It has become extremely important in recent years to do a better job in well planning to ensure that well cost estimates and drilling programs are as complete and accurate as possible. Comprehensive well programs and realistic estimates are necessary to determine which drilling prospects are most attractive considering current upstream economics.

Pore pressure analysis is the initial, and in most cases, the most important step in developing an accurate, complete well program. Casing setting depths, hole sizes, number of casing strings, mud programs, and hydraulics are examples of items in a well program which are influenced by the pore pressure profile determined for a well. Pore pressure analysis is especially critical for exploratory and delineation wells but until recently our predictive techniques were somewhat inadequate.

This paper will present the application of seismic correlative and seismic velocity (ITT) techniques to predict pore pressures on a North Sea exploratory well prior to drilling. Actual mud weights used on the prospect are compared to the predicted pressures.

The steps used to predict pore pressures will be discussed including sonic log pore pressure analysis correlated to the prospect, development of a regional pore pressure overlay for interval transit times, and analysis of ITT information developed from seismic shot points at the prospect and an offset well. Results from this interpretation of seismic information will be compared to the actual pressures determined after drilling the well to emphasize the effectiveness in using these techniques for pore pressure prediction.

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