Abstract:

Water lock generally exists in low permeability gas reservoir and seriously affects the exploration and development of gas reservoir. Reservoir parameter is the most important factor which affects the degree of water lock damage. However, accurate prediction of the degree of water lock damage is difficult because of the reservoir heterogeneity. 12 parameters which can reflect 4 different kinds of reservoir features including lithology, physical properties, cement type and micro-pore structure in a low permeability gas reservoir in Ordos Basin are optimized to build up the element anthology for the fuzzy multi-objective comprehensive evaluation. Different degrees of water lock damage build up the remark anthology. Complementary judgement matrix is used to determine the weight of factors, then ridge-shaped distribution function is used to define the comprehensive evaluation matrix, finally the second-order multi-objective comprehensive evaluation is formed. The evaluation results of 4 cores are consistent with laboratory test results, so the comprehensive evaluation method is accurate and valid. Based on the basic parameters of reservoir rocks, the appropriate evaluation method can be used to accurately predict the degree of water lock damage. So, the workload of gas-water flow experiments will be drastically reduced, cost will be saved, and the working system and production technology for the gas reservoir can be optimized.

Key words: reservoir, karstification, dolomitization, Lower Paleozoic buried hill, Zhuangxi-Chengdao area