Study On Division Method Of Tight Reservoir

Tight oil has become a hot spot in recent years,but its reservoir properties are poor,the pore and throat are narrow,and the area of single reservoir is small.Therefore,it is of great productive significance to evaluate the tight oil reservoir and to establish the classification standard of tight oil reservoir.In addition,the degree of fracturing of the tight oil reservoir greatly determines the production of the oil and gas,and the brittleness of the reservoir determines the degree of difficulty of fracturing.Therefore,the introduction of brittle index in the classification of tight reservoir is very important for the efficient exploitation of tight oil.In this study,the sedimentary characteristics,lithology and physical properties,the characteristics of micro pore throat,oil production capacity and brittle characteristics of tight oil reservoir are analyzed.The following results are obtained:(1)The study area is mainly fan delta deposition,and the reservoirs formed in different sedimentary environments have different physical properties.The results show that the porosity and permeability of the reservoir formed in the environment of former delta and shallow lake mud have not changed greatly.On the contrary,the porosity and permeability of the reservoirs formed in the environment of front sand sheet,channel mouth bar,offshore bar and distributary channel changed greatly.(2)Based on the experimental analysis,the mineral composition of the reservoir in study area is mainly plagioclase,and the next are quartz and potash feldspar.On the basis of logging data,the lithology of the study area is classified as mudstone,silty mudstone,argillaceous siltstone,siltstone and carbonaceous siltstone.By comparing the accuracy of the plate,finally,the intersection method of natural gamma and resistivity is used to identify the lithology of the study area.(3)In this dissertation,the method of capillary pressure curve,nuclear magnetic resonance and slice observation were used to study the characteristics of microscopic pore throat.The comprehensive performance of the tight reservoir in the oilfield of Daqingzi well is that the permeability is less than 1mD,the radius of pore throat is less than 0.4?m,the peak value of bound water is large,and the peak value of movable fluid is small.It reflects the poor fluidity and poor reservoir property.According to the slice observation,it is known that there are intergranular pores,dissolved pores,micropores and fractures in the reservoir of the target layer.Among them,intergranular pores are the most important primary pores,which are developed in each sand group of the target layer.(4)On the basis of previous studies,the tight reservoir of the study area is divided into three categories by optimized parameters such as physical property,capillary pressure characteristics,sedimentary facies,pore structure and brittleness index.The porosity of type I reservoir is more than 10%,the permeability is from 0.6 to 1mD,the displacement pressure is from 0.8 to 1.4MPa,the brittleness index is between 43% and 47.5%;The porosity of type II reservoir is from 8 to 10%,the permeability is between 0.4 and 0.6mD,and the displacement pressure is between 1.4 and 2.5MPa,and the brittleness index is from 44 to 50%;The porosity of type III reservoir is less than 8%,the permeability is less than 0.4mD,and the displacement pressure is greater than 2.5MPa,the brittleness index is from 46 to 52%.