Study On Shale Reservoir Characteristics Of Shanxi Formation In Yanchi Area,Ordos Basin

Ordos Basin is one of the important petroliferous basins in China.It is rich in oil and gas resources.Many sets of organic-rich shale developed in the Upper Paleozoic with wide distribution and large thickness,so it has become one of the targets of shale gas exploration and development.Yanchi area in ordos basin of shanxi formation of mud shale reservoir as the research object,first compiled predecessors'research results,combining well logging and various experiment data,the systematic analysis on reservoir characteristics was carried out,including the study area of shanxi formation of mud shale of sedimentary characteristics,the characteristics of the shale,shale reservoir conditions and the characteristics of hydrocarbon showings.According to the research results,it is recognized that the shale of Shanxi Formation in Yanchi area of the western Ordos Basin is continental facies,mainly meandering river delta front and shore-shallow lacustrine facies.The burial depth is large,ranging from 3,537 to 4,486.4 meters.The accumulated thickness of shale is between 56.84 and 98.28 meters,which is thin in the middle and thick in the east and west.The accumulated thickness of carbonaceous shale is between 3 and15 meters.Kerogen in the study area the?¹³C‰between 23.5‰to 23.7‰,belongs to the typical?kerogen,organic matter source for terrestrial higher plants;The measured TOC content was general,ranging from 0.11%to 3.42%,with an average of 1.18%.Ro values ranged from 1.76%to 2.17%,with an average value of 2.03%,which was located at the dividing line between high maturity and over-maturity.In mineral composition,clay mineral content is high,followed by brittle minerals such as quartz.Most of the reservoirs have strong brittleness and can produce fractures,while some layers have poor brittleness.Most of the lithofacies are siliceous clayey shale,and a small part is clayey shale.The pore structure is dominated by micropores,with a small number of large pores and microfractures.Organic pores can be seen in some places.The pore volume was mainly contributed by mesopores and macropores,accounting for 89%,while the micropores contributed only 11%.The contribution of micropores and mesopores to specific surface area was 99.8%,and the contribution of macropores was almost no.The results showed that the average face rate ranged from 6.45%to 13.08%,and the overall mean was 8.22%.The adsorbed gas content was poor,with an average value of 0.915m³/t.The TOC was positively correlated with the adsorbed gas content.The clay mineral content,pore volume and specific surface area were positively correlated with the adsorbed gas content,while the brittle mineral content was negatively correlated with the adsorbed gas content.