Geochemical and geological characteristics of Permian Lucaogou Formation shale of the well Ji174, Jimusar Sag, Junggar Basin, China: Implications for shale oil exploration

2017 ◽  
Vol 53 (5) ◽  
pp. 2371-2385 ◽  
Author(s):  
Tao Hu ◽  
Xiongqi Pang ◽  
Qifeng Wang ◽  
Shu Jiang ◽  
Xulong Wang ◽  
...  
Keyword(s):  
Junggar Basin ◽  
Shale Oil ◽  
Oil Exploration ◽  
Geological Characteristics ◽  
Lucaogou Formation

Characteristics of Micro/Nano Pores and Hydrocarbon Accumulation in a Continental Shale Oil Reservoir—A Case Study of the Lucaogou Formation in the Jimsar Sag, Junggar Basin, Northwest China

2021 ◽  
Vol 21 (1) ◽  
pp. 262-273
Author(s):  
Jun Jin ◽  
Zhao Yang ◽  
Xuekun Chen ◽  
Lulu Li ◽  
Hongxia Yang ◽  
...  
Keyword(s):  
Junggar Basin ◽  
Ct Scanning ◽  
Northwest China ◽  
Oil Reservoir ◽  
Shale Oil ◽  
Pore Characteristics ◽  
Mercury Analysis ◽  
Lucaogou Formation ◽  
Jimsar Sag ◽  
Intercrystalline Pores

This paper comprehensively studies the micro- and nanometer-scale pore characteristics and structure of the Lucaogou Formation shale oil reservoir in the Jimsar Sag using high-pressure mercury analysis, field emission scanning electron microscopy and nano-CT scanning technology. In addition, the occurrence states of crude oil in pores are analyzed combined with macro–micro characteristics. The results show that there are various reservoir types; the main reservoir pore structure is on the micron and nanometer levels, with other void spaces including intergranular pores, interparticle dissolution pores, intercrystalline pores and microfissures. Nanopores are generally oil-bearing and mostly in the adsorption state, which changes the traditional understanding that micron pores are the only microscopic pores in the reservoir and confirms that shale oil exists in ‘sweet spots’ and mud-shale sections of the Lucaogou Formation.

scholarly journals Characteristics and Genetic Mechanism of Pore Throat Structure of Shale Oil Reservoir in Saline Lake—A Case Study of Shale Oil of the Lucaogou Formation in Jimsar Sag, Junggar Basin

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8450
Author(s):  
Xiaojun Zha ◽  
Fuqiang Lai ◽  
Xuanbo Gao ◽  
Yang Gao ◽  
Nan Jiang ◽  
...  
Keyword(s):  
Sedimentary Environment ◽  
Junggar Basin ◽  
Genetic Mechanism ◽  
Formation Mechanisms ◽  
Oil Reservoir ◽  
Shale Oil ◽  
Pore Throat ◽  
Delta Front ◽  
Lucaogou Formation ◽  
Jimsar Sag

The shale oil reservoir of the Lucaogou Formation in the Jimsar Sag has undergone tectonic movement, regional deposition and complex diagenesis processes. Therefore, various reservoir space types and complex combination patterns of pores have developed, resulting in an intricate pore throat structure. The complex pore throat structure brings great challenges to the classification and evaluation of reservoirs and the efficient development of shale oil. The methods of scanning electron microscopy, high-pressure mercury injection, low-temperature adsorption experiments and thin-slice analysis were used in this study. Mineral, petrology, pore throat structure and evolution process characteristics of the shale oil reservoir were analyzed and discussed qualitatively and quantitatively. Based on these studies, the evolution characteristics and formation mechanisms of different pore throat structures were revealed, and four progressions were made. The reservoir space of the Lucaogou Formation is mainly composed of residual intergranular pores, dissolved pores, intercrystalline pores and fractures. Four types of pore throat structures in the shale oil reservoir of the Lucaogou Formation were quantitatively characterized. Furthermore, the primary pore throat structure was controlled by a sedimentary environment. The pores and throats were reduced and blocked by compaction and cementation, which deteriorates the physical properties of the reservoirs. However, the dissolution of early carbonate, feldspar and tuffaceous minerals and a small amount of carbonate cements by organic acids are the key factors to improve the pore throat structure of the reservoirs. The genetic evolution model of pore throat structures in the shale oil reservoir of the Lucaogou Formation are divided into two types. The large-pore medium-fine throat and medium-pore medium-throat reservoirs are mainly located in the delta front-shallow lake facies and are characterized by the diagenetic assemblage types of weak compaction–weak carbonate cementation–strong dissolution, early medium compaction–medium calcite and dolomite cementation–weak dissolution. The medium-pore fine throats and fine-pore fine throats are mainly developed in shallow lakes and semi-deep lakes. They are characterized by the diagenetic assemblage type of strong compaction–strong calcite cementation–weak dissolution diagenesis. This study provides a comprehensive understanding of the pore throat structure and the genetic mechanism of a complex shale oil reservoir and benefits the exploration and development of shale oil.

scholarly journals Revisiting Controls on Shale Oil Accumulation in Saline Lacustrine Basins: The Permian Lucaogou Formation Mixed Rocks, Junggar Basin

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-25
Author(s):  
Chenjia Zhang ◽  
Jian Cao ◽  
Erting Li ◽  
Yuce Wang ◽  
Wenyao Xiao ◽  
...  
Keyword(s):  
Carbonate Rocks ◽  
Junggar Basin ◽  
Type I ◽  
Hydrocarbon Generation ◽  
Shale Oil ◽  
Oil Accumulation ◽  
Hydrocarbon Generation Potential ◽  
Lucaogou Formation ◽  
Saline Lacustrine ◽  
Lacustrine Basins

Fine-grained mixed rocks in saline lacustrine basins are important targets for shale oil exploration. However, the controls on shale oil accumulation are complex due to the multi-source mixed deposition. This is a challenging issue in the study of shale oil. Here, we present a case study in the Middle Permian Lucaogou Formation in the Jimusar Sag, Junggar Basin, northwestern China. Results show that the Lucaogou Formation consists mainly of carbonate rocks, dolomitic or calcareous mudstones, tuffaceous or silty mudstones, and siltstones. The dolomitic/calcareous mudstones ( TO C average = 6.44   wt . % ) and tuffaceous/silty mudstones ( TO C average = 4.83   wt . % ) have the best hydrocarbon generation potential and contain type I–II1 kerogens that are in the peak oil generation stage. However, the shale oil potential is highest for the carbonate rocks and siltstones with average oil saturation index (OSI) values of 315.03 mg HC/g TOC and 343.27 mg HC/g TOC, respectively. This indicates that hydrocarbon generation potential is not the main factor controlling shale oil potential. Micro-nanoscale pores are the main control. Abundant dissolution pores provide excellent reservoir space for near-source migration and accumulation of shale oil. Different mixing processes between lithofacies control the accumulation of shale oil, and shale oil productivity is the best when multi-facies deposition in transitional zones formed the mixed rocks (facies mixing). In addition, local accumulations of calcareous organisms and adjacent carbonate components on terrigenous sediments (in situ mixing) are also conducive to shale oil enrichment. This is an unusual and special feature of saline lacustrine shale oils, which is different from freshwater lacustrine and marine shale oils. Comprehensive assessment of source rock and reservoir is needed to robustly establish a widely applicable method to determine the shale oil potential in such basins.

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