Dissolution Facies Window Identification of Carbonate Gas Reservoir by Using Electrical Image Logs: A Case Study from Sichuan Basin

Predicted reservoir results from conventional methods didn’t match the production performance in GS B well block in the Lower Sinian Dengying dolomite formation. The predicted gas production of vertical well is around 500k m3/day, but the real gas production is below 100k m3/day. In GS A well block, the predicted gas production of vertical well is consistent with the real gas production around 500k m3/day, and when meter cavie develops, test gas production can reach 1000k m3/day. It suggests the biggest challenge is to clarify reservoir characterization in GS B well block. However, due to the limited resolution of conventional logs and strong heterogeneity of carbonate reservoir, conventional open hole logs and seismic data has limitation to provide the details of secondary pore and fractures to clarify reservoir characterization. The electrical image logs provide high resolution images with high borehole coverage. It can provide abundant information about secondary pore and fracture to identify dominant dissolution facies window. Through electrical image logs, secondary pore and fracture classification in 50 vertical wells were performed in the Lower Sinian Dengying dolomite formation. Five facies were detected based on electrical image logs, including vug facies (honeycomb vug facies, algal stromatolite vug facies and bedding vug facies), cave facies, fracture-vug facies, massive dense facies and dark thin layer dense facies. With the five facies and top interface constraints from seismic data, 3D dissolution facies model was created, which can show different dissolution facies window of GS A and GS B well block. The method in this paper reveals the reason of confliction and agree test gas production. The case study presents how to identify five dissolution facies based on high-resolution electrical image logs with core data calibration. Besides, 3D dissolution facies model is created to show dissolution facies window of GS B well block to optimize well trajectory deployment during the development stage. Better understanding of reservoir characterization was instructive for acid fracturing design of Dengying dolomite gas reservoir as well.

Analysis of pore type and micro pore structure of reservoir in fault basin--Taking Wuerxun depression as an example

Wuerxun depression is the two main oil-bearing depressions in Hailaer basin. Nantun Formation of Wuerxun depression is the most important oil-gas exploration layer, and reservoir characteristics are the main factors controlling oil-gas enrichment. In this paper, the mineral composition and pore type of Nantun Formation reservoir are analyzed by XRD and SEM. It is clear that the main rock types are lithic sandstone and feldspar lithic sandstone. As a whole, it is compact, with poor connectivity of pores and coexistence of primary and secondary pores. Primary pore is mainly residual primary intergranular pore, and secondary pore is the main reservoir space of Nantun Formation, which lays a foundation for further oil and gas exploration. The rock types of the target layer in the study area are mainly lithic sandstone and feldspathic lithic sandstone. Among them, Tongbomiao formation in Wuerxun depression is dominated by conglomerate, while sandstone in Nantun Formation is mainly lithic arkose and feldspathic lithic sandstone; sandstone in Tongbomiao formation and Nantun Formation in Beier depression is dominated by lithic sandstone and feldspathic lithic sandstone. The rocks of Nantun Formation are compact as a whole, with poor connectivity of pores and coexistence of primary and secondary pores. The primary pores are mainly residual primary intergranular pores, mainly of three types. Secondary pore is the main reservoir space of Nantun Formation, including dissolution intergranular pore, dissolution intergranular pore, interstitial matter dissolution pore, intergranular micro pore and micro fracture of authigenic minerals, among which intergranular dissolution pore is the most developed and super large dissolution intergranular pore is the main one.

Structural and mechanistic insights into Hsp104 function revealed by synchrotron X-ray footprinting

Hsp104 is a hexameric AAA+ ring translocase, which drives protein disaggregation in nonmetazoan eukaryotes. Cryo-EM structures of Hsp104 have suggested potential mechanisms of substrate translocation, but precisely how Hsp104 hexamers disaggregate proteins remains incompletely understood. Here, we employed synchrotron X-ray footprinting to probe the solution-state structures of Hsp104 monomers in the absence of nucleotide and Hsp104 hexamers in the presence of ADP or ATPγS (adenosine 5′-O-(thiotriphosphate)). Comparing side-chain solvent accessibilities between these three states illuminated aspects of Hsp104 structure and guided design of Hsp104 variants to probe the disaggregase mechanism in vitro and in vivo. We established that Hsp104 hexamers switch from a more-solvated state in ADP to a less-solvated state in ATPγS, consistent with switching from an open spiral to a closed ring visualized by cryo-EM. We pinpointed critical N-terminal domain (NTD), NTD-nucleotide–binding domain 1 (NBD1) linker, NBD1, and middle domain (MD) residues that enable intrinsic disaggregase activity and Hsp70 collaboration. We uncovered NTD residues in the loop between helices A1 and A2 that can be substituted to enhance disaggregase activity. We elucidated a novel potentiated Hsp104 MD variant, Hsp104–RYD, which suppresses α-synuclein, fused in sarcoma (FUS), and TDP-43 toxicity. We disambiguated a secondary pore-loop in NBD1, which collaborates with the NTD and NBD1 tyrosine-bearing pore-loop to drive protein disaggregation. Finally, we defined Leu-601 in NBD2 as crucial for Hsp104 hexamerization. Collectively, our findings unveil new facets of Hsp104 structure and mechanism. They also connect regions undergoing large changes in solvation to functionality, which could have profound implications for protein engineering.

Enhancement of the photocatalytic activity of a TiO2/carbon aerogel based on a hydrophilic secondary pore structure

The surface/interface synergy effect plays a positive role on the spatial separation and utilization of electrons and holes in photocatalytic process, which suggests a potential strategy for designing high efficiency photocatalysts.