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The Fushan Depression is a hydrocarbon-rich depression in the Beibuwan Basin, South China Sea. In this study, 14 source rocks and 19 crude oils from the Chaoyang Step-Fault Zone and Southern Slope Zone were geochemically analyzed to determine their origins. The hydrocarbon generation, migration, and accumulation processes were also determined using two-dimensional basin modeling. Crude oils from the low-step area show a close relationship with the source rocks of the first and second members of the Eocene Liushagang Formation (Els1 and Els2). The oils from the middle-step area and the Southern Slope Zone are derived from the local source rocks in those areas, in the third member of the Eocene Liushagang Formation (Els3). Hydrocarbons generated from the Els3 source rocks of the Southern Slope Zone migrated along sand bodies to the Els3 reservoir. The fault system of the Chaoyang Step-Fault Zone controls hydrocarbon migration and accumulation in the low-step and middle-step areas. The resource potential of the middle-step area is limited by its shallow burial depth. The low-step area is a more favorable exploration area due to its proximity to the source kitchen. [ABSTRACT FROM AUTHOR]

The Myanmar region experienced the subduction of the Indian Ocean plate to the West Burma block and suffered from the land–land collision between the Indian continent and the West Burma block that occurred from the Late Cretaceous to the Cenozoic. Its tectonic evolution has been complex; thus, oil and gas exploration is difficult, and the overall degree of research has been low. Recent exploration has been hindered by a lack of knowledge on the evolution of the petroleum system. To address this, we conducted hydrocarbon generation and accumulation modeling using both the 2D MOVE and Petro-Mod software 2017 for a complex tectonic section in the Northern Central Myanmar Basin. The results show that the maturity threshold depth of the Cretaceous source rocks in the study area is shallow, and the underground depth of 1200 m to 1400 m has reached the hydrocarbon generation threshold, indicating the start of hydrocarbon generation. Since 48 Ma, the Ro of the source rocks has reached 0.7%, became mature quite early. The Late Cretaceous Paleocene and Eocene formation, located in the southeastern part of the study area, migrated and accumulated hydrocarbons towards the western arc zone in the Eocene and Miocene, respectively. It is worth noting that although the oil and gas potential of each layer in the island arc uplift zone is relatively low, which is conducive to the migration and accumulation of oil and gas generated by the source rocks of the depression towards the island arc zone, shallow areas with developed extensional faults should be avoided. This study is the first to conduct a preliminary assessment and prediction of oil and gas resources, which will provide exploration guidance and reference for the study area and its surrounding areas in the future. [ABSTRACT FROM AUTHOR]

The Fushan Depression is a hydrocarbon-rich depression in the Beibuwan Basin, South China Sea. In this study, 14 source rocks and 19 crude oils from the Chaoyang Step-Fault Zone and Southern Slope Zone were geochemically analyzed to determine their origins. The hydrocarbon generation, migration, and accumulation processes were also determined using two-dimensional basin modeling. Crude oils from the low-step area show a close relationship with the source rocks of the first and second members of the Eocene Liushagang Formation (Els1 and Els2). The oils from the middle-step area and the Southern Slope Zone are derived from the local source rocks in those areas, in the third member of the Eocene Liushagang Formation (Els3). Hydrocarbons generated from the Els3 source rocks of the Southern Slope Zone migrated along sand bodies to the Els3 reservoir. The fault system of the Chaoyang Step-Fault Zone controls hydrocarbon migration and accumulation in the low-step and middle-step areas. The resource potential of the middle-step area is limited by its shallow burial depth. The low-step area is a more favorable exploration area due to its proximity to the source kitchen.

Hydrocarbon enrichment in faulted basins is often controlled by the activity of faults with some degree of sealing capacity. However, the rules that control the migration and accumulation of hydrocarbons in reservoirs dominated by faults are poorly understood. The Liuzhuang fault in the Bohai Bay Basin is selected for hydrocarbon migration and accumulation research. Interpretation of seismic and log data, tests of rock mechanics, and quantitative fluorescence analysis are used to quantitatively evaluate the migration of hydrocarbons. The results reveal that the Liuzhuang fault has been a long-term active fault since the Cenozoic with gradually reduced fault activity from the NE to the SW. At least four fault-bounded traps with various degrees of trap filling in the lower segment of the first member of Shahejie Formation (Es1L) were identified in the hanging wall of this fault. This differences in the degree of filling are related to the continuity of the smear structure that formed from the Es1m cap rock in the brittle‒ductile transition stage. The development degree of the smear structure, which is quantitatively evaluated by the shale smear factor (SSF) and shale gouge ratio (SGR), directly affected the fault sealing capacity. Therefore, three cases of hydrocarbon migration and accumulation, i.e., continuous smearing along the fault and complete fault sealing with SSF values of < 3, reduced continuity of the smear structure and partial fault sealing with SSF values in the range of 3–5, and discontinuous smearing and ineffective fault sealing with SSF values of > 5, were defined. The new results have implications for further exploration in faulted basins, including the Bohai Bay Basin. [ABSTRACT FROM AUTHOR]

