1. Introduction Liquid loading has presented a major operational restriction in mature gas field ... more 1. Introduction Liquid loading has presented a major operational restriction in mature gas field the world over manifesting itself through pressure buildup in as a result of increase in the accumulated volume of non-evacuated fluid column in the well, decreasing the well's production rate and ultimately killing the well. In theory, every gas well is expected to approach the phenomenon of liquid loading in time, thus early diagnosis is needed. Diagnosis of the problem is difficult due to the sustained production over a long period of time as the early indicators such as the decline in the production curve, variation in pressure gradient, slug in the flow as observed at the surface, are seen long after liquid loading may have started. Though there are a number of proven techniques to deal with the problem of liquid loading and accumulation such as completion optimization, tubing size perforation interval, nodal analysis etc. the reliability of these predictive models has to be improved upon to help in better selection process for the control and mitigation of liquid loading from its onset. In view of weakness and reliability issues surrounding the existing predictive models, the diagnosis of the onset of liquid loading requires a review of the current predictive methods. It is hoped that the review will pave the way for the better understanding of the wellbore dynamics during liquid loading, leading to a better and more efficient development and implementation of guidelines for prompt intervention steps to avert the dangers of liquid loading and accumulation in pipes. Gas/oil multiphase flow is a common phenomenon in many chemical processes where liquid loading and accumulation occurs. The production and transportation of reservoir two phase oil and gas flow is one which is not new to the petroleum industry with very high occurrence in the petroleum exploration and processing operations and here liquid loading is a common place especially for the matured fields. The flow of multiphase fluid in pipes has arouse the interest of many researchers due to the merit of the understanding of the hydrodynamics of the fluid in pipelines affects the production level of the entire process. The various flow characteristics which may be seen in the various flow patterns are functions of the fluid flow parameters such as liquid holdup, fluid pressure gradient amongst others. Also influencing flow patterns are the fluid flow rate, pipe angle of inclination, diameter of pipe and the fluid properties. The combined effects of these factors yields a range of fluid flow behavior all of which are stochastic in nature having high non linearity making it difficult to understand and predict. For the transportation of gas/ liquid two phase flow in pipelines, a minimum carrying capacity must be attended below this minimum will results in liquid accumulation in pipeline an undesirable effect of liquid loading which will undermine the economics of the production by risking the efficiency of the multiphase flow assurance in deep water exploration and production as it causes the reduction in production, or may even stop the gas from flowing to the surface resulting in well death. Liquid accumulation occurs at the well bore when the liquid fraction is significant due to the reduced gas velocity below minimum value necessary to drag the entrained liquid to the surface. 1.1 Overview and Mechanism of Liquid Accumulation Process in Pipelines The inability of oil/gas pipeline to effectively and efficiently evacuate the oil that is associated with the produces gases results in liquid loading and accumulation. For the oil/gas flow through reservoirs, rates of about 90% have been recorded with effective use of technology like infield compression/ boosting. This recovery rate drops to about 70% with decreasing pressure as the petroleum reserves are produced as a result of geologically
1. Introduction Liquid loading has presented a major operational restriction in mature gas field ... more 1. Introduction Liquid loading has presented a major operational restriction in mature gas field the world over manifesting itself through pressure buildup in as a result of increase in the accumulated volume of non-evacuated fluid column in the well, decreasing the well's production rate and ultimately killing the well. In theory, every gas well is expected to approach the phenomenon of liquid loading in time, thus early diagnosis is needed. Diagnosis of the problem is difficult due to the sustained production over a long period of time as the early indicators such as the decline in the production curve, variation in pressure gradient, slug in the flow as observed at the surface, are seen long after liquid loading may have started. Though there are a number of proven techniques to deal with the problem of liquid loading and accumulation such as completion optimization, tubing size perforation interval, nodal analysis etc. the reliability of these predictive models has to be improved upon to help in better selection process for the control and mitigation of liquid loading from its onset. In view of weakness and reliability issues surrounding the existing predictive models, the diagnosis of the onset of liquid loading requires a review of the current predictive methods. It is hoped that the review will pave the way for the better understanding of the wellbore dynamics during liquid loading, leading to a better and more efficient development and implementation of guidelines for prompt intervention steps to avert the dangers of liquid loading and accumulation in pipes. Gas/oil multiphase flow is a common phenomenon in many chemical processes where liquid loading and accumulation occurs. The production and transportation of reservoir two phase oil and gas flow is one which is not new to the petroleum industry with very high occurrence in the petroleum exploration and processing operations and here liquid loading is a common place especially for the matured fields. The flow of multiphase fluid in pipes has arouse the interest of many researchers due to the merit of the understanding of the hydrodynamics of the fluid in pipelines affects the production level of the entire process. The various flow characteristics which may be seen in the various flow patterns are functions of the fluid flow parameters such as liquid holdup, fluid pressure gradient amongst others. Also influencing flow patterns are the fluid flow rate, pipe angle of inclination, diameter of pipe and the fluid properties. The combined effects of these factors yields a range of fluid flow behavior all of which are stochastic in nature having high non linearity making it difficult to understand and predict. For the transportation of gas/ liquid two phase flow in pipelines, a minimum carrying capacity must be attended below this minimum will results in liquid accumulation in pipeline an undesirable effect of liquid loading which will undermine the economics of the production by risking the efficiency of the multiphase flow assurance in deep water exploration and production as it causes the reduction in production, or may even stop the gas from flowing to the surface resulting in well death. Liquid accumulation occurs at the well bore when the liquid fraction is significant due to the reduced gas velocity below minimum value necessary to drag the entrained liquid to the surface. 1.1 Overview and Mechanism of Liquid Accumulation Process in Pipelines The inability of oil/gas pipeline to effectively and efficiently evacuate the oil that is associated with the produces gases results in liquid loading and accumulation. For the oil/gas flow through reservoirs, rates of about 90% have been recorded with effective use of technology like infield compression/ boosting. This recovery rate drops to about 70% with decreasing pressure as the petroleum reserves are produced as a result of geologically
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