岩石的脆性和可压裂性是非常规油气储集层体积压裂重要的岩石力学参数,为获得地层岩石的脆性和可压裂性指标,基于声波测井得到的井壁地层纵、横波速度的径向变化,求得地层的脆裂指数,指导储集层压裂改造作业。钻井过程中岩石破坏时在井壁地层中产生微裂缝,导致弹性波速度降低,波速在径向上发生由小到大的变化。采用测井纵波速度的层析成像和偶极弯曲波频散特征反演获得井壁周围地层纵、横波速度径向剖面,将两个剖面沿井径方向积分,得到纵、横波脆裂指数。脆裂指数与脆性指数、可压裂指数相关性较好,验证了用脆裂指数评估岩石脆裂性质的有效性;实际对测井数据的处理和分析亦证明了这种方法的可行性和有效性,结果对于储集层压裂优选层位和压裂改造实施有指导意义。图7表1参17
唐晓明
,
许松
,
庄春喜
,
苏远大
,
陈雪莲
. 基于弹性波速径向变化的岩石脆裂性定量评价[J]. 石油勘探与开发, 2016
, 43(3)
: 417
-424
.
DOI: 10.11698/PED.2016.03.12
Brittleness and fracability are two important rock properties in hydraulic fracturing of unconventional reservoirs. Based on the variation of compressional and shear velocity around borehole using acoustic measurement, an effective technique is developed to estimate these parameters to guide reservoir-fracturing. During drilling, when the rock is broken, a significant amount of drilling induced cracks will occur in the formation around the borehole, resulting in the drop of radial elastic wave velocity and the wave velocity variation from low to high in radial direction. The radial variation of compressional and shear velocities of formation rocks surrounding a borehole were respectively obtained from P-wave travel time tomography and dipole shear-wave dispersion inversion. By integrating the two variation profiles along the radial direction, the brittleness-fracability index is obtained to estimate the brittleness and fracability of formation rocks. The index shows fairly good consistency and correlation with rock brittleness and fracability, which demonstrates the practicability and effectiveness of the proposed approach. Well log data analysis examples are presented to demonstrate the effectiveness of our technique.
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