Title: The role of fault-zone architectural elements and basal altered zones on pore pressure propagation and induced seismicity

Abstract

Here, we used hydrogeologic models to assess how fault-zone properties promote or inhibit the downward propagation of fluid overpressures from a basal reservoir injection well (150 m from fault zone, Q = 5000 m³/day) into the underlying crystalline basement rocks. We varied the permeability of the fault-zone architectural components and a crystalline basement weathered layer as part of a numerical sensitivity study. Realistic conduit-barrier style fault zones effectively transmit elevated pore pressures associated with four years of continuous injection to depths of ~2.5 km within the crystalline basement while compartmentalizing fluid flow within the injection reservoir. The presence of a laterally continuous, relatively low-permeability altered/weathered basement horizon (k_{altered layer} = 0.1 × k_basement) can limit the penetration depth of the pressure front to ~500 m. On the other hand, the presence of a discontinuous altered/weathered horizon that partially confines the injection reservoir without blocking the fault fluid conduit promotes downward propagation of pressures. Permeability enhancement via hydromechanical failure was found to increase the depth of early-time pressure front migration by a factor of 1.3 to 1.85. Dynamic permeability models may help explain seismicity at depths of >10 km such as is observed within the Permian Basin, NM.

Authors:

Ortiz, John Philip  ^[1];

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Person, Mark A ^[2]; Mozley, Peter S ^[2]; Evans, James P ^[3]; Bilek, Susan L ^[2]

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+ Show Author Affiliations

1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. New Mexico Inst. of Mining and Technology, Socorro, NM (United States). Dept. of Earth and Environmental Science
3. Utah State Univ., Logan, UT (United States). Dept. of Geology

Publication Date:

Thu Aug 09 00:00:00 EDT 2018

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE; USGS National Earthquake Hazards Reduction Program (NEHRP); W.M. Keck Foundation

OSTI Identifier:

1467281

Report Number(s):

LA-UR-18-22111
Journal ID: ISSN 0017-467X

Grant/Contract Number:  

AC52-06NA25396; 2015-0068; 989941

Resource Type:

Accepted Manuscript

Journal Name:

Ground Water

Additional Journal Information:

Journal Volume: 57; Journal ID: ISSN 0017-467X

Publisher:

Wiley - NGWA

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; Induced seismicity; hydrologic modeling; fault-zone architecture; crystalline basement faults; basal reservoirs; triggered seismicity; damage zone