Search

With the improvement of the exploration degree, small complex fault block traps have become the key field of oil and gas exploration in the current uplift area. To clarify the reasons for the differential enrichment of oil and gas in the fault block trap in the West Liaoning uplift, the characteristics of weathering crust on the top of the buried hill in the uplift slope area are analysed by using three-dimensional seismic, logging, thin section and other data through three-dimensional streamline quantitative simulation. The "crust-fault" coupling migration model is established to describe the dominant migration path of oil and gas in the slope area to clarify the control effect of hydrocarbon migration along weathered crust on the differential enrichment of oil and gas in the convex fault block. The results show that ① the buried hill in the study area has experienced multistage tectonic movements, and the lithology of the buried hill is mainly lower Paleozoic carbonate rock and Archean granite. The lithology is brittle and easily weathered and denuded. The denudation pores and structural fractures of the weathering crust are widely developed and stably distributed, forming the main channel of lateral long-distance migration of oil and gas in the slope area. ② The middle zone of the slope is controlled by reverse faults to forma fault uplift structure. The migration of oil and gas along the weathering crust is blocked by the slope fault uplift zone, forming a "crust-fault" coupling oil and gas migration model. The fault throw of the fault uplift zone controls the lateral migration ability of oil and gas in the weathering crust. ③ Using the method of three-dimensional streamline quantitative simulation, the four-level dominant oil and gas migration channels in the study area are characterized, and the control effect of different levels of oil and gas migration channels on the degree of oil and gas enrichment in convex fault blocks is clarified. The research results effectively guide the practice of oil and gas exploration in the Liaoxi Uplift and fill the gap of the understanding and research method of oil and gas accumulation in mature uplift areas of oil-rich sags.

Copyright of Petroleum Geology & Oilfield Development in Daqing is the property of Editorial Department of Petroleum Geology & Oilfield Development in Daqing 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.)

From accumulation mechanisms and the identification of effective faults, hydrocarbon distribution in slope areas of petroliferous basins is assessed. In this study, we superimpose two methods to develop a set of key methods, which can identify effective faults for hydrocarbon accumulation in slope areas. The first of this set of methods includes locating the distribution area of the connected sand bodies and paleotectonic ridges overlying the formation where the sand bodies are located, which aids determining the lateral migration path of hydrocarbons in slope areas. The second set of methods includes identifying the lateral sealing parts of faults that are oriented perpendicular or oblique to the channel sand bodies, thereby determining the faults that are effective for hydrocarbon accumulation. By applying these methods, we identify the effective faults in the first member of the Nantun Formation (K1n1) on the Wunan slope of the Wuerxun Depression in the Hailar Basin. The results show that the effective faults in K1n1 are located mainly in its middle and northern parts, with a few distributed in the south-central part. This is conducive to reservoir development, since hydrocarbons which were generated in the western trough source rocks of K1n1, accumulated in the nearby trap formed from a suitable configuration of the fault and sand body of K1n1. This is consistent with previous exploration data, and the observation that hydrocarbons discovered in K1n1 on the Wunan slope are mainly distributed in the middle and northern parts of the region, and a small amount occur in the south-central part. The results show that this set of methods is feasible for determining effective faults for hydrocarbon accumulation in slope areas.

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum 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.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency 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.)

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience 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 Wuerhe-fengnan area (WFA) in the Junggar Basin, NW China, has recently obtained exploration success. These accumulations are characterized by oil from multiple source rocks with multiple-stage accumulation. However, the origin of oils and their charging history have been controversial, making it difficult to understand the general pattern of hydrocarbon accumulation. Here, we reconstruct this process mainly based on molecular and isotopic geochemistry of hydrocarbons and comprehensive fluid inclusion analysis. Four conclusions were reached. Firstly, oils in various regions came from different source rocks. The oil in the fault zone was derived from the Lower Permian Fengcheng Formation (P 1 f) argillaceous dolomite source rocks in situ in WFA and/or from Mahu depression. The oil in the slope area originated from the Middle Permian Lower Wuerhe Formation (P 2 w) mudstone source rocks in the Mahu depression. Secondly, oil reservoirs in various regions were charged at different times. Three episodes of P 1 f-sourced oil charging took place in Triassic reservoirs in the fault zone, which occurred at 230 Ma, 198 Ma and 125 Ma years ago, respectively. There are only two episodes of P 2 w-sourced oil charging in the slope area, namely, 196 Ma and 136 Ma before present. Thirdly, oil reservoirs in various regions have different hydrocarbon migration directions and mechanisms. Oils in the fault zone display obvious vertical migration characteristics. Hydrocarbons mainly migrated from lower structural positions to higher structural positions laterally, in other words, the hydrocarbons in the fault zone mainly migrated from southwest to northeast, while the hydrocarbons in the slope area mainly migrated from southeast to northwest. The oil migration in the fault zone is driven both by excessive formation pressure and buoyancy, while that in the slope area is likely driven by buoyancy. Finally, a comprehensive three-stage oil migration and accumulation model of Triassic reservoirs in WFA was established. The first-stage oil accumulation (P 1 f-sourced oils) occurred during the Middle Triassic (230 Ma), which was concentrated only in the fault zone. The second-stage and third-stage oil accumulation occurred during the Early Jurassic (200 Ma) and Early Cretaceous (140-120 Ma), respectively, with the P 1 f-sourced oils concentrated in the fault zone and the P 2 w-sourced oils concentrated in the slope area. In summary, oil reservoirs in various regions (fault zone and slope area) were derived from different source rocks, with different charging time and accumulation models. [ABSTRACT FROM AUTHOR]

Highlights: [•] The post-rift fault activities in Baiyun slope area are found to be caused by gravity. [•] Analogue modeling experiments were used to test the 3D deformation. [•] The gravity during post-rift stage might be caused by discrepant subsidence. [ABSTRACT FROM AUTHOR]

Abstract: To get a better understanding of the distribution pattern of favorable reservoir belts in the medium-deep clastic rocks in the Qikou sag of the Huanghua depression, and find out premium reservoir zone, the characteristics and controlling factors of the medium-deep reservoirs in the Qikou sag were analyzed. Comprehensive study into the structural setting, provenance, depositional system, and reservoir properties shows that the Paleogene in the Qikou sag has multi-sags and multi-slopes, with slopes accounting for over 70% of the total sag area. A number of large braided river (fan) delta front - gravity flow sand bodies matching with multi-slope zones lay a good material foundation for the formation of medium-deep effective reservoirs there. Generally buried at over 2500 m, the medium-deep clastic rocks are lithic feldspathic sandstone, with secondary pores and cracks as major reservoir space. Being in the medium diagenesis evolution stage, the medium-deep clastic rocks in the Qikou sag span over a large depth. Nine major factors affecting reservoir properties have been identified by mathematical geology. Although the medium-deep clastic rock interval is poor in physical properties and complex in pore structure, high sedimentation rate, medium geothermal field, high fluid pressure, high feldspar content, relatively high dissolution rate and early oil and gas charge have given rise to three to four belts with abnormally high porosity in it, which are all favorable hydrocarbon reservoir zones. [Copyright &y& Elsevier]