: 6 mm 2 /s to 79 mm 2 /s at 38 °C (100 °F) or 6 cSt to 79 cSt at 38 °C (100 °F); or
⎯ specific heat: 1,9 kJ/(kg⋅K) to 2,5 kJ/(kg⋅K) (0,45 Btu/lb⋅°F to 0,60 Btu/lb⋅°F);
⎯ thermal conductivity: 0,112 W/(m⋅K) to 0,138 W/(m⋅K) [0,065 Btu/(h⋅ft 2 ⋅°F/ft) to 0,08 Btu/(h⋅ft 2 ⋅°F/ft)];
A heating system must be capable of increasing the temperature of the oil bath by at least 3 °C/min (6 °F/min), along with a temperature-measuring system to monitor and control the cement slurry temperature at the centerline The slurry container should rotate at a speed of 150 r/min ± 15 r/min, and the consistency of the slurry must be measured as specified in section 10.2.2.1 Additionally, the paddle and all components of the slurry container that come into contact with the slurry must adhere to the dimensions outlined in Figures 10 through 12.
11 container drive table (rotates anticlockwise)
Figure 8 — Typical gear drive consistometer for pressurized specification thickening-time test
10 container drive table (rotates anticlockwise)
Figure 9 — Typical magnetic drive consistometer for pressurized specification thickening-time tests
Dimensions in millimetres (inches) unless otherwise indicated
NOTE The material is stainless steel, except the diaphragm and the hub
Figure 10 — Typical slurry container assembly for a pressurized consistometer
NOTE The material is stainless steel, except the diaphragm and the hub
Figure 11 — Typical slurry container assembly and paddle for a pressurized consistometer
Dimensions in millimetres (inches) unless otherwise indicated
1 trailing edge 2 leading edge 3 paddle shaft
NOTE 1 The paddle material is stainless steel 1,6 mm × 9,5 mm (0,062 5 in × 0,375 in)
Ensure that all leading edges are tapered out and down, while rounding all trailing edges Rotate the slurry container table counterclockwise when viewed from above the paddle The top plane of the paddle brace must remain perpendicular to the shaft at every point of contact.
Figure 12 — Typical paddle for a pressurized consistometer slurry container
Calibration
To accurately measure the thickening time of a cement slurry, it is essential to calibrate and maintain the operating systems of the pressurized consistometer This includes ensuring the proper functioning of consistency measurement, temperature measuring systems, temperature controllers, motor speed, timers, and gauges.
The consistency of a cement slurry is measured in Bearden units (B c) and must be determined using a calibrated potentiometer mechanism and voltage measurement circuit Calibration should occur within one month before use and after any adjustments or replacements of the calibration spring, resistor, or contact arm, following the method outlined in section 10.2.2.2.
10.2.2.2 A reference weight-loaded device (see Figure 13 for a typical potentiometer calibrating device and
A typical potentiometer mechanism, as shown in Figure 14, generates a series of torque equivalent values for consistent calibration Reference weights are applied to the potentiometer spring, utilizing the radius of the potentiometer frame as a lever arm As additional reference weights are added, the spring deflects, leading to an increase in the resulting DC voltage and/or B c, as detailed in Table 8.
NOTE See manufacturer's instruction manual for procedures
The calibrated torque-equivalent values, T, expressed in gram centimetres, are defined by Equation (2):
T = 78,2 + 20,02B c (2) where B c is the consistency, expressed in Bearden units
Table 8 — Slurry consistency vs equivalent torque
(for a potentiometer a mechanism with a radius of 52 mm ±1 mm)
2 080 400 100 a For a potentiometer mechanism with a different radius, an appropriate table with equivalent tolerances shall be used
Figure 13 — Typical potentiometer calibrating device
Figure 14 — Typical potentiometer mechanism for a pressurized consistometer
The temperature-measuring system shall be calibrated to an accuracy of ± 2 °C (± 3 °F) Calibration shall be no less frequently than quarterly The procedure described in Annex A is commonly used.
