Shale Oil And Gas Forming Conditions In Chang 7 Set Of Yanchang Formation In Zhidan-ganquan Region,the Ordos Basin.

Compared with geological conditions of North American, it can be found that the high-quality source rock constituted by a set of mudstone of Chang 7 Set,the Yanchang Formation of the Triassic,and it has certain geological conditions of the accumulation.However,the shale oil and gas forming condition,the rules of distribution,and the evaluation criteria,select parameters are need to be further studied. On the basis of former research results, this paper discuss the forming condition of continental shale of Chang 7 Set in Zhidan-Ganquan region by applying with cores observation,thin section identification, physical property and geochemical test, X-ray diffraction, sedimentation, well-logging and logging datas.Research results are as follows: Chang 7 Set of the Yanchang Formation mainly covers deep and half deep lake sedimentations, the shale is getting thinner from the southwest to the northeast, with good continuity and relatively stable distribution.The thicker area is located in the center of the basin sedimentation.The total organic carbon content of the study area is high,TOC of 84.2% samples are higher than 2%,with an average of 4.61%.The organic matter evolution has entered into mature stage. The main distribution of thermal maturity is between 0.6% and 1.1%, obvious trend of oil generative. Kerogen type are mainlyⅠand Ⅱ1.The shale contains high percentage of clay mineral,with an average of 56.3%, mainly including andreattite and goeschwitzite.The mineral contents of quartz, feldspar and carbonate are low.The average porosity is 3.34% and matrix permeability is 0.033×10-3μm2.Reservoir spaces include intergranular pore, intragranular pore, organic matter pore and microcrack. Organic matter pores are relatively less development.The test result of isothermal adsorption turns out that the Langmuir volume of shale changes between 0.56m3/t and 4.43m3/t. The TOC content and clay mineral content(mainly illite) have the most significant effect on adsorption characteristic.By establishing the formula between thermal maturity and maximum depth of oil-gas phase,it shows that oil-gas phase exist in the South of Zhidan and West of Ganquan.Combine with the shale thickness,the total organic carbon content,thermal maturity and clay mineral content,this paper establish the reservoir evaluation index,and predict favorable shale oil and gas exploration area.