Crisman Annual Report 2009 - Harold Vance Department of ...

Propagation of Induced Hydraulic Fractures near Pre-Existing Fractures
Objectives
Hydraulic fracturing is a widely used technology
for stimulating oil and gas wells. The intersection
of hydraulic fractures with natural fractures or
other discontinuities in a rock mass can give rise to
significant changes to fracture growth. The objective
of this project is to study the potential propagation
behaviors of hydraulic fractures near pre-existing
fractures considering linear and non-linear fault
behavior and poroelastic effects.
Approach
We use 2D boundary element method to model
the stress field ahead of a hydraulic fracture in the
vicinity of a pre-existing fracture. A unified structural
criterion is used to predict the crack propagation
behavior. The work initially considers fractures in an
elastic media. Poroelastic effects, which arise from
coupling of rock deformation and fluid flow inside the
fracture, are considered next. Propagation behaviors
of single pressurized crack and interaction between
multiple cracks are studied. And finally, interaction
between hydraulic fractures and natural fractures in a
homogeneous poroelastic media will be investigated.
Accomplishments
A 2D real DD boundary element method has been
developed and used to simulate fracture propagation
trajectories for single and multiple cracks. Parametric
studies are carried out for different crack propagation
Y, m
0.3
0.2
0.1
0
-0.2
-0.1
0
X, m
Crack A
Crack B
v = 1.e-1m/s, c/ t
= 1.1
v = 1.e-3m/s, c/ t
= 1.1
v = 1.e-1m/s, c/ t
= 1.5
v = 1.e-3m/s, c/ t
= 1.5
Crack propagation path near an inclined crack at different crack propagation
speeds (S H
= 1 MPa, S h
= 0.5 MPa, p = 3.5 MPa, c/σ t
= 1.1).
0.1
0.2
speeds, far field stresses, rock cohesion and internal
fluid pressures to investigate the influential factors
on fracture propagation in a poroelastic rock and the
results are compared with those given by an elastic
model. We find that matrix pore-pressure increase
could change crack propagation mode and direction.
Significance
This study will enable us to predict the potential
fracture patterns that can arise from the intersection
of a fluid-driven hydraulic crack with a pre-existing
fracture. The results will assist us in design of
fracture treatments in complex geo-mechanical
environment. Future work will consider various joint
properties, fluid injection rates as well as the impact
of reservoir depletion.
Project Information
2.4.2 Studies of Propagation of Induced Hydraulic Fractures
through Pre-Existing Fractures
Related Publications
Ghassemi, A., Zhang, Q. 2006. Poro-thermoelastic
Response of a Stationary Crack using the Displacement
Discontinuity Method. ASCE J. Engineering Mechanics 132
(1): 26-33.
Koshelev, V., Ghassemi, A. Complex Variable BEM for
Stationary Thermoelasticity and Poroelasticity. J. Eng.
Anal. with Boundary Elements 28 (2004) 825-832.
Xue, W., Ghassemi, A. Poroelastic Analysis of Hydraulic
Fracture Propagation. Paper 129, presented at the Asheville
Rocks 2009, 43rd US Rock Mechanics Symposium, Asheville,
North Carolina, 28 June–1 July.
Contacts
Ahmad Ghassemi
979.845.2206
ahmad.ghassemi@pe.tamu.edu
Wenxu Xue
CRISMAN INSTITUTE
50
Crisman Annual Report 2009