Characteristics And Sensitivity Of The Chang 6 And Chang 8 Reservoirs In The Heshui-Baoping Area Of ??the Ordos Basin

The Yanchang formation of Mesozoic in Ordos Basin is a typical representative of the tight sandstone reservoir.The paper takes Yanchang 6 and Chang 8 reservoirs of Ordos Basin in Heshui-Baibao area as research objects,conducted in-depth research on the characteristics and sensitivity mechanism of tight oil reservoirs,it is meaningful for guiding oil exploration and development of to carry out a research on reservoir characteristics and sensitivity mechanism of Chang 6 and Chang 8 section.Research shows that Chang 8 section in southwest lake basin was delta front deposition,reservoir sand body overlay each other,both with superposition of underwater distributary channel,and underwater distributary channel with distal bars;The Chang 6 section was underwater fan deposit,as multi-phase underwater turbidities superposition and truncated with each other,the sand layer is thicker in the local area.and the.Most of the Bauman sequence is incomplete development.The Chang 6 section has the characteristics of the interfluence of the multi-sources,mainly control by the northeast and the southwest source sedimentation.This results in a great difference between lithology,physical property,pore assembly,pore structure and diagenetic characteristics.The reservoir quality of northeast source sediments is obviously better than the southwest.the characteristics of the debris composition of the Chang 8 section are similar,and the differences of diagenesis results in the different reservoir quality.The Heshui area is dominated by the cementing of chlorite coating,the main pore assembly is intergranular pores,the reservoir quality is well,followed by the Baibao area and the Taerwan area.According to the characters of physical characteristics,diagenesis,pore assembly features,the diagenetic reservoir facies of Chang 6 and Chang 8 section are mainly including:chlorite coating and intergranular pores facies(type ?);Diagenetic fracture and dissolution pore facies(type ?);Pore filling(calcium,silica,clay,etc.)micropore facies(type ?).The sensitivity test of the Chang 6,Chang 8 section shows that the reservoir with the sensitivity of weak acid,no-weak water sensitivity,weak speed sensitivity,weak salt sensitivity and strong stress sensitivity.It is necessary to avoid or reduce the injection of medium may cause clay mineral crystal layer and intergranular expansion medium.The more densification degree of reservoir the stronger stress sensitivity,the deformation of the ultra-low permeability reservoir is unrecoverable,to the relatively high permeability reservoir deformation can partly recover,so it is of great significance for the development of low permeability reservoirs to maintain formation pressure.