Geological Foundation for Production of Natural Gas

贺梦准

Geological Foundation for Production of Natural Gas from Diverse Shale Formations

Shale gas development is takingplace in multiple Paleozoic formations in the Black Warrior basin and the Appalachianthrust belt of Alabama.The diversity of these formations, which range in age from Cambrian to Mississippian,provides an excellent opportunity to examine shale formations with a wide rangeof reservoir properties in varied geologic settings. To facilitate the developmentof shale gas reservoirs in the region, this study employs a systematic, multidisciplinaryapproach to the evaluation of shale reservoirs. Key geologic variables addressedare stratigraphy, sedimentation, structure, hydrodynamics, geothermics, petrology,geochemistry, gas storage, and permeability.

Stratigraphy and sedimentationare important because many of the fundamental characteristics of shale are determinedin the original depositional environment. Alabama shale reservoirs were deposited in euxinicsedimentary basins that were influenced by the development of cratonic carbonateramps and orogenic foreland basins. Numerous sedimentary processes were active inthese basins, and secular variation of physical, geochemical, and biological processesresulted in complex stratigraphic architecture and heterogeneous reservoir quality,which are important considerations for shale gas development. Folding and faultingaffect the geometry and continuity of reservoirs, and fracturing affects subsurfaceflow and the applicability of completion technology to shale formations. The BlackWarrior basin and Appalachian thrust belt contain a spectrum of extensional andcompressional tectonic structures, and these structures are expressed differentlyin each target shale formation.

Hydrodynamics and geothermicsin the study area are influenced by recharge along the frontal Appalachian structures,as well as gas pressure in the interiors of deep geologic structures. Heterogeneouspermeability in stacked geologic formations is a key determinant of subsurface fluidchemistry and reservoir pressure. All shale formations examined in this study havegenerated thermogenic hydrocarbons in the geologic past, and hydrocarbon pressurepersists today in many areas. Modern reservoir temperatures range greatly dependingon depth and geothermal gradient, and deep, warm reservoirs can have vastly differentreservoir properties than shallow, cool reservoirs.

Petrology and geochemistry areimportant for characterizing reservoir quality. All shale formations studied containa broad suite of detrital and authigenic minerals. Rock fabric was influenced bysedimentation, diagenesis, and hydrocarbon generation, and the degree of alignmentof platy clay minerals appears to reflect structure and basin hydrodynamics. Detritaland authigenic minerals, moreover, affect shale geomechanics and the applicabilityof hydraulic fracturing technologies. Most prospective shale reservoirs can be classifiedas type III or IV source rocks that are sufficiently mature to have exhausted mosthydrocarbon generative potential. However, analysis of gas storage and mobilityindicates that the shale units have favorable reservoir properties. Shale is a dual--‐porosityreservoir in which some gas is stored in a free state, and some is adsorbed on organic matter.

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Geological Foundation for Production of Natural Gas from Diverse Shale Formation.rar (5 MB, 下载次数: 8, 售价: 4 阳光币)

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Geological Foundation for Production of Natural Gas from Diverse Shale Formation.rar (4.12 MB, 下载次数: 7, 售价: 4 阳光币)

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zhyq1013

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