Study On The Seepage Rules And Numerical Simulation Technology Of Low-permeability Reservoirs In Daqing Oil Field

It is important to develop low-permeability reservoirs effectively inorder to increaserecoverable reserves and keep the stable production target of40million tons annually in DaqingOil Field. Study on the seepage rules and numerical simulation is the basis and key technicalmehod. In this thesis“Study on the Seepage Rules and Numerical Simulation Technology ofLow-permeability Reservoirs in Daqing Oil Field”, untabulated reservoirs inLamadian-Saertu-Xingshugang oil field and low-permeability reservoirs in the peripheral oilfields are the objects of study. The variation rules of the starting pressure and the characteristicsof relative permeability curves are obtained through a great deal of cores data statistics andlaboratory experimental study. On this basis, a fully implicit numerical simulation model and amathematical model for nonlinear seepage considering both starting pressure andcompression-sensitivity are developed. The nonlinear seepage simulation function for low-permeability reservoirs is carried out using the DQDual software which is self-developed byDaqing Oil Field for naturally fractured reservoirs. The simulation function is proved by aconceptual model and applied to some blocks in Daqing Oil Fields. Here are the main results:1）The data statistics and laboratory experimental study for the cores of untabulatedreservoirs in Lamadian-Saertu-Xingshugang oil field and peripheral low-permeability reservoirsare anylized. The results show that starting pressure and compression-sensitivity presents in thetwo types of reservoirs. The compression-sensitivity increases when the permeability is lower.Besides, there are some common characters in the relative permeability curves that theirreducible water and residual oil saturation are high, the oil-phase curve drops fast while thewater-phase curve increases slowly showing a character that the curve is concave to thesaturation axis.2）Based on the lab experimental results, we develop a three-dimensional and three-phasenonlinear seepage mathematical model, derive a fully implicit numerical model, and develop awell-grid flow equation for nonlinear seepage and the matrix including calculation formula forevery coefficient. Both starting pressure and compression-sensitivity are considered when all ofthe work above are carried out. The process of establishing the mathematical model anddeveloping the solution method is the mathematics basis for studying numerical simulation inlow-permeability reservoirs.3） DQDual1.0software is a numerical simulator for naturally fractured reservoirs ofDaqing Oil Field. By analyzing the source code, we modify and insert some modules and thendevelop a nonlinear numerical simulator DQDual2.0which can simulate starting pressure andcompression-sensitivity. The simulation result is tested by conceptual models and proved to bereasonable. So, the simulator is suitable for developing low-permeability reservoirs.4） The research results are applied in developing the untabulated low-permeabilityreservoirs in Lamadian-Saertu-Xingshugang oil field and the thin and poor reservoirs. Thenrecovery efficiency from different combined developing methods is presented. The history fittingprecision of the actual block application can reach87%in peripheral reservoirs of Daqing OilField.The studying content and result can help to make clear the seepage rules of thelow-permeability reservoirs in Daqing. An effective numerical simulation model which issuitable for developing peripheral reservoirs is developed to reflect the development laws oflow-permeability reservoirs. The studying result offers some theory basis and direction for thestudy of developing low-permeability reservoirs. It also offers the technique for makingdevelopment plans and predicting development effect. So the study has important theoretic valueand application foreground.