Accompanied with further development, fault blocks of multilayer complex heavy oil reservoirs will gradually face problems of great difficulty in stable production during late phase of CSS, low recovery efficiency of certain blocks and poor production of remaining oil between wells due to complicated geological conditions, deep buried oil reservoirs, high viscosity of heavy oil and other factors. Hence the way to effectively develop complex oil reservoirs and guarantee oil production is of great significance to realize the stable production of heavy oil reservoirs.

Based on different geologic characteristics and development statuses of complex oil and gas reservoirs, this project has carried out research and application through integrated utilization of various technologies and combination of innovations in development methods. In case of blocks with complicated structures, diversified depositional modes and substantial reservoir types, stratigraphic correlation based on logging and seismic data has been conducted, region-wide unified hierarchical model has been built to know the structure of entire region and build detailed 3-D geological models. Detailed profiling of structural characteristics and ‘four characters’ of reservoirs have been carried out, new standards for favorable oil reservoirs have been developed, and logging and seismic data have been combined to track favorable individual reservoirs. As for reservoirs with thin layers and microstructures, seismic inversion has been conducted for accurate identification, horizontal well techniques for thin layers have been used for overall development, optimal deployment of guide holes has been carried out, and steam flooding pilot test for extra heavy oil horizontal well in thin layers has been done to enhance recovery efficiency. In terms of problems of great difficulty in stable production of vertical well network during late phase of CSS and low recovery efficiency of certain blocks due to poor physical property and high viscosity, Technologies of overlapping horizontal well and multilateral horizontal well have been used in addition of accurate identification of oil-water relation for development, and the innovative development method of Gravity Drainage Assisted Steam Flooding has been created, which brought new ideas to viscous oil development.

This project has guaranteed crude production rate of blocks through geological research that used various technologies, innovations in development method as well as comprehensive and effective production of complex oil and gas reservoirs, which allowed it to have great importance in stable production of oilfields, and play a guiding role in improving development efficiency of complex oil and gas reservoirs!

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