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Shale softening is an important factor affecting fracturing effect. Through the Brinell hardness measurement of deep marine shale reservoir in South Sichuan Basin, the softening mechanism of shale after fracturing is explored. Through laboratory test, the key parameters of shale Brinell hardness measurement are proposed as follows: indenter size 5 mm, loading force 613 N, 1226 N, and 2452 N, and holding time>10 s. It is determined that the content of quartz and clay is the main factor controlling the Brinell hardness of dry shale samples, and the mineral composition, microstructure, and fluid system jointly affect the shale softening process. The results show that (1) the marine shale in the South Sichuan Basin softens obviously, with the Brinell hardness decrease by more than 50%, (2) microfracture propagation and clay hydration expansion accelerate the shale softening process, leading to the decreased porosity and the increased number of micro-pores, and (3) the softening process is different between middeep shale and deep shale, with the latter characterized by high initial hardness and low softening rate.

In recent years, casing deformation has become a key factor affecting the scale and efficiency of shale gas development. Consequently, a fast and efficient integrated prevention, control, and treatment technology for casing deformation is of great significance in terms of both theory and application. This paper combines a geological mechanics analysis and multi-cluster fracture propagation to investigate the risk evaluation, early warning and identification, and warning and identification technology relating to casing deformation and its application. It proposes a method for the dynamic and static evaluation of casing deformation risk levels and types, and establishes an index system incorporating stress, fracture, time, and space factors. This four-factor evaluation method is in greater alignment with field conditions. It also proposes a method for the early warning and identification of casing deformation based on fracture monitoring and an operation curve, and clarifies the dominant engineering factors around casing deformation. According to the findings, the total fluid volume per stage has a greater impact on casing deformation than a high pump rate. The prevention and control of casing deformation should preferably be realized by optimizing the fracturing parameters. Moreover, the paper reviews existing technologies for treating casing deformation, several of which are defined as major technologies: small-diameter bridge plug staged fracturing and small-size gun perforation, and long-stage multi-cluster asynchronous fracture initiation and composite temporary plugging and diversion. The study results provide support for a significant reduction in the casing deformation rate during fracturing, improving the effective stimulation degree in the casing deformation section in shale gas wells in the southern Sichuan Basin. These results could serve as references for subsequent research. [ABSTRACT FROM AUTHOR]

SUMMARY: The production of compact vectors for gene stacking is hindered by a lack of effective linkers. Here, we report that a 26‐nt nucleic acid linker, NAL1, from the fungus Glarea lozoyensis and its truncated derivatives could connect two genes as a bicistron, enabling independent translation in a maize protoplast transient expression system and human 293 T cells. The optimized 9‐nt NAL10 linker was then used to connect four genes driven by a bidirectional promoter; this combination was successfully used to reconstruct the astaxanthin biosynthesis pathway in transgenic maize. The short and efficient nucleic acid linker NAL10 can be widely used in multi‐gene expression and synthetic biology in animals and plants. [ABSTRACT FROM AUTHOR]