The cost of well construction can dramatically exceed budget if the drilling operations are plagued by wellbore instability problems. Excessive time is used to free stuck pipe or regain circulation. Subsequent well operations such as acquiring openhole logs or achieving zone isolation with a cement job are compromised, particularly in drilling extended-reach and horizontal wells. The development of a strength and stress profile for the well is the first step in understanding wellbore instability problems. These profiles are constructed using all suitable data, which include offset drilling experience, in-situ stress tests and strength measurements on recovered core. A wellbore stability forecast, guided by these strength and stress estimates, includes the identification of drilling hazards and the prediction of a suitable mud density. Real-time logging-while-drilling (LWD) data can be used to refine these profiles and help select the best remedial actions to optimize the drilling operations. Borehole images are essential for diagnosing the mechanism of wellbore failure and annular pressure while drilling data can help calibrate the strength and stress parameters. Although the majority of azimuthal images have been acquired to understand the geology and petrophysics of reservoirs, the images usually contain artifacts resulting from geomechanical processes. An analysis of these artifacts is important for understanding the geomechanics of the well and improving the geological and petrophysical interpretation. Time-lapse data are particularly important in monitoring dynamic processes such as formation failure and invasion. This paper shows several examples of how to use LWD data for a combined geological, petrophysical and geomechanical interpretation.
Logging-While-Drilling Images For Geomiechanical, Geological And Petrophysical Interpretations
Plumb, Dick, Krabbe, Helle, Rasmus, John, Li, Qiming, Bornemann, Ted, and Tom Bratton. "Logging-While-Drilling Images For Geomiechanical, Geological And Petrophysical Interpretations." Paper presented at the SPWLA 40th Annual Logging Symposium, Oslo, Norway, May 1999.
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