Geochemical Characterization Of Eagle Ford Organic Matter Rich Shale And Pore Evaluation

Cretaceous source rocks in south Texas Eagle Ford formation are characterized by variations in organic matter input and depositional environments.Organic matter input,sedimentary environments,redox condition and lithology of the source rocks as interpreted from bulk properties,residual oil chromatography,and biomarkers analysis.The source rocks investigated include samples from five wells of Eagle Ford formation.Combined with other geochemical and geological data reveal Eagle Ford shales and marls appears a Type II kerogen deposited in a marine environment under anoxic conditions,and it is likely the Eagle Ford kerogen that generated these high sulfur oils(up to 2.6%sulfur)also has elevated sulfur contents.As a consequence of the elevated sulfur contents in the First Shot field Eagle Ford kerogen,oil generation may have begun earlier in time at lower maturity levels than is characteristic of more typical Type II kerogens(Janell and Pitman,2010).It is important to document which unit or both units in the Eagle Ford Group are favorable to S-rich kerogen formation,and this issue hasn't been addressed yet since no low mature samples is available for the purpose.The redox condition of depositional environments is important to control organic matter marcel composition and organic matter preservation,resulting in variation of organic matter source type under various depositional facies.The difference,in turn,greatly affects organic matter conversion under geological conditions.Also thesedifferences in organic geochemical characterization could conbine with stratigraphy,petrography and chemostratigraphy help to indentify the boundry of the Cenomanian-Turonian,which is always a dispute in the Eagle Ford shale study.Together,the combination of pore characterization with SEM pore imaging and N2 adsorption isotherms and hydrocarbon geochemical characterization will constitute a comprehensive examination of the compositional and petrographic evolution of organic matter across a range of thermal maturity with the goal of refining our understanding of petroleum generation,migration,and storage.·Adsorption and desorption isotherms are powerful tools for determining pore volume and pore size distribution.·Residual oil is mainly stored in pores larger than 20 nm in width.·Both compaction and cementation and organic matter thermal maturation affect pore evolution of organic-rich Eagle Ford shales.·Organic matter thermal maturation is associated with the formation of OM-hosted pores<20nm in width.·The formation of oil might prohibit in some degree the loss of mineral-hosted pores>20nm in width during compaction and cementation.Integrated pore studies with SEM pore imaging will adequately define the genetic relationships between pore sizes and pore types.Also the pore network associated with the permability is related to the certain type of pores.