Study On The Effect Of Early Injection On Increasing Heavy Oil Reservoirs At Sea

Bohai heavy oil reservoirs is characterized by high permeability, thick oil reservoir, well spacing and serious non-homogeneous, Water recovery is less than20%. Under the guidance of new model for developing offshore oilfields and the limited of the offshore environment and characteristics of offshore development, it is formed a recovery technology by polymer flooding in Bohai oilfield.The early polymer flooding is applied on Bohai oilfield in the view of offshore platform life limitation and the investment risk and have achieved a good development result. Therefore, for improving the effect of offshore oilfields development and shorten the development cycle effectively, it requires further analysis of the main factors which affect the early injection.Properties of polymer solution, injection pattern and reservoir conditions are major factors which affecting polymer flooding. Combining the characters of reservoirs in SZ36-1oilfield, study on the polymer properties of hydrophobically associating polymer HAWP and the linear polymer HPAM first, investigate the percolation capacity and oil-displacement capacity in high-permeability heavy oil reservoirs. The results show that different properties of polymer solutions in which enhanced oil recovery have significant differences. Study on the displacement efficiency of HAWP and HPAM under the same conditions of development cycles in different injection timing. It is showed that when the injection time of HPAM and HAWP is0.141PV and0.203PV, respectively, the ultimate recovery is the highest. It came to a conclusion that the HPAM is only can shorten the development cycles while the HAWP not only shorten the development cycle but also increase ultimate recovery effectively. Therefore, HAWP solution of high flow control capabilities and can significant enhance the effects of early injection under the condition of high-permeability heavy oil reservoirs.Investigate the effect caused by concentration, injected slug, and non-homogeneous respectively to the displacement effective of HAWP solution after0.203PV water flooding. In the Concentration of2000mg/L with the same polymer dry powder (525mg/L-PV) has a best early polymer injection. The larger the polymer slug is, the best effect in early polymer injection when the viscosity of polymer solution is same as crude oil. Compared to the high water-containing polymer flooding, early polymer injection has a better flow control capabilities, and improved the injection profile, increasing the displacement effect in non-heterogeneous reservoirs. Early polymer injection in the reservoirs with high-permeability, high viscosity crude oils, and serious non-heterogeneity, using high flow control capability polymer help to improve the effect of polymer flooding in heavy oil reservoirs, and reducing risk while shortening the development cycle. According to the flow control requirements, under the same injection concentration, expanding the slug can improve the effect of heavy oil reservoirs with serious non-heterogeneity and lay a foundation for efficient development of heavy oil reservoirs.