Mark A. Herkommer
Localized models of abnormal formation pressure (geopressure) are important economic and safety tools frequently used for well planning and drilling operations. Simplified computer-based procedures have been developed that permit these models to be developed more rapidly and with greater accuracy. These techniques are broadly applicable to basins throughout the world where abnormal formation pressures occur.
An example from the Attaka field of East Kalimantan, southeast Asia, shows how geopressure models are developed. Using petrophysical and engineering data, empirical correlations between observed pressure and petrophysical logs can be created by computer-assisted data-fitting techniques. These correlations serve as the basis for models of the geopressure. By performing repeated analyses on wells at various locations, contour maps on the top of abnormal geopressure can be created.
Methods that are simple in their development and application make the task of geopressure estimation less formidable to the geologist and petroleum engineer. Further, more accurate estimates can significantly improve drilling speeds while reducing the incidence of stuck pipe, kicks, and blowouts.
In general, geopressure estimates are used in all phases of drilling operations: to develop mud plans and specify equipment ratings, to assist in the recognition of geopressured formations and determination of mud weights, and to improve predictions at offset locations and geologically comparable areas.
AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994