Decision Matrix Screening Tool to Identify the Best Artificial Lift Method for Liquid-loaded Gas Wells

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2010-10-12

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Liquid loading is a serious problem in gas wells. Many proven artificial lift methods have been used to alleviate this problem. However, a complete workflow to determine the most suitable artificial lift method for given well conditions does not exist. In 2008, Han Young Park presented his thesis of decision matrix tool using a decision tree technique for data mining that determined the best artificial lift method for liquid loading in gas wells from seven artificial lift methods: plunger lift, gas lift, ESP, PCP, rod pump, jet pump, and piston pump. He determined the technical feasibility and the cost evaluation of these seven techniques. His workflow consisted of three rounds. The first round was the preliminary screening round. By using all input well conditions, the impractical techniques were screened out. In the second round, all the techniques from round one were graded and ranked. In the third round, the economic evaluation was performed by using cost for each artificial lift method and assuming the constant additional gas production per day to determine net present value (NPV) and internal rate of return (IRR). In this thesis, we propose an extended workflow from the Han-Young?s thesis for the decision matrix tool. We added integrated production simulations (reservoir to wellhead) step with commercial software in between the second and third round. We performed simulations of the various artificial lift methods to see the additional gains from each technique. We used the additional gas production resulted from simulation to calculate economic yardsticks (the third round), NPV and IRR. Moreover, we made the decision matrix more complete by adding three more liquid unloading techniques to the decision matrix: velocity string, foam injection, and heated tubing. We have also updated all screening conditions, the technical scores, and the costs for the decision matrix from the previous study using literature reviews, information from the project?s sponsor, information from service company and our own judgment. The aim of the decision matrix is to allow operators to screen quickly and efficiently for the most suitable artificial lift method to solve the liquid loading problem under given well conditions.

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