Title: CO₂ injection-induced fracturing in naturally fractured shale rocks

Abstract

In this study, Niobrara shale cubes of 20 cm from Colorado were employed to investigate gas and supercritical CO₂ injection-induced fracturing in naturally fractured caprocks of deep aquifers/depleted reservoirs and fractured shale reservoirs. Under tri-axial stresses, gas or supercritical CO₂ was injected into the center of the cubes to induce fracturing. Real-time pressure and temperature, acoustic wave, pressure decay, fracture coloring, and gas fracturing were used to characterize the fracturing process and fracture morphology. Without pore pressure, CO₂ injection-induced fracturing occurred and completed instantly, accompanied by an evident temperature drop. Strongly bonded fractures barely affected transverse fracture propagation, whereas weakly bonded or open fractures arrested the injected fluid first and then allowed it to generate new fractures perpendicular to the minimum horizontal stress. Breakdown pressures for cubes with preexisting fractures using gas and supercritical CO₂ are much lower than both poroelastic predictions and slick-water fracturing pressure, and some are even lower than the minimum horizontal stress. This is attributed to unconformable preexisting fractures and the low viscosity of CO₂. Moreover, decreasing tri-axial stress levels and increasing stress differences tend to lower the breakdown pressure. In conclusion, this study is instructive for understanding and tackling geomechanical issues related to CO₂ geologicalmore » storage and fracturing of shale reservoirs.« less

Authors:

Wang, Lei ^[1]; Yao, Bowen ^[1]; Xie, Haojun ^[2]; Winterfeld, Philip H. ^[1]; Kneafsey, Timothy J. ^[3]; Yin, Xiaolong ^[1]; Wu, Yu-Shu ^[1]

---

+ Show Author Affiliations

1. Colorado School of Mines, Golden, CO (United States)
2. Colorado School of Mines, Golden, CO (United States); China University of Petroleum (East China) (China)
3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Publication Date:

Wed Aug 09 00:00:00 EDT 2017

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1532272

Alternate Identifier(s):

OSTI ID: 1549883

Grant/Contract Number:  

AC02-05CH11231; FE0023305

Resource Type:

Accepted Manuscript

Journal Name:

Energy

Additional Journal Information:

Journal Volume: 139; Journal Issue: C; Journal ID: ISSN 0360-5442

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES