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Technical Paper: The Use of Resistivity-at-the-Bit Images and Annular Pressure While Drilling in Preventing Drilling Problems
Paper 70130
Abstract
The cost of well construction can exceed budget dramatically if drilling operations are plagued by wellbore-instability problems and excessive time and resources are needed to free stuck pipe, regain circulation, or clean the hole efficiently. Annular pressure while drilling has been recognized recently as one of the key downhole measurements for aiding real-time diagnosis of the condition of the wellbore and drilling fluids. In addition to conventional drilling-mechanics measurements, time-lapse logging-while-drilling (LWD) documents the dynamic change in measured properties during well construction. This can be essential in diagnosing wellbore failure, and the mechanism of failure, in addition to dynamic processes such as cuttings buildup.
An example from a horizontal well in the North Sea is used to illustrate how LWD resistivity images can be used in conjunction with annular-pressure-while-drilling measurements to detect the onset of drilling-induced fractures. Although the majority of azimuthal images have been acquired to understand the geology and petrophysics of reservoirs, the images usually contain features resulting from geomechanical processes.
Analysis of these features reveals important information for optimizing drilling and understanding the geomechanics of the well. Coupling resistivity images to the pressure measurement enables problem identification and correct remedial actions to optimize the drilling operation, for example, ensuring that swab and surge pressures are kept to a minimum, and correct hole-cleaning procedures are used to prevent irreversible formation breakdown.
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