The eastern Kuqa Depression in the northern Tarim Basin, NW China, is rich in oil and gas. However, recent exploration has been hindered by a lack of knowledge on the evolution of the petroleum system. To address this, we conducted hydrocarbon generation and accumulation modeling using both the 2Dmove and PetroMod2017 software for a complex tectonic extrusion section in the Kuqa Depression. The results show that the source rocks in the northern slope zone became mature quite early at around 170 Ma, but the thermal maturity evolution stagnated subsequently because of tectonic extrusion and uplift. The source rocks in the central anticline zone, the southern slope zone, and the deep sag zone were of overall low maturity during the Jurassic to Paleogene but rapidly became mature to highly mature with the deposition of the Neogene Jidike and Kangcun formations. The main hydrocarbon generation periods are in the late Neogene and Quaternary, and the main hydrocarbon generation stratum is the lower Jurassic Yangxia formation. The amount of cumulative hydrocarbon generation gradually increases for carbonaceous mudstone, mudstone, and coal source rocks. Sourced from source rocks mainly in the northern slope zone, oil and gas migrated to anticlinal traps along sandstone transport layers and faults. Recent discoveries, such as the Tudong-2 gas field in the central anticline zone, underscore the richness of this region in petroleum resources. Some gas fields were also predicted in lithologic traps in the southern slope zone and the deep sag zone, as well as in fault-related traps in the northern part of the northern slope zone. [ABSTRACT FROM AUTHOR]

The Myanmar region experienced the subduction of the Indian Ocean plate to the West Burma block and suffered from the land–land collision between the Indian continent and the West Burma block that occurred from the Late Cretaceous to the Cenozoic. Its tectonic evolution has been complex; thus, oil and gas exploration is difficult, and the overall degree of research has been low. Recent exploration has been hindered by a lack of knowledge on the evolution of the petroleum system. To address this, we conducted hydrocarbon generation and accumulation modeling using both the 2D MOVE and Petro-Mod software 2017 for a complex tectonic section in the Northern Central Myanmar Basin. The results show that the maturity threshold depth of the Cretaceous source rocks in the study area is shallow, and the underground depth of 1200 m to 1400 m has reached the hydrocarbon generation threshold, indicating the start of hydrocarbon generation. Since 48 Ma, the Ro of the source rocks has reached 0.7%, became mature quite early. The Late Cretaceous Paleocene and Eocene formation, located in the southeastern part of the study area, migrated and accumulated hydrocarbons towards the western arc zone in the Eocene and Miocene, respectively. It is worth noting that although the oil and gas potential of each layer in the island arc uplift zone is relatively low, which is conducive to the migration and accumulation of oil and gas generated by the source rocks of the depression towards the island arc zone, shallow areas with developed extensional faults should be avoided. This study is the first to conduct a preliminary assessment and prediction of oil and gas resources, which will provide exploration guidance and reference for the study area and its surrounding areas in the future.

The prediction of continental tight sandstone gas sweet spots is an obstacle during tight sandstone gas exploration. In this work, the classic physical fluid charging experimental equipment is improved, the combination of the gas migration and accumulation process with the pore network numerical simulation method is investigated, and application of the permeability/porosity ratio is proposed to predict the gas saturation and sweet spots of continental formations. The results show that (1) as the charging pressure increases, the permeability of the reservoir increases because more narrow pore throats are displaced in the percolation process; and (2) based on pore network numerical simulation and theoretical analysis, the natural gas migration and accumulation mechanisms are revealed. The gas saturation of tight sandstone rock is controlled by the gas charging pressure and dynamic percolation characteristics. (3) The ratio of permeability/porosity and fluid charging pressure is proposed to predict the gas saturation of the formation. The ratio is verified in a pilot and proven to be applicable and practical. This work highlights the tight sandstone gas migration and accumulation mechanisms and narrows the gap among microscale physical experiments, numerical simulation research, and field applications. [ABSTRACT FROM AUTHOR]

