The Impact Of Organic Matter Type And Evolution Characteristics On The Enrichment Regularity Of Shale Gas And Shale Oil

With the fast development of oil industry, resource demand greatly increased than before. Now the development of oil industry is from conventional to unconventional resources. Unconventional resources that should be found and developed with unconventional methods mainly include the tight oil, shale oil and gas, coal-bed methane, fractured carbonate oil and gas, volcano rock oil and gas, oil or gas in metamorphic rocks, heavy oil, bitumen, oil shale, natural gas hydrate, etc. Among them, shale oil and gas becomes the focus of geologists all over the world with the successful exploration of shale oil and gas in North American.Compared with conventional oil and gas, shale oil and gas has no obvious trap line, more occurrence ways, higher demand of organic characteristics, strong heterogeneity and complicated variable porosity etc. These characteristics determine the exploration and development of shale oil and gas more complicated. At present enrichment regularity research of shale oil and gas in China is limited, especially in the case of shale oil. Theoretical knowledge has only just started, basically complying with the experience of exploration in American. But geological condition is complicated in our country and affected by multiphase tectonic evolution Accumulation has its unique complexity. The impact the enrichment regularity of shale gas and shale oil is still in the exploratory stage, especially organic matter characteristics on the impact of enrichment. As the place for generation and accumulation of shale oil and gas, its importance is no doubt. So the impact of research of organic characteristics in hydrocarbon source rock on shale oil and gas enrichment regularity is imminent.On the basis of a large number of research journals and datas at home and abroad, in combination with ChangNing and Weiyuan exploration region of the Southern part in Sichuan basin and the target of shale oil horizon of JiYang depression in BoHaiWang Basin, characteristics of many factors which influence the enrichment of shale oil and gas are analyzed comprehensively from source condition, reservoir characteristics and preservation conditions. Impact of the characteristics of organic matter on the enrichment regularity of shale oil and gas is analyzed fully with those comprehensive analysis and drillings、core samples、outcrop datas and geochemical experimental analyses of sample tests.Many factors affect rich integration of the shale oil and gas reservoir. From the hydrocarbon source condition, buried depth and thickness of mud shale, the type of organic matter, organic matter abundance and maturity, have a great influence on shale oil and gas generation. Porosity development, permeability distribution and inner clay minerals content have a great influence on the shale oil and gas reservoir. Tectonic conditions, the development of the regional cap rock, the distribution of temperature and humidity play a controlling role to the preservation of shale oil and gas.A more stable shale and mudstone formation distributes in the southern area of Sichuan province. Previously, in regular evaluation of exploration and development, Longmaxi Formation is a good marine source rock and has good condition to generate shale gas. Thickness of Longmaxi formation becomes thicker from Leshan-Longnv uplift to southeast. As the sedimentary center, Zigong-longchang-luzhou buried over 2000m. organic matter of Longmaxi Famation is type I and Ⅲ,which formed in the deep-water shelf deposit and has better material types. Thermal evolution level is high (Ro=2.0%～3.8%),in a period of large numbers of dry gas generation. The organic carbon content is very high(average TOC=2.52%). Concentrated distribution, superior organic matters and big hydrocarbon generaion potential provide important basis for shale gas enrichment. Shale members of Lower Es3 and Upper Es4 of the Paleogene in Jiyang depression is lacustrine source rock to oil generation. the main organic matter is type I and II and rich in algae fossils. Shale members of Lower Es3 have a more quality of TOC(between 0.5～18.5),mostly between 2%～6%. Upper Es4 TOC(between 0.30～11.2),mostly between 1.6%～6%. shale members of Lower Es3 and Upper Es4 have a widely thermal evolution level(Ro=0.34%～1.45%). But mostly distribution is from low mature to mature level. Maturity increases with the depth. The peak of Ro is 1.55%. According to the data statistics, Ro of Lower Es3 is0.51%～0.80% and Upper Es4Ro=0.55%-1.43%.Different types of kerogen shows big differences to adsorption capacity of the methane. The lnK(The maximum adsorption amount) has a good relationship with the reciprocal of temperature. Adsorption of the methane in Longmaxi Famation shows that the type of kerogen is between I and II and has a good ability of adsorption. Different type of kerogens at different evolutionary stages have the different product. At the aspect of Shale oil, oil adsorption of type I have a more than ten times to type II or III, which shows that type of kerogen controls the oil contents importantly.The more content the organic carbon has, the more ability of adsorption of shale has. High TOC contents are the main factor to increase the nanometer pore reservoir and Specific surface area. It can also promote the development of micro cracks in shale. One factor of the high contents of shale gas in Longmaxi Formation is the high TOC contents.In Jiyang depression, TOC contents of the high Industrial oil wells are usually more than 2% and chloroform bitumen A is greater than 0.4%.But the TOC index have no obvious relationship with the production of single well. Maturity is not the main control factor of shale gas enrichment. But the high Ro can promote organic micro pore growth and increase more favorable space of the enrichment of shale gas. High Ro shows the high rate of gas conversion. Abundance of good organic matters and thermal evolution degree determine the high gas generation and contents in Longmaxi formation.With maturity increases, the gas oil ratio goes up. The peak of thermal maturity corresponds to the maxim of oil saturation in shale and mudstone. The maximum oil saturation and porosity of the maximum has good correlation, and it can be seen that both the maximum of the peak corresponds to the hydrocarbon generation.