1. 1. Outline Introduction MWD vs. LWD LWD vs. Wireline Decision Making MWD output Signal Transmission Methods MWD System Components Geosteering Conclusion
2. 2. Introduction What is MWD? Measurement While Drilling (MWD) systems measure formation properties (e.g. resistivity, natural gamma ray, porosity), wellbore geometry (inclination, azimuth), drilling system orientation (tool face), and mechanical properties of the drilling process.
3. 3. MWD vs LWD Logging while drilling (LWD) is closely related to MWD. LWD provides formation measurements, while MWD provides drilling mechanics and survey measurements. MWD Inclination, azimuth, tool face Rotational speed of the drill string Smoothness of that rotation Type and severity of any vibration downhole Downhole temperature Torque and weight on bit Mud flow volume LWD density porosity resistivity acoustic-caliper inclination at the drill bit (NBI) magnetic resonance formation pressure
4. 4. LWD vs. Wireline LWD
5. 5. Wireline vs. LWD Wireline small, light and delicate since the 30s high data speeds easy communication good borehole contact powered through cable takes time after-the-fact problem at high deviation susceptible to hole condition LWD big, heavy and tough since the 70s slow telemetry limited control subject to drilling batteries and mud turbine real-time can log in any direction more capable in tough environment
6. 6. Real-time Surveys for Directional Control Inclination Azimuth Toolface
7. 7. Inclination Inclination is the angle between a vertical line and the path of the well bore at that point. An inclination of 0 is a vertical hole. An inclination of 90 is a horizontal hole.
8. 8. Azimuth is the angle between North Reference and a horizontal projection of the current Survey position. A hole drilled due North has an azimuth of 0. Azimuth
9. 9. Magnetic North and True North The Flow of liquid Iron(Fe) in the earths outer core generates electric currents, which in turn, produce magnetic fields. Originates at the poles The northernmost point on the earth that lies at the top axis of rotation. Also called geographic North.
10. 10. ToolFace ToolFace is the angle which describes where the bend of the motor is pointing.
11. 11. ToolFace Angles Toolface angle = 0 - the bent sub or steerable motor is pointing upwards, the azimuth should remain steady. Toolface angle = 90- the hole azimuth should turn to the right Toolface angle = 270- the hole azimuth should turn to the left
12. 12. Directional Sensors The sensors used in steering tools and MWD/LWD tools are solid-state electronic devices known as magnetometers and accelerometers which respond to the earth's magnetic field and gravitational field respectively.
13. 13. The MWD downhole tools
14. 14. The MWD Surface System Surface sensors for measuring surface drilling parameters, as well as the wells depth. A transducer at the surface to receive the measurement signals from the MWD tool. A computer for decoding downhole data at the surface. A computer for processing, storing, and using all of the data.
15. 15. How the Data is Transferred Mud Pulse Telemetry Electromagnetic Telemetry
16. 16. Mud Pulse Telemetry Positive mud pulse telemetry (MPT) uses hydraulic poppet valve to momentarily restrict mud flow through an orifice to generate increase in the pressure in form of positive pulse which travel back to the surface to be detected .
17. 17. Negative MPT uses a controlled valve to vent mud momentarily from the interior of the tool into the annulus . This process generates a decrease in the pressure in the form of a negative pulse which travels back to the surface . Mud Pulse Telemetry
18. 18. Electromagnetic Telemetry The EM does not use the drilling mud to send pressure waves. The tool sends either a magnetic pulse or electrical current through the ground to the surface. On the surface the data is received through ground antennas and the data is processed. EM systems are significantly faster (10x) than conventional mud pulse
19. 19. EM & MPT EM systems have no moving parts and does not create significant restrictions in the drill string. As a result, it is more reliable and there is less damage from erosion caused by drill solids. EM tools have depth limitations which are a function of how much power can be supplied by batteries for the duration of the drilling interval, and at higher power settings the battery costs may be significant.
20. 20. Geosteering Geosteering is the science, or art, of maintaining a near horizontal well bore within a pre-defined geological layer (payzone).
21. 21. Geosteering South Target Reservoir
22. 22. Real-time decision making and well steering Effective placement of a well Maximize reservoir exposure Identify geohazards
23. 23. Collect available offset wells data Build Pre-drilling geological model Monitor the real time data and Update the geological model
24. 24. MWD/LWD technology is showing tremendous potential to replace open hole wireline logging The MWD/LWD will continue its growth by using technology to increase the efficiency and decrease the cost of drilling and evaluating wellbores. Geosteering enhances early production by maximizing reservoir contact Geosteering is proved technology for successful drilling
25. 25. References Baker Hughes. (1997). Baker Hughes INTEQ's Guide to Measurement While Drilling. Information Guide, 1-142. Cathedral Energy Services. (2014, March 10). MWD, Electromagnetic. Choudhary, D. (2011, July 5). Directional Drilling Technology. Retrieved from Basic Terminologies Related to Directional Drilling: http://directionaldrilling.blogspot.com/2011/07/basic-terminologies- related-to.html Crain, E. R. (2014). Geosteering With MWD Data. P. Eng. Lamont-Doherty Earth Observatory. (February 2008). An Introduction to Logging While Drilling. Seminar to Marine Geophysics, 1-5. Middle East Technical University. (n.d.). Chapter 4, Measurement While Drilling. Mottahedeh, R. (2014). Horizontal Well Geo-Navigation: Planning, Monitoring, and Geosteering. Schlumberger. (2007). Schlumberger Logging School. Houston. Schlumberger. (2014, March 10). Oilfield Glossary. Retrieved from Gravity Toolface: http://www.glossary.oilfield.slb.com/en/Terms/g/gravity_toolface.aspx