The Longfengshan area is an important hydrocarbon enrichment area in the Changling Fault Depression. Most of the oil and gas are distributed near the fault zone. It is of great significance to discuss the relationship between faults and hydrocarbon migration and accumulation. Combined with seismic, logging, core, microscopic thin sections, fluid inclusion observations and temperature measurement data, the relationship between section morphology, fault activity characteristics and hydrocarbon migration and accumulation is comprehensively analyzed on the basis of fault static characteristics and fault zone structure identification. The results show that a large number of fractures are developed in the fault-induced fracture zone, which can effectively improve the physical properties of volcanic rocks, and the fault can be used as the dominant migration channel for hydrocarbons. The "convergent" section shape of the grade Ⅰ fault controls the main enrichment location of hydrocarbons. The fault activity matches well with the first stage of reservoir formation, and faults can be used as a dominant channel for transporting hydrocarbons. In the later stage, the fracture of the fault zone is filled with quartz and calcite, and the fault zone mainly plays a sealing role in the volcanic oil and gas reservoirs.

The eastern Kuqa Depression in the northern Tarim Basin, NW China, is rich in oil and gas. However, recent exploration has been hindered by a lack of knowledge on the evolution of the petroleum system. To address this, we conducted hydrocarbon generation and accumulation modeling using both the 2Dmove and PetroMod2017 software for a complex tectonic extrusion section in the Kuqa Depression. The results show that the source rocks in the northern slope zone became mature quite early at around 170 Ma, but the thermal maturity evolution stagnated subsequently because of tectonic extrusion and uplift. The source rocks in the central anticline zone, the southern slope zone, and the deep sag zone were of overall low maturity during the Jurassic to Paleogene but rapidly became mature to highly mature with the deposition of the Neogene Jidike and Kangcun formations. The main hydrocarbon generation periods are in the late Neogene and Quaternary, and the main hydrocarbon generation stratum is the lower Jurassic Yangxia formation. The amount of cumulative hydrocarbon generation gradually increases for carbonaceous mudstone, mudstone, and coal source rocks. Sourced from source rocks mainly in the northern slope zone, oil and gas migrated to anticlinal traps along sandstone transport layers and faults. Recent discoveries, such as the Tudong-2 gas field in the central anticline zone, underscore the richness of this region in petroleum resources. Some gas fields were also predicted in lithologic traps in the southern slope zone and the deep sag zone, as well as in fault-related traps in the northern part of the northern slope zone.

The Ordovician strike-slip faults system in the Tahe area of the Tarim Basin provides an important opportunity for using 3D seismic data to document the structural characteristics, formation, and evolution of strike-slip faults and their relationship with oil and gas. With high-resolution 3D seismic data, the strike-slip faults are interpreted, classified, and described using the seismic coherence technique. The geometric characteristics, active periods, formation, and evolution process of strike-slip faults are analyzed, and the relationship between strike-slip faults and hydrocarbon accumulation and charging is discussed in this research project. On the map, the primary strike-slip faults on the east and west sides of the Tahe area are relatively sheared to each other, showing an "X" type conjugate fault, and the secondary strike-slip faults are scattered. In the cross-section, the primary strike-slip faults are inserted downward into the Cambrian basement and up to Devonian, and "Single line", "Y", "Flower", and "Parallel lines" structures are observed. Bounded by the top of Ordovician, the deep and shallow parts are vertically segmented, with different structure styles. The switch of the structural style of strike-slip faults is attributed to principal stress. A deep "positive flower" shape of faults was developed in the mid-Ordovician period under the effect of compressive stress. Meanwhile, a shallow "negative flower" shape of faults was developed from the late Ordovician to the mid-Devonian period under tensile stress. The "Compound Flower" shape of deep "positive flower" shape and shallow "negative flower" shape formed by compressive and tensile activities has a wider fracture range, which leads to deep fluid migration and shallow karstification. There are two combinations of deep Ordovician strike-slip faults in the section: "Lower single branch-upper flower type" and "lower single branch-upper single branch type". The primary faults of the former insertion into the Cambrian basement are associated with homologous secondary faults, while the latter has no derived secondary faults. It has an important impact on reservoir reconstruction and distribution, and the reservoir is controlled by faults. Strike-slip faults not only control the channel of oil and gas migration, but also the horizontal and vertical distribution of oil and gas. The closer the carbonate reservoir is to the primary fault, the more likely it is to form a high yield area. There are four types of oil and gas charging models controlled by strike-slip faults. In the area where the structure is high and the strike-slip faults are sheared relatively to each other, the larger the scale of faults, the more conducive it would be to oil and gas migration and accumulation. Among them, the charging model related to the primary fault has higher oil and gas migration efficiency. This research contributes to analyzing the relationship between strike-slip faults and oil and gas as well as playing a significant role in applications of oil and gas exploration in practical works. [ABSTRACT FROM AUTHOR]

