Survey Programme Example

If the maximum dogleg severity or maximum inclination is exceeded, the Drilling Supervisor must be consulted prior to taking any corrective action. An additional MMS should be taken while drilling, if…

Surveying Wells with Anticipated Well Control Problems

This article describes the surveying guidelines for wells with potential well control problems.

Magnetic Single Shot / MWD

In Exploration, Appraisal or Development well hole sections, where mobile…

Surveying Wells with No Anticipated Well Control Problems

Surveying guidelines for wells with no potential well control problems.

In Exploration, Appraisal or Development wells hole sections, where mobile hydrocarbons are not present or potential well…

Best Practices for Running Recoverable Survey Instruments

Best practices for running a recoverable surveying instrument:

  • the time drillstring is set on slips shall be minimised. The pipe should be picked up on elevators as soon as possible after making…

Magnetic Multi-Shots

The Magnetic Multi-Shot survey (MMS) differs from the Magnetic Single-Shot survey (MSS) in that the camera contains a continuous film roll, which is exposed and advanced at pre-set time intervals.


Introduction to Magnetic Surveys

When running a magnetic surveying instrument, the following guidelines shoud be adhered to:

  • to eliminate external magnetic interference, surveys shall not be taken within 30 ft of a casing shoe
  • all…

Surveying definitions

Definitions of various surveying terms:


A series of measurements made to determine the borehole trajectory. A survey comprises position (North, East and True Vertical Depth) and/or direction…

Surveying Responsibilities

Surveying Responsibilities:

1. Drilling manager:

- anti-collision strategy is in place;
- blow-out contingency plan is available to ensure that as soon as there is a potential or actual blow-out at…

Conventional multi-shots magnetic survey tools: Pre-survey checklist & Running procedure

This article presents a pre-survey checklist & running procedure for conventional multi-shots magnetic survey tools:

Pre-survey Checklist

MMSs are normally run by a Survey Engineer. The…

Running procedures for solid state magnetic multi-shot directional survey tools

Running procedures for solid state magnetic multi-shot directional survey tools.

  1. Check that the battery voltage and amperage conform to specification.
  2. Load the battery pack.
  3. Connect the directional…

Electronic Magnetic Multi-Shots

Electronic Magnetic Multi-Shots (EMMS) are a definitive multi-shot surveying instruments. However, MWD data may be accepted as the definitive survey provided QA/QC results are within the acceptable…

Survey program and report

This article describes the data required for a survey program and report.

1 General well data

·well name / ·wellhead co-ordinates (North, East, TVD, latitude and longitude) /…

Correction for Magnetic Azimuths

The difference between the current Magnetic North for the location and Grid North is monitored for every survey by the Deviation Contractor and the Operations Engineer.

All drilling plots and…

Measurement While Drilling (MWD) General Guidelines

Measurement While Drilling (MWD) General Guidelines

This article describes the general handling and running guidelines for Measurement While Drilling (MWD)

Handling Guidelines for Measurement While Drilling (MWD) tools

Considerable care should be taken…

Directional Drilling Planning

The Drilling Programme shall be checked by the Drilling Supervisor to ensure that all the information necessary for the preparation and commencement of directional operations has been included.


Guidelines for Rotary Directional Drilling

All rotary BHA’s have a tendency to build and directional control is maintained by selecting a BHA which gives the desired build up rate (BUR).

Due to the strong build tendency, it is preferable to…

Survey tools and techniques

The following survey tools and techniques are recommended/ available:

  • Solid state magnetic survey tools
  • Conventional magnetic survey tools
  • Conventional gyroscopic survey tools
  • North seeking gyro…

Well Plots

This article describes the data to be includd in the various well plots.

All plots, whether standard or non-standard shall include a:

‘Check/Signature’ box for the Operations Engineer and Petroleum…

Positional Uncertainty

During the drilling operations phase the positional uncertainty must be monitored, especially when drilling in hole sections which exhibit collision risk.

