The low-permeability project team observed the core in the field
At present, China's low-permeability oil reserves have reached 6 billion tons, with an annual output of nearly 40 million tons, accounting for almost half of the total output of China's crude oil, which has become an important pillar of the sustained and steady development of China's petroleum crude oil production. The reservoir faces many bottleneck technical problems such as poor reservoir conditions, high heterogeneity, prominent water-driven displacement, difficulty in establishing an effective displacement system and low oil recovery.
To this end, starting from the 11th Five-Year Plan, the research team for the development of low-permeability reservoirs of the China Petroleum Exploration and Development Research Institute relies on major national special projects and persists in the long-term work in such fields as Changqing, Qinghai and Xinjiang. Theoretical basic research and a large number of physical workloads. After nearly 10 years of hard work, a breakthrough has been made in the technology of waterflood recovery enhancement for low-permeability reservoirs, forming a series of major innovations with world-leading level. The field application With remarkable results. The research results won the first prize of the 2017 Scientific and Technological Progress Award of China Petroleum and Chemical Industry Federation.
The project is mainly completed by Song Xinmin, Tian Changbing, Hou Jianfeng, Lei Zhengdong, Wang Youjing, Wang Wenhuan, Long Guoqing, Li Jun Shi, Huigang, Peng slowly, Hu Yafei, Wang Fang, Zhao Hui, Li Jiahong, Qin Yong and so on.
It is very difficult to improve the recovery efficiency of waterflooding in low permeability reservoirs. The key problem is that the understanding of the characteristics of underground reservoirs and the distribution of remaining oil is not clear enough. It faces four technical challenges: first, in multi-scale fractures of low permeability reservoirs, The theory of traditional water flooding seepage is poorly adapted for micro-scale seepage, and water-flooding and seepage theory are urgently needed in low-permeability reservoirs. Second, natural fractures in low-permeability reservoirs generally require fracturing, fracture systems and matrix sand bodies It is difficult to understand how to recognize and characterize the heterogeneity of reservoirs. Thirdly, the multi-scale fractures and matrix microscale effects of low-permeability reservoirs play a dual role in the long-term In the process of water injection and fracturing, the stress field changes obviously, resulting in complicated flow of oil and water. The traditional dual medium model and software have poor adaptability. Numerical simulation methods and software to adapt to low permeability reservoirs are urgently needed to improve the precision of the remaining oil and development schemes. Reliability; Fourth, the old seam network has been developed unreasonable configuration, the lack of effective rational water injection technology policy optimization methods, the urgent need to develop the establishment of The same type of well pattern adjustment of oil wells, research and formulate a reasonable water injection technology policy, to achieve continuous and effective displacement of low permeability reservoirs and maximize volume.
In view of the above technical challenges, the research team of the low permeability reservoir development of the China Petroleum Exploration and Development Research Institute aims at expanding the volume of water flooding and forming a continuous and effective displacement, deepening the rational matching of dynamic fractures and seam networks in low permeability reservoirs, Homogeneity and water flooding, realizing the transformation from basic well pattern to rational well pattern, conventional water flooding to fine water flooding and establishing the concept of three developments of displacement to continuous flooding, and achieved important international leading The level of innovative technological achievements.
The team explored the establishment of a dynamic seam identification and characterization technology.For low permeability reservoirs, the concept of dynamic seam was first proposed, and a dynamic seam identification plate was established, its formation mechanism and control factors were clarified, and based on lithofacies and multifractal , And established a geological modeling method of discrete fracture network with multi-attribute constraints such as rock mechanics, in-situ stress and phase-controlled matrix heterogeneity, and provided technical support for accurate prediction and quantitative characterization of dynamic fracture.
The numerical simulation of dynamic slot in low permeability reservoirs has been innovated, a multi-medium flow model based on flow matrix and dynamic discrete fractures has been established, a dynamic unstructured grid technology has been established and a flow-based adaptive fine grid technology , The simulation time is greatly saved, the strong coupling model of seepage field and stress field and the dynamic discrete three-dimensional fracture model are established, the low permeability dynamic discrete fracture numerical simulation software with independent intellectual property rights is developed, and the dynamic fracture extension and expansion process Fine simulation greatly improves the accuracy and reliability of residual oil quantification and forecasting of development scheme indicators and reduces the risk of well pattern adjustment.
The paper has developed and established a pattern of well pattern adjustment for different types of reservoirs, deepened understanding of waterflooding laws in low-permeability reservoirs, clarified three major types and six regularities of remaining oil distribution in low-permeability reservoirs, Control degree and the ratio of multi-directional waterflooding to realize the reasonable match between dynamic fracture and well pattern. By using the lateral displacement of dynamic fractures to expand water flooding and volume as the core goal, the well pattern of network optimization is developed, and the low permeability reservoir Different patterns of well pattern matching for well matching provide a solid foundation for the development and adjustment of water flooding in low permeability reservoirs.
Developed a reasonable waterflooding technology policy.According to the deepening understanding of reservoir heterogeneity and water-driving conditions in low-permeability reservoirs, the principle of "one-third control" was proposed, and the types of sub-reservoirs , Established a fine sub-standard; put forward the optimization of "waterflooding" to "efficient and efficient waterflooding" transition, "avoidance" to "rational use and control of seam" optimization, and established the optimization diagram of low permeability reservoir water injection policy , Developed a reasonable water technology policy boundaries.
Nowadays, the technical tackling of this project is combined with the actual production of oilfield. The research results have been popularized and applied in a number of oil fields such as Changqing Ansai, Nanliang, Jidongnanpu and Tuhajianshan, and the waterflood recovery has been improved by 3-8 A new percentage of newly recoverable reserves of 25 million tons and newly added profits of 1.711 billion yuan.The preliminary assessment of potential shows that among the reserves of 6 billion tons that PetroChina has already developed with low permeability, the promotion of technological achievements can cover 3 billion tons of geological reserves, Increase recoverable reserves of about 150 million tons.This technology provides a powerful technical support for the sustained and steady development of China's petroleum crude oil production for China's similar low permeability, ultra-low permeability reservoir water drive development has played an important guiding role in promoting Low permeability, tight oil development theory and technology has made important contributions to the development.
