New Generation Impulse Testing: An Environmentally Friendly Well Testing Solution for Tight Reservoirs to Acquire Accurate Reservoir Information

Abstract

Exploration, appraisal, and production well tests have always been a primary source of information for reservoir characterization, well deliverability estimation, and monitoring of field development. Well test operations are one of the most challenging operations performed at the wellsite today, especially in tight oil and gas reservoirs with limited capability or inability of the well to flow naturally and produce reservoir hydrocarbons to surface. Conventional drill stem tests (DSTs) may also not be applicable in some cases due to the high cost of operations or other constraints. Over time, environmental considerations and regulations have become stricter and one of the most significant limiting factors for conducting conventional DST operations in some geographical areas. DST operations in tight reservoirs have always been limited and deemed challenging due to complexities associated with the ability to create enough pressure drawdown, high risks associated with the inability of the well to flow to surface to unload the liquids from the wellbore, and clean-up of the well to unlock true reservoir potential. Therefore, for the last several decades, the oil industry has been trying to find the most effective ways to flow test these wells to determine essential reservoir information and minimize field development risks. Impulse testing is not a new concept and enables testing a well using a simple DST or tubing-conveyed perforating (TCP) string with no flow of hydrocarbon to surface. This method also reduces cost in comparison with conventional DST operations or other standard testing methods. Until recently, the application of this type of test has been limited, mainly by the complexity of interpreting the test data, limited functionalities of the tools, low success rate, and poor quality of acquired data. With the evolution of downhole DST tool technology and enhancements in well test design, along with the appropriate equipment selection, a new generation of low flow rate impulse tests have been engineered for success by bringing together a multidisciplinary team and emphasizing the importance of the job design. The paper describes cost-effective, practical, and proven impulse testing methods for tight oil and gas reservoirs. The proposed methods are versatile and adaptive to the operating environment and the operator's requirements. The zero-emission well testing solution is based on proven conventional well test interpretation methods and a combination of technologies, workflows, and unique equipment arrangements that make it possible to flow test the wells to determine key reservoir dynamic parameters and the productivity indices of new wells during DST or TCP operations or during workover operations if the wells are currently in production. This paper also presents several field examples from operations performed around the globe, with results of the successful pressure transient analysis of the data recorded during the tests that enabled characterizing the reservoir economically and in two cases, with no environmental impact.