dos Observation out-of Blame Permeability Enhancement During the Fluid Injection Tests

By in lavalife visitors with 0 Comments

dos Observation out-of Blame Permeability Enhancement During the Fluid Injection Tests

Within this research, i focus on injection-caused “aseismic” slip and you may, specifically, how the improvement off blame permeability impacts the growth off slip. To help you unravel potential controls with the aseismic sneak, i basic review the fresh new advancement out-of fault permeability associated with the aseismic deformations seen while in the an out in situ check out from fluid shot into a densely instrumented blame for the an effective carbonate formation (Guglielmi, Cappa, mais aussi al., 2015 ). Second, i make paired hydromechanical simulations from water injection in one planar blame under stress and you will water stress standards exactly like the individuals based in the in situ experiment. We focus on the aftereffect of the change inside the blame permeability for different initially worry criteria and you can rubbing guidelines so you can clarify how this could change the development of aseismic sneak.

where ?f is the viscosity of fluid (Pa.s) and w is the fault width (m). In a parametric analysis, we find values of hydraulic aperture that minimize the misfit between model predictions and observed pressure and flow rate histories at the injection point. The permeability is then defined from the best fit value of hydraulic aperture. Thus, this experiment offers ideal conditions to evaluate how fault permeability evolves with accumulated displacements, both during aseismic deformation and seismic activity, and to constrain further hydromechanical modeling analyses of fault slip (see section 4).

step 3 Hydromechanical Acting away from Fault Sneak of the Water Injection

Findings exhibited an intricate interplay ranging from liquid pressure, fault distortion, and fault permeability transform. Guglielmi, Cappa, et al. ( 2015 ) indicated that the increase during the liquid tension induces fault beginning and you may aseismic slip from the treatment. The new seismicity will be caused ultimately well away regarding injection from the co to jest lavalife fret import in the propagating aseismic slip. Duboeuf mais aussi al. ( 2017 ) verified which mechanism inside a series of eleven injections tests at the same site. Within these experiments, seismic situations had been found anywhere between step one and you will a dozen yards on shot facts where in fact the mentioned blame sneak is aseismic. After that, Guglielmi, Cappa, mais aussi al. ( 2015 ) discover an effective fourteen-flex boost of your own blame permeability away from 0.07 to 1.0 ? ten ?ten m dos over the course of aseismic sneak, symbolizing in the 70% of your overall cumulative permeability improve (20-fold) for the shot several months (Figure step 1). In contrast, through the a consequent age of seismic activity far away regarding injection, the fault permeability just expands from just one.0 ? 10 ?10 to one.thirty five ? 10 ?10 meters dos . Which, this type of intricate findings from fault permeability enhancement throughout fault activation stress the evolution out-of blame hydraulic details is very important to understand the organization out-of slip during liquid shot. Certainly, the increase inside water tension causes blame beginning and you may sneak that lead to permeability transform. Upcoming, the different modes off fault permeability alter seem to determine the slip behavior.

step three.step 1 Model Setup

The method has been used to test the new hydromechanical choices out of fractured stones and blame areas throughout the liquid pressurization (Cappa ainsi que al., 2006 ; Guglielmi ainsi que al., 2008 ), demonstrating that the advancement from blame hydraulic diffusivity is a completely coupled disease dependent on worry and you can water stress (Guglielmi, Elsworth, mais aussi al., 2015 ).

We select a simplified yet representative 2-D model (200 m ? 50 m) that considers fluid injection into a horizontal flat fault in a homogeneous elastic and impervious medium (Figure 2a). The remote normal (?n) and shear stress (?) resolved on the fault plane are constant. During injection, the fluid pressure in the fault is increased step by step in 0.5-MPa increments every 150 s. Injection occurs in a point source (Figure 2a) in order to reproduce a loading path consistent with the in situ data presented in Figure 1. The total time of injection is 1,050 s. We focus on the period of largest increase of fault permeability observed in the in situ experiment (Figure 1b). For numerical accuracy, the mesh size is refined along the fault (0.15 m) and gradually increases to 0.5 m in the direction normal to the fault toward model boundaries.

Share This
About The Author