5 1 dir drilling and surveying

• Lecture ObjectivesAt the end of this lecture YOU will be able to: – Define directional drilling techniques – Identify well types, – Describe the related terminologies, – Understand the

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Network of Excellence in Training

Introduction to

Directional Drilling

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Introduction to Directional

Drilling • Lecture Contents

– Lecture Objectives, – Definition,

– Well Types, – Terminology, – Applications, – Basic Survey Calculation Methods, – Directional Drilling Tools.

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• Lecture Objectives

At the end of this lecture YOU will be able to:

– Define directional drilling techniques – Identify well types,

– Describe the related terminologies,

– Understand the applications of directional drilling, – List surveying and calculation methods,

– Describe Various BHAs and Downhole Tools.

Drilling

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• Definition

– Directional Drilling is the practice of deviating a well

bore along a planned course to a subsurface target whose location is a given lateral distance and direction from the vertical.

Drilling

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• Significant Events

< 1950 Magnetic Single Shot

(survey after drilling) 1960’s Mud Motor

(versatile kick off tool)

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• Well Types

Drilling

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• Applications

Drilling

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• Applications

Short, Medium, & Long Radius Relief well

Drilling

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MN Introduction to Directional

Drilling

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• Terminology;

– TVD; Vertical distance to a position on the well trajectory,

– MD; Distance to a position on the well trajectory

measured along the hole (AHD),

– KOP; Kick-off Point – EOB; End of Build Up Section, – Dir; Angle measured from the north, – HD; Horizontal displacement to target

Drilling

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Surveying

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advanced ones such as:

– Steerable mud motors, – MWD,

– Andergauge Stabilizers, – LWD

• These tools, in combination, could provide a 3D well profiles without changing BHA and have enabled the drilling of

horizontal and multi lateral wells.

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Drilling •

Wellbore Survey

– Why are Surveys Required?

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• Camera Captures

the image on Film,

• Timer Turns-on the Light

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• Wellbore Surveys

Drilling

– Gyro Survey Tool

• Balanced spinning mass,

• Free to rotate on one or more axis,

• Is resistant to external forces ,

• Gyro is accurately aligned to reference before use,

• Maintains this heading throughout survey interval,

• No interference due to magnetism,

• Is used when compass heading not dependable,

• Corrections for change in heading can be applied later.

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• Wellbore Surveys

– Gyro Survey Tool

Drilling

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– Taken at timed intervals,

– Survey record is stored on film.

• Gyro Multishot

– Surveys taken in magnetic environment,

– Survey record is stored on film

• Electronic Multishot

– Requires non-magnetic environment,

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– Downhole sensors are located in the MWD which made-up inside a non magnetic DC,

– Data from the sensor is transmitted through the mud column in the drillstring and the signal is decoded at the surface,

– This procedure is known as mud pulse telemetry, – The whole procedure does not require wireline operations.

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• Magnetic Declination Angle

Drilling

TRUE NORTH

MAGNETIC NORTH

LAT 75.5N

X

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Magnetic Declination Angle

• Magnetic surveys need to be corrected to True North

• True north is the Geographic North or Map North

• Magnetic North is Compass North

• Magnetic North changes over time

• Current location of Magnetic North is updated often

• Can be displayed on maps or computer databases

Drilling

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Magnetic Declination

• DEFINITION: The angle between

True North and Magnetic North as measured from True.

• Easterly Declination (clockwise) is positive.

• Westerly Declination clockwise) is negative.

(anti-• Declination is added to Magnetic

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Map Projection Problem

• Maps used in directional drilling are flat but the earth

is an oblate spheroid.

• How to represent the position of a physical point on

or in the spherical earth on a flat piece of paper.

– There must be compromises to obtain an

acceptable solution, AND:

– There will always be some error

Drilling

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Map Projection

Solution

• Cartography provides the Map Projection

• The Map Projection:

– Is a mathematical definition.

