Abstract
Porosity is the most common form of reservoirs, and its size, shape, and connectivity directly affect the capacity of oil and gas storage and production. To study the micro–nano-pore structure characteristics of shale oil reservoirs and quantitatively characterize its heterogeneity, this work uses high-precision high-pressure mercury intrusion (HPMI) experimental techniques to study the micro–nano-pore structure characteristics of shale oil, and based on the experimental data, fractal theory is used to quantitatively characterize its heterogeneity. The results of the study show that the micro–nano-pores in the shale oil reservoir are concentrated and continuous, and the pore radius is mainly distributed among the range of 30–500 nm, nanoscale pores are an important part of the pores of the shale oil reservoir. The fractal dimension of the shale oil reservoir is larger than the fractal dimension of typical tight oil reservoirs, indicating that the heterogeneity of shale oil reservoir is stronger. The research results have some theoretical and practical significance for the production of inter-salt shale oil reservoirs.
Highlights
Since 2010, some scholars have carried out large-scale research in the unconventional oil and gas field and gradually formed an unconventional oil and gas geological theory system (Zou et al 2012b)
The maximum intrusive mercury saturation of the shale oil core has a small decrease compared with the tight sandstone, but it still reaches more than 80%, indicating that the high-pressure mercury injection experiment is an effective method to study the microscopic pore structure of the shale oil reservoir
It can be found that the micro–nano-pore fractal dimension of shale oil reservoirs is not much different and larger than the fractal dimension of the selected tight oil reservoir, indicating that its heterogeneity is stronger
Summary
Since 2010, some scholars have carried out large-scale research in the unconventional oil and gas field and gradually formed an unconventional oil and gas geological theory system (Zou et al 2012b). The main experimental methods of studying the pore structure characteristics of shale oil reservoirs include nuclear magnetic resonance (NMR), low-temperature nitrogen adsorption (LTNA), and high-pressure mercury injection (HPMI). We use high-pressure mercury intrusion experiment technology to conduct in-depth research on the micro–nano-pore structure characteristics of shale reservoirs, analyze the micro–nano-pore throat distribution, and compare it with typical domestic tight oil reservoirs. (The minimum test pore size is about 2 nm.) The capillary pressure curve obtained by the mercury intrusion method can provide information on the microscopic pore structure of the reservoir. To further study the pore structure characteristics of this block of the reservoir, we selected four typical rock samples in the J Basin and analyzed the mineral composition using X-ray diffraction technology, the analysis results, and basic core data which are shown in Table 1 and Table 2. It is an important parameter to characterize the micropore structure of the core of a lowpermeability tight reservoir and affects the seepage capacity of the reservoir fluid
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