Abstract: Integration of Well and Seismic Data Using Geostatistics

Katy Withers, D. J. Wolf, M. D. Burnaman

The "geostatistical method" can be applied to quantitatively relate well and seismic data, give an assessment of how good the resulting map is, and estimate the probability of success directly from the available data. To illustrate the steps of the geostatistical method, a case study will be presented in which the thickness of an oil-bearing sand was estimated using seismic amplitude from a 3-D seismic survey as a guide.

The geostatistical method is a four step procedure that calls on several statistical tools. The-first step is to quantify the spatial continuity of the well data using variogram analysis. The second step is to find and quantify a relationship between the well and seismic data. The third step is to use what has been learned to grid the well data using the seismic as a guide via kriging with external drift. This results in an "expected value" map. The last step is to assess the accuracy of the expected value map. Conditional simulation is a geostatistical tool that yields a quantitative measure of map uncertainty.

In the case study, the geostatistical method was used to estimate the expected value and error in a sand isochore. Cumulative probability distributions and risk maps are two tools that were used to display the range of error in the isochore. These tools were used with economic threshold information to directly derive the probability of success from the data available. Two wells drilled after geostatistical analysis confirmed that using the geostatistical method is more accurate than traditional (non-geostatistical) methods.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994