A simulation study was carried out to investigate the temporal evolution of H_(2)S in the Huangcaoxia underground gas storage (UGS), which is converted from a depleted sulfur-containing gas field. Based on the rock an...A simulation study was carried out to investigate the temporal evolution of H_(2)S in the Huangcaoxia underground gas storage (UGS), which is converted from a depleted sulfur-containing gas field. Based on the rock and fluid properties of the Huangcaoxia gas field, a multilayered model was built. The upper layer Jia-2 contains a high concentration of H_(2)S (27.2 g/m^(3)), and the lower layer Jia-1 contains a low concentration of H_(2)S (14.0 mg/m^(3)). There is also a low-permeability interlayer between Jia-1 and Jia-2. The multi-component fluid characterizations for Jia-1 and Jia-2 were implemented separately using the Peng-Robinson equation of state in order to perform the compositional simulation. The H_(2)S concentration gradually increased in a single cycle and peaked at the end of the production season. The peak H_(2)S concentration in each cycle showed a decreasing trend when the recovery factor (RF) of the gas field was lower than 70%. When the RF was above 70%, the peak H_(2)S concentration increased first and then decreased. A higher reservoir RF, a higher maximum working pressure, and a higher working gas ratio will lead to a higher H_(2)S removal efficiency. Similar to developing multi-layered petroleum fields, the operation of multilayered gas storage can also be divided into multi-layer commingled operation and independent operation for different layers. When the two layers are combined to build the storage, the sweet gas produced from Jia-1 can spontaneously mix with the sour gas produced from Jia-2 within the wellbore, which can significantly reduce the overall H_(2)S concentration in the wellstream. When the working gas volume is set constant, the allocation ratio between the two layers has little effect on the H_(2)S removal. After nine cycles, the produced gas’s H_(2)S concentration can be lowered to 20 mg/m^(3). Our study recommends combining the Jia-2 and Jia-1 layers to build the Huangcaoxia underground gas storage. This plan can quickly reduce the H_(2)S concentration of the produced gas to 20 mg/m^(3), thus meeting the gas export standards as well as the HSE (Health, Safety, and Environment) requirements in the field. This study helps the engineers understand the H_(2)S removal for sulfur-containing UGS as well as provides technical guidelines for converting other multilayered sour gas fields into underground storage sites.展开更多
Anammox bacteria grow slowly and can be affected by large pH fluctuations.Using suitable buffers could make the start-up of anammox reactors easy and rapid.In this study,the effects of three kinds of buffers on the ni...Anammox bacteria grow slowly and can be affected by large pH fluctuations.Using suitable buffers could make the start-up of anammox reactors easy and rapid.In this study,the effects of three kinds of buffers on the nitrogen removal and growth characteristics of anammox sludge were investigated.Reactors with CO_(2)/NaHCO_(3)buffer solution(CCBS)performed the best in nitrogen removal,while 4-(2-hydroxyerhyl)piperazine-1-ethanesulfonic acid(HEPES)and phosphate buffer solution(PBS)inhibited the anammox activity.Reactors with 50 mmol/L CCBS could start up in 20 days,showing the specific anammox activity and anammox activity of 1.01±0.10 gN/(gVSS·day)and 0.83±0.06 kgN/(m^(3)·day),respectively.Candidatus Kuenenia was the dominant anammox bacteria,with a relative abundance of 71.8%.Notably,anammox reactors could also start quickly by using 50 mmol/L CCBS under nonstrict anaerobic conditions.These findings are meaningful for the quick start-up of engineered anammox reactors and prompt enrichment of anammox bacteria.展开更多
The pressure response for the composite reservoirs with a sealing fault locating in inner and outer region is different,which neglected by previous researchers,would cause significant errors during well-test interpret...The pressure response for the composite reservoirs with a sealing fault locating in inner and outer region is different,which neglected by previous researchers,would cause significant errors during well-test interpretations.Based on seepage theory,a well-test model of two-region radial composite reservoir with infinite outer boundary has been built in this study considering wellbore storage and skin effects.The solutions for this model and characteristics of the type curves have been analyzed by applying the method of mirror image,Laplace transformation and superposition principle,including a straight fault,a perpendicular fault and parallel faults cases.The study shows that the dimensionless pressure derivative curves would be obviously different in two cases:the well to fault distance is larger,and smaller than the half length of the inner-region radius.Therefore,type curves are presented with reasonable parameters to analyze the distance effect on the dynamic pressure response.The results in this study are of great significance。展开更多
基金supported by the China Postdoctoral Science Foundation(2022M722637)as well as the Natural Science Foundation of Sichuan Province(2022NSFSC0190).
