CER Corp., Las Vegas, has recommended a rehabilitation program it believes could boost deliverability by 20% in a major gas field in China.
The recommendations resulted from a 4 year, multimillion dollar study of Weiyuan field in Central China's Sichuan province.
Sichuan province is China's major gas producing province, with current flow of about 671 MMcfd and potential recovery pegged at 280 tcf. China's government recently announced a shift in its exploration and development emphasis to natural gas (OGJ, Jan. 6, p. 30).
Funded by World Bank, CER's study found that a workover program, infill drilling, and wellbore dewatering program could significantly increase reserves.
RECOMMENDATIONS
CER's Mark Malinowsky, Weiyuan project manager, said the study diagnosed the water encroachment mechanism in various parts of the field.
The company recommended recompleting 20 wells, a move expected to reduce water encroachment volumes 20-50%, Malinowsky said.
CER recommended a pilot program to test feasibility of workovers, and the Southwest Mining District of the Sichuan Petroleum Administration will decide which wells to use for the pilot project.
CER recommended dewatering wells using plunger lift, intermittent gas lift, and continuous flow gas lift. The company designed a pilot dewatering program to test efficiency of the techniques.
CER also suggested drilling three infill wells to achieve maximum depletion of the reservoir.
BACKGROUND
Weiyuan field is one of the largest gas fields in China, with more than 100 wells that average 10,000 ft in depth.
CER noted the reservoir is highly fractured. Produced gas contains a significant amount of hydrogen sulfide and water, which caused reservoir management and production engineering problems.
CER assembled background data and developed a geologic model of the field. A computer simulation based on the model was developed and modified until the 25 year production history of the field could be reproduced by computer calculation.
The history match enabled CER to use computer simulation to predict field performance.
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