The various types of reservoir space in carbonate reservoirs make the process of hydrocarbon migration and accumulation very complex. How to quantitatively characterize the characteristics of hydrocarbon migration and accumulation in carbonate reservoirs is one of the key problems for carbonate hydrocarbons exploration and exploitation. Taking the Ordovician in the Daniudi area of Ordos Basin as an example, three types of source rock-reservoir-cap assemblages, namely upper-generation assemblage, lateral variable assemblage, and self-generation-reservoir-cap assemblage, were determined by characterizing the forming elements of carbonate reservoirs. Petromod software is used to build a two-dimensional profile model, and vitrinite reflectance of source rock and porosity of the reservoir were used as correction parameters, and the hydrocarbon migration and accumulation process was simulated by the invasion percolation algorithm. It is confirmed that the Ordovician Majiagou formation in the study area has three periods of hydrocarbon charging and three periods of hydrocarbon adjustment. The hydrocarbon migration pathways in carbonate rocks include lateral contact in the pinch-out area, source rock-reservoir contact in the trough area, fault-connected, and source rock-reservoir superposition. The source rock-reservoir-cap assemblages of upper-generation assemblage and lateral variable assemblage correspond to the lateral contact in the pinch-out area, source rock-reservoir contact in the trough area, fault-connected, while self-generation-reservoir-cap assemblage corresponds to the fault-connected, and source rock-reservoir superposition. The high part of the structure and fault zone are the strongest structural deformation parts, whose fractures are relatively developed, controlling the location of hydrocarbon accumulation, meanwhile, the reservoir quality directly controls the degree of hydrocarbons saturation. The research results are beneficial to establish a more accurate quantitative evaluation method of hydrocarbon migration and accumulation in carbonate rocks and to understanding the controlling factors of hydrocarbon migration and accumulation in carbonate rocks. [ABSTRACT FROM AUTHOR]

Authigenic calcite abundantly forms during various diagenesis stages of shales. It meticulously records information on diagenetic fluid (organic/inorganic) migration and fluid-rock interactions, is important for understanding the burial diagenetic evolution, tectonic history, burial history, hydrocarbon generation and accumulation in sedimentary basins. Calcium sources for authigenic calcite include pore water, calcium minerals dissolution, and clay mineral transformation. Organic carbon sources of authigenic calcite refer to organic matter that undergoes diagenetic thermal evolution, redox reactions, and bacterial effects. Inorganic carbon primarily arises from carbonate dissolution, magma degassing, and thermal decomposition of carbonates during metamorphism. During early burial diagenesis, the sulfate-methane transition zone maintains high porewater alkalinity through anaerobic oxidation of methane, promoting calcite nodule formation. Upon entering the hydrocarbon generation window, periodic opening and closing of fractures occur at lamina interfaces due to overpressure from hydrocarbon phase transitions and crystallization forces. In these fractures, calcite solubility decreases with fluid pressure reduction, leading to fibrous vein precipitation under strong overpressure conditions and bladed or equant crystal formation under weak overpressure conditions. Influenced by tectonic shear and compressive stresses, fibrous and bladed crystals intersect the fracture plane obliquely at varying angles. Authigenic calcite in shale strata serves as a valuable tracer for sedimentary basin evolution, fluid evolution, and burial history due to its extensive and multi-stage formation process. However, its complex history retains characteristics from various sources and evolution stages, resulting in distinct isotope fractionation features. Calcite formed during early burial diagenesis undergoes late-stage diagenetic alteration, accumulating carbon isotope features from multiple processes. This complexity presents difficulties in retracing the formation process. Utilizing physical and numerical simulations based on burial conditions aids in analyzing authigenic calcite genesis and reconstructing its formation history. The formation history can be determined through in-situ micro-area isotope testing and analyzing fluid inclusions for temperature, pressure, and composition. [ABSTRACT FROM AUTHOR]

Based on the analysis of fault and structural characteristics by using the three-dimensional seismic method, this paper studies the Fuyu oil layer fault condensed belts in Anda west area in northern Songliao Basin to determine the characteristics of the fault condensed belts and its controlling effect on hydrocarbon migration and accumulation. The results of study show that the fault condensed belts of Fuyu oil layer in Anda west area mainly strike near the SN and NNW direction. According to the fault rupture horizon and fault activity in the study area, four type of fault systems are classified, mainly the depression stage. The hydrocarbon migration path the accumulation of the parts of the Fuyu oil layer in Anda west region will be controlled by fracture density. Under the condition of oil supply from the source reservoir docking and parallel with the source reservoir fracture zone, reverse fault footwall is advantage of oil migration path, and when the vertical oil and fracture density, fracture density belt conversion will control the oil migration path. The interstice between the fault condensed belts and the conversion of the fault condensed belts are the advantageous oil accumulation sites. [ABSTRACT FROM AUTHOR]

