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Li L.,Southwest Petroleum University | Liu J.,Southwest Petroleum University | Zhang W.,Shaanxi Nuclear Industry Engineering Investigation Institute | Zhang G.,Southwest Petroleum University | And 2 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2012

Combined a scaling prediction model for multiphase equilibrium developed, the present paper studied scaling conditions and variation laws of inorganic salts in formation fluids of in-situ gas reservoirs using a high-temperature and high-pressure formation-fluid scaling test device. The influence of phase behavior changes at different positions of a wellbore or reservoir on laws of inorganic salt scaling was emphatically analyzed. The results showed that the evaporation of formation water and the solution and precipitation of acid gases are the main influence factors of phase changes in inorganic salt scaling. The scaling state of an actual gas-reservoir fluid results from comprehensive influences of chemical reactions and phase changes of various fluid components. Phase changes and scaling rules of formation fluids are mainly determined by reservoir pressure in reservoirs and by temperature in wellbores. If the influence of phase behavior changes were not taken into consideration, the prediction scaling amount would be obviously lower, and with the decrease of pressure and the increase of temperature, the deviation would increase continually.


Li L.,Petrochina | Liu J.-Y.,Southwest Petroleum University | Zhang W.,Shaanxi Nuclear Industry Engineering Investigation Institute | Zhang G.-D.,Shaanxi Nuclear Industry Engineering Investigation Institute | Wang Y.-P.,Sinopec
Oilfield Chemistry | Year: 2012

The prediction results by the scaling model without the influence of phases proposed in previous article was contracted with other models. The scaling test of real gas field fluid was carried out using the scaling test equipment under the condition of high temperature and high pressure, through which the new scaling prediction model considering multiphase equilibrium for gas field containing water was tested and verified. The results showed that the amount of scale buildup of real reservoir fluid increased with decreasing pressure. The results predicted by model and that tested by laboratory experiment were accordant. The new method could accurately predict the amount of scale of gas field fluid under multiphase equilibrium, and the average deviation was about 2% . If the influence of phase behavior change was not considered, the average deviation of predicted scaling amount from experiment results was about 15% , and the deviation increased with decreasing pressure. During the production, the evaporation of water under the influence of oil and gas phase behavior intensified with decreasing reservoir pressure, which caused the concentration of ions in formation water to increase. If phase behavior changes of reservoir fluid were not considered, the predicted amount of scale would be lower obviously.


Li L.,Petrochina | Liu J.-Y.,Southwest Petroleum University | Zhang W.,Shaanxi Nuclear Industry Engineering Investigation Institute | Zhang G.-D.,Southwest Petroleum University | Xiao L.-X.,Petrochina
Oilfield Chemistry | Year: 2012

During the exploitation of gas reservoir with water, there always existed scaling problems of reservoir fluid, which badly affected the normal production of gas well. Different from the scaling situation in oil field, phase behavior changes had important influence on the scaling of inorganic salt. Especially the dissolve and exhalation of gas components in reservoir water and the evaporation of water itself all seriously influenced the scaling condition of reservoir fluid. From thermodynamics, a new scaling prediction model considering the gas-liquid ( liquid hydrocarbon ) -liquid ( electrolyte solution ) -solid ( inorganic salts scale ) multiphase equilibrium of gas reservoir fluid was put forward. For the complexity of the direct solution for phase equilibrium system with chemical reaction, a simplified computing method by respectively computing phase change and chemical equilibrium step-by-step was introduced, which gave the effective method for researching and predicting the scaling rules of gas reservoir fluid during the exploitation.

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