文摘A simulation study was carried out to investigate the temporal evolution of H_(2)S in the Huangcaoxia underground gas storage (UGS), which is converted from a depleted sulfur-containing gas field. Based on the rock and fluid properties of the Huangcaoxia gas field, a multilayered model was built. The upper layer Jia-2 contains a high concentration of H_(2)S (27.2 g/m^(3)), and the lower layer Jia-1 contains a low concentration of H_(2)S (14.0 mg/m^(3)). There is also a low-permeability interlayer between Jia-1 and Jia-2. The multi-component fluid characterizations for Jia-1 and Jia-2 were implemented separately using the Peng-Robinson equation of state in order to perform the compositional simulation. The H_(2)S concentration gradually increased in a single cycle and peaked at the end of the production season. The peak H_(2)S concentration in each cycle showed a decreasing trend when the recovery factor (RF) of the gas field was lower than 70%. When the RF was above 70%, the peak H_(2)S concentration increased first and then decreased. A higher reservoir RF, a higher maximum working pressure, and a higher working gas ratio will lead to a higher H_(2)S removal efficiency. Similar to developing multi-layered petroleum fields, the operation of multilayered gas storage can also be divided into multi-layer commingled operation and independent operation for different layers. When the two layers are combined to build the storage, the sweet gas produced from Jia-1 can spontaneously mix with the sour gas produced from Jia-2 within the wellbore, which can significantly reduce the overall H_(2)S concentration in the wellstream. When the working gas volume is set constant, the allocation ratio between the two layers has little effect on the H_(2)S removal. After nine cycles, the produced gas’s H_(2)S concentration can be lowered to 20 mg/m^(3). Our study recommends combining the Jia-2 and Jia-1 layers to build the Huangcaoxia underground gas storage. This plan can quickly reduce the H_(2)S concentration of the produced gas to 20 mg/m^(3), thus meeting the gas export standards as well as the HSE (Health, Safety, and Environment) requirements in the field. This study helps the engineers understand the H_(2)S removal for sulfur-containing UGS as well as provides technical guidelines for converting other multilayered sour gas fields into underground storage sites.
基金supported by the National Natural Science Foundation of China(No.52070162)。
文摘Anammox bacteria grow slowly and can be affected by large pH fluctuations.Using suitable buffers could make the start-up of anammox reactors easy and rapid.In this study,the effects of three kinds of buffers on the nitrogen removal and growth characteristics of anammox sludge were investigated.Reactors with CO_(2)/NaHCO_(3)buffer solution(CCBS)performed the best in nitrogen removal,while 4-(2-hydroxyerhyl)piperazine-1-ethanesulfonic acid(HEPES)and phosphate buffer solution(PBS)inhibited the anammox activity.Reactors with 50 mmol/L CCBS could start up in 20 days,showing the specific anammox activity and anammox activity of 1.01±0.10 gN/(gVSS·day)and 0.83±0.06 kgN/(m^(3)·day),respectively.Candidatus Kuenenia was the dominant anammox bacteria,with a relative abundance of 71.8%.Notably,anammox reactors could also start quickly by using 50 mmol/L CCBS under nonstrict anaerobic conditions.These findings are meaningful for the quick start-up of engineered anammox reactors and prompt enrichment of anammox bacteria.
基金This work was financially supported by National Science and Technology Major Project no.2016ZX05015-003 and no.2017ZX05009-004.
文摘The pressure response for the composite reservoirs with a sealing fault locating in inner and outer region is different,which neglected by previous researchers,would cause significant errors during well-test interpretations.Based on seepage theory,a well-test model of two-region radial composite reservoir with infinite outer boundary has been built in this study considering wellbore storage and skin effects.The solutions for this model and characteristics of the type curves have been analyzed by applying the method of mirror image,Laplace transformation and superposition principle,including a straight fault,a perpendicular fault and parallel faults cases.The study shows that the dimensionless pressure derivative curves would be obviously different in two cases:the well to fault distance is larger,and smaller than the half length of the inner-region radius.Therefore,type curves are presented with reasonable parameters to analyze the distance effect on the dynamic pressure response.The results in this study are of great significance。
