Effect of fluid penetration on the damage processes and microseismicity due to the hydraulic fracturing of rocks

Author

• Catarina Baptista-Pereira, New Jersey Institute of Technology

Author ORCID Identifier

0000-0001-7423-1897

Document Type

Dissertation

Date of Award

8-31-2022

Degree Name

Doctor of Philosophy in Civil Engineering - (Ph.D.)

Department

Civil and Environmental Engineering

First Advisor

Jay N. Meegoda

Second Advisor

Taha F. Marhaba

Third Advisor

Matthew J. Bandelt

Fourth Advisor

Andrew Ciancia

Fifth Advisor

Mark McClure

Sixth Advisor

Stephen Morgan

Abstract

The hydraulic fracturing is used when fluids are injected inside the matrices of rocks to allow the creation of new cracks while, the propagation of the existent cracks can also occur. This process has been widely used for the past decades in the deep earth energy sector which comprises four main subsectors: 1) recovery of geothermal resources, 2) CO₂ and hydrogen sequestration; 3) wastewater and nuclear waste disposal, and 4) recovery of (non)conventional fluids. By creating new flow paths or enhancing the existing ones, the pores are allowed to connect and, thus, it increases the permeability of rocks. For the past decades efforts have been made to understand the effects hydraulic fracturing. However, it is not yet fully understood, especially when coupling the effects of injecting fluids in porous rocks with i) pressures (injected, breakdown and pore pressures), ii) fracturing processes (micro-damage; initiation, propagation, and coalescence of fractures), but also iii) the seismic energy released during hydraulic fracturing. Also, when fluids interact with clay-rich rocks, their softening can occur, along with change in their mechanical properties (strength, Young modulus, Poisson's ratio, density, anisotropy, etc.). This research is divided into three studies. The first study uses cubic shale samples that are introduced inside a hydrothermal reactor that is filled with De-ionized water, and later pressurized with compressed nitrogen gas at different pressures for 72h and immersed in a constant temperature water bath. This setup allows one to enable the softening processes to start. The samples are then extracted from inside the hydrothermal reactor, studied and compared to the initial conditions. The second and third studies use two injection rates (20 and 2 ml/min) in soft gypsum and hard granite that have a prismatic shape and two pre-fabricated flaws. By introducing a novel transparent membrane into a hydraulic fracturing setup, the loads are only applied to front and back surfaces and inside the inner surfaces of those flaws. Thus, the fluid is only allowed to penetrate the matrix through the pre-fabricated flaws and the pore pressures are allowed to develop, attempting to simulate real-life hydraulic fracturing projects in the field. The setup uses two cameras (high-resolution and high-speed) which allow one to record the fracturing processes during the entire experiments, while helping quantifying the pore pressures that buildup inside the rock matrices. To measure the micro seismicity, acoustic emission sensors are attached to the specimen and later processed into four source mechanisms (tensile, compressive, shear and mixed-mode). The 1^st study evaluates the anisotropy of rocks and softening processes that occur when shales interact with water-based fluids. The 2^nd study evaluates the a) breakdown and fracturing pressures; b) volumes injected; c) growth of injected fluid fronts; d) pore pressures, and e) fracturing patterns, such as white patching (or micro-damage), fracturing and coalescence patterns. The 3^rd study, by using the same experimental tests and data of the 2^nd study, evaluates the a) rate and amplitude of micro seismic events; b) types of source mechanisms, c) their location and e) energy of the system. Finally, by comprising the information of the three different studies, a better understanding of the processes involved in a hydraulic fracturing project is given to the reader.

Recommended Citation

Baptista-Pereira, Catarina, "Effect of fluid penetration on the damage processes and microseismicity due to the hydraulic fracturing of rocks" (2022). Dissertations. 1915.
https://digitalcommons.njit.edu/dissertations/1915