– It takes a point on the surface of the curved earth, – Defines it by latitude and longitude,

– And plots it on a flat piece of paper defined by a

North and East grid.

Drilling

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Grid Convergence

• Quantifies the

amount of distortion for each mapping area

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Grid Convergence

• DEFINITION: The angle between True North and Grid North as

measured from True North

• Easterly Convergence (clockwise) is

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Total Correction

• Also called Local

Declination or Grid Declination

• Corrected surveys

are corrected from Magnetic North to Grid North

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Corrected Azimuth

• Reservoirs are mapped with geologic surveys

• Numerous mapping systems exist

• The well is planned using the same system

as the geologic survey

• Surveys must be corrected to the same

system used to plan the well

Drilling

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• Basic Survey Calculations

Survey Calculation Methods

– Tangential Method, – Average Angle Method, – Circular Arc Method (Minimum Curvature), – Radius of Curvature Method.

Drilling

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– Tangential Method

• TVD = MD x cos Θ ,

• DISPL = MD x sin Θ.

C ou rs

e L en gth TVD

Θ

Drilling

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– Tangential Method

• North = DISPL x cos AZ,

• East = DISPL x sin AZ

DIS PLA CEM

EN T

C O U R S E L

E N G TH

EAST

Drilling

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– Average Angle Method

Assumed Well Path

Actual Well Path

Latitude Error

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– Average Angle Method

• Averages previous drift and azimuth with current survey station,

– N/S = MD sin (I avg) cos (A avg),

– E/W = MD sin (I avg) sin (A avg),

Drilling

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DL

Drilling

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– Minimum Curvature

• Takes the space vectors defined by the inclination and the azimuth at the survey points,

• Smooths these onto a spherical arc which is defined by the curvature of the well,

• THIS CURVATURE IS: DOGLEG SEVERITY

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– Minimum Curvature

• Ratio Factor:

– Inclination and Azimuth define straight line directions in space,

– Line segments are smoothed using RF.

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– Radius of Curvature Method

• Assumes well path is a smooth curve and can be fit to the surface of a cylinder of a specific radius,

• Greatly improves the accuracy.

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– Radius of Curvature Method

Drilling

), cos

cos (

), sin

sin (

) (

180

2 1

1 2

A A

Rh East

A A

Rh North

A A

H Rh

(

), sin sin

(

) (

180

2 1

1 2

I I

Rv H

I I

Rv TVD

I I

MD Rv

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• Basic Survey Calculation Comparison

– Relative Accuracy of Different Methods:

Method Error on TVD (ft) Error on Disp (ft)

Tangential -25.38 + 43.09, Average Angle + 0.19 + 0.11,

Radius of Curvature 0.00 0.00, Minimum Curvature 0.00 0.00.

Drilling

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Horizontal Displacement

NORTH FOR EACH SURVEY STATION

EAST FOR EACH SURVEY STATION

FOR SOUTH OR WEST RESPECTIVELY

Target

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VERTICAL SECTION IS THE PROJECTION OF THE SURVEY STATION ONTO THE PLANE OF

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Bottom Hole

Assemblies

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directional drilling an expensive.

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As the distance reduces it’s effect goes from none, when the tangent is the same distance as

if no stabilizer was run, to maximum build when it

becomes a Near Bit Stabilizer.

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Bottom hole Assembly Two Stabilizer

by controlling their relative position to the bit one can

create almost any behavioral tendency required.

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• Bottom hole Assembly

• Examples

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• Bottom hole Assemblies

– Deflection Tools

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CIBP

Shear Pin

Starting Mill

Drill pipe

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• Now YOU should be able to :

– Define directional drilling techniques – Identify well types,

– Describe the related terminologies, – Understand the applications of directional drilling,

– List surveying and calculation methods, – Describe Various BHAs and Downhole Tools.

Drilling

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Directional Drilling

End of Module

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