Comparison on injection and pressure drop measuring and test results of different well completion type coal reservoir parameters

In order to get the reservoir parameters,an injection and pressure drop method was applied to the comparison tests and analysis on the coal reservoir para meters under the open hole,casing,perforation in casing,different stage after the fracturing and other different well completion type.The results showed that under the stabl e condition of the well hole,an open hole type well test method should be applied.Under a quite poor stability condition of the well hole an inner casing test would be applie d and the injection and pressure drop test would be conducted after the perforation in casing.The open hole type well test results could more accurately reflect the coal res ervoir features and the fracturing test results could directly guide the initial drainage and extraction work of the coalbed methane well.After the perforation in the casing,due the tests influenced by the well cementation,perforation and other procedure,the test results would not be accurate to the test results of the open well and fracturing well.Th e well test in casing should expand the test time ,injection pressure and other controlled factors in order to have more reliable test results.