scholarly journals Characteristics of the temperature–pressure field evolution of Middle Permian system in the northwest of Sichuan Basin

2018 ◽  
Vol 36 (4) ◽  
pp. 705-726 ◽  
Author(s):  
Qiuchen Xu ◽  
Nansheng Qiu ◽  
Wen Liu ◽  
Anjiang Shen ◽  
Xiaofang Wang ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Oil And Gas ◽  
Vitrinite Reflectance ◽  
Middle Permian ◽  
Key Factors ◽  
Reduction Stage ◽  
Three Stages ◽  
The Sichuan Basin ◽  
Thermal Indicators ◽  
Oil Cracking

The Sichuan Basin is one of the richest oil and gas basins in China. The Middle Permian units (the Qixia and Maokou Formations) in the northwest Sichuan Basin have great potential for gas exploration. A new thermal history was reconstructed using the integrated thermal indicators of apatite and zircon (uranium–thorium)/helium ages, zircon fission tracks, and vitrinite reflectance data. The modeled results indicated that the northwest Sichuan Basin experienced gradual cooling, during which the heat flow at Middle Permian time (70–90 mW/m2) decreased to its current level of approximately 50 mW/m2. This study used basin modeling to reconstruct the paleo-pressure, which showed that the Middle Permian in the northwest Sichuan Basin generally developed overpressure. The pressure evolution of the Middle Permian can be divided into three stages: (1) a slight overpressure stage (T2–T3), (2) an intensive overpressure stage (J1–K2), and (3) an overpressure reduction stage (K2–present). Oil cracking and rapid tectonic subsidence are key factors that affect overpressure. The evolution of temperature–pressure has great significance with respect to hydrocarbon accumulation.

An introduction to seismic exploration of the Micang-Dabashan foothill belt in the Sichuan Basin

2018 ◽  
Vol 6 (4) ◽  
pp. SM39-SM50
Author(s):  
Jingbo Wang ◽  
Zhongshan Qi ◽  
Penggui Jing ◽  
Tianfa Zheng ◽  
Yanqi Li ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Oil And Gas ◽  
Seismic Exploration ◽  
Small Scale ◽  
Marine Strata ◽  
Piedmont Zone ◽  
Migration Imaging ◽  
Imaging Results ◽  
Platform Margin ◽  
The Sichuan Basin

Geologic studies indicate that the platform-margin reef-shallow facies in Permo-Triassic marine strata in the Micang-Dabashan foothill belt in the Sichuan Basin are favorable exploration targets for oil and gas exploration. However, the typical dual-complexity problem (complex surface condition and subsurface structure) brings a great challenge for seismic technology targeting of those potential oil and gas reservoirs. To overcome this problem, varieties of advanced seismic acquisition and processing methods have been used to improve the imaging quality of piedmont seismic data since 2000. Some improvements have been achieved: The reflection waves from the far offset and deep layer can be acquired in shot gathers from limestone outcropped areas, and the signal-to-noise ratio (S/N) of reflection and diffraction waves in the stack section has been enhanced significantly so as to reveal amounts of valuable geologic information. The resolution and the S/N of seismic migration imaging for the strong fold zone in marine strata have been improved partially, so that the structure of the step-fault zone and the enveloping of gypsum rock are clearer than those revealed by the old seismic section. Even so, actual drilling data demonstrate that the subsurface structures of the foothill belt are far more complex than those revealed by the current seismic imaging results. Therefore, postdrilling evaluation for the validity of seismic techniques implemented in the Nanjiang and Zhenba piedmont zone has been carried out. The results indicate that the current acquisition scheme and processing workflow cannot completely fulfill the requirements of high-precision velocity modeling and migration imaging of complex structures (such as footwalls of thrust fault and small-scale fault blocks) in the piedmont zone, especially when the rugged surface and the widespread limestone outcrop appear simultaneously. Finally, we have developed some potential needs of seismic theories and techniques in the foothill belt, including seismic wave propagation, acquisition, and processing technology.

Quantitative prediction of oil and gas prospects of the Sinian-Lower Paleozoic in the Sichuan Basin in central China

Energy ◽  
2019 ◽  
Vol 174 ◽  
pp. 861-872 ◽  
Author(s):  
Wenyang Wang ◽  
Xiongqi Pang ◽  
Zhangxin Chen ◽  
Dongxia Chen ◽  
Tianyu Zheng ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Oil And Gas ◽  
Central China ◽  
Quantitative Prediction ◽  
Lower Paleozoic ◽  
The Sichuan Basin

scholarly journals Sequence stratigraphic features of the Middle Permian Maokou Formation in the Sichuan Basin and their controls on source rocks and reservoirs

2015 ◽  
Vol 2 (5) ◽  
pp. 421-429 ◽  
Author(s):  
Wang Su ◽  
Qingchun Jiang ◽  
Zhiyong Chen ◽  
Zecheng Wang ◽  
Hua Jiang ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Source Rocks ◽  
Middle Permian ◽  
Sequence Stratigraphic ◽  
The Sichuan Basin

scholarly journals Basic characteristics and accumulation mechanism of Sinian−Cambrian giant highly mature and oil-cracking gas reservoirs in the Sichuan Basin, SW China

