A concomitant effect of a hydraulic fracturing experimenting is frequently fluid permeation into the rock matrix, with the injected fluid permeating through the porous rock matrix (leak-off) rather than contributing to the buildup of borehole pressure, thereby slowing down or impeding the hydro-fracturing process. Different parameters, such as low fluid viscosity, low injection rate and high rock permeability, contribute to fluid permeation. This effect is particularly prominent in highly permeable materials, therefore, making sleeve fracturing tests (where an internal jacket separates the injected fluid in the borehole from the porous rock matrix) necessary to generate hydraulic fractures. The side effect, however, is an increase in pressure breakdown, which results in higher volume of injected fluid and in higher seismic activity. To better understand this phenomenon, we report data from a new comparative study from a suite of micro-hydraulic fracturing experiments on highly permeable and on low-permeability rock samples. Experiments were conducted in both sleeve fracture and direct fluid fracture modes using two different injection rates. Consistent with previous studies, our results show that hydraulic fracturing occurred only with low permeation, either due to the intrinsic low permeability or due to the presence of an inner silicon rubber sleeve. In particular, due to the presence of quasi-impermeable inner sleeve or borehole skin in the sleeve fracturing experiment, fracturing occurs, with the breakdown pressure supporting the linear elastic approach considering poroelastic effects, therefore, with low stress drop and consequently low microseismicity. Rock matrix permeability also controls the presence of precursory Acoustic Emission activity, as this is linked to the infiltration of fluids and consequent expansion of the pore space. Finally, permeability is shown to mainly control fracturing speed, because the permeation of fluid into the newly created fracture via the highly permeable rock matrix slows down its full development. The application of these results to the field may help to reduce induced seismicity and to conduct well stimulation in a more efficient way.

水力压裂试验的伴随效应经常是流体渗透到岩石基质中，注入的流体渗透通过多孔岩石基质（泄漏）而不是促进钻孔压力的增加，从而减慢或阻碍水力压裂。压裂过程。不同的参数，例如低流体粘度、低注入率和高岩石渗透率，都有助于流体渗透。这种影响在高渗透性材料中尤为突出，因此，必须进行套筒压裂试验（其中内部夹套将钻孔中注入的流体与多孔岩石基质分离）以产生水力压裂。然而，副作用是压力击穿增加，这导致注入的流体量增加和地震活动增加。为了更好地理解这种现象，我们报告了来自对高渗透率和低渗透率岩石样品进行的一系列微水力压裂实验的新比较研究的数据。使用两种不同的注入速率在套筒压裂和直接流体压裂模式下进行了实验。与之前的研究一致，我们的结果表明，水力压裂仅发生在低渗透率的情况下，这是由于固有的低渗透率或由于内部硅橡胶套管的存在。特别是由于套管压裂实验中存在准不透水内套管或钻孔表皮，发生压裂，破裂压力支持考虑多孔弹性效应的线弹性方法，因此应力降低，微震性低。岩石基质渗透率还控制着先兆声发射活动的存在，因为这与流体的渗透和随之而来的孔隙空间的扩张有关。最后，渗透率显示出主要控制压裂速度，因为流体通过高渗透性岩石基质渗透到新产生的裂缝中会减缓其充分发展。将这些结果应用于现场可能有助于减少诱发地震活动并以更有效的方式进行井增产。因为流体通过高渗透性岩石基质渗透到新产生的裂缝中会减慢其全面发展。将这些结果应用于现场可能有助于减少诱发地震活动并以更有效的方式进行井增产。因为流体通过高渗透性岩石基质渗透到新产生的裂缝中会减慢其全面发展。将这些结果应用于现场可能有助于减少诱发地震活动并以更有效的方式进行井增产。