Polymer Flooding Mathematical Model Algorithm Improvement And Application

The process of oilfield development is based on detailed detection results and productionpractice information, in order to improve the recovery ratio, which is on the basis of makeimplementation strategies for master plan of oilfield development and the whole procedurefrom first start to the development eventually end. Daqing Oilfield is the largest onshoreoilfield in China, after primary oil recovery and water flooding extraction secondaryexploitation, has been in the later period of the development of water flooding extraction andthe oil output reduced gradually these years. During constant production practices andlong-term technical research in China and abroad, Chemical Flooding method is determinedto be the core technology, according to the practical situation of tertiary recovery in DaqingOilfield. Since the Polymer Flooding technology was putted into industrial application in1996, the oil production output level has been keeping at10million tons and the cumulativeproduction is over1billion tons. Recently, Daqing Oilfield chemical flooding technologyleads the development tendency all over the world, which contains Experimental Theoryresearch and cognitive degree of Oil displacement mechanism. And that for the past few yearsPolymer Flooding is developing rapidly, and has become the major replace technology ofmaturing onshore oilfields in China.Because oil reservoir is important non-renewable resource, the development process isnonreversible which has properties of high technology, high cost and high risk, and thecharacteristics of polymer flooding trigger it to be more complex changeable than otherConventional development methods. Oil reservoir numerical simulation is such a keytechnology which can help to make the important decisions of oilfield development in thestrict scientific way. The simulation software based on previous method is used to numericallysimulate the possible process from the very beginning to the end of oilfield development inthe corresponding plan and future reservoir production performance can be predicted by thesimulation software, too. So Numerical Simulation Technology turns into an important tool inthe reservoir development process, and the oil reservoir mathematical model can supplydynamic descriptions and solutions for the real reservoir development. Optimal fielddevelopment programs are selected by relevant reservoir numerical simulation computing results, in order to reduce the development risk and greatly save the cost. Because of polymerflooding numerical simulation methods is widely used in the production practice of DaqingOilfield, the original polymer flooding numerical models are unable to meet the requirementsof intraday variations, so this paper provides an improved model with pinch out areasprocessing methods, in order to achieve the purposes of simplified calculation, calculationaccuracy improvement and test and verify the idea by programs.Lot of pinch out areas exists in the oil deposit, and these is no description function in theoriginal polymer flooding mathematical model,, so a large number of redundant computinggives rise to reduce the computing speed and the accuracy of the results. This paper improvesthe original solving method of polymer flooding mathematical models, enables the pinch outarea description function. Concrete realization method in this paper is that using samemathematical model and numerical format in and other normal area, pinch-out area isprocessed as an irregular boundary problem of the partial differential equation, preprocessingaccording to the property of gamma free flux in pinch out area numerical model solvingprocess, and realizing pinch out area description function exactly in the model.This paper also uses conservation of mass equations as its basic mathematical model.The model solution is that the pressure equation, saturation equation and chemicalcomponents concentration equation are deduced by mass conservation of equation first. Thenthe reservoir physical chemical property is described accurately from three aspects. Thepressure equation is parabolic form, which is difference by seven center difference schemediscrete general form. The saturation equation is realized by using upstream sort and implicitexpression upwind scheme Newton Iteration method. The concentration equation is divide todiffusion item and convection item by using operator splitting method according todominance, the former is computed by implicit expression upwind scheme and upstream sortmethods and actually has explicit advantages by using this strategy, the latter is calculate incrisscross finite difference form. The numerical simulation model is divided into five differentparts by previous method. At the end of this paper, the points mentioned above are proved tobe right and proved to excellent by four cases. The paper provides a reliable scientific basis toDaqing oilfield polymer flooding production process and development plan selection and alsomakes is possible to predict development effects and proceed mechanism research.