Determination of Lithology From Well Logs by Statistical Analysis

Summary This paper presents a method of predicting lithology by statistical analysis of wireline log measurements with calibration to a core lithology standard. Although an example of the technique applied to the Shublik formation of the Prudhoe Bay area, North Slope, AK, is developed and presented, the method can be applied to any field where some core has been taken. The Shublik, a complex mixture of seven clastic and carbonate rock types, presents a common problem: how can the rock lithology best be identified from wireline logs? During recent work on the reservoir description of the Shublik, it became necessary to answer this question. A lithology standard must be available to calibrate against during development of a log model of lithology. For the Shublik, the core available provided an excellent sample of the total formation. Using the statistical technique of discriminant analysis, we were able to evaluate a number of log models and to choose the most appropriate one. The final log model chosen for the Shublik formation works quite well and correctly predicts lithology 75% of the time.