Wettability and Productivity Characterization of Low Permeability Gas Formations.Topical Report, January 1990-July 1992

摘要

Tight gas sands are characterized by porosities of 5% to 15% and permeabilitiesranging from 0.1 to 0.01 md. To date, formation evaluation of these sands has been done by core analysis, log interpretation, conventional wireline testing, and well testing. However, these techniques have significant drawbacks. In low permeability formations, irregular invasion complicates core fluid analysis, making it difficult to accurately determine a zone's gas-bearing potential. Log interpretation, while useful for measuring porosity and saturation, cannot be used for permeability determinations. The conventional wireline formation tester does not yield reliable pressure measurements because complete pressure buildups can seldom be achieved and the interpretation of these buildups is inaccurate. Furthermore, data necessary to correct for supercharging is not available. Conventional well testing covers large intervals, and some aspects of production cannot be pinpointed accurately. To remedy these shortcomings, the project focused on three major objectives: to establish the theory, to test equipment, and to develop an interpretation technique for single-pad formation testers that will perform well in tight gas formations. The project has resulted in a better understanding of wireline formation testing in general and its application to low permeability formations in particular. The study has resulted in improved test design and procedures and has defined a new interpretation technique that yields more representative permeability values.