various forms of dolomitization (sabkha, reflux, and burial dolomitization, and cementation) increased the resistivity of these rocks to chemical and physical compaction and porosity destruction. In the deep burial domain, medium- to coarse-crystalline dolomite cements and saddle dolomite precipitated at fluid temperatures of 120- 160℃ and 160 - 220℃, respectively. The significance of deep burial dissolution is critically discussed and constrained by: (i) corrosion of late diagenetic minerals, (ii) pores cross-cutting (or forming around) stylolites, and (iii) the occurrence of solid bitumen in the center of secondary pores. Vuggy, inter- and intracrystalline pores developed during a late and deep burial stage, and comprise ca. 20% of the overall Dengying reservoir porosity. Mechanisms which induced corrosion at this burial stage include hydrothermal pulses and thermochemical sulfate reduction. Similar to many carbonate reservoirs in the Phanerozoic, this study documents that the platform margin has better porosities and higher gas production compared to the platform interior due to its specific carbonate rock properties and diagenesis. Data shown here document the complex multiphase dolomitization history and high potential for gas production from deeply buried Precambrian dolostone reservoirs.

Huang, H., Wang, X., Gong, S., Krake, N., Jin, M., Li, N., Birgel, D., Peckmann, J., Cheng, M., Roberts, H.H., Chen, D., Feng, D., 2020. New constraints on the formation of hydrocarbon-derived low magnesium calcite at brine seeps in the Gulf of Mexico. Sedimentary Geology 398, 105572.

http://www.sciencedirect.com/science/article/pii/S0037073819302246 Hydrocarbon-rich brine seeps - representing extreme environments typified by halophilic and chemotrophic organisms - may provide insight into the ecology of microorganisms on an early Earth and possibly other planetary bodies. Authigenic low magnesium calcite (LMC) is common at brine seeps and represents an archive of fluid compositions, fluid origin, and the conditions under which this carbonate mineral formed. Here we present the analysis of authigenic LMC from three hydrocarbon-rich brine seeps (GB260, ~ 460 m; GB697, ~1280 m; AC601, ~2340 m) from the Gulf of Mexico. The formation of LMC was favored by brine fluids with extremely low Mg/Ca mole ratios (e.g. <2) relative to seawater (Mg/Ca mole ratio of ~5.2). Petrographic 13 observations reveal that the studi ed LMC is of primary origin. Its δ C values vary from -53.5‰ to 14.0‰, 13 indicating variable carbon sources that include C-depleted methane, crude oil, seawater dissolved inorganic 13 carbon, and C-enriched residual carbonate species reflecting methanogenesis. In contrast, LMC shows 13 predominantly relatively high δ C values (from -39.0‰ to -25.7‰), suggesting an unrecognized local org 18 source of nutrients fueling the local production of biomass. The δ O values of LMC (as high as 6.0‰) are too high for precipitation in equilibrium with seawater, probably reflecting the involvement of deep formation 87 86 fluids. The wide range of Sr/ Sr ratios and the enrichment of Sr and Ba in LMC is in accordance with pore fluids deriving from the dissolution of the Louann salt or alteration of silicates in deep sediments. Given the stability of LMC, its petrographic and geochemical characterization achieved in this study can be used to better constrain brine seep activities throughout the geological record.

Huang, Z., Zhang, S., Yang, R., Wu, X., Li, R., Zhang, H., Hung, P., 2020. A review of liquid nitrogen fracturing technology. Fuel 266, 117040.

http://www.sciencedirect.com/science/article/pii/S0016236120300351 Hydraulic fracturing is an efficient stimulation means for the exploitation of unconventional oil/gas resources as well as geothermal energy. However, there are several issues for traditional hydraulic fracturing, e.g. excessive water consumption, formation damage and flow-back-fluid contamination. In recent decades, these problems have led research efforts to investigate waterless fracturing technology as an alternative to traditional hydraulic methods. Liquid nitrogen (LN ) is considered as one of the potential water-free fracturing fluids. Due to its 2 unique low-temperature characteristics, severe thermal stress will be created in the rock under down-hole conditions during the LN fracturing process. As a result, not only several primary fractures, but also secondary 2 cracks perpendicular to the primary fractures can be generated in a reservoir, creating a more complicated fracture network than that in conventional hydraulic fracturing. This review aims to outline the current developments of LN fracturing technology from several aspects, including the effect of thermal shock on rock 2 physical properties, the heat transfer characteristics of LN , the rock-breaking performance of an LN jet, and 2 2