The Ordovician strike-slip faults system in the Tahe area of the Tarim Basin provides an important opportunity for using 3D seismic data to document the structural characteristics, formation, and evolution of strike-slip faults and their relationship with oil and gas. With high-resolution 3D seismic data, the strike-slip faults are interpreted, classified, and described using the seismic coherence technique. The geometric characteristics, active periods, formation, and evolution process of strike-slip faults are analyzed, and the relationship between strike-slip faults and hydrocarbon accumulation and charging is discussed in this research project. On the map, the primary strike-slip faults on the east and west sides of the Tahe area are relatively sheared to each other, showing an “X” type conjugate fault, and the secondary strike-slip faults are scattered. In the cross-section, the primary strike-slip faults are inserted downward into the Cambrian basement and up to Devonian, and “Single line”, “Y”, “Flower”, and “Parallel lines” structures are observed. Bounded by the top of Ordovician, the deep and shallow parts are vertically segmented, with different structure styles. The switch of the structural style of strike-slip faults is attributed to principal stress. A deep “positive flower” shape of faults was developed in the mid-Ordovician period under the effect of compressive stress. Meanwhile, a shallow “negative flower” shape of faults was developed from the late Ordovician to the mid-Devonian period under tensile stress. The “Compound Flower” shape of deep “positive flower” shape and shallow “negative flower” shape formed by compressive and tensile activities has a wider fracture range, which leads to deep fluid migration and shallow karstification. There are two combinations of deep Ordovician strike-slip faults in the section: “Lower single branch-upper flower type” and “lower single branch-upper single branch type”. The primary faults of the former insertion into the Cambrian basement are associated with homologous secondary faults, while the latter has no derived secondary faults. It has an important impact on reservoir reconstruction and distribution, and the reservoir is controlled by faults. Strike-slip faults not only control the channel of oil and gas migration, but also the horizontal and vertical distribution of oil and gas. The closer the carbonate reservoir is to the primary fault, the more likely it is to form a high yield area. There are four types of oil and gas charging models controlled by strike-slip faults. In the area where the structure is high and the strike-slip faults are sheared relatively to each other, the larger the scale of faults, the more conducive it would be to oil and gas migration and accumulation. Among them, the charging model related to the primary fault has higher oil and gas migration efficiency. This research contributes to analyzing the relationship between strike-slip faults and oil and gas as well as playing a significant role in applications of oil and gas exploration in practical works.

In this paper, the Hubbert fluid potential model is used to restore the fluid potential of the key reservoir forming period at the end of Paleogene in Shijiazhuang Sag. At the end of Paleogene, the high potential area of Shijiazhuang Sag is mainly located in the Western trough belt of the sag, which is the main flow supply area. The low potential area of the sag is mainly distributed in the Gao cheng tectonic belt in the middle, which is the main discharge area. The overall performance is the distribution law of the trough to the central buried hill belt, and the potential energy gradually decreases. The sag is further divided into three major oil and gas migration and accumulation units, namely, the southern oil and gas migration and accumulation unit (III), the central oil and gas migration and accumulation unit (I), and the northern oil and gas migration and accumulation unit (II). Among them, the central oil and gas migration and accumulation unit (I) is the best oil and gas migration and accumulation unit, which receives multi-source hydrocarbon supply and has favorable reservoir forming conditions. [ABSTRACT FROM AUTHOR]

The Eocene Niubao Formation is the primary research target of oil exploration in the Lunpola Basin. Crude oil was extracted from Well Z1 on the northern margin of the basin in 1993. In this study, an integrated evaluation of the source rock, geothermal, and maturity histories and the fluid inclusion and fluid potential distributions was performed to aid in predicting areas of hydrocarbon accumulation. Due to the abundance of organic matter, the kerogen types, maturity, and oil-sources correlate with the geochemical data. The middle submember of the second member of the Niubao Formation (E2n2-2) is the most favorable source rock based on the amount of oil produced from the E2n2-3 and E2n3-1 reservoirs. One- and two-dimensional basin modeling, using BasinMod software, shows that the E2n2-2 source rock started to generate hydrocarbon at 35-30 Ma, reached a maturity of R0=0.7% at 25-20 Ma, and at present, it has reached the peak oil generation stage with a thermal maturity of R0=0.8% to less than R0=1.0%. By using fluid inclusion petrography, fluorescence spectroscopy, and microthermometry, two major periods of oil charging have been revealed at 26.1-17.5 and 32.4-24.6 Ma. The oil accumulation modeling results, conducted by using the Trinity software, show a good fit of the oil shows in the wells and predict that the structural highs and lithologic transitions within the Jiangriaco and Paco sags are potential oil traps. [ABSTRACT FROM AUTHOR]