The motor shall rotate the slurry container at 150 r/min ± 15 r/min (2,5 r/s ± 0,25 r/s) and shall be checked annually
Timers shall be accurate to within ± 30 s per hour and shall be checked annually
Calibration shall be conducted annually against a dead-weight tester or master gauge Gauges shall be calibrated at 17 MPa, 34 MPa, and 52 Mpa ± 1,7 MPa (2 500 psi, 5 000 psi, and 7 500 psi ± 250 psi).
Procedure
Follow the detailed operating instructions provided by the operator or the equipment manufacturer, ensuring they align with the specifications of ISO 10426 Grease should only be applied to the threaded surfaces of the slurry container.
10.3.2.1 Pour the slurry (prepared in accordance with Clause 7) into the inverted slurry container
Slurry segregation may happen during the filling process, but this can be minimized by stirring the slurry with a spatula while pouring To further reduce segregation issues, it is important to keep the time between stopping the mixing and finishing the filling operation as short as possible.
10.3.2.2 When the slurry container is full, strike the outside of the container and remove air that rises to the top of the slurry
10.3.2.3 Then, secure the slurry container base in place
10.3.2.4 Then, secure the centre plug (pivot bearing) into the container base
To initiate the process, position the slurry container on the drive table within the pressure vessel, activate the rotation of the slurry container, engage the potentiometer mechanism with the shaft drive bar, and commence filling the vessel with oil.
10.3.3.2 Close the head assembly of the pressure vessel securely, insert the thermocouple, and partially engage its threads
10.3.3.3 After the pressure vessel is completely filled with oil, tighten the threads of the thermocouple
10.3.3.4 Initiate the test by applying pressure and temperature within 5 min after cessation of mixing
During the testing phase, it is essential to elevate the temperature and pressure of the cement slurry in the container according to the specified schedules outlined in Tables 9, 10, or 11 For schedules 4, 5, and 6, maintain the temperature within ± 3 °C (± 6 °F) and the pressure within ± 2 MPa (± 300 psi) of the designated targets based on elapsed time.
Within 10 minutes after the ramp concludes, the temperature and pressure must remain within ± 1 °C (± 2 °F) and ± 0.7 MPa (± 100 psi) of the specified values To determine the temperature of the cement slurry for specification testing, utilize a temperature-measuring device positioned at the center of the sample container.
The thermocouple tip must be vertically positioned within the paddle shaft of the slurry cup, specifically between 45 mm (1.77 in) and 89 mm (3.5 in) above the base of the sample container Due to the variety of consistometer models with differing dimensions, it is crucial to ensure that the thermocouple is compatible with the specific consistometer and that its tip is correctly placed as specified.
Table 9 — Schedule 4 specification thickening-time test for classes A, B, C and D cement
Table 10 — Schedule 5 specification thickening-time test for classes G and H cement
Table 11 — Schedule 6 specification thickening-time test for Class D cement
Thickening time and consistency
The thickening time for the test is defined as the duration from the initial application of pressure and temperature to the pressurized consistometer until a consistency of 100 B c is achieved.
Report the maximum consistency during the 15 min to 30 min period after the initiation of the test.
Specification acceptance requirements
The acceptance criteria for maximum consistency during the 15 to 30-minute period following the test initiation is set at 30 B c for all cement classes produced under this section of ISO 10426 Additionally, the thickening time acceptance requirements must align with the specifications outlined in Table 12.
Table 12 — Thickening time acceptance requirement
Class Schedule Minimum thickening time min Maximum thickening time min
Each shipment of well cement must include specific information for compliance For sacked cement, this information should be clearly marked on each sack, while for bulk cement, it should be indicated on the bill of lading The required details include the manufacturer's name, the class and sulfate-resistance grade of the cement, and the net mass.
Well cement shall be furnished in bulk or in sacks
Each sack shall contain a specified net mass of ± 2 % The average net mass of 5 % of all sacks in a shipment, taken at random, shall not be less than the specified mass
Cement sacks must be moisture-resistant, durable during handling, and easy to cut for transfer to bulk facilities Typically, these sacks are made of up to six paper layers, each with a minimum area mass of 70 g/m² (0.014 lbm/ft²), and may include up to two additional layers of polyethylene or polypropylene.
