Stress Reversals near Hydraulically Fractured Wells Explained with Linear Superposition Method (LSM)

Ruud Weijermars and Jihoon Wang
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Ruud Weijermars: Center for Integrative Petroleum Research (CIPR) & Department of Petroleum Engineering, College of Petroleum Engineering and Geosciences (CPG), King Fahd University of Petroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia
Jihoon Wang: Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, Korea

Energies, 2021, vol. 14, issue 11, 1-22

Abstract: Prior studies have noted that the principal stress orientations near the hydraulic fractures of well systems used for energy extraction may wander over time. Typically, the minimum and maximum principal stresses—in the horizontal map view—swap their respective initial directions, due to (1) fracture treatment interventions, and (2) pressure depletion resulting from production. The present analysis shows with stress trajectory visualizations, using a recently developed linear superposition method (LSM), that at least two generations of stress reversals around hydraulic fractures occur. The first generation occurs during the fracture treatment; the second occurs immediately after the onset of so-called flow-back. During each of these stress swaps in the vicinity of the hydraulic fractures, reservoir directions that were previously in compression subsequently exhibit extension, and directions previously stretching subsequently exhibit shortening. The pressure change in the hydraulic fractures—from over-pressured to under-pressured (only held open by proppant packs)—caused the neutral points that separate domains with different stress states to migrate from locations transverse to the fracture to locations beyond the fracture tips. Understanding such detailed geo-mechanical dynamics, related to the pressure evolution in energy reservoirs, is extremely important for improving both the fracture treatment and the well operation, as future hydrocarbon and geothermal energy extraction projects emerge.

Keywords: stress reversal; stress trajectories; stress cage; fracture cage; hydraulic fracture; pressure depletion; geothermal reservoir; oil and gas reservoir (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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