To reveal the effect of shale reservoir characteristics on the movability of shale oil and its action mechanism in the lower third member of the Shahejie Formation(Es3l), samples with different features were selected ...To reveal the effect of shale reservoir characteristics on the movability of shale oil and its action mechanism in the lower third member of the Shahejie Formation(Es3l), samples with different features were selected and analyzed using N2 adsorption, high-pressure mercury injection capillary pressure(MICP), nuclear magnetic resonance(NMR), high-speed centrifugation, and displacement image techniques. The results show that shale pore structure characteristics control shale oil movability directly. Movable oil saturation has a positive relationship with pore volume for radius > 2 μm, as larger pores often have higher movable oil saturation, indicating that movable oil is present in relatively larger pores. The main reasons for this are as follows. The relatively smaller pores often have oil-wetting properties because of organic matter, which has an unfavorable effect on the flow of oil, while the relatively larger pores are often wetted by water, which is helpful to shale oil movability. The rich surface provided by the relatively smaller pores is beneficial to the adsorption of immovable oil. Meanwhile, the relatively larger pores create significant pore volume for movable oil. Moreover, the larger pores often have good pore connectivity. Pores and fractures are interconnected to form a complex fracture network, which provides a good permeability channel for shale oil flow. The smaller pores are mostly distributed separately;thus, they are not conducive to the flow of shale oil. The mineral composition and fabric macroscopically affect the movability of shale oil. Calcite plays an active role in shale oil movability by increasing the brittleness of shale and is more likely to form micro-cracks under the same stress background. Clay does not utilize shale oil flow because of its large specific surface area and its block effect. The bedding structure increases the large-scale storage space and improves the connectivity of pores at different scales, which is conducive to the movability of shale oil.展开更多
Based on anatomy of key areas and data points and analysis of typical features of shell layer in Guanyinqiao Member, basic characteristics of key interfaces, mainly bentonite layers, in the Upper Ordovician Wufeng For...Based on anatomy of key areas and data points and analysis of typical features of shell layer in Guanyinqiao Member, basic characteristics of key interfaces, mainly bentonite layers, in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in the Sichuan Basin and its surrounding areas and the relationship between these key interfaces with the deposition of organic-rich shale have been examined systematically. The Wufeng Formation-Longmaxi Formation has four types of marker beds with interface attributes, namely, the characteristic graptolite belt, Guanyinqiao Member shell layer, section with dense bentonite layers, and concretion section, which can be taken as key interfaces for stratigraphic division and correlation of the graptolite shale. The shell layer in Guanyinqiao Member is the most standard key interface in Wufeng Formation-Longmaxi Formation, and can also be regarded as an important indicator for judging the depositional scale of organic-rich shale in key areas. There are 8 dense bentonite sections of two types mainly occurring in 7 graptolite belts in these formations. They have similar interface characteristics with the shell layer in Guanyinqiao Member in thickness and natural gamma response, and belong to tectonic interfaces(i.e., event deposits). They have three kinds of distribution scales: whole region, large part of the region, and local part, and can be the third, fourth and fifth order sequence interfaces, and have a differential control effect on organic-rich shale deposits. The horizon the characteristic graptolite belt occurs first is the isochronous interface, which is not directly related to the deposition of organic-rich shale. Concretions only appear in local areas, and show poor stability in vertical and horizontal directions, and have no obvious relationship with the deposition of the organic-rich shale.展开更多
