Study On The Remaining Oil Distribution In The Morichal Section Of The Super Heavy Oil Reservoirs In MPE3 Block,Venezuela

The rapid development of China's economy has increased the dependence on crude oil,which makes the oversea blocks become the important production areas for exploration and development.The Orinoco heavy oil belt in the southeastern part of the Venezuela Basin is currently the world's largest and least developed petroleum enrichment zone.The MPE3 block has been operating since 2006.Up to now,the horizontal well recovery rate is only 2.5%,and a large amount of remaining oil remains underground.The remaining oil problem in the ultraheavy oil reservoir is unclear.It is imperative to carry out research on its main controlling factors and distribution characteristic to improve the production effect of horizontal well.Based on the study of braided river reservoir architecture,dynamic analysis of super-heavy oil reservoirs and reservoir numerical simulation,the paper studies the main controlling factors and distribution characteristic of remaining oil in super-heavy oil reservoirs and obtains the following understanding:(1)The fluids of Venezuelan super heavy oil reservoir exhibit “foamy oil” characteristics in the development process.The driving force for production includes the force caused by the producing pressure and the gravitational differentiation of oil and gas.In the early stage,the development effect of horizontal wells was relatively good with the high oil recovery rate and the lower gas-oil production ratio.The horizontal well cold recovery rate is calibrated by 9.62%.(2)The relative permeability curve of the zones and chemical equation of the foamy oil were used to improve the accuracy of numerical simulation of the super-heavy oil reservoir.It is considered that the seepage law of underground fluids is controlled by the internal structure of the sand body of the reservoir and the gravitational differentiation of oil and gas.Longitudinally,the remaining oil which in the lower part of the reservoir,place of architecture interface and reservoir heterogeneity is relatively rich;the remaining oil rich-area on the plane is distributed in strips including the area of main sand body,horizontal wells and faults that are not coupled.The accumulation of remaining oil in the single sand body is mainly distributed in the contact zones of different sand bodies such as braided bar,flood plains,and braided channel sand bodies.(3)It is pointed out that the internal structure of the reservoir is the main geological factor controlling the distribution of remaining oil in the study area.Different levels of reservoir interface affect the gravity differentiation of oil and gas,and lead to the accumulation of remaining oil.The interfaces and architecture units of different genetic types constitute the heterogeneity of the reservoir and affect the enrichment of remaining oil.The characteristic parameters of horizontal wells are the main engineering factors affecting the distribution of remaining oil,including the location of horizontal wells in reservoirs and the spacing between horizontal wells.The distribution of formation pressure between horizontal wells and rows,and the uncoupling of horizontal well patterns and faults are also important factors in controlling the remaining oil in the study area,which result in local enrichment of the remaining oil.