Study On Remaining Oil Potential And Potential Tapping Scheme Of Yan 9 Low Permeability And High Water Cut Reservoir In Jingbian DW Area

Although most of the oil fields where developed by water injection in China have entered the high water-bearing stage or even the very high water-bearing stage,the remaining oil reserves is still very considerable,especially in the low-permeability oil fields where about 2/3 of the remaining oil reserves remain underground and cannot be extracted,showing the characteristics of“highly dispersed overall and relatively enriched locally”.The remain oil with the long-term water injection development method is affected by reservoir non-homogeneity,deposition positive and negative rhythm,non-corresponding injection and extraction relationship,imperfect well network,bottom water cone in,etc.The distribution of the remaining oil is more complicated.Therefore,figuring out the main controlling factors and distribution laws of remaining oil in low-permeability and high-water-cut oilfields,and proposing scientific and reasonable precise potential tapping countermeasures,has strong guiding significance for the potential of remaining oil in the same type of oilfield which is tapped.In this article,we focus on the problems of high water cut,complex distribution of remaining oil and difficulty in accurate potential tapping after long-term water flooding development of low permeability reservoirs with bottom water development in Yan 9side of Yan an Formation in Jingbian DW area.We make use of fine reservoir description technology and reservoir engineering method to study the geological characteristics of Yan 9 reservoir development from both macro and micro aspects,including micro structure,sedimentary microfacies and sand body distribution,micro pore throat characteristics and oil and gas enrichment law.On this basis,we analyze the development characteristics of Yan 9 reservoir,and evaluate the effect of water injection development from nine aspects,such as water flooding control degree,water flooded well characteristics,pressure maintenance level,etc.,to find out the main factors affecting the effect of water injection development.We use the material balance method to calculate the distribution of remaining oil reserves in DW area,and divide the single well according to the formation coefficient,clarify the plane and vertical distribution characteristics of remaining oil,study the main controlling factors of remaining oil distribution,and use the inter-layer and plane distribution characteristics of remaining oil to divide the remaining oil types.We put forward precise tapping measures for different types of remaining oil,and carried out on-site operation of precise tapping of remaining oil.The achievements and conclusions are listed as follows:(1)The overall micro-structure is dominated by monoclinic,and on this basis,multiple rows of nose-shaped uplifts with large amplitude are developed,which control the distribution of oil and water;(2)Yan 9 reservoir is a fluvial facies sedimentary system,which develops two microfacies of channel microfacies and floodplain microfacies;(3)Yan 9 reservoir mainly develops large and medium pore coarse throat,medium pore and coarse throat;(4)Yan 9 reservoir is a structural-lithologic reservoir driven by edge and bottom water,and the activity of edge and bottom water is low;(5)The remaining geological reserves of Yan 9 reservoir is 497.81×10~4t calculated by volume method,and the average remaining geological reserves of single well is 2.45×10~4t,which shows that the reservoir has great development potential;(6)The causes of remaining oil can be divided into single layer remaining oil,double layer interlayer remaining oil and complex multi-layer inter-layer remaining oil;(7)According to the different types of remaining oil,the key points of precise tapping potential are different.Through corner well injection,perfect injection-production correspondence,precise hole filling and other measures,the direction of liquid flow can be achieved to achieve the purpose of precise tapping of remaining oil;(8)The implementation of the on-site scheme proves that the recovery factor of the reservoir after water flooding development can be greatly improved by carrying out precise potential tapping of remaining oil.Compared with the test wells before the measures,the average daily oil production of the test wells increases by 215%,and the comprehensive water cut decreases by 11.5%on average.The ability of potential tapping measures to reduce water and increase oil has been further verified.