Hu, Zhenhua (PetroChina Liaohe Oilfield Company) | Zhang, Shenqin (PetroChina Qinghai Oilfield Company) | Wu, Fangfang (Schlumberger) | Liu, Xunqi (Schlumberger) | Wu, Jinlong (Schlumberger) | Li, Shenzhuan (Schlumberger) | Wang, Yuxi (Schlumberger) | Zhao, Xianran (Schlumberger) | Zhao, Haipeng (Schlumberger)
The igneous reservoir of Shahejie formation in eastern sag of Liaohe depression is characterized by complex geological environment, variable lithology and high heterogeneity. Reservoir evaluation is difficult only based on conventional logs due to complex lithology and pore structures. Effective igneous reservoirs were identified and reservoir controlling factors were analyzed based on effective porosity calculation, pore structure analysis, lithology identification, lithofacies analysis, fracture evaluation and heterogeneity analysis by combing nuclear magnetic resonance data, micro-resistivity image data, conventional logs as well as mud logging data.
Based on our study, the igneous reservoirs in the study area are more related with effective porosity and pore connectivity, and less related with fractures. Good reservoirs are mainly distributed on the top part of explosive facies and effusive facies, where lithologies are mainly Trachyte, volcanic breccia and breccia-bearing tuff. The weathering leaching process is quite important for igneous reservoirs, but the reservoir qulity would not be good if the weathering process is too strong as it will lead to low effective porosity.
The accuracy of igneous reservoir evaluation gets improved a lot by this integrated approach and the conclusion from this study will help to optimize igneous reservoire exploration plan.
LIN, CUI (PetroChina Liaohe Oilfield Company)
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!