Using Decision Analysis to Estimate 3-D Seismic Value - Minas Field, Sumatra, Indonesia

Kent M. Mangold, Timothy P. Whitacre, and Seffibudianti

Decision Analysis has been used to estimate the value added from a 3-D seismic survey recorded over Minas field, Central Sumatra. The method involves comparing the expected values which result from the various decision options, such as acquiring 3-D or not. Probabilities must be assigned to the various branches of the decision tree. These include for example, the expected reliability of the 3-D data as well as the subsequent interpretation.

Anticipated drilling results with and without 3-D are assessed after reviewing historical data and interviewing experts to obtain 10th, 50th and 90th percentile results for various scenarios. In this way the expected value, or cumulative distribution of the expected value of the 3-D can be computed and risk can be assessed.

The Minas 3-D survey is the largest (450 square kilometers) of over 25 development 3-D surveys recorded by Caltex Pacific Indonesia (GPI) over its fields in Central Sumatra. This survey was conducted after nearly 50 years of production from more than 750 wells.

CPI's 3-D experience has shown that increasing the subsurface resolution within complex high angle faulted areas results in new drilling locations in older mature fields such as Minas. Better knowledge of the oil producing reservoirs can also be used to optimize pattern waterflood locations, horizontal drilling and other tertiary recovery studies.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California