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Gas Hydrate Occurrence and Volume Estimate in the Northern Gulf of Mexico

Majumdar, Urmi
http://rave.ohiolink.edu/etdc/view?acc_num=osu1524234199337282

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Geological Sciences.
The northern Gulf of Mexico is a world-class location for exploration and production of oil and natural gas resources. Natural gas hydrate has also been investigated in the Gulf of Mexico for over forty years, but the existing data set of petroleum industry well logs have been barely used for gas hydrate assessment. In this research, I use this extensive data set of publicly available petroleum industry well logs to identify occurrences of natural gas hydrate and henceforth provide a new estimate of the gas hydrate-bound natural gas in the northern Gulf of Mexico. In addition, I use the empirical data set of gas hydrate occurrences in petroleum industry wells to find the relationship between the occurrences of gas hydrate and the presence of bottom-simulating reflections. I use a data set of 798 petroleum industry wells with electrical resistivity and gamma ray well logs recorded within the gas hydrate stability zone. Based on an increase in resistivity of 0.5 Om or greater relative to the interpreted resistivity of brine-saturated sediment, I find evidence that gas hydrate occurs in 124 wells. I compiled a data set of the analyzed wells that includes information such as the well surface location, depth intervals and resistivity of potential gas hydrate accumulations. Wells are categorized by the potential gas hydrate accumulations, based on the thickness of gas hydrate accumulations and the resistivity log increase. I find that even though subsurface gas hydrate occur throughout the northern Gulf of Mexico, accumulations of higher quality gas hydrate occur five to eight times more frequently along the rims of mini-basins and over salt ridges than inside mini-basins in the northern Gulf of Mexico. I use this empirical data set of gas hydrate occurrences in the northern Gulf of Mexico to find the volume of gas hydrate-related gas. I develop a Monte Carlo simulation to produce a probabilistic range of the volume from 10th percentile to 90th percentile, with the mean estimate being the most likely value. I run 10000 Monte Carlo trials through repeated sampling of five variables which includes the thickness of the gas hydrate stability zone, the fraction of the gas hydrate stability zone occupied by gas hydrate, porosity of sediments, saturation of gas hydrate (based on host lithology) and hydrate to gas volume conversion factor. I find that the northern Gulf of Mexico hosts 53 x 1012 m3 of gas hydrate-related gas. I also combine the well log data set with a data set of bottom-simulating reflections (BSR) in the same area identified from 3-D seismic data to analyze the correlation between gas hydrate accumulations and BSR occurrences. Along with finding the precise depth of the base of gas hydrate stability zone in submarine sediments, BSRs are also frequently used as a geophysical indicator of the presence of gas hydrate. I find that a BSR increases the chances of finding gas hydrate by 2.6 times as opposed to drilling outside a BSR. The wells within a BSR also contain thicker and overall higher quality hydrate accumulations. Even so, over half of the wells drilled through BSRs have no detectable gas hydrate accumulations, and gas hydrate occurrences and BSRs do not coincide in most cases.
Ann Cook (Advisor)
84 p.
Earth; Geology
Gas hydrate; Gulf of Mexico; Industry wells

Recommended Citations

Citations

  • Majumdar, U. (2018). Gas Hydrate Occurrence and Volume Estimate in the Northern Gulf of Mexico [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524234199337282

    APA Style (7th edition)

  • Majumdar, Urmi. Gas Hydrate Occurrence and Volume Estimate in the Northern Gulf of Mexico. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1524234199337282.

    MLA Style (8th edition)

  • Majumdar, Urmi. "Gas Hydrate Occurrence and Volume Estimate in the Northern Gulf of Mexico." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524234199337282

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.