The Economic Low Limit Research Of Extra-Low Permeability By Hydraulic Fracturing

As the petroleum industry highly progresses, marketable and effective development of petroleum seems quite important. Currently, accumulated proved oil reserves of China is 212.89×108t, accumulated proved reserves of low permeability oil reservoir is 90.97×108t, which is about 43 percent of the whole. It's obvious that low permeability oil reservoir resources play an important role on resource strategy. And as petroleum exploration degree deepens gradually in the future, ratio of low permeability oil reservoir resources to the whole is increasing continuously. After reformation and opening, requirement of petroleum energy in internal increases day by day, and in recent years, the changes and development of international state are mainly caused by the ownership of petroleum energy in great extent. Therefore, it's quite necessary for us to master the abilities of developing domestic energy in order to adapt the needs of public financial development. As for low and extra low permeability oil and gas reservoirs, right now there are two effective developing styles internationally, one is drilling horizontal well and drilling multiple branch well, however, the cost of this method is relatively high; the other is hydraulic fracturing and acid reconstructing of low and extra-low permeability oil and gas reservoirs, which can in utmost promote output of single well and decrease developing cost as well as promote developing effectiveness. The method of developing extra-low permeability oil reservoirs by using fracturing is studied in this paper. Hydraulic fracturing goes through more than 50-year's development, arranging from single well fracturing to whole fracturing then to developing fracturing. Developing fracturing is the further development of fracturing technique in the recent years, through which optimally constitutes developing pattern system and fracture system of low permeability oil reservoirs in the purpose of improving producing rate and produced degree and decreasing the cost of investment, furthermore, improving the usable degree and developing level of low permeable hard usable reserves, and developing fracturing is an important components of low permeability oilfield developing plans. It's one of key techniques for high-effectively using and developing and producing extra-low permeability oil reservoirs to study and know extra-low permeability oil reservoirs and to establish optimal constitute of patterns and hydraulic fracture. Optimization of developing patterns of extra-low permeability oil reservoirs, selection of pattern density and optimum of hydraulic fracture system are studied concretely in this paper. And production forecast method of fracturing reconstruct as well as financial evaluation of fracturing reconstruct of extra-low permeability oil reservoirs are proposed in this paper. It shows that as for extra-low permeability oil reservoirs, rectangular pattern with high-accumulated production, large economic net present value and short payback period is suitable to extra-low permeability oil reservoirs. And through correlation, as for extra-low permeability oil reservoirs, effect of fracturing reconstruct is most positive when penetration ratio of hydraulic fracture is 0.8. And under this standard, developing and usable inferior limit of extra-low permeability oil reservoirs is given as well. While, long conductivity and threshold pressure are two keys to extra-low permeability oil reservoirs, and the two keys can influence the production and financial benefit. Finally, some instructive conclusions and proposals are worked out.