Characteristics And Controlling Factors Study Of Sandstone Reservoir From Shahejie Formation In The Part Of Northern Sub-sag Of Liaozhong Sag

Liaodongwan area is one of the important oil-bearing zones in Bohai and even in the eastern part of China.Since 1970 s,a great deal of breakthroughs have been made in the exploration of Liaodongwan area,and many large oil and gas fields have been discovered in Luda 10-1,Jinxian 1-1,Jinzhou 25-1s and so on.The research area is located in the north of the northern sub-sag of Liaozhong sag,the destination stratum is the Shahejie Formation,the burial depth is about 3000 m.Previous studies have often focused on the source rocks of Shahejie Formation,but neglected the study of reservoir properties and the data are relatively weak,which has greatly restricted the further exploration in this area.This research area combines the research results of previous generations of scholars,and guided by the theories of sedimentary petrology,petroleum and gas geology,reservoir physics,geotectonics,etc.adopts a macro,micro and re-micro analysis system from core observation to thin slice identification to scanning electron microscope analysis,supplemented by mudstone vitrinite reflectance measurement,carbon and oxygen isotope determination.Advanced experimental means such as homogenization temperature of inclusions,systematically analyze and summarize the petrological characteristics,reservoir characteristics,sedimentary characteristics and diagenesis characteristics of sandstone in Shahejie formation,and clarify the main controlling factors of sandstone reservoir in Shahejie formation.The strata of Shahejie Formation in northern sub-sag of Liaozhong sag are braided river delta and lacustrine sedimentary environment.The rock types of sandstone in the study area are mainly lithic feldspathic sandstone and feldspar lithic sandstone.The matrix content is relative high,and the main cement is carbonate cement.while the second is siliceous cement,and the authigenic clay minerals are rare,mainly Illite and kaolinite.The most late diagenetic stage of sandstone reservoir in the study area is the middle diagenetic A subage while part enters the middle diagenetic B subage.The diagenesis mainly includes mechanical compaction,dissolution,cementation and so on.The sandstone reservoir in the study area has moderate physical properties,the porosity is mainly mid-level pore,the permeability is mainly ultra-low permeability,and the correlation between porosity and permeability is poor.Combined with the research results and production practice,the reservoir evaluation criteria are established.The reservoir in Shahejie Formation can be divided into three types.The main characteristics of beneficial reservoir are coarse grain size,better sorting,higher feldspar content,less matrix content,beneficial high-energy sedimentary environment,relatively weak mechanical compaction and strong dissolution.