Abstract
Small-angle neutron scattering and high-pressure mercury intrusion capillary pressure testing are integrated to analyze the pore size distribution of the broad sense shale oil reservoir samples of the Permian Lucaogou Formation in the Jimsar Sag, Junggar Basin, China. The results show that, compared with the measurement method integrating gas adsorption and mercury intrusion, combination of small-angle neutron scattering and mercury intrusion can more accurately characterize full-scale pore size distribution. The full-scale pore size distribution curve of the rock samples in the study area includes two types: the declining type and submicron pore-dominated type. The declining type is mainly found with silty mudstone and dolomitic mudstone, and most of its pores are smaller than 80 nm. Silt-fine sandstones and dolarenite are mostly of the submicron pores-dominated type, with most pores smaller than 500 nm. They also present large specific pore volumes and average pore diameters of macropores and are the favorable lithogenous facies for development of high-quality reservoirs.
Highlights
Small-angle neutron scattering and high-pressure mercury intrusion capillary pressure testing are integrated to analyze the pore size distribution of the broad sense shale oil reservoir samples of the Permian Lucaogou Formation in the Jimsar Sag, Junggar Basin, China
By studying the Longmaxi shale samples, it was found that the pore volume distribution presents a power-law pattern; the measured pore size distribution is consistent with the result of the N 2 adsorption method in the same size range; the specific surface area and porosity of the PDSP method increase with growth of total organic carbon (TOC)[28]
The mercury intrusion capillary pressure testing (MICP) test, affected by the low mercury intrusion saturation when dealing with nano-scale pores, cannot cover all nano pores, and high pressure may lead to occurring of secondary pores, which lead to inaccurate measurements
Summary
Small-angle neutron scattering and high-pressure mercury intrusion capillary pressure testing are integrated to analyze the pore size distribution of the broad sense shale oil reservoir samples of the Permian Lucaogou Formation in the Jimsar Sag, Junggar Basin, China. Non-optical probing methods such as the diffraction method and electron microscopy have gradually replaced the optical microscopy and serve as the main tool for investigating nano-scale structures, which successfully raise the measurement precision of pore sizes from microns to n anometers[4] Scholars in both China and other countries have extensively applied the gas adsorption method to investigate the properties of both the adsorbent and adsorbate, fractal dimensions, and pore types[18,19,20,21,22,23], and this method is combined with the fluid intrusion method to carry out systematic research on pores with diameters above 0.35 nm. Jitendra Bahadur et al studied the microstructure of New Albany shale samples with different thermal maturities, and extracted information about the size range and number density of micropores from the relative fluorescence scattering intensity observed in the range of a large scattering vector Q They compared the results of the model-independent Porod invariant method with the calculation results of the PDSP m odel[30]. This research pointed out that the water absorption capacity of the sample is positively correlated with the total porosity, with the help of the dynamic water steam adsorption technique[31]
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