Under Gasikule Youshashan V2 Oil Reservoir Sedimentary Microfacies Study Group

Qinghai Gasikule oilfield has entered the later period of development with middle water-containing. Because of the rise of the water content, production is gradually reduced. The situation of low production rate and development lasted for a long time. The reservoir injection-production ratio is low, and the formation voidage was serious. A large number of remaining oil is still in the sand body. Gasikule N21reservoir core data indicate that the part of sandstone has water-washing seriously, and the other part is rich of remaining oil. Substantial remaining oil reserves does not conform to the development effect. And it fully shows that the question of oil reservoir microfacies is still unanswered at the present stage. Therefore, starting with accurate description of the sedimentary microfacies is necessary. And describing sedimentary characteristics is satisfied the need of oil field development.This paper is guided by the sequence stratigraphy, sedimentary petrology, structural geology, logging geology, reservoir geology, petroleum geology theory, based on core data, logging data and dynamic monitoring data. And "fine, digital, quantitative, multidisciplinary integration" is the principle. With the help of coring data, logging data and dynamic data, the characteristics of the cycle of sedimentary strata is mainly contrast markers of fine stratigraphic correlation. And in this research the studied section is divided into3short term cycles,10ultrashort cycles and divided into10small layers. By the results of stratigraphic correlation, the study area is a faulted nose structure with a high position in the east. In this paper, a small layer is the mapping unit. And drawing10small layer sandstone thickness maps and maps of distribution of sedimentary microfacies characteristics is one of results in this paper. Distribution of microfacies is affected by source coming from the north-west and distribution channel of north-west to south-east. Underwater distributary channel microfacies is found in the northwest of study area. And fan-shaped mouth bar is found at the end and edge of channel. Shallow lake sand bars and shallow lake muds is in the southeast. In the direction of north-west to south-east underwater distributary channel and mouth bar have good continuity. The continuity of shallow lake sand bars is not good.The research shows that the Gasikule oilfield lower Youshashan formation (N21) V2formation belongs to c shore-shallow lake-braided river delta sedimentary system, and mainly developed braided river delta front and shore-shallow lake subfacies, delta fron. Because of delta progradation, prodelta parfacy is not developed. The main reservoir rock is underwater channel, mouth bar and shallow lake sand bar. V2formation experienced a complex set of water into the process. Rock granularity is getting small from button. The formation formed a normal cycle.Through the research of sedimentary microfacies, sand body and distribution characteristics of sedimentary microfacies in the study area is figured out. And it is good for recognition of petroleum geologic in Gaskule oilfield, finding remaining oil, development of rolling and further exploration.