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

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 systems, the term MWD is commonly used in the industry to mean systems with non-wireline data transmission systems. The disadvantage of the mud pulse MWD … Wireline steering techniques

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 and retrieved on wireline, wireline steering tools and Measurement While Drilling (MWD) tools.Solid state magnetic single and multi-shot directional survey tools are more accurate than conventional … Solid state magnetic survey tools

Running procedures for solid state magnetic multi-shot directional survey tools. Check that the battery voltage and amperage conform to specification. Load the battery pack. Connect the directional survey tool to the computer (or printer) via the interface. Start the software program. Take readings of the directional survey tool in various orientations to verify the measurement … Running procedures for solid state magnetic multi-shot directional survey tools

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 mud pulse or electromagnetic telemetry.Measurement While Drilling (MWD) surveys can be used both as orientation surveys with steerable BHAs, or to replace magnetic multi-shot surveys while … Measurement while drilling (MWD) – Introduction