S.K. Steve Chang received a B.S. in Electrical Engineering from National Taiwan University, and an M.S. and Ph.D. in Electrical Engineering and Computer Science from University of California, Berkeley. He joined Schlumberger in 1979, and for 15 years conducted research in borehole acoustic and electromagnetic logging at Schlumberger-Doll Research in Ridgefield, Connecticut. He became the director of geoacoustic research in 1990. He moved to Sugar Land, Texas, in 1994 to manage the logging while drilling (LWD) product line. In 1997, he became manager of groups in directional drilling software and logging interpretation. He moved to Beijing, China, as general manager to build the Schlumberger Beijing Geoscience Center in 2000. In 2005, he moved to Japan as the oil field services acoustic métier manager. Steve has 19 U.S. patents and more than 80 journal and conference papers in acoustics and electromagnetics.
2007 SEG Honorary Lecturer, South and East Asia
Recent advances in borehole geophysics applications
Recent advances in borehole seismic and sonic technologies have expanded borehole geophysics beyond the traditional applications.
For example, it is now possible to enhance drilling decisions using real-time borehole seismic while drilling. A drill collar is instrumented with ruggedized sensors and a high-precision clock synchronized to an uphole clock. Data are acquired during the "quiet" time while the drillers are adding new drill pipe sections. Real-time check shots can help drillers drastically reduce depth uncertainties for locating faults, abnormal pressure zones, and target formations. On numerous occasions depth corrections ranging from tens of feet up to 1000 ft have enabled the drillers to avoid intermediate casing runs and unnecessary sidetracks, saving days of rig time. Real-time waveforms sent uphole via the MWD (measurement while drilling) telemetry not only provide data for quality control but also allow drillers to look ahead of the drill bit to anticipate drilling targets and drilling hazards.
It is now common practice to acquire wireline borehole seismic data using a large array of multicomponent sensors. As a result, walk-away, walk-around and 3D VSP datasets of up to a million traces can be effectively acquired. Some of the advanced applications for this new technology include high resolution imaging, anisotropy estimation and risk management for subsalt drilling. Placing the array borehole sensors in listening mode, the data can be used to map the source locations of microseismic events in real-time during hydraulic fracturing of tight formations. Hydraulic fracture monitoring from microseismic events can provide vital data for optimizing field development plans. Event locations can also provide information to revise hydraulic fracturing parameters to achieve desirable results.
A high fidelity sonic logging tool not only produces reliable compressional and shear velocity logs but also provides information for anisotropy and stress-strength related formation perturbation near the wellbore. This information can be used to calibrate rock stress and mechanical properties which are key parameters in planning drilling and completion jobs.
This presentation includes examples which illustrate some of these borehole geophysics applications.