Full-Scale Testing Shows Advantages of a Quantitative Approach to Interpreting Inflow Tests
- Reza Rahmani (National Oilwell Varco) | Darryl Bourgoyne (Bourgoyne Engineering, LLC) | John R. Smith (Louisiana State University)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- May 2014
- Document Type
- Journal Paper
- 78 - 87
- 2014.Society of Petroleum Engineers
- 4.3.4 Scale, 3 Production and Well Operations, 1.11 Drilling Fluids and Materials
- Inflow test, Inflow, Well control, Integrity test, Negative pressure test
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- 339 since 2007
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An inflow (commonly known as negative pressure) test is an important step in proving well integrity for some well operations. Although the concept is straightforward, there are no standard procedures for conducting and interpreting inflow tests. Recent industry experience has shown the potential for these tests to be misinterpreted, with disastrous results. This paper describes proper quantitative interpretation of both successful and unsuccessful tests demonstrated on two full-scale test wells. Tests with and without leaks are simulated in two vertical wells with 2,971- and 5,884-ft depths. Test results are interpreted quantitatively to distinguish successes from failures. In addition, the impacts of leak rate and the differential pressure between the leak source and well are investigated. The impacts of gas as a leak fluid, different well volumes, different surface-piping arrangements, and measuring with different-sensitivity tanks are also shown. The success of a test should be verified with both flow and pressure checks. For the flow check, the trend between bleed-off pressure and volume of bleedoff can be predicted on the basis of fluid compressibility, tubing expansion, and drainage from surface piping. Deviations from that trend will identify the onset of a leak. Early detection and control of a high-rate leak can reduce the formation-fluid volume entering the well and the consequent risks. Detecting a low-rate leak is difficult if the test duration is too short. Therefore, a 30-minute test duration was evaluated for detection of low-rate leaks. The fundamental differences between a leak and no leak are demonstrated conclusively with quantitative results. Approaches for overcoming complications that interfere with conclusive test results are explained and demonstrated. The demonstration test results and the proposed interpretation methods are applicable to vertical wells. Drilling-fluid properties, multiple fluids, and thermal expansion can also influence results, but were not investigated in this study. Nevertheless, these results should provide a basis for improving field procedures and minimizing the risk of misinterpreting a leak as a successful test.
|File Size||1 MB||Number of Pages||10|
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