Directional Drilling Services
Measurement While Drilling (MWD)
The MWD system utilised by Transmark-EDS is the Geolink Orienteer System and is renowned for providing simple, highly reliable and functional solutions for all types of directional surveying and steering operations. The Transmark-EDS / Geolink MWD has a proven track record of high reliability.
Industry standard MWD tri-axial magnetometer/accelerometer sensor matched with high stability electronics and rigorous calibration provide best-in-class accuracy. Quality control factors (total magnetic field and dip) are transmitted as part of the survey. Tool face format can be programmed according to customer requirements – fast where orientation is dynamic or energy saving when a consistent sliding orientation is achieved. Special tool face modes are available for combination with logging data to provide efficient data transmission. The Geolink transmission options are based on proven patented technologies which provide customers with the flexibility to select the appropriate option for their operating environment.
Extra services available within our MWD system are logging while drilling and resistivity.
The MWD tool measures the magnetic environment surrounding it. Therefore, any drill string magnetisation from magnetic components will have an effect on the MWD surveys. For this reason Transmark-EDS has elected to use raw data correction software. This software corrects raw MWD data for magnetic influences from the drill string, thereby eliminating the need for additional and relatively expensive non-magnetic drilling equipment (i.e. additional non-magnetic drill collars and stabilisers). It corrects the MWD azimuths for drill string interference, and at the same time results in a smaller error ellipse. This software has proven to be very reliable and, as an integral part of the MWD system, is sufficient to accurately survey the well trajectory. The MWD system consists of the following main components:
Survey Electronics Assembly, (SEA)
The SEA contains industry standard tri-axial magnetometers, inclinometers and control electronics. They allow full directional survey and steering operations over the complete inclination range of 0-180°. The SEA is programmable both on surface and downhole.
Negative Pulse Transmitter, (TRA)
The Geolink Negative Pulse Transmitter generates a sequence of small pressure losses in the circulating system with the purpose of transmitting MWD data, recorded downhole to surface. All Geolink Transmitters are compatible and interchangeable with the standard Geolink MWD/LWD system. The transmitter sends the encoded data to surface via different means, depending on the option selected. Our MWD Coordinator will be pleased to advise which option is appropriate to the customer's expected operating environment.
The Transmitter contains a small, normally closed valve which is actuated by a solenoid that opens a flow path between the drill string interior and the annulus. A valve open time of 0.5 seconds typically generates a pressure drop of 30 to 50 psi at surface. An integral pressure switch allows control of the tool functions from surface.
The TRA has the following features:
- Rugged Beryllium-Copper construction provides high reliability in the most demanding drilling environments.
- Consistent signal and downhole programmable transmission modes.
- Single Transmitter fits subs from 4 3/4in to 9 1/2in O.D.
- Minimum wear parts - easy and cost effective to maintain.
- Geolink Navigator surface software provides user friendly interface.
Actuator Power Controller, (APC)
The APC receives encoded data from the Survey Electronics Assembly and changes it in order to activate the transmitter and send downhole data to surface.
Power Supply Assembly, (PSA)
The PSA supplies power to the complete Survey Electronics Assembly, the Power Controller Assembly and the Transmitter Assembly.
The Geolink Sentinel Vibration Sensor enables continuous monitoring of downhole shock and vibration. Using this information the driller can maximise ROP and minimise bit and string damage. The Real-Time Screen displays the various data required to monitor the data output from the MWD or LWD system. The screen includes a display of axial and lateral vibration levels (mid height, right) which is mirrored on the driller’s display.
Shock sensors are added as standard to all tools. They consist of two solid state accelerometers, orthogonally mounted in the X (lateral) and Z (axial) axes of the MWD tool, on the Survey Electronics PCB. The Survey Electronics Assembly monitors the shock levels measured by the accelerometers over consecutive periods of 16 seconds and categorises the current level as being either Low (safe), Moderate (warning) or High (damage likely) for both axial and lateral readings. Normally the tool will only transmit readings to surface if the latter two conditions are present - by means of a single pulse at the end of each dynamic transmission. The data is presented graphically to the driller on the Rig Floor Display - allowing him to monitor conditions and make appropriate changes to drilling parameters (e.g. Changing Weight on Bit or Rotary Speed). Establishing smooth, shock and vibration-free drilling helps to optimise penetration rates and prevents damage to the drill string and downhole tools.
- Fitted as standard in all sizes (from early 2006).
- Robust and highly reliable - low maintenance.
- Simple operation - only reports potentially damaging conditions.
- Compatible with all Geolink MWD Systems.
- Graphical representation for easy interpretation.
- Data can be displayed in Real-Time on the RFD and laptop or plotted against depth for later analysis.