Evaluation Of Lower Permerbility Reservoir And Oil Potential Of Fuyu Oil-bearing In The Northern Of Xing Bei Area

With the speed of industrialization accelerating, the demand for crude oil production is to rise rapidly. In the newly discovered reserves each year, more than 60% of which are low permeability and ultra low permeability, so for the development of the ultra low permeability reservoir has become a top priority. Fuyu formation in Xingbei area develops ultra low permeability reservoir which already stepped into a large-scale development stage. Since the production distribution of exploration wells in the study area vary greatly in the plane, oil and gas are mainly distributed in the northern and southwest slope of the central anticline belt and the main factors controlling this distribution difference remain unclear, needing the further study. Based on the study of reservoir lithology characteristics, reservoir physical property and microscopic pore structure characteristics of Fuyu oil layer in Xingbei area, the paper summarizes the origin and type of the reservoir in the study area, determines the reservoir oil contents and analyzes the oil-gas distribution and main controlling factors, providing reliable geological basis for subsequent reservoir development and adjustment.Comprehensive utilization of geology, well logging, seismic, well test and production test etc, on the basis of the reservoir fine division and contrast, starting from the lithology characteristic to study the physical property and the micro pore structure characteristics of the low permeability reservoir and to analyze the the main controlling factors that influencing the oil content of low permeability reservoirs. The results show that Fuyu oil layer in Xing bei area has medium porosity and ultra low permeability, the lithology is mainly fine sandstone and siltstone, rock type is mainly fine-grained feldspar lithic sandstone whose reservoir space is mainly residual primary intergranular pore, followed by silicate particles dissolved pore(especially feldspar dissolved pore). The reservoir develops a large number of fractures which can be divided into high-angle filling fracture, vertical stress relief fracture, drilling-induced fracture, etc., which mainly filled with calcite, clay and oil. In terms of percolation characteristics, Fuyu oil layer belongs to water wetting, water sensitivity, weak salt sensitivity,alkali sensitivity, medium-weak velocity sensitivity and no acid sensitivity. Fuyu reservoir types mainly include distributary channel(underwater distributary channel), sheet bar/class Ⅰthin overbank sand and sheet sand/class Ⅱthin overbank sand, but the effective reservoir is mainly the channel and sheet bar/thin overbank sand, and the upper part of Fuyu oil layer is more developed. The oil saturation of the Fuyu reservoir is 51.2% on average and the occurrence is mainly the oil stain and the oil spots. On the plane, the western steep slope has higher oil potential, the central is the best and the eastern gentle slope strip has substantially no oil which is mainly controlled by tectonic characteristics and oil sources. Vertically, the development degree of the channel sand leads to the current oil and water distribution.