The Comparative Study Of The Triassic Gas Hydrates Evaluation Method In Qinghai Province In Southern Qilian Basin Muli Region

Muli region of the southern Qilian basin is an important source of coal resources in Qinghai Province. In recent years,gas hydrate resources was found in this area,which has two aspects of research significance of land-based "combustible ice" and "coalbed gas",attracting great enthusiasm of domesticand foreign scholars. At the present,natural gas hydrate study is one of the hot energy research,especially the various resources characters and resource potential of gas hydrate in the shallow strata of Muli region,has important practical significance.Based on the Qinghai province Muli southern Qilian basin as the study area,select the Triassic strata as the research object. Through the evaluation of formation in samples of organic matter abundance,type and maturity of organic matter those three indicators, complete the first evaluation of hydrocarbon source rocks of Triassic strata. According to the hydrocarbon source rocks evaluation method of oil and gas reservoir prospecting,the " limestone and siltstone and carbonate source rock " part of Galede Temple group formation has the ability to generate natural gas,as well as Dajialian group formation part of limestone can be obtained natural gas hydrate formation in the production. In order to more closely to the actual situation of natural gas hydrate resource assessment,I put forward a new evaluation method for the study of natural gas hydrate resources,and the formation of the Triassic(6 groups) was reevaluated by this way. Affected by the lack of porosity and permeability data of some strata(4groups),finally it receives the natural gas hydrate evaluation results of Galede Temple group and Atta Temple group only. But comparing with the traditional methods of evaluation above, the new evaluation method can get information more intuitive and detailed. Finally: the siltstone,sandstone of Triassic Galede Temple group can produce natural gas by pyrolysis,but the gas accumulation in terms of little significance; the carbonaceous shale, mudstone,carbonaceous mudstone source rock will not output natural gas by pyrolysis, neither become a reservoir of natural gas; the carbonaceous shale,mudstone,carbonaceous mudstone source rock will not output natural gas by pyrolysis,but if the cracks grow in the strata,they turn to become reservoirs or dense reservoirs of natural gas. The feldspar quartz sandstone and siltstone of Atta Temple group can be a formation of natural gas but not an accumulation of natural gas resources.Through the study of the development of natural gas hydrate evaluation work,I think a new evaluation method can be considered. Firstly,all strata of the study are according whether can produce natural gas or not should be divided into two categories by their organic matter maturity of source rocks. Secondly the two categories shall be further classified in more detail by porosity and permeability to get the reservoir capacity evaluation of each lithology for natural gas. At last there should be a conclusion summed up the different lithology of the entire study area in each stratum for gas hydrate reservoir capacity.