Major breakthroughs of shale oil exploration have been made recently in the upper member of Paleogene Lower Ganchaigou Formation of Yingxiongling area, Qaidam Basin. However, the low total organic carbon content of sa...Major breakthroughs of shale oil exploration have been made recently in the upper member of Paleogene Lower Ganchaigou Formation of Yingxiongling area, Qaidam Basin. However, the low total organic carbon content of saline-lacustrine source rock, and unclear genetic mechanism, evaluation criteria and resources potential of the shale oil have restricted the exploration and evaluation of Yingxiongling shale oil. Through analysis of large amounts of cores, well drilling, seismic, laboratory test data and integrated study, focusing on the shale and mixed types of shale oil reservoirs characterized by high-frequency interbedded organic-rich laminated shale and limy dolomite, it is concluded that the shale oil in the upper member of Lower Ganchaigou Formation in the Yingxiongling area have six geological characteristics:(1) two-stage hydrocarbon generation of hydrogen-rich source rock and large amount of retained oil;(2) multiple types of reservoir space and good reservoir properties;(3)source-reservoir integration, thick “sweet spot” and high oil-bearing grade;(4) high pressure coefficient between and under salt layers, and sufficient formation energy;(5) high content of light components, high gas-oil ratio, and good quality of the crude oil;(6) high content of brittle minerals and good fracability. The evaluation criterion of shale oil is preliminarily established based on the eight parameters: total organic carbon content, maturity, effective porosity, oil saturation, brittle mineral content,pressure coefficient, lamellation density, and burial depth. Combined with parameters of E32 source rock thickness, area, vertical distribution of oil layers, and free hydrocarbon content, the shale oil resources have been preliminarily estimated as 21×10^(8) t.The structurally stable area is the predominant objective of shale oil exploration and the favorable exploration area for Yingxiongling shale oil is nearly 800 km^(2).展开更多
Based on 991 groups of analysis data of shale samples from the Lower Member of the Cretaceous Eagle Ford Formation of 1317 production wells and 72 systematic coring wells in the U.S. Gulf Basin, the estimated ultimate...Based on 991 groups of analysis data of shale samples from the Lower Member of the Cretaceous Eagle Ford Formation of 1317 production wells and 72 systematic coring wells in the U.S. Gulf Basin, the estimated ultimate recovery(EUR) of shale oil and gas of the wells are predicted by using two classical EUR estimation models, and the average values predicted excluding the effect of engineering factors are taken as the final EUR. Key geological factors controlling EUR of shale oil and gas are fully investigated. The reservoir capacity, resources, flow capacity and fracability are the four key geological parameters controlling EUR. The storage capacity of shale oil and gas is directly controlled by total porosity and hydrocarbon-bearing porosity, and indirectly controlled by total organic carbon(TOC) and vitrinite reflectance(Ro). The resources of shale oil and gas are controlled by hydrocarbon-bearing porosity and effective shale thickness etc. The flow capacity of shale oil and gas is controlled by effective permeability, crude oil density, gas-oil ratio, condensate oil-gas ratio, formation pressure gradient, and Ro. The fracability of shale is directly controlled by brittleness index, and indirectly controlled by clay content in volume. EUR of shale oil and gas is controlled by six geological parameters: it is positively correlated with effective shale thickness, TOC and fracture porosity, negatively correlated with clay content in volume, and increases firstly and then decreases with the rise of Ro and formation pressure gradient. Under the present upper limit of horizontal well fracturing effective thickness of 65 m and the lower limit of EUR of 3×10^(4) m^(3), when TOC<2.3%, or Ro<0.85%, or clay content in volume larger than 25%, and fractures and micro-fractures aren’t developed, favorable areas of shale oil and gas hardly occur.展开更多
The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source ...The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source rock in the Western Qaidam Depression,Qaidam Basin,NW China.Three main factors result in low TOC values of saline lacustrine source rock of the Qaidam Basin:relatively poor nutrient supply inhibits the algal bloom,too fast deposition rate causes the dilution of organic matter,and high organic matter conversion efficiency causes the low residual organic carbon.For this type of hydrogen-rich organic matter,due to the reduction of organic carbon during hydrocarbon generation,TOC needs to be restored based on maturity before evaluating organic matter abundance.The hydrocarbon generation of saline lacustrine source rocks of the Qaidam Basin is from two parts:soluble organic matter and insoluble organic matter.The soluble organic matter is inherited from organisms and preserved in saline lacustrine basins.It generates hydrocarbons during low-maturity stage,and the formed hydrocarbons are rich in complex compounds such as NOS,and undergo secondary cracking to form light components in the later stage;the hydrocarbon generation model of insoluble organic matter conforms to the traditional“Tissot”model,with an oil generation peak corresponding to Ro of 1.0%.展开更多
基金the National Science and Technology Major Project of China(Grant Nos.2017ZX05036-002-004.2017ZX05005-001-003)National Basic Research Program of China(Grant No.2014CB239105)for financial support.
