Abstract

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.

中文翻译：

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综合矿物含量、弹性参数、地应力条件和测井分析定量表征深层页岩脆性

摘要

深层页岩储层（3500-4500 m）与中深页岩储层（2000-3500 m）表现出显着不同的应力状态。因此，深层页岩的脆性响应机制也不同。为了满足日益迫切的深层页岩气开发需求，迫切需要研究深层页岩脆性评价方法。本文将原位应力条件下三轴压缩试验得到的杨氏模量除以泊松比的商作为SSBV（静态标准脆性值）。开发了一种新的实用技术来确定静态脆性指数，该指数考虑了弹性参数、矿物含量和原位应力条件 (BIEMS)。 BIEMS和SSBV的决定系数对于实验数据达到0.555，对于现场数据达到0.805。与 SSBV 相比，该系数高于其他脆性指数。 BIEMS 可以详细了解各种条件下的页岩脆性，包括不同的矿物成分、深度和应力状态。该技术可为单井工程“甜点”选择以及不同地区页岩气产层脆性比较提供坚实的数据基础。