All borehole position calculations for well…

Declination and Grid Convergence Definition

Declination and Grid Convergence Definition

The following definition of declination and grid convergence should be adhered to:

In this example:

Declination D is positive ‘+’

Grid Convergence G is positive ‘+’

Survey evaluation

The quality of a survey is determined by comparing the actual measured borehole uncertainties against the theoretical uncertainties of the survey tool. Survey uncertainties can be divided into tool,…

North seeking gyro survey tools

North Seeking gyro directional drilling survey tools provide substantially more accurate survey data than conventional gyro tools. In the conventional gyroscopic survey tool, the gyro is oriented to a…

Definition of Surveying Terms

Definition of Surveying Terms from accelerometer to wireline


A device for measuring the acceleration of a body in a particular direction. Accelerometers are used in solid state magnetic…

Directional drilling plan with 12.25" pilot hole, 22" hole hole opener and 24" underreamer

This article describes an example of a directional drilling plan. The hole will be kicked-off  below the 26" conductor shoe. The hole will be directionally drilled to the 18 5/8" casing setting…

Survey policy

The survey accuracy requirements are dictated by the following:

1. Targets

The geological target should be as large as possible to minimize costs (directional drilling and surveying), considering the…

Directional Drilling Exercices

Directional Drilling no.1

After a survey in a deviated well it is apparent that the target will be missed. A correction run must be made but it is uncertain whether the target can be reached within…

Measurement While Drilling (MWD) Tool

Measurement While Drilling (MWD) Tool

A Measurement While Drilling (MWD) tool is a combined magnetic steering and surveying instrument run near the bottom of the BHA. It accurately measures azimuth and inclination as well as toolface.


Tie-In Data

Tie-in data shall be provided by the Operations Engineer and sent to the rig for the Drilling Supervisor after completion of quality assurance check on each multi-shot MWD survey.

The tie-in data will…

Gyro Multi-Shots

Gyro Multi-Shots (GMS) shall only be run in preference to EMMS to verify the surveys used to drill a hole section where magnetic interference may not be corrected. Gyro Multi-Shots are also used for…

Survey Programme

1.0 Reasons for Directional Surveys

Surveys are taken to better define the position of the wellbore, generally relative to the surface location. The reasons for wanting this information include:

Gyro Surveys - QA/QC

QA/QC Instrument Tests to be performed for Gyro Surveys.

1. Inclination Values (In-run and Out-run)

The variance between the in-run and out-run inclination values for survey data from the same survey…

Conventional gyro: pre-survey checklist and running procedure

This article presents pre-survey checklist and running procedure for conventional gyro survey.

Pre-wellbore survey checklist

  • Before starting to drill a new well and before every new wellbore survey,…

Steerable Systems

Deviated wells are normally drilled using a steerable system which is a combination of bent sub, motor and MWD allowing both rotary drilling and sliding without tripping for directional changes.


Correction programmes for magnetic survey

The correction programme corrects the inclination and azimuth values for cross-axial and axial magnetic interference of the drillstring (including magnetic hot-spots in NMDCs), bias uncertainties of…

Gyro Single Shots

The Gyro Single Shot is used for orienting purposes only. While drilling, Gyro Single Shot surveys shall be taken instead of magnetic surveys or  MWD whenever magnetic interference may be…

Conventional magnetic single-shot survey tools: Pre-survey checklist and Running procedures

Conventional magnetic single-shot survey tools: Pre-survey checklist and Running procedures

Pre-survey checklist & Running procedures for conventional magnetic single-shot survey tools:

Magnetic single-shot survey tools - Pre-survey checklist

MSS tools are normally run by the Driller.…

Slim hole, coiled tubing and under-balanced drilling surveying

Since the mid eighties there has been an interest in drilling wells with smaller hole sizes, typically 4-1/8", 4-3/4" or 5-7/8" hole sizes, with the smaller holes taking a 3-1/2" liner.

1. Slim hole…

Conventional magnetic survey tools

Conventional magnetic survey tools consist of a mechanical inclinometer, i.e. a pendulum and a compass to determine azimuth. They are used as magnetic single-shot (MSS) and magnetic multi-shot (MMS).…

Magnetic Single Shots

The Magnetic Single Shot survey (MSS) is an accurate field-proven instrument measuring inclination and magnetic azimuth, which consists of an electronic timer, camera and combined compass /…

Directional BHA considerations

All mudmotors, non-magnetic drill collars, stabiliser mandrels and subs shall be inspected as per Company inspection programme. All tools supplied to the rig shall be accompanied by the appropriate…

