This work investigated the pore structure characteristics and reservoir features of the finegrained tight reservoirs in the lower member of the Xinhe Formation(J2x1) in the Xiaohu subsag,Yabulai Basin based on core sa...This work investigated the pore structure characteristics and reservoir features of the finegrained tight reservoirs in the lower member of the Xinhe Formation(J2x1) in the Xiaohu subsag,Yabulai Basin based on core samples through various techniques. Interbedded silt/fine sandstones and mudstones are developed in the study area. Scanning electron microscopy(SEM) images were used to delineate different types of pores, including primary intergranular pores, secondary intergranular and intragranular pores, organic pores and fractures. The pore types were distinguished by pore size, pore area, location and formation process. The pore radii of the fine-grained rocks range from 1 nm to 1.55μm, mainly concentrated between 5 and 300 nm by low pressure N2adsorption and MICP analyses. The pore structure parameters of pore throat size and pore throat sorting coefficient are both positively correlated with porosity, while pore throat sorting coefficient has a negative correlation with permeability. The pore structures of the studied samples are much related to the mineral type and content and grain size, followed by TOC content. In these rocks with relatively low TOC and low maturity, the rigid minerals protect pores with pressure shadow from collapse, and dissolution-related pores contribute a lot to inorganic porosity. In contrast, these rocks with abundant TOC contain a large number of organic pores. The permeability of the fine-grained tight reservoir is mainly dominated by larger pore throats, while a large number of small pores(mostly <0.1 μm) contribute considerably to porosity. These results have deepened our understanding of the interbedded fine-grained tight reservoirs and can be applicable to fine-grained reservoirs in a similar setting.展开更多
The Shahejie Formation is a fundamental rock unit for hydrocarbon exploration and production in the Nanpu Sag,Bohai Bay Basin.Methodology including thin sectioning,core observations,fluorescence,scanning electron micr...The Shahejie Formation is a fundamental rock unit for hydrocarbon exploration and production in the Nanpu Sag,Bohai Bay Basin.Methodology including thin sectioning,core observations,fluorescence,scanning electron microscopy,cathodoluminescence,fluid inclusion,laser scanning confocal microscopy and geochemical analysis(C,O isotopes)were all utilized to investigate the reservoir characteristics and origin of the Es_(1)Sandstone.Thin section study showed that the reservoir rock consisted of feldspathic litharenite and lithic arkose.The reservoir pores are categorized as intergranular pores,fracture pores,dissolution pores and intergranular cement dissolution pores.The studied sandstone had good porosity(0.05%–35%)and permeability(0.006–7000 mD).The Es_(1) reservoir is classified as a fractured reservoir,a primary intergranular pore-associated reservoir and a dissolution reservoir.Deposition,diagenesis and tectogenesis are the main factors that played important roles in the development of the reservoir.Sedimentation is the foundation and assumption for reservoir development,but the effective reservoir is primarily controlled by primary pores,fractures,lithofacies,tectonic elements and dissolution pores.Moreover,compaction,fracture filling and cementation were the primary sources of reservoir densification.The reservoir was progressively formed through the influence of different geological and diagenetic events.The present study provides significant information and references for hydrocarbon exploration and development in the Nanpu Sag.展开更多
基金financially supported by the National Natural Science Foundation of China (grant No. U1762217)the State Key Development Program for Basic Research of China (grant No. 2014CB239002)+1 种基金the National Science and Technology Special Grant (grant No. 2016ZX05006-007)the Fundamental Research Funds for the Central Universities (grant No. 15CX06009A)
文摘This work investigated the pore structure characteristics and reservoir features of the finegrained tight reservoirs in the lower member of the Xinhe Formation(J2x1) in the Xiaohu subsag,Yabulai Basin based on core samples through various techniques. Interbedded silt/fine sandstones and mudstones are developed in the study area. Scanning electron microscopy(SEM) images were used to delineate different types of pores, including primary intergranular pores, secondary intergranular and intragranular pores, organic pores and fractures. The pore types were distinguished by pore size, pore area, location and formation process. The pore radii of the fine-grained rocks range from 1 nm to 1.55μm, mainly concentrated between 5 and 300 nm by low pressure N2adsorption and MICP analyses. The pore structure parameters of pore throat size and pore throat sorting coefficient are both positively correlated with porosity, while pore throat sorting coefficient has a negative correlation with permeability. The pore structures of the studied samples are much related to the mineral type and content and grain size, followed by TOC content. In these rocks with relatively low TOC and low maturity, the rigid minerals protect pores with pressure shadow from collapse, and dissolution-related pores contribute a lot to inorganic porosity. In contrast, these rocks with abundant TOC contain a large number of organic pores. The permeability of the fine-grained tight reservoir is mainly dominated by larger pore throats, while a large number of small pores(mostly <0.1 μm) contribute considerably to porosity. These results have deepened our understanding of the interbedded fine-grained tight reservoirs and can be applicable to fine-grained reservoirs in a similar setting.
基金This study was funded by the Natural Science Foundation of China Project(No.41602138)National Science and Technology Special Grant(No.2016ZX05006-007)+1 种基金China Postdoctoral Science Foundation-funded project(No.2015M580617,2017T100524)the Fundamental Research Funds for the Central Universities(No.15CX08001A).
文摘The Shahejie Formation is a fundamental rock unit for hydrocarbon exploration and production in the Nanpu Sag,Bohai Bay Basin.Methodology including thin sectioning,core observations,fluorescence,scanning electron microscopy,cathodoluminescence,fluid inclusion,laser scanning confocal microscopy and geochemical analysis(C,O isotopes)were all utilized to investigate the reservoir characteristics and origin of the Es_(1)Sandstone.Thin section study showed that the reservoir rock consisted of feldspathic litharenite and lithic arkose.The reservoir pores are categorized as intergranular pores,fracture pores,dissolution pores and intergranular cement dissolution pores.The studied sandstone had good porosity(0.05%–35%)and permeability(0.006–7000 mD).The Es_(1) reservoir is classified as a fractured reservoir,a primary intergranular pore-associated reservoir and a dissolution reservoir.Deposition,diagenesis and tectogenesis are the main factors that played important roles in the development of the reservoir.Sedimentation is the foundation and assumption for reservoir development,but the effective reservoir is primarily controlled by primary pores,fractures,lithofacies,tectonic elements and dissolution pores.Moreover,compaction,fracture filling and cementation were the primary sources of reservoir densification.The reservoir was progressively formed through the influence of different geological and diagenetic events.The present study provides significant information and references for hydrocarbon exploration and development in the Nanpu Sag.
