Pre-Job Planning Based on Nuclear Modeling Leads to Successful Downhole Mineralogy Determination in Extremely Challenging Logging Conditions
- Haijing Wang (Chevron U.S.A. Inc.) | Lorelea Samano (Chevron U.S.A. Inc.) | Kenneth D. Kelsch (Chevron U.S.A. Inc.) | Ela Manuel (Chevron U.S.A. Inc.) | Janet Yun (Chevron U.S.A. Inc.)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- SPWLA 60th Annual Logging Symposium, 15-19 June, The Woodlands, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2019. held jointly by the Society of Petrophysicists and Well Log Analysts (SPWLA) and the submitting authors
- 3 in the last 30 days
- 83 since 2007
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New-generation nuclear spectroscopy logging tools can provide downhole mineralogy and total organic carbon measurements in both open and cased wells. This technology is made possible by a combination of advanced physical measurements, data processing, and petrophysical interpretation. There is an emerging need to educate petrophysicists, core analysts, geologists, and other earth scientists on this technology to further expand its application, a task that requires a collective effort of nuclear experts in both logging and operating companies.
Here we demonstrate such an effort from an operator’s perspective using a case study in a carbonate reservoir. The downhole mineralogy is successfully determined despite extremely challenging logging conditions, namely a large borehole of 17.5 inch in diameter and mud salinity of 130 parts per thousand (ppk) in an upper open-hole section, and logging through 7” casing in a lower section. To justify the logging program in these extreme conditions, Monte Carlo nuclear modeling is applied during the pre-job planning process to optimize logging parameters and mitigate potential unfavorable effects of a large borehole and high salinity. During and after data acquisition, detailed data quality control with a complete set of raw and intermediate processing data helps to identify additional corrections needed for metal debris in the cased-hole section. The elemental dry weights are finally incorporated into multimineral analysis, improving the accuracy of mineralogy determination over the traditional method based on gamma ray-neutron-density-sonic logs, and enabling the formation evaluation through casing.
This case study is used to demonstrate best practices of nuclear spectroscopy logging and interpretation, including accurate pre-job planning, in-depth data quality control using complete raw and intermediate processing data, customized environmental corrections, and appropriate mineral models being applied. Collaborative work between logging and operating companies is critical towards expanding the operating envelope of new logging technology and advancing the general knowledge of the industry.
|File Size||2 MB||Number of Pages||16|