Novel Deliverability Test Method for HPHT Sour Gas Wells

Abstract Sour gas reservoirs with H2S and/or CO2are widely spread in the whole world, especially in France, Canada, America and China. Most of sour gas reservoirs in China are HPHT tight gas reservoirs which require long testing duration to reach steady state when conducting deliverability test while long testing time leads to huge operation risk because testing tools are used close to critical temperature and pressure condition. In order to resolve the contradiction among testing duration, operation risk and interpretation results' accuracy, a new deliverability test method is proposed by using pressure buildup transient data. The deliverability calculation model is built by integrating wellbore fluid flow and formation seepage considering fluid flow from formation to wellbore after well shut-in. The formation parameters are interpreted by one pressure buildup transient data, based on which, four daily production rates are designed to simulate the wellbore flow pressure until the well reaches steady state flow, and then the deliverability equation can be derived from the pressure & daily rate points under steady state flow. Filed case comparison is made between interpretation of actual test data and data from the new method. Results show that the new deliverability test method can get more accurate deliverability equation and AOF by only 1 time pressure buildup and greatly reduces the duration for testing, so it is very practicable because it can greatly decrease the operation risk and increase interpretation accuracy for HPHT sour gas reserviors. This new deliverability test method has wide application prospect in HPHT sour gas reservoirs and can be extended to other oil/gas reservoirs' application for quick AOF determination, rate allocation, and economic evaluation.