| The class â… reservoirs in the Lamadian oilfield of Daqing has all been transferred to subsequent water flooding after polymer flooding since it was put into operation. The class â… reservoirs have been in the high water cut, high recovery rate degree, and recoverable reserves are decreasing day by day. In order to further enhance oil recovery, the class â…¡ reservoirs begin to expand polymer flooding in 2007. Compared with the class â… reservoirs, the class â…¡ reservoirs have the characteristics of thin layer thickness, low permeability, strong heterogeneity, small river sand development scale, poor connectivity of sand body, and so on. Particularly, a series of changes in pore structure, fluid distribution, reservoir physical property parameters have been produced in the reservoirs, which has experienced a long period of water flooding into the high water cut stage. These changes of reservoir and fluid parameters not only affect the storage layer of fluid motion state, but also lead to formation of the ineffective circulation in reservoirs. It makes the reservoirs enter into the high level water flooded and the injection water into a single trend, so as to reduce the vertical and horizontal sweep volume of the injected water. Through the intense adjustment of the oil and water wells in recent years, polymer flooding in class â…¡ reservoirs has achieved good development effect. But there are still some problems such as reservoirs are unbalanced used, and polymer injection amount is large, tons of polyethylene increased amount of oil is low, the development efficiency is poor. Polymer flooding development methods of the class â… reservoirs are not applicable to the class â…¡ reservoirs. To study remaining oil and ineffective circulation distribution characteristics, formulate adjustment countermeasures to produce remaining oil and control ineffective circulation, is of great significance to improve the polymer flooding oil recovery, control ineffective circulation, further produce remaining in class â…¡ reservoirs.According to the actual situation of the class â…¡ reservoirs of B block in the Lamadian oilfield, this paper analyzes the factors influencing the ineffective circulation of dynamic and static and selectes the main factors affecting the formation of ineffective circulation by the use of gray collection. Based on the well logging data, a method of dividing flow units of ineffective circulation is introduced. The same flow units have similar sedimentary characteristics, and have similar hydrodynamic characteristics. Use the PETREL software to model the block’s geological model, and use Eclipse software to simulate the development of water flooding and polymer flooding stage. According to the results of numerical simulation, through the division of flow unit and formation time of the ineffective circulation, we get the characteristics of the ineffective circulation where are easy to form during polymer flooding in the class â…¡ reservoirs. The application of this method to the study of the class â…¡ reservoirs is more deeply than the simple research from the sedimentary characteristics. Different types of flow units correspond to different ineffective circulation and remaining oil distribution characteristics. It provides a more convenient way to achieve the fine description of the reservoirs and realize the combination of static and dynamic data to determine the formation of ineffective circulation and take effectively appropriate adjustment measures to exploit other class â…¡ reservoirs. |
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