Reservoir Characteristic And Damage Mechanism Study Of Xiashihezi Formation In Zhe South Of Zichang Area, Ordos Basin

The study area is located at the northern gas district of Yanchang oilfield.Because of having not many exploratory wells,the district is a weak exploration area.It is the important potential resource district of Yanchang oilfield. Xiashihezi formation especial the eighth member is the important oil and gas reservoir in Ordos basin.in Daniudi,Sulige and Yanan areas, Xiashihezi formation saves sizable oil and gas reserves. So Xiashihezi formation has good exploration prospect. The oil-gas exploration and development of Xiashihezi formation has important meaning for the sustainable development of Yanchang oilfield.This paper aims at Xiashihezi clastic reservoir detailed study to explore the north of the district.This paper promises to provide guidance to the northern part.In this paper,the author synthetieally applied well logging, sedimentology stratigraphy and petroleum geology,ect, on the basis of studying on the drilling core in the district, full use of logging,drilling and testing datas,to research and discuss the study area Xiashihezi sedimentary system, diagenesis and physical characteristics of in-depth study, and the main results and understanding are as follows:According to sedimentary structures, profile structure, lithology and logging flag, braided river delta and lacustrine depositional system were recognized in Xiashihezi formation, parting and researching the sedimentary facies and microfacies within the systems, establishing a depositional model.Xiashihezi has entered the late diagenetic stage of the A-B period. The main types of diagenesis are compaction, pressure solution, cementation, alteration and metasomatism, dissolution. Compaction, pressure solution and cementation are destructive diagenesis, alteration and metasomatism on reservoir properties of the reservoir is not obvious, dissolution and fracturing constructive diagenesis.The pore types in Xiashihezi are residual intergranular pores, intergranular dissolution pores, particles within the solution pores, intergranular pore authigenic minerals, micro-pores, micro cracks.most of the Pores are induced porosity.most of pore composite types are dissolved pores.Range of porosity is 0.1% to 9.8%, an average of 2.21%.The range of permeability values (0.014-0.657) x 10-3μm2with an average of 0.191 x 10-3μm2. The core data analysis showed a poor relationship between porosity and permeability. from granularity and penetrance datas, Xiashihezi has the strong heterogeneity, and uneven penetration type of the majority.The experimental analysis of reservoir damage demonstrate that Xiashihezi has strong middle overall sensitivity:the high stress sensitivity, the strong middle acid sensitivity, moderate weak alkali sensitivity, water and salt sensitivity sensitivity for the weak, speed sensitive to non-weak.