The article discusses the inclusion of 15 g/m² (0.003 lbm/ft²) to 24 g/m² (0.005 lbm/ft²) materials between the first and fifth layers of paper Additionally, it mentions that up to two asphalt or bitumen layers can be added to enhance damage resistance.
Flexible bulk cement containers must ensure a minimum tensile strength with a safety factor of 5 to 1 Additionally, they should be resistant to ultraviolet radiation when constructed with polyethylene or polypropylene layers and effectively moisture-proof.
Bentonite is a naturally occurring clay mineral, composed primarily of smectite Non-treated bentonite, for use in well cementing, is dried and ground, but not chemically treated during processing
Bentonite meeting the requirements of this part of ISO 10426 for use in well cementing shall meet all the requirements for non-treated bentonite in accordance with ISO 13500
Table 13 — Bentonite acceptance requirements Requirement Specification
Yield point/plastic viscosity ratio 1,5 maximum Dispersed plastic viscosity 10 cP minimum Dispersed filtrate volume 12,5 ml maximum
NOTE See ISO 13500 for test procedures
Calibration procedures for thermocouples, temperature measuring systems, and controllers
Several effective methods exist for calibrating thermocouples, including those provided by equipment manufacturers For a comprehensive overview of these procedures, refer to ASTM E220 However, it is important to note that there are no ASTM procedures available for the calibration of temperature measuring systems.
The calibration process requires specific apparatus tailored to the chosen technique, with key features that demand special attention outlined in sections A.2.1.2 to A.2.1.4.
For effective calibration, the heating medium must ensure adequate immersion of both the test thermocouple and the reference thermometer Additionally, the apparatus should maintain a stable and uniform temperature throughout the test section.
The reference temperature of the heating medium can be determined using a thermometer or a thermocouple It is essential that the accuracy of the measuring device is traceable to a national standards body, such as the NBS certification in the USA, to ensure reliable temperature measurement.
When utilizing a thermocouple to measure reference temperature, it is essential to determine the voltage output from both the reference and test thermocouples in accordance with relevant national standards, such as ASTM E220.
To determine the temperature using a thermocouple, refer to the tables of temperature versus voltage specific to the thermocouple type Alternatively, a direct-reading, temperature-compensated instrument can be utilized, ensuring that its accuracy is traceable to national standards certification.
The specific procedures, excluding the indicating instruments, are outlined in relevant national standards like ASTM E220 Special attention is required for the items listed in sections A.2.2.2 through A.2.2.6, which pertain to the use of indicating type equipment.
A.2.2.2 The test and reference thermocouples or thermometers should be placed as close together as possible in the heating medium
A.2.2.3 After each change in heating level, the temperature should be allowed to remain at a stable value for
15 min before reading the reference temperature (or voltage) and the test thermocouple temperature (or voltage)
A.2.2.4 Several (more than three) test temperatures that span the operating range of the equipment should be used in the calibration procedure
To ensure accurate temperature readings from the test thermocouple, it is essential to create a calibration curve that corrects any discrepancies in the indicated temperatures Minor inaccuracies in the thermocouple's response can often be adjusted during the calibration process of the associated temperature measuring system.
If the error of the test thermocouple exceeds the manufacturer's specifications, it is essential to replace it with one that adheres to the required accuracy limits The ASTM E220 classification identifies the "special" type J thermocouple, which offers error limits of ± 1 °C (± 2 °F) up to a temperature of 277 °C (530 °F).
A.3 Calibration of temperature measuring systems and controllers
Calibrating temperature-measuring systems and controllers necessitates a millivolt source, the appropriate thermocouple extension cable, and potentially a thermometer along with a reference voltage table There are two main types of signal sources: uncompensated and cold-junction-compensated Many commercial calibrators are available that are cold-junction-compensated and feature a digital display showing the temperature corresponding to the supplied millivolt signal It is essential that the accuracy of all calibration equipment is traceable to national standards certification Additionally, older galvanometer-type instruments may require a stronger signal for accurate operation compared to newer potentiometric and digital systems, necessitating a calibrator with adequate signal strength for precise calibration.
A.3.2.1 The manufacturer's procedure for calibrating temperature-measuring systems and controllers should be followed The items in A.3.2.2 to A.3.2.5 require special attention