A new method for performing reduced cost injection/falloff tests in under-pressured reservoirs has been developed at the GRI sponsored Rock Creek research site. The new method referred to as the "Tank Test" uses gravity drainage from a water storage tank to inject water into the reservoir. The primary advantages of Tank Test over the traditional injection/falloff tests are reduced costs and improved test results. The tank test eliminates the need for expensive pumping equipment and the manpower required for manual pump rate adjustments. Further cost savings can also be made by using gauges intended for ground water monitoring in place of oil field gauges when downhole shutin is not required. The low cost of the Tank Test allows longer duration tests to be economically performed so that the radius of investigation of a test is extended. The Tank Test also reduces the possibility of fracturing the reservoir during the injection portion of the test which is a common problem when testing shallow low permeability reservoirs. This paper describes the circumstances under which the Tank Test is most applicable, the equipment that is required and how to perform the test. The paper presents results of field tests performed on coal seams and a test performed on an Antrim Shale well. A simple Tank Test design procedure is also provided.

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