Optimization Design of Gravity Assisted Gas Drainage Combined with Pattern Flooding and the Application in Pilot in H Reservoir

Abstract

Gas flooding is one of the important technologies to enhance oil recovery and contributes over one third of world's EOR production. This paper provide a research method based on the combination of gravity assisted gas drainage and pattern gas flooding, trying to solve the problem that formation structure is complex possessing large dip angle and small formation amplitude concurrently. This design is finally applied in scheme of H Reservoir which includes H-L Reservoir and H-Y Reservoir. Gravity assisted gas drainage and pattern gas flooding has been applied separately in the development of structural higher part and structural lower part. Laboratory physical simulation experiment, fine reservoir description and residual oil distribution have been researched to obtain higher oil recovery and gas-oil exchange rate. Multiple series of well patterns have been designed to according with multi-layer reservoirs. Stereoscopic well pattern will be reconstructed with gas flooding in the lower layers and existing development mode in the upper layers. This design has been used in the reservoir scheme of sandstone reservoir H. The combination gas flooding design and relative research methods proposed in this paper have been implemented in the reservoir scheme of H Reservoir. The design and development model was applied in the H-L Reservoir enhanced recovery program and field practice. After 20 years’ prediction, the cumulative gas injection was about 100 Bcf, the cumulative oil production was about 15 MMBbls, the water content at the end of the period was reduced to 60%, and the degree of recovery was improved by more than 20 percentage points compared with the water drive. The design and development model was applied in the H-Y Reservoir enhanced recovery program and field practice. After 30 years’ prediction, the cumulative condensate oil production was about 15 MMBbls, and the cumulative condensate gas production was more than 1000 Bcf. The EOR at the end of the test period was improved by over 28 percentage points compared with that of the depletion program. The improved EOR technique of combination of gravity assisted gas drainage and pattern gas flooding is creatively applied in formation with large dip angle and small structure amplitude concurrently in this paper, and bring about a striking effect. Other technologies such as fine reservoir description, stereoscopic well pattern, perforation upward layer by layer, GAGD, et al. will also achieve jelly results. In addition, the application of CO2 GAGD - pattern flooding could converse into CCUS later, while HC- GAGD - pattern flooding could converse into gas storage later.