The Reservoir Characteristics And Controlling Factors In The Chang2₁Oil-bearing In The East Of Jiyuan Area

As one primary oil-bearing series of Ordos Basin, exploration and exploitation of Chang21reservoir of Yanchang formation in Jiyuan area have an important place in the reserves and oil productions of Changqing Oilfield in the past few years. However, short of recognition of prominent geologic feature such as low porosity, low permeability, low pressure, low resistivity and stronger reservoir heterogeneity and so on of the Chang21reservoir affects the progress of exploration and exploitation of this area thoroughly. This paper gives the details of stratigraphic division and sedimentary characteristic of the chang2reservoir in zhoujiawan-haojiaping area Combination of sedimentology and geophysics by a comprehensive study using core analysis data、log date well、logging date and laboratery analysis data. Using reservoir geology theory and complementary research methods as the guide, it takes a systematic and thorough study into the area characteristics of reservoir rocks, diagenesis, characteristics of properties, pore structure characteristics and the characteristics of the heterogeneity. Ultimately the chang2reservoir of this area is classified and evaluated from the geological point.Research shows:The Chang21reservoir of this area was subdivided into Chang211、 Chang212andChang213; The bedthickness is steady.The old river of NingShan and MengShan which get through this area have corroded the most layer of chang2and chang1. The majority of them are the delta plain subfacies and the main sand body microfacies are distributary channel; The main reservoir sandstone are miliary arkose and fine-grained arkose having characteristics of low compositional maturity and high textural maturity in the mass; Reservoir property which belongs to mesporosity and low-permeability is bad; Solution pores-intergranular pore is the main types of pore and eservior space is small pore and thin throat;The chang21reservoir of this area have existed serious intraformational、interlamination and plane anisotropy.Through analysis by synthesis,The reservoir can divided4types.The main type of every reservoir is type Ⅱ and the most growth reservoir is chang213.The main governing factors of reservoir characteristic in this area are sedimentation and diagenesis.The study shows that distributary channel and the thicker lithology control the better physical property.Compaction、carbonate cementation and kaolinite cementation are the governing factors of constructive diageneses. Chlorite cementation、dissolution and tectonic movement are the governing factors of destructive diageneses.