Enhanced Wireline Formation Tests in Low-Permeability Formations: Quality Control Through Formation Rate Analysis (2000)

Enhanced Wireline Formation Tests in Low-Permeability Formations: Quality Control Through Formation Rate Analysis Jaedong Lee; Jaedong Lee Baker Atlas Search for other works by this author on: This Site Google Scholar John Michaels John Michaels Baker Atlas Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Rocky Mountain Regional/Low-Permeability Reservoirs Symposium and Exhibition, Denver, Colorado, March 2000. Paper Number: SPE-60293-MS https://doi.org/10.2118/60293-MS Published: March 12 2000 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Lee, Jaedong, and John Michaels. "Enhanced Wireline Formation Tests in Low-Permeability Formations: Quality Control Through Formation Rate Analysis." Paper presented at the SPE Rocky Mountain Regional/Low-Permeability Reservoirs Symposium and Exhibition, Denver, Colorado, March 2000. doi: https://doi.org/10.2118/60293-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Rocky Mountain Petroleum Technology Conference / Low Permeability Reservoirs Symposium Search Advanced Search AbstractWireline Formation Test (WFT) tools are used to measure formation pressures at discrete depths and to obtain fluid samples. From these pressure tests, fluid density and fluid contacts can be derived.The transient pressure response created by a WFT pressure test has typically been analyzed by methods that originated from well test analysis. In 1996 a new method based on the formation flow rate was developed that simultaneously considers both drawdown and buildup portions of the data. Because the new method is based on material balance from the beginning of the test, it accounts for the storage effect in the tool. By a simple, graphical technique or multi-regression analysis, the method determines fluid compressibility, mobility, and undisturbed formation pressure (P*).Pressure tests in low-permeability formations have been hampered by problems, such as excessively long buildup time, supercharging, and loss of packer seals. In addition, pressures with insufficient drawdown volume are confused with tight formation tests. These problems result in abandonment of tests or incorrect formation pressures that eventually give false pressure gradients, and waste rig time.We have analyzed numerous field and test-well jobs and have found that good pressure tests in a low-permeability formation can be achieved in less time by implementing quality control procedures through the new method. The ability to repeat a pressure test provides a good basis for applying quality control measures while logging. When the new method indicates a tight formation for the initial test, the drawdown rate for a subsequent test is controlled to a very low rate (less than 0.5 cc/s) and a real time cross plot of formation rate versus pressure is monitored to ensure the quality of the data.The new method can also detect tool plugging and the presence of pressure supercharging. These abilities can assess the validity of a test during testing and thereby provide a way to assure that a test is successful.IntroductionWireline formation testers (WFT) are used to measure formation pressure at discrete depths along a wellbore. From these data information on formation fluid type, fluid contact depth, and formation connectivity to another wells is eventually obtained. In probe-type wireline formation tests, a tube or conduit is extended to the formation and a small volume of fluid, typically 10 cc or less, is withdrawn from the formation. An initial-test starts from the hydrostatic pressure and repeat-tests thereafter start from the prior buildup pressure (presumably the formation pressure).The pressure change during the drawdown and the buildup period are recorded and then analyzed for the formation pressure, mobility, and the fluid compressibility. Various conventional analysis techniques, drawdown, spherical-flow, cylindrical-flow analyses, have been used in the industry.1,2,3 Analysis methods with storage and skin based on a spherical model was developed and supported by numerical simulation studies.4,5 These techniques are designed to analyze tests after the job is complete, or just to estimate the pressure and mobility of the formation during the job, but they do not provide any information on whether the test itself is valid or not.WFT pressure tests can be hampered by various reasons, including insufficient drawdown volume, tool or formation plugging during a test, imperfect sealing, or pressure supercharging, that result in false pressure information. Pressure tests with a drawdown rate that is too fast or that provide insufficient drawdown volume should be avoided. Too fast of a drawdown rate can cause excessive pressure drop and long buildup time. If the formation cannot provide enough fluids, the pressure response will be dominated by the compressibility of fluid in the tool. The pressure can go below the bubble point pressure and gas will evolve from the solution occupying the flowline of the tester. Keywords: artificial intelligence, piston rate, drawdown, spe 60293, pressure transient analysis, formation rate, compressibility, pressure transient testing, upstream oil & gas, bubble point pressure Subjects: Formation Evaluation & Management, Pressure transient analysis, Formation test analysis (e.g., wireline, LWD) This content is only available via PDF. 2000. Society of Petroleum Engineers You can access this article if you purchase or spend a download.