Study On Natural Gas Enrichment Rules And Sweet Spot Evaluation Of He8 Member In Daning-Jixian Area

The research of tight gas in the Upper Paleozoic He8 member of the Daning-Jixian area is weak,and the enrichment regulation of tight gas is unclear.There is no theoretical support for exploration and development,and the production effect of a single well has not met the development expectations.There are significant differences in production among different well locations.Therefore,it is crucial to optimize the‘sweet spot area’and establish sweet spot evaluation standards.In this paper,through observation of outcrop profile and core,analysis of microscopic observation data and geochemical data,combined with test gas production data and cumulative production data,comprehensive basic research is carried out on the He 8 member of Daning-Jixian area,systematically analyzing the geological characteristics of Upper Paleozoic gas reservoir in Daning-Jixian area.Finally,the main controlling factors and enrichment rules of accumulation in the study area were summarized and the evaluation criteria of sweet spot were established.The enrichment law of Daning-Jixian area is not controlled by single geological conditions,but by multiple coupling relationships such as source rocks,reservoir and cap rocks.Natural gas is mainly accumulated in the area with good coupling relationship between geological factors:high-quality source rock conditions provide good gas source basis for natural gas enrichment;Favorable sedimentary facies and favorable reservoir conditions provide storage space for gas enrichment.The study shows that the underwater distributary channel in the study area has thicker sand,better physical property conditions,and when the porosity is greater than 5.4%,it is conducive to gas accumulation.Good argillaceous cap provides good shielding conditions for gas enrichment.According to the above characteristics of natural gas enrichment law,combined with static geological parameters and dynamic production parameters,the enrichment coefficient EF was established.Based on this,the evaluation criteria for sweet spots were determined.The favorable zones of class Ⅰ are as follows:gas thickness>3m,gas saturation>70%,porosity>6.0%,that is,EF>0.160.Class Ⅱ favorable zones are:gas layer thickness>1.6m,gas saturation>66%,calculated porosity>5.4%,EF>0.058.Based on the evaluation criteria,two’Class Ⅰ’sweet spots(7.10km~2)and four’Class Ⅱ’sweet spots(10.14km~2)were selected from the He8 Member in Daning-Jixian area.Based on the natural gas enrichment regulation and‘sweet spot’evaluation criteria of the He8 member in the research area,it can provide reference for the research of later tight sandstone gas reservoirs and guide the exploration and development of tight sandstone gas in the area.