Sonic-Magnetic Resonance Method: A Sourceless Porosity Evaluation in Gas-Bearing Reservoirs (1999)

Sonic-Magnetic Resonance Method: A Sourceless Porosity Evaluation in Gas-Bearing Reservoirs Chanh Cao Minh; Chanh Cao Minh Schlumberger Search for other works by this author on: This Site Google Scholar Greg Gubelin; Greg Gubelin Schlumberger Search for other works by this author on: This Site Google Scholar Raghu Ramamoorthy; Raghu Ramamoorthy Schlumberger Search for other works by this author on: This Site Google Scholar Stuart McGeoch Stuart McGeoch Shell Company of Australia Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Houston, Texas, October 1999. Paper Number: SPE-56767-MS https://doi.org/10.2118/56767-MS Published: October 03 1999 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Minh, Chanh Cao, Gubelin, Greg, Ramamoorthy, Raghu, and Stuart McGeoch. "Sonic-Magnetic Resonance Method: A Sourceless Porosity Evaluation in Gas-Bearing Reservoirs." Paper presented at the SPE Annual Technical Conference and Exhibition, Houston, Texas, October 1999. doi: https://doi.org/10.2118/56767-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractFor environmental reasons, there are times when the use of radioactive chemical sources for density and neutron logging is not possible. The inability to use these logging tools seriously affects porosity determination in gas-bearing reservoirs. Several tools, such as the nuclear magnetic resonance (NMR) tool, the sonic tool or a minitron-based tool, determine porosity without using a radioactive source. These tools, however, are influenced by many effects and, when used alone, cannot deliver an accurate gas-independent porosity.A new methodology that combines sonic and NMR logs for improved porosity evaluation in gas-bearing reservoirs is proposed. The first variant of the method uses the sonic compressional transit time and the total NMR porosity (TCMR) to determine the total porosity, corrected for the gas effect, and the flushed zone gas saturation. In this approach, a linear time-averaged equation corrected for compaction is applied to the sonic compressional log. The simplicity of the solution (much like the previously published DMR1Density-Magnetic Resonance Interpretation Method) allows fast, easy computation and a complete error analysis to assess the quality of the results.In the second variant of the method, we show that the rigorous Gassman equation has a very similar response to the Raymer-Hunt-Gardner (RHG) equation for a water-gas mixture. This allows substitution of the complex Gassman equation by the much simpler RHG equation in the combined sonic-NMR (SMR) technique to estimate total porosity and flushed zone gas saturation in gas-bearing formations.The technique is successfully applied to an offshore gas well in Australia. In this well, the porosity in the well-compacted sands is in the 20–25 p.u. range and the compaction factor is around 0.77. The sonic-magnetic resonance results compared favorably to the established density-magnetic resonance results and also to core data. In another offshore gas well from the North Sea, the porosity in the highly uncompacted sands is in the 35–40 p.u. range and the compaction factor is around 1.85. The SMR technique was able to produce a very good porosity estimate comparable to that estimated from the density-neutron logs. Keywords: sourceless porosity evaluation, wyllie, gas-bearing formation, equation, saturation, sonic-magnetic resonance method, tcmr, spe 56767, slowness, porosity Subjects: Formation Evaluation & Management, Open hole/cased hole log analysis This content is only available via PDF. 1999. Society of Petroleum Engineers You can access this article if you purchase or spend a download.