scholarly journals Broad ion beam-scanning electron microscopy pore microstructure and multifractal characterization of shale oil reservoir: A case sample from Dongying Sag, Bohai Bay Basin, China

2019 ◽  
Vol 38 (3) ◽  
pp. 613-628
Author(s):  
Pengfei Zhang ◽  
Shuangfang Lu ◽  
Junqian Li ◽  
Xiangchun Chang ◽  
Jijun Li ◽  
...  
Keyword(s):  
Pore Structure ◽  
Pore Diameter ◽  
Ion Beam ◽  
Bohai Bay ◽  
Shale Oil ◽  
Bohai Bay Basin ◽  
Average Pore ◽  
Dongying Sag ◽  
Pore Types ◽  
Elementary Area

Pore structure and its heterogeneity are critical factors controlling the storage capacity and transportation properties of hydrocarbons. Broad ion-beam-milling scanning-electron microscopy allows for the study of a larger planar at high resolution than other methods and can provide insight into shale microstructures. In this study, we investigate the microscopic pore structure of a shale oil reservoir sample from Paleogene Shahejie Formation in Dongying Sag, Bohai Bay Basin, based on the broad ion-beam cross-section, and discuss the heterogeneity of the major pores using multifractal theory. The representative elementary area of the sample was first inferred to be ∼100 × 100 µm2 (25 single images) for the broad ion-beam cross-section with an area of 1.054 × 0.915 mm2. Five pore types (interparticle, intraparticle clay, dissolution, inter-crystalline, and organic) were subsequently identified and analyzed in the selected typical representative elementary area. The results showed that interparticle, intraparticle clay, and dissolution pores were the major pore types and made a significant contribution to the total visible surface porosity (98.34%), whereas inter-crystalline and organic pores were not of great importance. Interparticle pores exhibited the most complex pore morphologies, the largest average pore diameter, and the simplest pore structure. Moreover, interparticle pores that were sub-parallel to the bedding plane showed the best connectivity. Intraparticle clay pores, on the other hand, had the smallest average pore diameter, the most complex pore structure, and their distribution in a two-dimensional plane was the most homogeneous. Dissolution pores were characterized by the least complex pore morphologies but more heterogeneous pore distribution. Both intraparticle clay and dissolution pores were abundant but possessed poor connectivity. We conclude that for shale oil storage and transportation in the Dongying Sag, interparticle pores play an important role in shale oil seepage, whereas intraparticle clay and dissolution pores provide the main space for the occurrence of shale oil.

scholarly journals Pore Structure and Fractal Character of Lacustrine Oil-Bearing Shale from the Dongying Sag, Bohai Bay Basin, China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Pengfei Zhang ◽  
Shuangfang Lu ◽  
Zhiping Zeng ◽  
Xiangchun Chang ◽  
Junqian Li ◽  
...  
Keyword(s):  
Pore Structure ◽  
Fractal Dimensions ◽  
Nitrogen Adsorption ◽  
Bohai Bay ◽  
Shale Oil ◽  
Bohai Bay Basin ◽  
Average Pore ◽  
Dongying Sag ◽  
Shahejie Formation ◽  
Fractal Character

To better understand the pore structure and fractal character of lacustrine shales and their influence on liquid hydrocarbon occurrences, in this study, a total of 29 lacustrine oil-bearing shale samples collected from the Shahejie Formation in the Dongying Sag, Bohai Bay Basin, were investigated based on nitrogen adsorption (NGA) analysis combined with TOC, Rock-Eval pyrolysis, X-ray diffraction (XRD), and field emission-scanning electron microscopy (FE-SEM) experiments. The relationships among the compositions (TOC, minerals, and oil content), pore structures, and fractal dimensions of the lacustrine shale samples were discussed. The results showed that the adsorption and fractal characteristics of lacustrine oil-bearing shales differ at relative pressures of 0-0.1 and 0.5-1. Two corresponding fractal dimensions D 1 and D 2 were determined by the FHH model according to the nitrogen adsorption branches. Specifically, D 1 varies from 2.4292 to 2.6109 (mean 2.5245), and D 2 varies between 2.4680 and 2.8535 (mean 2.6889). The specific surface area (SSA) ranges from 1.512 m2/g to 34.002 m2/g, with an average of 13.656 m2/g, the total pore volume is between 6.0 × 10-3 cm3/g and 48.4 × 10-3 cm3/g (mean 24.5 × 10-3 cm3/g), and the average pore diameter is in the range of 4.22 nm to 19.57 nm (mean 9.35 nm). Both D 1 and D 2 increase with increasing SSA and increase with decreasing average pore diameters but have no correlation with pore volume. Moreover, D 1 and D 2 exhibit positive relationships with clay minerals and negative correlations with carbonate minerals (calcite and dolomite). The relationship between fractal dimensions ( D 1 and D 2 ) and TOC contents is expressed as a U-shaped curve, characterized by the minimum D values at approximately 3% TOC. The shale oil content is controlled by the pore structures and fractal dimensions, and lacustrine shales with lower SSAs and smaller fractal dimensions would have more free oil. Therefore, lacustrine shales in the oil window with TOC contents ranging from 2% to 4% are probably the preferred shale oil exploration target in the Shahejie Formation, Dongying Sag, Bohai Bay Basin. The results indicate that fractal analysis can provide insight into the pore structure characteristics and oil storage capacity of lacustrine shales.

scholarly journals Movability of lacustrine shale oil: A case study of Dongying Sag, Jiyang Depression, Bohai Bay Basin

2014 ◽  
Vol 41 (6) ◽  
pp. 703-711 ◽  
Author(s):  
Linye ZHANG ◽  
Youshu BAO ◽  
Juyuan LI ◽  
Zheng LI ◽  
Rifang ZHU ◽  
...  
Keyword(s):  
Bohai Bay ◽  
Shale Oil ◽  
Bohai Bay Basin ◽  
Jiyang Depression ◽  
Dongying Sag ◽  
Lacustrine Shale

A new method for continental shale oil enrichment evaluation

2017 ◽  
Vol 5 (2) ◽  
pp. T209-T217 ◽  
Author(s):  
Siyuan Su ◽  
Zhenxue Jiang ◽  
Zhiye Gao ◽  
Chuanxiang Ning ◽  
Zhi Wang ◽  
...  
Keyword(s):  
Saturation Index ◽  
Source Rocks ◽  
New Method ◽  
Bohai Bay ◽  
Shale Oil ◽  
Bohai Bay Basin ◽  
Jiyang Depression ◽  
Reservoir Rocks ◽  
Dongying Sag ◽  
Porosity And Permeability

We have evaluated continental shale oil enrichment via experiments. Rock pyrolysis, nuclear magnetic resonance, and pulse permeability tests were conducted to establish the pore saturation index (PSI), which comprehensively evaluates the enrichment of shale oil features using the characteristics of self-generation and self-preservation, the parameters of which include the pyrolysis-free hydrocarbon ([Formula: see text]) and total organic carbon of source rocks as well as the porosity and permeability of reservoir rocks. The correlation of the oil content ([Formula: see text]) and PSI values indicated that PSI values greater than 50 generally indicate good oil enrichment plays, whereas those smaller than 50 imply poor conditions for oil enrichment. This conclusion was successfully applied to the Zhanhua Sag with shale oil plays in the Jiyang Depression, Bohai Bay Basin, China. In addition, the shale oil plays of the Dongying Sag in the Jiyang Depression were investigated to verify the effectiveness and reliability of the new method.

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