The influence of water pollution and welding defects on MIC (microbiologically influenced corrosion) was studied. The open circuit potential (OCP) was measured during MIC test. It was found that OCP shifted to a highe...The influence of water pollution and welding defects on MIC (microbiologically influenced corrosion) was studied. The open circuit potential (OCP) was measured during MIC test. It was found that OCP shifted to a higher level when the system was inoculated with bacteria while the OCP of those samples in water without bacteria was kept at a low level. The OCP decreased dramatically when MIC started in polluted water. Combination of weld defect heat tint, polluted water and adding bacteria causes MIC happen at high rate. Some elements inside the tubercle were analyzed with EDXA. The pits and biofilm were observed with SEM. Microbiological analysis revealed the difference of bacteria between corroded and uncorroded samples.展开更多
Gas well deliverability evaluation and analysis are challenging due to the frequent abnormalities of deliverability test data of gas condensate wells caused by seepage of oil and gas phases in the reservoirs.To this e...Gas well deliverability evaluation and analysis are challenging due to the frequent abnormalities of deliverability test data of gas condensate wells caused by seepage of oil and gas phases in the reservoirs.To this end,based upon the pseudo-single-phase seepage equation and the oilegas two-phase seepage equation,a new deliverability evaluation method was established which is applicable to the following two cases when the flow of a gas well reaches the quasi-steady stage,i.e.,the pseudo-single-phase stable point deliverability evaluation for the case when the formation pressure is above the dew pressure;the gaseliquid two-phase stable point deliverability evaluation for the case when the formation pressure is below the dew pressure.Using this established deliverability evaluation method,based on the basic parameters of the Yaha gas field,Tarim Basin,the IPR curves were first obtained of gas wells do not get this at the same production gaseoil ratio and at the formation pressure above and below the dew point pressure;then,according to the four condensate gas fields,such as Yaha,Tazhong I,Qianmiqiao and Dina 2,the absolute open flow(AOF)potentials of condensate gas wells under different gaseoil production ratios were calculated.Finally,through statistical analysis of the calculation results from typical wells,the following findings were obtained.This new deliverability evaluation method under the two states of condensate gas wells with quasi-single-phase and gaseliquid two-phase stable points can be used to avoid cases due to the oilegas flow in a condensate gas well which has remained unresolved by the classical deliverability evaluation methods.Also,with the increase of gaseoil ratios in gas condensate wells,a variable discrepancy is gradually reduced in AOF potentials calculated respectively by the quasi-single-phase and gaseliquid two-phase stable point deliverability evaluation equations.For the condensate gas wells with high condensate content and low condensate gas production rates,the AOF potentials calculated by the gaseliquid two-phase stable point deliverability equation is more appropriate and reliable compared with that obtained by classical methods.展开更多
Predicting the deliverability change laws of a gas well in the early stage is one of the technical difficulties in natural gas development.The commonly used steady seepage analysis methods have relatively large errors...Predicting the deliverability change laws of a gas well in the early stage is one of the technical difficulties in natural gas development.The commonly used steady seepage analysis methods have relatively large errors.And this problem cannot be solved effectively by the classical methods of production decline analysis and pressure transient well test analysis.To solve this problem,this paper did calculation based on the well test model of constant-pressure production,changed the previous approximate method of simplifying the calculation of the exponential integral function,and accurately calculated the analytical solution of absolute openflow potential of a gas well.In addition,the deliverability instability characteristics of different types of gas wells were quantitatively described by taking vertical wells in homogeneous reservoirs as the reference benchmark.Then,combined with the deliverability evaluation needs of a new well,a new practical method focusing on solving the problems of gas formation testing analysis was researched and developed,and also applied on site at some key wells in the hot spots of natural gas development in the Sichuan Basin.And the following research results were obtained.First,the accurate formula for the analytical solution of well test model significantly enhances the adaptability to short-term test conditions.Second,the newly established chart briefly reveals the quantitative relationship between the unstable deliverability characteristics of a gas well and the main influencing factors.Third,if the char-acteristic parameter of turbulence effect is unknown,it is necessary to perform iterative calculation of the variable skin factor when the well test model of constant-pressure production is used to analyze the change trend of the absolute openflow potential of a gas well.Fourth,by con-ducting comparative analysis on the calculation results of typical cases,the decline laws of the absolute openflow potential of different types of gas wells can be understood further.It is concluded that this new method is capable of improving the prediction accuracy of the unstable deliverability of gas wells.Therefore,it can be widely applied to the deliverability evaluation of gas wells in the exploration stage,the evaluation stage of early development and the commissioning stage of new development and production wells,which is conducive to the formulation of natural gas exploration and development decision.展开更多
