Research On The Reservoir Characteristics Of Yichuan And Huanglong Area Of The Upper Paleozoic Sandstone In The Southeast Of The Ordos Basin

The prospect of natural gas resources in Ordos Basin is very impressive.The total resources is 10.8x1012 m~3.While the natural resources in the Upper Paleozoic basins have 8.3x1012 m~3.It shows that the exploration prospect in the Upper Paleozoic is huge and the field is very broad.It is the main layer of natural gas exploration in the basin.However,natural gas exploration in the southern Ordos Basin has been slow compared to the north.Especially in the southeastern part of the basin,the exploration degree is also lower,the number of exploration wells are less.In addition,the predecessors of the Ordos Basin in the Late Paleozoic northern,central reservoir,provenance and gas reservoir characteristics have a higher degree of research.Relatively speaking,the southeastern part of the basin has a lower degree of research because the data is limited and the geological knowledge is not clear.Therefore,based on previous studies.The purpose of this paper is to study the petrological characteristics,interstitial characteristics and reservoir physical properties of the sandstone in the northeastern part of the Ordos Basin in the Late Paleozoic Huanglong and Yichuan.At the same time,the control factors of its reservoir quality are deeply studied and discussed,and get the following conclusions and recognization :(1)The distribution of the four types of rocks in the Yichuan area are relatively regular.The rock types of the Taiyuan Formation to the upper Shihezi formation are from the quartz sandstone to the lithic sandstone,and finally the lithic feldspar sandstone.The rock types in the Huanglong area are dominated by lithic sandstone and lithic feldspar sandstone,and the overall trend is that the feldspar content is increasing.The overall maturity of the sandstone in both regions is lower in maturity and maturity.The reservoir space is mainly composed ofintergranular dissolution pore,followed by inter-granular pores and iintergranular dissolution pore.(2)The Huanglong area's Shiqianfeng Formation,the Lower Shihezi formation and the Yichuan area's Shanxi Formation are relatively well-defined horizons of permeability,and the pore permeability of the Huanglong area is better than that of the Yichuan area.The pore structure parameters of sandstone reservoirs in the study area are poor.According to the Changqing Oilfield Exploration and Development Research Institute for the Yulin gas field in the second paragraph of the reservoir classification evaluation criteria,mainly belong to class ? reservoir.(3)The sedimentary facies of the study area in different strata are mainly composed of delta facies.In the sedimentary micro-facies with relatively strong hydrodynamics such as diversion channel and estuary dam,the composition maturity and structural maturity of sandstone are relatively high,and the inter-granular pores will be developed and the permeability of sandstone will be higher.The foreign matter content is relatively small and the compaction is relatively weak.Pore water is easy to flow.The inter-granular cements are relatively less precipitated,which is conducive to the preservation of inter-granular pores and the formation of dissolved holes,is conducive to the formation of a good reservoir.(4)The source of the rock characteristics of the control,the performance is: a)The tectonic action leads to the transformation of the source from the northern part of the basin of the Taiyuan Formation to the northern Qinling area.The early distant source sedimentary quartz content is more,sorting,grinding round degree is good;Shanxi group began to near-source deposition,quartz content reduction,sorting,grinding round degree deterioration,feldspar and cuttings increased.The composition of cuttings is mainly composed of metamorphic rocks in Benxi and Taiyuan,and the post-igneous rocks are increased.b)Shanxi group and its later strata are the North Qinling area,however,in the Yichuan area,the early period is the Taowan group,and later due to the formation of erosion,material source into the North Qinling source,feldspar content increased.However,the source of Huanglong area is closer to the North Qinling belt and Taowan group.In general,feldspar is rich,and because of the adjacent Yanshanian granite,igneous rock gradually formed the main cuttings.(5)The diagenetic effects of sandstone in the study area affect the reservoir property: The dissolution is a constructive diagenetic effect,destructive diagenesis includes compaction,siliceous cementation,formation of carbonate minerals,formation of hydromica and chlorite.Therefore,these effects are the main cause of the decrease in porosity.