Based on the seismic data analysis, source rock geochemistry and reservoir physical properties, the source reservoir allocation and reservoir forming conditions in the Linhe-Jilantai area in Hetao Basin were studied. The results show that the source rocks of the Lower Cretaceous and the Oligocene in the study area reach the standard of fair-good source rocks, and the lithology of reservoirs is mainly feldspar sandstone and lithic feldspathic sandstone with good physical properties. Combined with vertical and lateral migration pathways, three hydrocarbon accumulation models of near source, far source and inside source are proposed. The research results can provide reference and guidance for the further hydrocarbon exploration in Hetao Basin. [ABSTRACT FROM AUTHOR]

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Graphical abstract Highlights • Restoration of geological sections reveals three stages of tectonic deformation. • Tectonic deformation promoted the fracturing and the deviation of fluid potential. • Dropping of fluid pressure occurred near the faults attributed to fracturing. • The primary charging of oil and gas occurred at the late Himalayan. Abstract Himalayan deformation substantially impacts the hydrocarbon migration and accumulation in the western Qaidam Basin. In order to investigate how the Himalayan deformation influences the hydrocarbon migration and accumulation in fracture type reservoir, we took Shizigou oil field in the western Qaidam Basin as an example and studied the Himalayan deformation history based on the results from the balanced cross-section restoration of 2 sections across the Shizigou oil filed at first. Then we simulated the fluid potential of one particular section at different tectonic episodes by the numerical method to investigate how the Himalayan deformation effects on it. We conclude that the Himalayan deformation influences the hydrocarbon migration and accumulation in three aspects. Firstly, the faults which form during the structural evolution and communicate with the source rock can act as the primary pathways for the hydrocarbon migration. Secondly, the fracturing of rocks occurs during structural evolution owing to significant compression, which prefer occurring near the faults especially in hanging wall and the hinge zone of folds. These fractures significantly improve the permeability of the rock and result in good pathways for hydrocarbon migration and high-quality reservoirs for hydrocarbon accumulation. Thirdly, influenced by tectonic deformation, compaction of rock bulk volume generates the rising of fluid potential in the soft formation where fracturing is restricted, in contrast, expansion of rock bulk volume generates the dropping of fluid potential in the position where fracturing is enhanced. The change of fluid potential allows the hydrocarbon to migrate and accumulate rapidly along the faults where low fluid potential occurs attributed to fracturing. The impact of tectonic deformation on the hydrocarbon migration and accumulation results in that the hydrocarbon accumulates in fracture type reservoirs near the faults. [ABSTRACT FROM AUTHOR]

Abstract It is well known that salt-gypsum evaporites play a significant role in controlling the physio-mechanical performance of the earth's upper mantle as well as forming extensive "halokineticˮ structures that are directly linked to lithologic hydrocarbon reservoirs and petroleum accumulation. Under many geological conditions, hot saline groundwater frequently intrudes into salt-gypsum evaporite sequences. However, relatively little is known regarding the micromechanical behaviour of salt-gypsum in these saline environments, and this behaviour governs the macro-mechanical behaviour and the overall deformation. In this study, we examine the microstructural evolution of salt-gypsum and its weakening mechanisms under varied brine conditions (or coupled thermal-hydrological-chemical environments). A series of laboratory tests, including scanning electron microscopy and micro-computed tomography (MCT), were conducted to study how the petrographic characteristics, including porosity, pore size distribution and fractal dimension, evolved. In total, 81 specimens were prepared and then soaked in brines of 3 different concentrations and at 3 different temperatures. The results showed the following: 1) after brine treatment, the MCT slices of the specimens generally contained four areas: a residual porous skeleton area, an undissolved area, a cracked area and an interface area. 2) For a given concentration, the porosity and fractal dimensions of the specimens gradually increased with temperature, while for a given temperature, the porosity and fractal dimension tended to decrease as the brine concentration increased. 3) Because the nucleation or initiation rate of new voids was slower than the growth and coalescence rate of the original voids, the proportion of 0–1 μm pores gradually decreased over time. However, the proportion of 5 to + ∞ μm pores gradually increased over time. To study the effects of each factor and the interactions between them on the response variables (porosity and fractal dimension), 2 × 2 and 2 × 3 factorial designs were employed to assess the brine concentrations and temperatures. The results verify that the water temperature significantly weakened the salt-gypsum, while the chlorine ions had a much weaker effect. [ABSTRACT FROM AUTHOR]

