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Abstracts: 2008

Mesozoic (Upper Jurassic-Lower Cretaceous) deep gas reservoir play, central and eastern Gulf coastal plain

The Mesozoic (Upper Jurassic-Lower Cretaceous) deeply buried gas reservoir play in the central and eastern Gulf coastal plain of the United States has high potential for significant gas resources. Sequence-stratigraphic study, petroleum system analysis, and resource assessment were used to characterize this developing play and to identify areas in the North Louisiana and Mississippi Interior salt basins with potential for deeply buried gas reservoirs. These reservoir facies accumulated in Upper Jurassic to Lower Cretaceous Norphlet, Haynesville, Cotton Valley, and Hosston continental, coastal, and marine siliciclastic environments and Smackover and Sligo nearshore marine shelf, ramp, and reef carbonate environments. These Mesozoic strata are associated with transgressive and regressive systems tracts. In the North Louisiana salt basin, the estimate of secondary, nonassociated thermogenic gas generated from thermal cracking of oil to gas in the Upper Jurassic Smackover source rocks from depths below 3658m (12,000 ft) is 4800 tcf of gas as determined using software applications. Assuming a gas expulsion, migration, and trapping efficiency of 2-3%, 96-144 tcf of gas is potentially available in this basin. With some 29 tcf of gas being produced from the North Louisiana salt basin, 67-115 tcf of inplace gas remains. Assuming a gas recovery factor of 65%, 44-75 tcf of gas is potentially recoverable. The expelled thermogenic gas migrated laterally and vertically from the southern part of this basin to the updip northern part into shallower reservoirs to depths of up to 610 m (2000 ft).

Examination of the development of liquefied natural gas on the Gulf of Mexico

This research examines the role, importance, and development of liquefied natural gas (LNG) regasification facilities along the Gulf of Mexico (GOM). The central conclusion of the research is that the GOM is perhaps the best situated location for the development of LNG regasification facilities given the region's proximity to a wide range of energy infrastructure assets that can help support, and serve as a market to, these new LNG investments.

The research provides historic context on LNG development in the U.S. and the factors that are making the current spate of LNG development different than what occurred during the late 1970s and early 1980s. Changes in natural gas markets have been examined and the role that new environmental pressures are placing on natural gas-fired power generation and industrial applications discussed. The LNG "value chain" is examined at length, as well as the respective costs, and estimated break-even prices needed to import natural gas into the U.S.

The interaction of these new LNG facilities with existing GOM energy infrastructure is examined in considerable depth. The research notes that GOM pipeline and storage infrastructure in the region is perhaps one of the most important sets of energy assets that will help facilitate the movement of imported gas across the region, and into other regions of the U.S. Gas processing and other supporting gas infrastructure is also examined.

Perhaps the biggest area of concern for many policy makers along the GOM is the ability of imported natural gas to help dampen both the increases and volatility of natural gas prices to all end users in the region, particularly those end users in the petrochemical sector. The research examines the challenges that high natural gas prices are having on these large energy using sectors, and the regional job losses that have occurred in the aftermath of the large natural gas price run up of 2000-2001.

The conclusion of the research is that the development of LNG regasification facilities along the GOM will be supplemental, and even complementary, to the existing set of energy infrastructure in the region. These facilities will provide new sources of revenue for pipelines, storage, and gas processing facilities, which in turn, can be used to service existing and ongoing domestic natural gas production. As a result, currently anticipated expansions of existing infrastructure (i.e., storage, pipelines, processing) in certain areas are anticipated to be more complementary, as opposed to competitive, with existing domestic natural gas production.

Hydrocarbon generating potential: Jurassic Cotton Valley - Bossier Group, North Louisiana Salt Basin

Geological/geochemical evaluation of Upper Jurassic Cotton Valley - Bossier core samples from the North Louisiana Salt Basin (NLSB) indicates that fine-grained rocks associated with these units are thermally mature and represent petroleum source rock that generated and expelled mostly gas and some oil. These findings are based on source rock characterization of samples from wells within the NLSB, Vernon Field, Jackson Parish, using total organic carbon (TOC), Rock-Eval pyrolysis, and visual kerogen data.

The data indicate that these rocks at their present maturity level have low to moderate TOC contents and Type III kerogen. Original kerogen types in the immature stage, as assessed by kerogen petrography, were mainly gas-prone Type III and some oil- and gas-prone Type II/III. The principal macerals are partly oxidized, unstructured amorphous organic matter (liptinite) and vitrinite in varying proportions. Amorphous material was derived from degraded marine algal and humic matter (higher plant materials). Visual kerogen data support the predominantly gas-prone nature of the source rocks. Vitrinite reflectance (Ro) values (0.94% to 2.62%) and thermal alteration indices (TAI) (2.8 to 3.7) suggest that these source rocks entered the late oil window to main gas maturity window and thus have generated mostly gas with some oil. Thin section petrography of geochemically analyzed intervals documents the following rock types: muddy fine-grained sandstone, laminated fine-grained sandstone, sandy mudstone, and silty mudstone. These combined analytical results indicate that abundant woody organic material of continental origin was deposited in offshore areas in association with fine siliciclastic sediments in a marine prodelta environment during Jurassic time. The thickness and widespread deposition of predominantly gas-prone rocks within the NLSB and their high thermal maturity led to sourcing of mainly gas with some oil in overlying Jurassic and Cretaceous reservoirs, particularly in the Bossier and Cotton Valley.