文摘To reveal the effect of shale reservoir characteristics on the movability of shale oil and its action mechanism in the lower third member of the Shahejie Formation(Es3l), samples with different features were selected and analyzed using N2 adsorption, high-pressure mercury injection capillary pressure(MICP), nuclear magnetic resonance(NMR), high-speed centrifugation, and displacement image techniques. The results show that shale pore structure characteristics control shale oil movability directly. Movable oil saturation has a positive relationship with pore volume for radius > 2 μm, as larger pores often have higher movable oil saturation, indicating that movable oil is present in relatively larger pores. The main reasons for this are as follows. The relatively smaller pores often have oil-wetting properties because of organic matter, which has an unfavorable effect on the flow of oil, while the relatively larger pores are often wetted by water, which is helpful to shale oil movability. The rich surface provided by the relatively smaller pores is beneficial to the adsorption of immovable oil. Meanwhile, the relatively larger pores create significant pore volume for movable oil. Moreover, the larger pores often have good pore connectivity. Pores and fractures are interconnected to form a complex fracture network, which provides a good permeability channel for shale oil flow. The smaller pores are mostly distributed separately;thus, they are not conducive to the flow of shale oil. The mineral composition and fabric macroscopically affect the movability of shale oil. Calcite plays an active role in shale oil movability by increasing the brittleness of shale and is more likely to form micro-cracks under the same stress background. Clay does not utilize shale oil flow because of its large specific surface area and its block effect. The bedding structure increases the large-scale storage space and improves the connectivity of pores at different scales, which is conducive to the movability of shale oil.
基金Supported by the PetroChina Science and Technology Project(2021DJ1904)PetroChina Exploration and Production Company Marine Shale Gas Selection Project(kt2018-01-06)。
文摘Based on anatomy of key areas and data points and analysis of typical features of shell layer in Guanyinqiao Member, basic characteristics of key interfaces, mainly bentonite layers, in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in the Sichuan Basin and its surrounding areas and the relationship between these key interfaces with the deposition of organic-rich shale have been examined systematically. The Wufeng Formation-Longmaxi Formation has four types of marker beds with interface attributes, namely, the characteristic graptolite belt, Guanyinqiao Member shell layer, section with dense bentonite layers, and concretion section, which can be taken as key interfaces for stratigraphic division and correlation of the graptolite shale. The shell layer in Guanyinqiao Member is the most standard key interface in Wufeng Formation-Longmaxi Formation, and can also be regarded as an important indicator for judging the depositional scale of organic-rich shale in key areas. There are 8 dense bentonite sections of two types mainly occurring in 7 graptolite belts in these formations. They have similar interface characteristics with the shell layer in Guanyinqiao Member in thickness and natural gamma response, and belong to tectonic interfaces(i.e., event deposits). They have three kinds of distribution scales: whole region, large part of the region, and local part, and can be the third, fourth and fifth order sequence interfaces, and have a differential control effect on organic-rich shale deposits. The horizon the characteristic graptolite belt occurs first is the isochronous interface, which is not directly related to the deposition of organic-rich shale. Concretions only appear in local areas, and show poor stability in vertical and horizontal directions, and have no obvious relationship with the deposition of the organic-rich shale.