Xihu Sag is the focus of oil and gas exploration in the East China Sea Shelf Basin, but the hydrocarbon migration and accumulation units have not been systematically divided. This restricts the study of regional reservoir formation and the optimization of exploration targets. Distribution and cause of oil and gas accumulation are discussed in terms of the dynamics of oil and gas migration, based on the evolution of tectonic activity in the large number of hydrocarbon generation and expulsion stages of the Sag. The fluids’ potential after the deposition of the Liulang Formation is calculated on the corresponding structural features and sedimentary research results. As a result, the characteristics of petroleum migration and accumulation during the period are recognized. This indicates that the fluid potential is of succession and consistency, characterized by its descending movement from the middle to the east and west. Accordingly, Xihu Sag can be divided into nine oil-gas migration and accumulation units. I, II, III, V and VI are better oil and gas accumulation units, and are advantageous to the long-term migration and accumulation of oil and gas. They are the main potential areas for future exploration in Xihu Sag. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Upper Triassic tight sand oil in the Ordos Basin has gradually become a focus of research; however, compared to the centre of the basin, studies on the margin have been relatively weak. In this study, an integrated approach involving oil–source correlation, charge history, and pressure evolution is used to investigate the migration characteristics of each stage and to establish a migration and accumulation process model of the tight sand oil in the Yanchang Formation of Honghe Oilfield in combination with reservoir densification process. The results show that, based on the fluid inclusion analysis and authigenic illite K–Ar dating technique in combination with burial and thermal modellings, the accumulation periods were 145–130, 120–90, and 90–80 Ma, which corresponds to the Cretaceous. According to the relative content of C30‐diahopane and drimane series compounds, the crude oil from Chang 8(T3ch8) and Chang 9(T3ch9) both originated from the oil shale of Chang 7(T3ch7) in the Upper Triassic Yanchang Formation. The migration characteristics and directions are comprehensively analyzed using the maturity parameters and key elements. In the early stage of the Early Cretaceous, with east‐dipping strata, crude oil migrated from northeast to southwest. During the late Early Cretaceous, the middle‐late Yanshanian movement promoted the development of strike‐slip faults and fractures, and the oil migrated vertically downwards along them. Tectonic inversion changed the strata dip direction to west‐dipping, and lateral migration was also changed to two directions of southwest and northeast. After the Late Cretaceous, the migration dynamics weakened due to strata uplift and cessation of hydrocarbon generation. Only slight adjustments to the crude oil occurred during the Himalayan movement; therefore, the current distribution pattern of the tight sand oil is still affected primarily by the stage of late Early Cretaceous. The migration and accumulation model of the Upper Triassic in the Honghe Oilfield, Ordos Basin, provides a theoretical basis for further exploration and is of general applicability to tight sand reservoirs in the margins of various basins. [ABSTRACT FROM AUTHOR]

The hydrocarbon migration and accumulation of the Suqiao deep buried-hill zone, in the Jizhong Subbasin, the Bohai Bay Basin, eastern China, was investigated from the perspective of paleo-fluid evidence by using fluid inclusions, quantitative fluorescence techniques (QGF), total scanning fluorescence method (TSF) and organic geochemical analysis. Results show that the current condensate oil-gas reservoirs in the study area once were paleo-oil reservoirs. In addition, the reservoirs have experienced at least two stages of hydrocarbon charge from different sources and/or maturities. During the deposition of the Oligocene Dongying Formation (Ed), the deep Ordovician reservoirs were first charged by mature oils sourced from the lacustrine shale source rocks in the fourth member of Shahejie and Kongdian Formations (Es 4 +Ek), and then adjusted at the end of Ed period subsequently by virtue of the tectonic movement. Since the deposition of the Neogene Minghuazhen Formation (Nm), the reservoirs were mainly charged by the gas that consisted of moderate to high-maturity condensate and wet gas sourced from the Es 4 +Ek lacustrine shale source rocks and mature coal-derived gas sourced from the Carboniferous-Permian (C-P) coal-bearing source rocks. Meanwhile, the early charged oil was subjected to gas flushing and deasphalting by the late intrusion of gas. The widely distributed hydrocarbon inclusions, the higher QGF Index, and FOI (the frequency of oil inclusions) values in both gas-oil and water zone, are indicative of early oil charge. In addition, combined with the homogenization temperatures of the fluid inclusions (<160 °C) and the existence of solid-bitumen bearing inclusions, significant loss of the n -alkanes with low carbon numbers, enrichments of heavier components in crude oils, and the precipitation of asphaltene in the residual pores suggest that gas flushing may have played an important role in the reservoir formation. [ABSTRACT FROM AUTHOR]

