| There is a good prospect for tight oil exploration in Yanchang oilfield.However,the exploration degree of tight oil of Chang 8 in the study area is not high,and the mechanism of tight oil accumulation and the model of hydrocarbon accumulation are unclear.In order to clarify the distribution law of tight oil and the main control factors of tight oil enrichment of Chang 8 member,and predict the tight oil dessert distribution area of Chang 8 member,the known tight reservoirs of Chang 8 are anatomized from the basic geologic elements of oil and gas accumulation.Single-factor planar superposition data statistics method was used to analyze the planar and vertical distribution characteristics of tight oil,and the main controlling factors and accumulation rules of tight oil enrichment were summarized:high-quality source reservoirs control the distribution of tight oil,good source and reservoir matching affect the efficiency of tight oil accumulation,and cracks determine high production of tight oil reservoir.The weighting factor of the dessert evaluation index was calculated using the expert rating method and the multivariate mathematical statistics principal component analysis method.The results show that the source rock thickness of the Chang 9 is 11.6%,the source rock thickness of the Chang 7 is 11.6%,the hydrocarbon expulsion intensity is 11.4%,the organic carbon content is 12.9%,the porosity is 6.8%,the cumulative thickness of the sand body is 8.1%,the permeability is 7.6% and the fracture development index is 30.0%.Based on these,a mathematical geological model for the probability of sweet spots distribution of tight oil of Chang 8 was established,and a superposition map of the probability distribution of desserts and tight oil reservoirs for Chang 8 was drawn,and the sweet spots distribution area of tight oil of Chang 8 was summarized to guide the next exploration of Chang 8 tight oil in Yanchang Oilfield. |
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