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Deep shale reservoirs (3500–4500 m) exhibit significantly different stress states than moderately deep shale reservoirs (2000–3500 m). As a result, the brittleness response mechanisms of deep shales are also different. It is urgent to investigate methods to evaluate the brittleness of deep shales to meet the increasingly urgent needs of deep shale gas development. In this paper, the quotient of Young's modulus divided by Poisson's ratio based on triaxial compression tests under in situ stress conditions is taken as SSBV (Static Standard Brittleness Value). A new and pragmatic technique is developed to determine the static brittleness index that considers elastic parameters, the mineral content, and the in situ stress conditions (BIEMS). The coefficient of determination between BIEMS and SSBV reaches 0.555 for experimental data and 0.805 for field data. This coefficient is higher than that of other brittleness indices when compared to SSBV. BIEMS can offer detailed insights into shale brittleness under various conditions, including different mineral compositions, depths, and stress states. This technique can provide a solid data-based foundation for the selection of 'sweet spots' for single-well engineering and the comparison of the brittleness of shale gas production layers in different areas. [ABSTRACT FROM AUTHOR]

Objective The sulfur remover suitable for oil-based drilling fluid was studied to solve the problems, such as pollution of oil-based drilling fluid by hydrogen sulfide and safety risk caused by hydrogen sulfide overflow in the drilling process of sulfur-bearing gas reservoir in northeastern Sichuan. Methods The evaluation method and parameters of oil-based drilling fluid contaminated by hydrogen sulfide were established. The formulation of high efficiency sulfur removal agent and compound sulfur removal system for oil-based drilling fluid were optimized. Results The single agents with excellent sulfur removal effect were liquid sulfur removal agent YT-1, zinc carbonate basic JD-2 and alcohol ether amide CLC, with the saturation of 56.48 mg/g, 21.13 mg/g and 5.8 mg/g, respectively, the high temperature aging sulfur removal rates of 90.10%, 82.60% and 75.23%, and they showed good compatibility with oil-based drilling fluid. The compound sulfur removal system formulation of 4%YT-1+2%JD-2 was optimized. For the 75 mg/L hydrogen sulfide contaminated oil-base drilling fluid, the time to reach the outlet concentration of 0.015 mg/L was only 1.21 min, which reached 171.8 min after adding the compound sulfur removal system. The H2S concentration of the contaminated oil-based drilling fluid was 0.078 mg/L after high temperature aging, and the H2S concentration was 0 mg/L after adding the compound sulfur removal system, and the sulfur removal rate reached 100%. Conclusions The single agent of sulfur removal can improve the sulfur removal effect, providing technical support for the safe and efficient drilling in the high sulfur formation in northeastern Sichuan. [ABSTRACT FROM AUTHOR]

The extent of fracture development is associated with the degree of enrichment of a natural gas reservoir and its productivity. Based on numerical simulation results of the paleotectonic stress field, a set of evaluation methods for determining the degree of development of reservoir tectonic fractures were established using rock rupture criteria. Taking the fourth member of the Leikoupo Formation in the Pengzhou area of western Sichuan as an example, a finite element (FE) method was employed to simulate the paleo-tectonic stress field during the period of fracture development, and the degree of tectonic fracture development was further evaluated using the above methods. The results indicated that effective fractures were created in the Himalayan period. In this time, mainly NE–NEE and nearly E–W strike tectonic fractures were developed in the target layer. The fractures were mainly low-angle and oblique fractures, while the high-angle fractures were less developed. According to the integrative fracture index (F), five typical fracture development areas were determined: the fault zone, and the northern, eastern, southeastern, and central regions of the study area. The reliability of the fracture prediction results was verified using fracture distribution statistics and gas production test results. [ABSTRACT FROM AUTHOR]

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Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to solve the poor quality of cementing production casing of horizontal wells, the gas channeling control property design of the cement slurry was taken as the break point, and the influence of different cement slurry to gas channeling was analyzed through lab experiments. And the adaptability of evaluation methods for gas channeling control was evaluated. Then the multi-factor evaluation method was put forward for gas channeling control performance of cement slurry on horizontal wells, considering the horizontal well trajectory features. It was the evaluation method for modified A value or SPN value under none free water and filter loss less than 50 mL. The successful application of the new method on cementing the middle-shallow horizontal wells in West Sichuan area provided a theoretical direction for the horizontal well cementing in West Sichuan. [ABSTRACT FROM AUTHOR]