Middle and lower Ordovician carbonate rock in the Tabei Uplift of the Tarim Basin forms important fractured reservoir beds. Core and log data indicate that tectonic fractures, as the main fractures in the Tabei Uplift, could be mainly classified into two types: oblique fractures and approximately vertical fractures. The fractures are mainly NNW-trending and NNE-trending, coincident with the large faults nearby. Fracture abundance was also controlled by lithology, and faults nearby played a significant role. Cores, thin sections and tests show that these carbonate rocks have as much as 2.5% fracture porosity and as much as 150 md fracture permeability. Based on the intersection of fractures in cores, together with fluid inclusion temperature data, and the timing of faulting from seismic profiles, tectonic fractures were considered to be mainly formed in three periods: the late Silurian when the first-stage oblique fractures were formed, the late Permian when approximately vertical fractures were formed, and the late Tertiary when the second-stage oblique fractures were formed. Lower Cambrian source rocks started to enter the stage of generous hydrocarbon generation and expulsion in the Silurian. Ordovician source rocks started to enter the stage of generous hydrocarbon generation and expulsion in the Permian and enter the over-mature stage in the late Tertiary when light oil was generated. Timing of tectonic fractures formation and burial history analysis suggest that fractures formation might coincide with oil accumulation when fractures provided the pathway and storage space for the low permeability and low porosity reservoir beds caused by previous compaction and cementation. Considering the presence of a large amount of fracture-developed dolomite in the deeper Ordovician Penglaiba Formation, the undrilled Penglaiba Formation should be paid more attention. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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[Display omitted] • Basin modeling proved that a lateral migration occurred in the Majella Area. • Basin modeling constrained the source rock to lie below the Bonanno oil field. • Triassic anoxic basins must have a minimum width of 3 km to justify the oil volumes. • Lateral migration probably is a primary process on carbonate-ramp petroleum systems. A two-dimensional basin and petroleum system modeling approach was applied to the Burano-Bolognano petroleum system (Central Italy) to constrain some factors (position, lateral extension and maturity of the source rock, the role of fractures and faults in hydrocarbon migration) which influenced its structural evolution and the related migration pathways. The petroleum system extends from the Majella Mountain to the northern Cigno, Vallecupa, Bonanno oil fields, intensively explored during the past century. Some features, such as the location and extension of the source rock and its maturity, and hydrocarbon pathways, are still undefined. Thus, we developed a 3D geological static model of the Cenozoic carbonate succession and then, we performed basin modeling along a 2D geological section, integrating the petrophysical properties of rocks measured in laboratory. Our results prove that the Burano source rock reached a low-middle maturity, and the best representation of the actual hydrocarbon occurrences is reached when the source rock is at north of the Majella Mountain with a minimum extension of 3 km. For the BBPS a strong lateral migration and a gradual oil biodegradation towards the Majella area must be considered. Moreover, modeling results highlight a minor control of the faults on the migration in this area. This basin modeling is relevance for investigations in similar settings since carbonate-ramp reservoir studies are usually very challenging to be correctly modeled due to their high heterogeneities. [ABSTRACT FROM AUTHOR]

Highlights: [•] Integrated analyses of fluid inclusion, oil source correlation and basin modeling. [•] Source rock in the Heidimiao depression has a large hydrocarbon generation potential. [•] Hydrocarbons likely migrate from the first member of the Qingshankou Formation upward. [•] Tectonic inversion changed the previous fluid potential and migration routes. [•] Hydrocarbon migration is primarily controlled by structural morphology. [Copyright &y& Elsevier]

The unconformity surface at the bottom of the Paleogene, located in the Sikeshu Sag of the Junggar Basin, Northwest China, is one of the most important hydrocarbon migration pathways and characterized by 3 layers of upper coarse clastic rock, lower weathering crust and leached zone. The upper coarse clastic rock displays features of higher density, lower SDT and gamma-ray logging while the weathering crust in the lower part displays opposite features. The formation water is of NaHCO type but at lower mineralization degree. The QGF indices are generally between 2.19 and 3.77 and the GOI parameters vary from 1% to 5%. From the southeast to the northwest of the sag, the content of saturated hydrocarbon increases from 30.81% to 53.74% while that of non-hydrocarbon and asphaltene decreases. The Pr/ nC decreases from 0.65 to 0.47 while the Ph/ nC decreases from 0.66 to 0.27, and the content of benzo[c] carbazole declines while the benzo[a] carbazole amount and (alkyl carbazole)/(alkyl+benzo carbazole) ratio both increase. These revealed that the hydrocarbons migrated from the sag to the ramp region along the unconformity surface. [ABSTRACT FROM AUTHOR]