Impact of coexisted clay mineral and organic matter on pore growth in Lower Jurassic Da'anzhai lacustrine shale reservoir in the Northeast Sichuan Basin, West China

Understanding pore growth is of great significance to investigating reservoir performance in shale-gas systems. However, different from the marine shale reservoir, the lacustrine shale reservoir is commonly rich in clay minerals, resulting in a complicated and poorly understood pore system. We have investigated the impact of coexisting clay mineral and organic matter on pore growth in the Lower Jurassic Da’anzhai Shale in the Northeast Sichuan Basin, West China, through performing total organic carbon (TOC) analysis, XRD, field-emission scanning electron microscopy, focused ion beam-scanning electron microscopy (FIB-SEM), N2 and CO2 adsorption experiment, and high-pressure mercury intrusion porosimetry. Our results indicate that the Da’anzhai Shale is dominated by clay-mineral-hosted pores, which are commonly filled or partly filled by pyrobitumen. Controlled by organic maceral, organic pores are poorly and heterogeneously developed in pyrobitumen, and minor or even no organic pores grow in vitrinite. Mesopore and macropore are popular in the Da’anzhai Shale reservoir with complex shapes, e.g., slit- or plate-like shapes combined with “ink-bottle” shapes, confirming a pore system dominated by clay-mineral-hosted pores. The weak positive correlation between the clay mineral content and the meso/macropore volume confirms that the clay mineral is a positive contributor to the storage space, and the weak negative correlation between the TOC and the mesopore volume suggests that infilling of pyrobitumen decreases the pore volume significantly. Similar correlations occur between specific surface area and clay mineral/TOC. FIB-SEM observation confirms that the pore system, e.g., the pore size, pore shape, and pore volume, is controlled by the coexisting clay mineral and pyrobitumen filling in a later stage. The calculated plane porosity of the initial inorganic pore and the unfilled inorganic pore in the Da’anzhai Shale is in the range of 3.66%–10.95% and 0.79%–1.46%, respectively, suggesting that 76.66% of inorganic pores is inactive due to pyrobitumen filling. All of this evidence suggests that pore growth in the Da’anzhai Shale is positively contributed by clay minerals, but it is negatively contributed by pyrobitumen filling. Further discussion suggests that pyrobitumen infilling between clay minerals in the Da’anzhai lacustrine shale can decrease the original pore volume significantly, which work together to govern the pore system in shale reservoirs.

High-density micro- and nanogranular ceramics. Transition of open pores to closed ones. Part 3. Sintering of workpieces without external pressure

An explanation of the processes occurring in obtaining high-density micro- and nanogranular ceramics without the use of external pressure on the basis of data accumulated in the literature is proposed. It is known that pore growth begins after the beginning of the transition of open pores to closed ones, which begins at about 30 % open porosity. It is necessary to maintain open pores to the maximum possible total density of sintered ceramics. The article describes different methods of sintering ceramics, allowing to obtain high-density non-porous ceramics. Ill. 6. Ref. 74. Tab. 1.

High-density micro- and nanogranular ceramics. Transition of open pores to closed ones. Part 2. Removing ligaments from the workpiece

An explanation of the processes that occur when producing high-density micro- and nanogranular ceramics without the use of external pressure is proposed, based on the data accumulated in the literature. It is known that pore growth begins after the beginning of the transition of open pores to closed ones, which begins at about 30 % open porosity. It is necessary to maintain open pores to the maximum possible total density of sintered ceramics. This mode can be implemented in various ways, including at the stage of ligament removal. At this stage, defects can occur in the workpiece at the macro, micro, and sub levels. There are many ways to remove the ligament. The article describes the basic methods to reduce the number of defects. Ref. 67.