Research On Profile Control And Flooding Of Polymer-Weak Gel In Thick Layer Of Conventional Heavy Oil Reservoir At High Water Cut Stage

The in-depth profile control method, an important measure to develop the intraformational remaining oil in thick layers, has boomed in recent years. However, due to the complex rhythmicity and structure, the mature interlayers, and the great change in formation parameters during developement, the effect of profile control becomes worse and worse, which indicates that the adopted measure can not adapt to the exploitation of intraformational remaining oil in thick layers. Therefore, aimed at the characteristics of thick layers and performance of heavy oil development, it is of great value to research the law of profile control and flooding of polymer-weak gel in thick layers for conventional heavy oil reservoir.Based on the consideration above mentioned, aimed at the defects of the profile control and flooding in thick layers for conventional heavy oil reservoir, and the distribution mode of interlays in thick layers, physical experiment of production performance in thick layers at high water cut stage is firstly carried out. with the consideration of the mechanism of polymer-weak gel flooding and the distribution mode of interlayers and the remaining oil, the reservoir numerical simulator is improved and programmed. Then the mechanism of polymer-weak gel profile control in thick layers at high water cut stage is studied. And finally, a set of methods is presented to tap the remaining oil in thick layers at high water cut stage. There are mainly four parts included in the paper:(1) Experiments of polymer-weak gel flooding in conventional heavy oil reservoir.Based on the similarity theorem, with the consideration of formation, fluids and performance, the physical model and working conditions for water, polymer and weak gel flooding in thick layer are designed, and then the experiments are carried out. Firstly, with the one dimensional long core experiment, characteristic parameters and flooding mechanism of polymer-weak gel are obtained. Then, the distribution of remaining oil in section model and stratified model under the three dimensional homogeneity and heterogeneity conditions are quantitatively studied and flooding mechanism is also studied. It is indicated that the interlayers have a tremendous impact on the effect of profile control and flooding.(2) Mathematical model and programming for the three dimensional three phases and six components polymer-weak gel flooding.Based on the experiments, with the consideration of some mechanisms such as adsorption, viscosifying, most importantly, the threshold pressure gradient, etc. of polymer and weak gel, the three-dimension, three-phase, six-component mathematical model and difference model are built. And then the numerical simulator is programmed and compared with the softwares ECLIPSE, GRAND to verify the correctness and rationality of it. It is found that the calculated results of the software can match those of the softwares above mentioned to some extent. Besides, the software can simulate the flooding process on models at core size and block size level, and can reappear the flooding process of water, polymer and weak gel flooding.(3) Law of in-depth profile control and flooding in thick layers of conventional heavy oil reservoir.With the numerical simulation software, the experiment results are firstly matched, and then a typical model is built. Based on these, the law of profile control and flooding of polymer-weak gel in thick layers is studied from the aspects of formation characteristics, fluid properties and agents, and then the mechanism and magnitude of some influencing factors such as location and seal of interlayers, rhythmicity, heterogeneity, viscosity, and plug parameters of polymer and weak gel are quanlitatively and quantitatively studied. Finally, the reference standard for the reservoir engineering design of profile control and flooding in thick layers is achieved.(4) Field application.Based on the researches above mentioned, the profile control and flooding is applied in the exploitation of remaining oil in Gudao oilfield, a conventional heavy oil reservoir with oil viscosity 70 mPa·s. the scheme of profile control and flooding are firstly designed and satisfactory results are obtained .