Study On Gas Well Productivity Evaluation Of Reservoirs Which Contain CO₂

In recent years, the development of gas reservoirs which contain CO₂ has achieved great attention around the world with the increasing levels of exploration and development, as well as the CO₂ flooding enhanced oil recovery in low permeability oilfield with satisfactory results. However, the characteristic of such gas reservoir and the flow law in complex porous media are not clear, the method of dynamic analisis and productivity evaluation are also to be resolved.At present, the development of gas reservoir with CO₂ contains the following problems: The PVT parameters calculation method for gas reservoir with CO₂ is not perfect and the influence of CO₂ content to the gas physical parameters is unclear;The mechanism of fluids flow in complex porous media of gas reservoir with CO₂ has not been fully realized.The impact analysis of various flow characteristics （Starting Pressure Gradient、Slippage Effect、Stress-sensitive Effect） and CO₂ content on gas well productivity evaluation is not comprehensive enough.To solve the above problems, the conventional calculation method of gas PVT parameters was modified considering the characteristics of gas reservoir with CO₂ and a new calculation method which is fit for gas with CO₂ was put forward. By comparing the calculation results with experimental datas ,the correctness of the modified method was verified .And the physical parameters sensitivity analysis also was finished.Then based on the gas flow mechanism theory, the gas production equation which considers the comprehensive effects of Starting Pressure Gradient, Slippage Effect, and Stress-sentive Effect was established.By using VB6.0 programming language, the gas well productivity evaluation computer program was developed, the sensitivity analysis about CO₂ content and the different factors on gas well productivity was made then. Study shows that the impacts of various factors on gas productivity are different.Stress-effective Effect can reduce gas well productivity, and influence the gas well productivity much more than Starting Gradient Pressure and Slippage Effect, so it must be considerd fully enough.Starting Pressure Gradient slightly reduced the productivity of gas wells, while Slippage Effect is benefit for the productivity of gas wells.Finally, the productivity of XuShen gas field in Daqing was calculated, the correctness of the productivity equation was verified, a new evaluation method which can provide some scientific references for gas reservoir development with CO₂.was proposed.