Transient Gas-Well Testing In Consideration Of Wellbore-Temperature Changing

Natural gas is the third energy in the world,after coal and oil.With the decrease of oil and aggravating of environmental pollution problems,the exploitation and utilization of natural gas are becoming more and more valued and will be the main energy in the twenty-one century.Well test can provide effective information of depicting the dynamic formation parameters,which helps to develop the gas reservoir reasonably.However,the well test mode in previous studies neglected the wellbore temperature change, because the high temperature and pressure of gas owing to gas reservoir is buried deep,it will produce remarkable influence on the results of well test without considering the influence of wellbore temperature changes.In this paper,on the basis of mechanism of wellbore heat loss and flow characteristics of gas in formation,mathematical modes of well test interpretation of single-phase flow in homogeneous gas reservoir and fractured gas reservoir are derived,which allow for the influence analysis of change of wellbore temperature and variable wellbore storage and skin factor. Obtaining the solutions of models by numerical difference method and drawing the log-log curves of bottom hole pressure and pressure derivative . Analysis of the impact of factors on the pressure and pressure derivative log-log curves deep.Parameters sensitivity analysis indicate that: in homogeneous gas reservoir, the starting position of pressure and pressure derivative curves move up,and pressure derivative curves occur concave before it achieve final horizontal line and the curve shape is similar to the features of double medium gas reservoir;in the fractured gas reservoir, pressure derivative curves occur concave before it reaches first radical flow and the curve shape is similar to the features of triple medium gas reservoir.Therefore,in the actual well test data analysis,only considering geology and other aspects of information comprehensivly can we make the right and reasonable judgments.Finally,automatic matching well test analysis methods have been researched systematically.Gas well test interpretation software considering wellbore temperature change is developed,in which Auto-fitting technique using genetic algorithms is unifid.The software gains satisfactory results by interpretation and analysis of actual site data..