Study On Reservoir Evaluation Of T₁f In Lei Yinpu?QiLixia Structure

With the deepening of oil and gas exploration,more and more carbonate reservoirs have been discovered.However,due to the fact that carbonate reservoirs have a long period of burial,experienced complex structures and diagenesis,leading to a strong heterogeneity of reservoirs,it is very difficult to adjust gas reservoir development schemes,stable production,water control and recovery.So it is very necessary to evaluate carbonate reservoirs from aspects of petrological characteristics,types of reservoir space,and spatial distribution of reservoirs in order to use the evaluation results in the exploration and development of oil and gas fields.In this paper,the T₁f of LeiYinpu-QiLixia structure in the northeastern Sichuan Basin is taken as the research object.The reservoir is evaluated by using existing core,cuttings,physical property analysis,thin section identification and high-pressure mercury injection.It is found that there are many types of rocks in the Feixianguan Formation reservoir in the study area,including granular dolomite,grain dolomite,dissolved pore Oolitic Limestone and mud fine powder grainite,and the transition rocks between them.The reservoir space of Feixianguan formation includes pores,fractures and a small number of karst caves.The main fractures are structural fractures,diagenetic fractures and structural dissolution fractures.Through the analysis of the thin sections,physical properties,cores,and cuttings of the castings,it can be known that the reservoirs in the T₁f Formation of the study interval are not only affected by sedimentation and diagenesis,but also controlled by tectonism.According to the display characteristics of high-pressure mercury intrusion data,reservoirs can be divided into? types from the microstructure.Among them,the first type of reservoir is the best reservoir in the T₁f Formation of the study area,and the proportion is relatively large.It mainly develops in fine-crystalline dolomite and fine-powder-crystalline relic-ooid dolomite.The pore type is mainly composed of intergranular dissolution pores-intragranular dissolution pores-intergranular dissolution pores.The pore throat is relatively thick,the throat is mainly necking throat,and there are few tubular throats;The proportion of type ? reservoirs is smalland it is less than 10%.It mainly develops in fine-grained dolomite and calcite dolomite,the pore type is mainly composed of dissolution joint-dissolution hole-intergranular dissolution hole,which is characterized by medium-fine pore,coarse-thin and fine throat.The throat mainly consists of some sheet-like tunnels and constricted tunnels.The type ? reservoirs are mainly developed in calcite dolomite and fine-powder-crystalline relic-ooid dolomite.The pore type is mainly composed of dissolved pores and intergranular pores.The medium-fine pore throat and throat are mainly tubular throats,and a few throat throats.The type ? reservoirs account for a large proportion,close to 30%.This type of reservoir is mainly developed in dolomitic oolitic limestone,calcite dolomite,and fine-grained dolomite,the pore types are mainly matrix micropores,some intercrystalline micropores,and small pore throats;The type? reservoirs are mainly developed in dense muddy limestone,muddy mudstones,mudstones,and oolitic limestones.The pore types are mainly matrix micropores,with small pore throats and poor reservoir capacity.Due to the fact that the drilling interval in the work area is not only completed at a large interval and the T₁f Formation are just Crossing wells,it is lead to the well logging interpretation results,cores,cuttings,physical properties,and rock analysis tests of some wells are relatively lacking.In order to evaluate the target region of the entire region,using the existing logging interpretation results,combined with the drilling data,a stepwise identification procedure in the mathematical geology method was used to qualitatively identify the reservoir and non-reservoir.The discriminant functions of reservoir and non-reservoir were established respectively.The discriminant coincidence rates were 84.58%and98.69%respectively,and the total discriminant coincidence rate was 94.09%.Apply this function to quantitatively analyze the thickness of the entire reservoir.It is not difficult to see from the statistical results that the T₁f Formation reservoir in the study area has a distribution in the T₁f¹ to the T₁f³,and there is almost no reservoir distribution in the T₁f⁴.Combining the classification criteria for carbonate reservoirs in the Sichuan Basin,the reservoirs with porosity greater than 12%were classified as the type I reservoirs,and those with porosity between 6%and 12%were the type ? reservoirs.Reservoirs with a porosity of between 2%and 6%are the Type ? reservoirs,and those with a porosity of less than 2%are the type ? reservoirs.The training samples with the interpretation results of the well formation segment as the reservoir type identification use multiple discriminant functions to qualitatively discriminate well segments in the region without log interpretation results.Judging from the results of the discrimination,the T₁f Formation in the region is dominated by the type ? reservoirs,and it develops in the first segment of T₁f Formation to the third segment of T₁f Formation.The thickness of the reservoir varies greatly,ranging from a few meters to several tens of meters;the type ? reservoirs are rarely developed and are mainly distributed in the central and southern part of the project area.The maximum thickness is only about 10 meters.The type I reservoir is sporadicly developed,with only wells such as Qili 8and Qili 28 developed,and the thickness is only a few meters.From the relationship between reservoir type and drilling display,wellbore and gas leaching appear in most wells of the type I and the type ? reservoirs,the type ? reservoirs show no obvious,and the type ? is non-reservoir.