Evaluation of Hydrocarbon Accumulation Conditions of Fault-related Traps in D Sub-sag of Weixinan Sag Based on Fuzzy Mathematics

D Sub-sag of Weixinan Sag has experienced several intense tectonic movements. Multistage faults are developed. The fault-related trap is the most important type of hydrocarbon-bearing traps. Hydrocarbon accumulation conditions are complex in different traps and horizons. Exploration target optimization has high risks. Based on the fuzzy mathematics evaluation, this paper recognized reservoir characteristics, charge modes of oil and gas, lateral sealing ability of faults and spatial matching types between faults and caprocks as the key geological factors controlling the hydrocarbon accumulation, and quantified the evaluation of the four factors. The results show that when the comprehensive evaluation value D≤0.618, it is a super-high risk trap. When 0.618<D≤0.691, it is a high risk trap. When 0.691<D<0.807, it is a medium risk trap. And when D≥0.807, it is a low risk trap. The new evaluation process is more objective and comprehensive, and provides a quantitative reference for the exploration in this area.