基金Supported by the National Natural Science Foundation of China(42090025)the PetroChina Science and Technology Major Project(2019E-2601)。
文摘Major breakthroughs of shale oil exploration have been made recently in the upper member of Paleogene Lower Ganchaigou Formation of Yingxiongling area, Qaidam Basin. However, the low total organic carbon content of saline-lacustrine source rock, and unclear genetic mechanism, evaluation criteria and resources potential of the shale oil have restricted the exploration and evaluation of Yingxiongling shale oil. Through analysis of large amounts of cores, well drilling, seismic, laboratory test data and integrated study, focusing on the shale and mixed types of shale oil reservoirs characterized by high-frequency interbedded organic-rich laminated shale and limy dolomite, it is concluded that the shale oil in the upper member of Lower Ganchaigou Formation in the Yingxiongling area have six geological characteristics:(1) two-stage hydrocarbon generation of hydrogen-rich source rock and large amount of retained oil;(2) multiple types of reservoir space and good reservoir properties;(3)source-reservoir integration, thick “sweet spot” and high oil-bearing grade;(4) high pressure coefficient between and under salt layers, and sufficient formation energy;(5) high content of light components, high gas-oil ratio, and good quality of the crude oil;(6) high content of brittle minerals and good fracability. The evaluation criterion of shale oil is preliminarily established based on the eight parameters: total organic carbon content, maturity, effective porosity, oil saturation, brittle mineral content,pressure coefficient, lamellation density, and burial depth. Combined with parameters of E32 source rock thickness, area, vertical distribution of oil layers, and free hydrocarbon content, the shale oil resources have been preliminarily estimated as 21×10^(8) t.The structurally stable area is the predominant objective of shale oil exploration and the favorable exploration area for Yingxiongling shale oil is nearly 800 km^(2).
基金Supported by the PetroChina Science and Technology Department Project(2012A-4802-02)National Key Basic Research and Development Program(2014CB239000)。
文摘Based on 991 groups of analysis data of shale samples from the Lower Member of the Cretaceous Eagle Ford Formation of 1317 production wells and 72 systematic coring wells in the U.S. Gulf Basin, the estimated ultimate recovery(EUR) of shale oil and gas of the wells are predicted by using two classical EUR estimation models, and the average values predicted excluding the effect of engineering factors are taken as the final EUR. Key geological factors controlling EUR of shale oil and gas are fully investigated. The reservoir capacity, resources, flow capacity and fracability are the four key geological parameters controlling EUR. The storage capacity of shale oil and gas is directly controlled by total porosity and hydrocarbon-bearing porosity, and indirectly controlled by total organic carbon(TOC) and vitrinite reflectance(Ro). The resources of shale oil and gas are controlled by hydrocarbon-bearing porosity and effective shale thickness etc. The flow capacity of shale oil and gas is controlled by effective permeability, crude oil density, gas-oil ratio, condensate oil-gas ratio, formation pressure gradient, and Ro. The fracability of shale is directly controlled by brittleness index, and indirectly controlled by clay content in volume. EUR of shale oil and gas is controlled by six geological parameters: it is positively correlated with effective shale thickness, TOC and fracture porosity, negatively correlated with clay content in volume, and increases firstly and then decreases with the rise of Ro and formation pressure gradient. Under the present upper limit of horizontal well fracturing effective thickness of 65 m and the lower limit of EUR of 3×10^(4) m^(3), when TOC<2.3%, or Ro<0.85%, or clay content in volume larger than 25%, and fractures and micro-fractures aren’t developed, favorable areas of shale oil and gas hardly occur.
基金Supported by the PetroChina Science and Technology Project(2021DJ1808).
文摘The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source rock in the Western Qaidam Depression,Qaidam Basin,NW China.Three main factors result in low TOC values of saline lacustrine source rock of the Qaidam Basin:relatively poor nutrient supply inhibits the algal bloom,too fast deposition rate causes the dilution of organic matter,and high organic matter conversion efficiency causes the low residual organic carbon.For this type of hydrogen-rich organic matter,due to the reduction of organic carbon during hydrocarbon generation,TOC needs to be restored based on maturity before evaluating organic matter abundance.The hydrocarbon generation of saline lacustrine source rocks of the Qaidam Basin is from two parts:soluble organic matter and insoluble organic matter.The soluble organic matter is inherited from organisms and preserved in saline lacustrine basins.It generates hydrocarbons during low-maturity stage,and the formed hydrocarbons are rich in complex compounds such as NOS,and undergo secondary cracking to form light components in the later stage;the hydrocarbon generation model of insoluble organic matter conforms to the traditional“Tissot”model,with an oil generation peak corresponding to Ro of 1.0%.
