Advanced Formation Evaluation Concepts of the Well Data System (WDS) for Evaluating Geothermal Reservoirs

Abstract

Advanced and integrated formation evaluation techniques are vital in geothermal reservoirs that are lithologically complex and unfamiliar. The lack of complete log suites in geothermal wells, often due to operational problems in the high temperature environment, make both lithology identification and fracture evaluation difficult. However, a more meaningful interpretation can be obtained by integrating all the available open hole, cased hole, production and core data results into the interpretation models. Recent technological advances in new logging tools and interpretation techniques have helped in achieving a more reliable evaluation of geothermal reservoirs. A new system for analyzing well data, utilizing a 80386 32 bit processor microcomputer, incorporates state of the art statistical interpretation programs to integrate all available data and provide a realistic and accurate evaluation of these reservoirs. An interactive dip log computation program and a program to enhance acoustic images provide a visual means to detect and compute orientation and dip angle of the bedding and fracture planes. The unique combination of these evaluation techniques and the portability of PC machines makes the system ideal for processing and interpreting the data at either the well site or the company headquarters. Several examples illustrate use of newly developed logging instruments and these new techniques for evaluating geothermal reservoirs.