Directional drilling plan with hole opener and under-reamer

This article describes an example of a directional drilling plan. The hole will be kicked-off  below the 26" conductor shoe. The hole will be directionally drilled to the 18 5/8" casing setting…

Directional Surveying Standards

The following directional surveying standard are recommended:

  • All exploration wells shall be surveyed from the surface conductor shoe to TD
  • All development wells shall be surveyed from the wellhead…

Wireline Surveying Techniques

Most directional survey tools take surveys at discrete directional survey stations, with manual input of the wireline depth. The standard instrumentation on a wireline unit is the Gearhart Owen…

Measurement While Drilling (MWD) - QA/QC

Measurement While Drilling (MWD) - QA/QC

This article describes the the QA/QC tests for Measurement While Drilling (MWD).

1. Surface Function Test

The MWD tool shall be function tested at surface according to contractor procedures.

Two tools…

Inertial Navigation Survey Systems

Inertial Navigation Systems (INSs) are capable of accurately measuring the position of boreholes e.g. the Ferranti Inertial Navigational Directional Surveyor (FINDS) and the Ring laser Inertial…

Wireline steering techniques

Wireline steering techniques

This technique has the advantage of real time readings from down hole, but the disadvantage of the wireline and associated handling problems.

Although technically wireline steering tools are also MWD…

Magnetic surveying techniques

Magnetic surveying techniques

The azimuth of the borehole is determined from the Earth's magnetic field using a magnetic survey tool.

Two basic types of tools exist, i.e. conventional photo-mechanical and solid state tools. For…

Borehole representation

The wellpath is defined by a survey which gives the positions of the well at a number of points along the wellbore.

The position is defined with the co-ordinates in the North, East and Vertical…

Solid state magnetic survey tools

Solid state magnetic survey tools

The tools measure Earth's gravity and magnetic field with solid state accelerometers and magnetometers (raw sensor data), respectively. Survey tools can be used as single and multi-shot tools dropped…

Introduction to Gyro Surveys

Gyro surveys will be taken when the casing has been run if it was not possible to perform an MMS in the open hole. There are two distinct groups of slim, surface reading, gyro surveying tools:

  1. those…

Horizontal well surveying

High inclination wells (above 70°) and specially horizontal wells have specific difficulties for obtaining accurate surveys. Two main problems arise with high inclination surveying:

  • getting wireline…

North Seeking gyro - Common tools description

Desription of typical North Seeking gyro:  Seeker (Baker Hughes Inteq), Wellbore surveyor (gyro/data), Finder (SDI), GCT (Schlumberger ), G2 (Sperry-Sun)

Seeker (Baker Hughes Inteq)

1 directional…

Non-Magnetic Drill Collars

Requirements relating to NMDC use when surveying with magnetic instruments..

NMDC Length

Every magnetic compass placed in a steel BHA will exhibit an azimuth error. This is caused by the interference…

Wellpath planning and anti-collision monitoring - COMPASS

The Drilling Engineer must ensure that the wellhead co-ordinates and the target co-ordinates are given in the same co-ordinate system (origin, azimuth depth reference).

When storing the well proposal,…

Teledrift - Inclination-only MWD

Teledrift - Inclination-only MWD

Teledrift is an inclination-only mud pulse MWD system that can measure inclinations up to 10.5º. The system is available from Scientific Drilling International (SDI).

The Teledrift is a purely…

Conventional Gyroscopic Survey Tools

The heart of a conventional gyroscope is the gyro wheel, which spins at high speed symmetrically about an axis. A perfect gyro wheel will maintain its orientation in inertial space for as long as no…

Directional Drilling Responsibilities

The following table lists the responsibilities for the implementation, execution, and quality control of directional drilling and surveying activities:



Quality Control…

Measurement while drilling (MWD) - Introduction

Measurement while drilling (MWD) - Introduction

The term Measurement While Drilling (MWD) includes any tool that can be used while drilling, including wireline steering tools. In practice it means 'wire-less' measuring systems, e.g. systems using…

Single-shot inclination-only survey tools (TOTCO)

Single-shot inclination-only survey tools (TOTCO)

Single-shot inclination-only survey tools are mechanical inclination indicators, often called by the trade name 'TOTCO' although they are also made by other manufacturers. They are normally owned and…