The use of resistivity-at-the-bit images and annular pressure while drilling in preventing drilling problems

The cost of well construction can exceed budget dramatically if drilling op erations are plagued by wellbore-instability problems and excessive time an d resources are needed to free stuck pipe, regain circulation, or clean the hole efficiently. Annular pressure while drilling has been recognized rece ntly as one of the key down-hole measurements for aiding real-time diagnosi s of the condition of the wellbore and drilling fluids. In addition to conv entional drilling-mechanics: measurements, time-lapse logging-while-drillin g (LWD) documents the dynamic change in measured properties during well con struction. This can be essential in diagnosing wellbore failure, and the me chanism of failure, in addition to dynamic processes such as cuttings build up. An example from a horizontal well in the North Sea is used to illustrate ho w LWD resistivity images can be used in conjunction with annular-pressure-w hile-drilling measurements to detect the onset of drilling-induced fracture s. Although the majority of azimuthal images have been acquired to understa nd the geology and petrophysics of reservoirs, the images usually contain f eatures resulting from geomechanical processes. Analysis of these features reveals important information for optimizing dri lling and understanding the geomechanics of the well. Coupling resistivity images to the pressure measurement enables problem identification and corre ct remedial actions to optimize the drilling operation, for example, ensuri ng that swab and surge pressures are kept to a minimum, and correct hole-cl eaning procedures are used to prevent irreversible formation breakdown.