The electrochemical corrosion behaviour of three Zr-Ag alloys (Zr-1Ag, Zr-3Ag and Zr-5Ag) was investigated. Open circuit potential, linear potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) ...The electrochemical corrosion behaviour of three Zr-Ag alloys (Zr-1Ag, Zr-3Ag and Zr-5Ag) was investigated. Open circuit potential, linear potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were employed in aerated artificial saliva (pH = 4.0) at 37°C. Silver alloying additions are found to be effective in enhancing the corrosion resistance of zirconium in artificial saliva environment. In fact, Zr-Ag alloys exhibit higher open circuit potentials, larger breakdown potentials and higher impedance values as compared to cp Zr. This behaviour can be ascribed to the formation of a thicker and more stable passive film with increasing compactness, able to provide better protection against the corrosion attack.展开更多
The electrochemical behaviour of three duplex stainless steels,(SAF 2101,SAF 2304,SAF 2205)was investigated.Open circuit potential,EOC,measurements,and electrochemical impedance spectroscopy(EIS)were employed both in ...The electrochemical behaviour of three duplex stainless steels,(SAF 2101,SAF 2304,SAF 2205)was investigated.Open circuit potential,EOC,measurements,and electrochemical impedance spectroscopy(EIS)were employed both in phosphate-buffered saline solution(PBS,pH=7.2)and in PBS simulating in vitro inflammatory conditions(PBS+H2O2,pH=5.0).It has been established that the tendency of the investigated steel materials towards corrosion de-creases in the following order:SAF 2101<SAF 2304<SAF 2205 in both ag-gressive environments.The superior corrosion resistance exhibited by SAF 2205 is ascribed to the formation of a passive film with enhanced protective effectiveness than the one formed on SAF 2101 and SAF 2304,and this im-provement is ascribed to a synergistic effect of Mo+N owing to the high mo-lybdenum content in the alloy.展开更多
Calculating the absolute open flow potential timely and investigating production capacity so as to adjust working system of production wells is one of main means to effectively recovery gas reservoirs during intermedi...Calculating the absolute open flow potential timely and investigating production capacity so as to adjust working system of production wells is one of main means to effectively recovery gas reservoirs during intermediate and late development stage.In order to obtain the open flow potential of gas wells accurately,a new method which utilized a single steady point was proposed in this research,which was based on deliverability formula of a gas well in pseudo-steady state flow with pseudo-pressure form.The influence on factor B in binomial productivity equation caused by the changed permeability was taken into consideration.According to the stable production data,reservoir permeability K can be determined by iterative method firstly,and the coefficient A,B in binomial productivity equation can be calculated with the open flow potential subsequently.It illustrated clearly by a practical example that the new method was suitable for gas wells especially when the producing pressure drop is large.Additionally,the error between the open flow potential value and interpretation result from the multi-point test was small,which proved it to be more simple,economic and effective than the common one.展开更多
文摘The influence of water pollution and welding defects on MIC (microbiologically influenced corrosion) was studied. The open circuit potential (OCP) was measured during MIC test. It was found that OCP shifted to a higher level when the system was inoculated with bacteria while the OCP of those samples in water without bacteria was kept at a low level. The OCP decreased dramatically when MIC started in polluted water. Combination of weld defect heat tint, polluted water and adding bacteria causes MIC happen at high rate. Some elements inside the tubercle were analyzed with EDXA. The pits and biofilm were observed with SEM. Microbiological analysis revealed the difference of bacteria between corroded and uncorroded samples.
基金supported by the PetroChina Major Science and Technology Project(No.2014E-3203)。
文摘Gas well deliverability evaluation and analysis are challenging due to the frequent abnormalities of deliverability test data of gas condensate wells caused by seepage of oil and gas phases in the reservoirs.To this end,based upon the pseudo-single-phase seepage equation and the oilegas two-phase seepage equation,a new deliverability evaluation method was established which is applicable to the following two cases when the flow of a gas well reaches the quasi-steady stage,i.e.,the pseudo-single-phase stable point deliverability evaluation for the case when the formation pressure is above the dew pressure;the gaseliquid two-phase stable point deliverability evaluation for the case when the formation pressure is below the dew pressure.Using this established deliverability evaluation method,based on the basic parameters of the Yaha gas field,Tarim Basin,the IPR curves were first obtained of gas wells do not get this at the same production gaseoil ratio and at the formation pressure above and below the dew point pressure;then,according to the four condensate gas fields,such as Yaha,Tazhong I,Qianmiqiao and Dina 2,the absolute open flow(AOF)potentials of condensate gas wells under different gaseoil production ratios were calculated.Finally,through statistical analysis of the calculation results from typical wells,the following findings were obtained.This new deliverability evaluation method under the two states of condensate gas wells with quasi-single-phase and gaseliquid two-phase stable points can be used to avoid cases due to the oilegas flow in a condensate gas well which has remained unresolved by the classical deliverability evaluation methods.Also,with the increase of gaseoil ratios in gas condensate wells,a variable discrepancy is gradually reduced in AOF potentials calculated respectively by the quasi-single-phase and gaseliquid two-phase stable point deliverability evaluation equations.For the condensate gas wells with high condensate content and low condensate gas production rates,the AOF potentials calculated by the gaseliquid two-phase stable point deliverability equation is more appropriate and reliable compared with that obtained by classical methods.
