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:a. Directional Control: To ensure the wellbore will reach its target.b. Well control: provide information for drilling relief wells.c. Reservoir development/exploitation: accurate description of the well’s position … Survey Programme

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 survey tools Inertial navigation survey systems Approval of tools Inclination-only tools are not regarded as survey tools but as inclination indicator tools. They can at best only be used to … Survey tools and techniques

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, the Drilling Engineer shall specify the horizontal and the vertical wellhead position uncertainty. Once entered, the position uncertainty numbers are defaults for future storage of that … Wellpath planning and anti-collision monitoring – COMPASS

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 the accelerometers and magnetometers of the survey tool and toolface dependent misalignment. The method does not correct for external disturbing magnetic fields such as from nearby casings or magnetic … Correction programmes for magnetic survey

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 directions (N,E,V). In addition Along-Hole Depth (AHD), inclination and azimuth of the survey station are included as most surveys measure … Borehole representation

Definition of Surveying Terms from accelerometer to wireline Accelerometer A device for measuring the acceleration of a body in a particular direction. Accelerometers are used in solid state magnetic tools, surface read out gyros, North Seeking Gyro tools and Inertial Navigation systems to sense changes of direction of the tool with respect to the Earth’s … Definition of Surveying Terms

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 Guidance System (RIGS). An INS comprises a triad of accelerometers and gyroscopes respectively. The system is designed to measure the tool movement from its reference point. This is achieved … Inertial Navigation Survey Systems

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, technique and running environment uncertainties. The magnitude of tool uncertainties can be derived from quality assurance and quality control parameters. The magnitude of technique and, in … Survey evaluation

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 conventional tools the length of NMDC should be such that the interference from the steel drillstring is acceptable. For solid state survey instruments, a … Magnetic 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 wireline speed and length measuring system with a Martin Decker 0-4,550 kg (0-10,000 lbs) weight indicator to measure the cable tension. Typical accuracies are about 0.002 … Wireline Surveying Techniques