Mapping of pore pressure, in-situ stress and brittleness in unconventional shale reservoir of Krishna-Godavari basin
Mapping of pore pressure, in-situ stress and brittleness in unconventional shale reservoir of Krishna-Godavari basin
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DOI：
10.1016/j.jngse.2017.10.021
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发表时间：
2018-02
影响因子：
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通讯作者：
B. Das;R. Chatterjee
中科院分区：
文献类型：
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作者：
B. Das;R. Chatterjee
证明了一种方法来估计脆性系数和地应力测井数据连接叠后地震数据在非常规Raghavapuram页岩储层的克里希纳-戈达瓦里盆地，印度。利用叠后地震资料，通过多层前向神经网络（MLFN）模型从测井资料中估计孔隙压力、地应力。将叠后地震资料的声阻抗转换为剪切阻抗，并结合测井资料，生成剪切阻抗剖面和密度剖面。反演的声阻抗，剪切阻抗，密度和纵横波速度比（Vp/Vs）已被用来训练MLFN模型映射孔隙压力和垂直应力从测井得到。计算了各向异性泥质介质的最小水平应力。差应力比（DHSR）截面是使用MLFN模型从最大和最小水平应力幅值生成的。将由静态弹性模量和泊松比估算的脆性系数映射到叠后剖面。利用偶极横波测井资料计算裂缝指数。Raghavapuram页岩的脆性系数为20-45%，DHSR为7-16%，断裂指数为20-46%。这些区域表现出相对较高的脆性系数值和相对较高的DHSR。裂缝将在高DHSR区域对齐，并朝向最大水平应力的方向。这些信息可用于裂缝类型预测和水力压裂增产措施设计。
A methodology is demonstrated to estimate brittleness coefficient and in-situ stress from well log data linking post-stack seismic data in the unconventional Raghavapuram Shale reservoir of Krishna-Godavari basin, India. Post-stack seismic data has been used to estimate pore pressure, in-situ stress from well logs through multilayered feedforward neural network (MLFN) model. Shear impedance and density sections from post-stack seismic data are generated from conversion of acoustic impedance to shear impedance linking with well log data. Inverted acoustic impedance, shear impedance, density and compressional to shear wave velocity ratio (Vp/Vs) have been used to train the MLFN model for mapping pore pressure and vertical stress obtained from well logs. Minimum horizontal stress is computed for anisotropic shale medium. Differential stress ratio (DHSR) section is generated from maximum and minimum horizontal stress magnitudes using MLFN models. Brittleness coefficient estimated from static Young's modulus and Poisson's ratio is mapped into post-stack section. Fracture index is computed from dipole shear sonic log data. The brittleness coefficient of 20–45% and DHSR of 7–16% with 20–46% fracture index are noticed in the Raghavapuram Shale. This zones exhibit relatively high values of brittleness coefficient and relatively high DHSR. Fractures will be aligned in high DHSR zones and oriented to the direction of maximum horizontal stress. This information may be useful for fracture type prediction and designing hydraulic fracture stimulation.