基金Project supported by the National Major Science and Technology Project“Demonstrative Project of Large Carbonate Gas Field Development in Sichuan Basin”(No.2016ZX05052).
文摘Predicting the deliverability change laws of a gas well in the early stage is one of the technical difficulties in natural gas development.The commonly used steady seepage analysis methods have relatively large errors.And this problem cannot be solved effectively by the classical methods of production decline analysis and pressure transient well test analysis.To solve this problem,this paper did calculation based on the well test model of constant-pressure production,changed the previous approximate method of simplifying the calculation of the exponential integral function,and accurately calculated the analytical solution of absolute openflow potential of a gas well.In addition,the deliverability instability characteristics of different types of gas wells were quantitatively described by taking vertical wells in homogeneous reservoirs as the reference benchmark.Then,combined with the deliverability evaluation needs of a new well,a new practical method focusing on solving the problems of gas formation testing analysis was researched and developed,and also applied on site at some key wells in the hot spots of natural gas development in the Sichuan Basin.And the following research results were obtained.First,the accurate formula for the analytical solution of well test model significantly enhances the adaptability to short-term test conditions.Second,the newly established chart briefly reveals the quantitative relationship between the unstable deliverability characteristics of a gas well and the main influencing factors.Third,if the char-acteristic parameter of turbulence effect is unknown,it is necessary to perform iterative calculation of the variable skin factor when the well test model of constant-pressure production is used to analyze the change trend of the absolute openflow potential of a gas well.Fourth,by con-ducting comparative analysis on the calculation results of typical cases,the decline laws of the absolute openflow potential of different types of gas wells can be understood further.It is concluded that this new method is capable of improving the prediction accuracy of the unstable deliverability of gas wells.Therefore,it can be widely applied to the deliverability evaluation of gas wells in the exploration stage,the evaluation stage of early development and the commissioning stage of new development and production wells,which is conducive to the formulation of natural gas exploration and development decision.
文摘The electrochemical corrosion behaviour of three Zr-Ag alloys (Zr-1Ag, Zr-3Ag and Zr-5Ag) was investigated. Open circuit potential, linear potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were employed in aerated artificial saliva (pH = 4.0) at 37°C. Silver alloying additions are found to be effective in enhancing the corrosion resistance of zirconium in artificial saliva environment. In fact, Zr-Ag alloys exhibit higher open circuit potentials, larger breakdown potentials and higher impedance values as compared to cp Zr. This behaviour can be ascribed to the formation of a thicker and more stable passive film with increasing compactness, able to provide better protection against the corrosion attack.
文摘The electrochemical behaviour of three duplex stainless steels,(SAF 2101,SAF 2304,SAF 2205)was investigated.Open circuit potential,EOC,measurements,and electrochemical impedance spectroscopy(EIS)were employed both in phosphate-buffered saline solution(PBS,pH=7.2)and in PBS simulating in vitro inflammatory conditions(PBS+H2O2,pH=5.0).It has been established that the tendency of the investigated steel materials towards corrosion de-creases in the following order:SAF 2101<SAF 2304<SAF 2205 in both ag-gressive environments.The superior corrosion resistance exhibited by SAF 2205 is ascribed to the formation of a passive film with enhanced protective effectiveness than the one formed on SAF 2101 and SAF 2304,and this im-provement is ascribed to a synergistic effect of Mo+N owing to the high mo-lybdenum content in the alloy.
基金Fund project:National Basic Research Program of China(973 Program-2014CB239205).
文摘Calculating the absolute open flow potential timely and investigating production capacity so as to adjust working system of production wells is one of main means to effectively recovery gas reservoirs during intermediate and late development stage.In order to obtain the open flow potential of gas wells accurately,a new method which utilized a single steady point was proposed in this research,which was based on deliverability formula of a gas well in pseudo-steady state flow with pseudo-pressure form.The influence on factor B in binomial productivity equation caused by the changed permeability was taken into consideration.According to the stable production data,reservoir permeability K can be determined by iterative method firstly,and the coefficient A,B in binomial productivity equation can be calculated with the open flow potential subsequently.It illustrated clearly by a practical example that the new method was suitable for gas wells especially when the producing pressure drop is large.Additionally,the error between the open flow potential value and interpretation result from the multi-point test was small,which proved it to be more simple,economic and effective than the common one.
