Calculation of porosity by combining the nuclear magnetic resonance and sonic logs in gas bearing reservoir at Sienna Field of WDDM concession in Egypt

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Petroleum & Energy Engineering Department

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Research Article

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World Applied Sciences Journal

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The estimated porosity may be inaccurate when calculated from conventional logs (unless corrected for gas and shale effect) and also underestimated when derived from nuclear magnetic resonance (NMR) logs due to the effect of the lower hydrogen index of natural gas in gas-bearing sandstones. A technique of calculating porosity by combining the NMR log with the conventional interval transit time log is proposed and it is based on principle of NMR log and the results obtained from a physical rock volume model which constructed on the basis of interval transit time logs. For wells with the NMR log acquired from the MRIL-C tool, this technique is reliable for evaluating the effect of natural gas and obtaining accurate porosity in any borehole. The NMR porosity should be first corrected by using the deep lateral resistivity log in wells with NMR log acquired from the CMR-Plus tool and with collapsed borehole. Two field examples of tight gas sandstones, in the studied concession, illustrate that the porosity calculated by using this technique matches the core analyzed results very well. Another field example, in this paper, of conventional gas-bearing reservoir (Sienna Field), verifies that this technique is usable not only in tight gas sandstones, but also in any gas-bearing reservoirs. This study is applied on a well in Sienna Field which is located in the west delta deep marine concession (WDDM). © IDOSI Publications, 2014.

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