Formation and Distribution of Different Pore Types in the Lacustrine Calcareous Shale: Insights from XRD, FE-SEM, and Low-Pressure Nitrogen Adsorption Analyses

Abstract

Pore types and pore structure parameters are the important factors affecting the storage capacity of a shale oil reservoir. Pore morphology and mineralogical composition of shales have diverse effects on the upgrading of various phases of shale oil. To interpret the formation and distribution of different pore types and their structure parameters in the lacustrine calcareous shale, a combination of polarizing microscopy, X-ray diffraction, total organic carbon (TOC), field-emission scanning electron microscopy, and low-pressure nitrogen adsorption experiments were conducted on the Es3x shale of the Eocene Shahejie Formation in the Zhanhua Depression. The interpretations regarding pore types, pore structure parameters, and pore size distribution indicate that the pore morphology and pore size distribution in the lacustrine shale are very complicated and demonstrate strong heterogenic behavior. Inorganic pores (interparticle pores, intraparticle pores, intercrystalline pores, dissolution pores, and microfractures) are the most commonly distributed pore types in the studied shale. However, organic matter pores are poorly developed due to the lower thermal maturity of the Es3x shale. The Brunauer–Emmett–Teller specific surface and pore volume range from 0.026 to 1.282 m 2 /g (average 0.697 m 2 /g) and 0.003 to 0.008 cm 3 /g (average 0.005 cm 3 /g), respectively. The shape of the pores varies from slit-like to narrow slit. Different minerals develop different types of pores with various sizes extending from micropores (<2 nm), mesopores (2–50 nm), to macropores (>50 nm). The relationship between mineral components and pore parameters indicates that the carbonate minerals act as the main contributors to the formation and distribution of different pore types in the studied shale. Pore volume and the pore specific surface area did not show a good relationship with mineral composition and TOC due to disordered pores, but pore size shows a good relationship with mineral composition and TOC of the Es3x shale. The whole pore system description showed that the mesopores and macropores are abundantly distributed and are the main contributors to the pore system in the Es3x shale. A comprehensive understanding of the formation mechanism and structural features of various sized pores in a variety of different minerals can provide a good tool for the exploration and development of shale oil reservoirs.

Cooperative Heterogeneous Catalysis with a Robust Acid–Base Bifunctional Zinc-Based Metal–Organic Framework Nanostructure in the Diastereoselective Henry Reaction

“…This activated sample was then used to measure the nitrogen sorption at 77 K. As shown in Figure S8, Zn-(L-GluBenz) was found to exhibit a type IV reversible isotherm with a maximum nitrogen uptake of 43.78 cm 3 g −1 , specifically the mixture of H3 and H4 types for N 2 at 77 K. This corroborates with its surface morphology having aggregated flaky particles, resulting in a mixture of the wedge and slit-shaped pores. 44 The Brunauer−Emmet−Teller (BET) surface area (16.2 m 2 g −1 ) was found to be low, indicating a lack of abundant interaction sites for N 2 . The pore-size distribution calculated from the nonlinear density functional theory simulation in the data analysis software shows two types of pores with diameters of 1.28 and 3.7 nm (inset, Figure S8), manifesting the mixture of microporous and mesoporous nature of the framework.…”

Microscopic Reservoir Characteristics of the Lacustrine Calcareous Shale: An Example from the Es4s Shale of the Paleogene Shahejie Formation in Boxing Sag, Dongying Depression

“…The LPNA test was carried out at −195.8 °C temperature to characterize the pore structure . The pore surface area is calculated by using the BET model, while the BJH model is used to compute PSD and pore volume. , The isotherms and hysteresis loops were analyzed based on previously defined models, as shown in Figure .…”

“…Currently, the research on reservoir properties in the Jiyang Sub-basin is a prime focus of many researchers. ,, In this study, we conducted a detailed analysis of whole-rock mineral composition, thin section petrography, field-emission scanning electron microscopy (FE-SEM) analysis, and low-pressure N 2 adsorption analysis to describe the reservoir characteristics of the Es 4 s shale of the Boxing Sag, Dongying Depression. The main objectives of this research work are (i) microscopic characteristics of lacustrine shale pore types, (ii) the role of mineralogical heterogeneity in pore evolution, and (iii) the effect of TOC contents in pore evolution.…”

“…Figure10. Classifications of adsorption hysteresis loop curves and pore types (modified from Khan et al45 ).…”

Occurrence Characteristics and Threshold Pore Throat Radius of Movable Fluids for Dolomite Intercrystalline Pores of Lacustrine Carbonate Rocks

“…The proportions of stored movable fluids in samples are dependent on the pore type, pore throat distribution, pore structure, and contact surface property [46][47][48]. The tested samples are observed with extensive development of dolomite intercrystalline pores and intercrystalline dissolved pores.…”