2017 ◽  
Vol 36 (4) ◽  
pp. 568-590 ◽  
Author(s):  
Bing Luo ◽  
Yu Yang ◽  
Gang Zhou ◽  
Wenjun Luo ◽  
Shujiao Shan ◽  
...  
Keyword(s):  
Natural Gas ◽  
Lower Cambrian ◽  
Sichuan Basin ◽  
Large Scale ◽  
Oil And Gas ◽  
Source Rocks ◽  
Burial Depth ◽  
Sw China ◽  
Accumulation Mechanism ◽  
Oil Cracking

Old Mesoproterozoic−Cambrian successions have been regarded as an important frontier field for global oil and gas exploration in the 21st century. This has been confirmed by a recent natural gas exploration breakthrough in the Sinian and Cambrian strata, central Sichuan Uplift, Sichuan Basin of SW China. However, the accumulation mechanism and enrichment rule of these gases have not been well characterized. This was addressed in this work, with aims to provide important guidance for the further exploration while enriching the general studies of the oil and gas geology in the old Mesoproterozoic–Cambrian strata. Results show that the gas field in the study area is featured by old target layers (Sinian–Lower Cambrian), large burial depth (>4500 m), multiple gas-bearing intervals (the second and fourth members of the Sinian Dengying Formation and the Lower Cambrian Longwangmiao Formation), various gas reservoir types (structural type and structural–lithologic type), large scale (giant), and superimposing and ubiquitous distribution. The giant reserves could be attributed to the extensive intercalation of pervasive high quality source rocks and large-scale karst reservoirs, which enables a three-dimensional hydrocarbon migration and accumulation pattern. The origin of natural gas is oil cracking, and the three critical stages of accumulation include the formation of oil reservoirs in Triassic, the cracking of oil in Cretaceous, and the adjustment and reaccumulations in the Paleogene. The main controlling factor of oil and gas enrichment is the inherited development of large-scale stable paleo-uplift, and the high points in the eastern paleo-uplift are the favorable area for ​natural gas exploration.

scholarly journals New progress and prospect of Middle Permian natural gas exploration in the Sichuan Basin

2021 ◽  
Vol 8 (1) ◽  
pp. 35-47
Author(s):  
Yueming Yang ◽  
Yu Yang ◽  
Long Wen ◽  
Xihua Zhang ◽  
Cong Chen ◽  
...  
Keyword(s):  
Natural Gas ◽  
Sichuan Basin ◽  
Middle Permian ◽  
The Sichuan Basin

scholarly journals Discovery of a shoal-controlled karst dolomite reservoir in the Middle Permian Qixia Formation, northwestern Sichuan Basin, Southwest China

2017 ◽  
Vol 36 (4) ◽  
pp. 686-704 ◽  
Author(s):  
Di Xiao ◽  
Benjian Zhang ◽  
Xiucheng Tan ◽  
Hong Liu ◽  
Jirong Xie ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Middle Permian ◽  
Karst Water ◽  
Karst System ◽  
Reservoir Properties ◽  
Parent Rocks ◽  
Porosity And Permeability ◽  
The Sichuan Basin ◽  
Intercrystalline Pores

The dolomites of the Middle Permian Qixia Formation have been important targets of natural gas exploration in the Sichuan Basin for decades. However, more and more exploration and research indicate that the formation of the reservoir might be related to karstification. To testify this hypothesis, we conduct comprehensive outcrop, core, and logging analyses based on a case study in the representative northwestern Sichuan Basin, which has obtained exploration breakthroughs recently. Results show that the Qixia dolomite reservoirs are mainly developed within fine-crystalline dolomites formed by a series of diagenetic modifications, which can be further divided into three types according to the macro- and micro-occurrences of dolomites: euhedral-subhedral crystalline dolomites in the quasi-stratiform karst system (mean porosity and permeability is 3.51% and 3.11 mD, respectively), euhedral-subhedral crystalline dolomites in the leopard porphyritic karst system (mean porosity and permeability is 3.36% and 1.22 mD, respectively), and allotriomorphic mosaic crystalline dolomites with residual parent rock fabrics (mean porosity and permeability is 0.94% and 0.92 mD, respectively). Their reservoir qualities decrease along the order. The formation mechanism of the reservoir is shoal-controlled karst. The preservation of residual intergranular pores within the thin-layer grainstones of shoal facies provides favorable channels for karst water. In the vadose zone, the heterogeneous dissolution within grainstones leads to the formation of leopard porphyritic dissolution features. In the phreatic zone, the karst water flowing along the stratiform grainstones results in the formation of quasi-stratiform dissolution features. The karst system is filled with loose carbonate sands and gravels, whose reservoir properties are far superior to parent rocks, and they can provide migration channels for the hydrothermal fluids with rich Mg2+ in the burial stage. The replacement of hydrothermal fluid results in the redistribution of pores and vugs of inter-fillings within karst system and the formation of intercrystalline pores and residual vugs, but the reservoir space of parent rocks keeps the same as the original condition. Therefore, the exploration of the Qixia dolomite reservoir should be changed to shoal-controlled karst.

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