Xiashihezi Ⅲ Gas Reservoir Degressive Rule Analysis In Daniudi Gas Field

Daniudi gas field he3gas reservoir is a lithologic gas reservoir in the low amplitude structure. Its reservoir with the characteristic of complicated reservoir spreading, it also has a feature of poor reservoir physical property which represents in low porosity and permeability. According to classification standard of the single gas well productivity, Stable condition and Producing water condition,175single well were classified. There were21prolific wells,70middle shafts,84stripper wells in175single gas wells of H3reservoir,in which there were96stable yield wells and79non stable yield wells. All the175single gas wells are stripper wells.Based on the pressure decreases linearly theory of the closed constant-volume gas reservoirs,wellhead pressure of the96stable yield wells were fitted. The casing pressure lapse rate of the prolific wells were from0.0024MPa/d to0.0079MPa/d, and the average value was0.0056MPa/d; the casing pressure lapse rate of middle shafts were from0.0027MPa/d to0.0102MPa/d; and the average value was0.0062MPa/d; the casing pressure lapse rate of stripper wells were from0.0030MPa/d to0.0131MPa/d, and the average value was0.0064MPa/d. There was such a law which the casing pressure lapse rate of stripper wells was the greatest,and the prolific wells was the minimum.The facters were discussed which afected the decline of the casing pressure,and then there wre3results. The first, there are5facters in the negative influence on pressure lapse rate: Reservoir types, Flow unit, Permeability, Average water production and Open flow capacity. The second, there was lfacter in the positive influence on pressure lapse rate: Operation time. The third, there were2facters in the uncorrelated influence on pressure lapse rate: Porosity and Fracturing scale.Based on the Arps decline theory, Constant voltage drop production test wells were discussed. The initial decline yield and the initial decline rate were definated. Production decline curve was drawed in the Matlab software. There are3characteristics: quick, simple, accurate.The facters were discussed which afected the decline of the production decline curve from the3facters: chart parameter, the geological characteristics of reservoir and the development engineering. The first, there are6facters in the positive influence on the production curve: Reservoir types and Flow unit, Porosity, Permeability, Water production Fracturing scale and Air faucet. The second, there were2facters in the negative influence on the production curve: Well control dynamic reserves and remaining recoverable reserves.The results of this research have the guiding significance to the achievement of sustained stableing of the gas reservior, and to improve the development technologies level of the gas reservoir.