Hydraulic fracturing of weak rock during waterflooding

Abstract

This paper describes a KGD-type model of a hydraulic fracture created by injecting fluid in weak, poorly consolidated rocks. The model is based on the key assumption that the hydraulic fracture is propagating within a domain where the hydraulic fields are quasi-stationary. By further assuming a negligible toughness, the fracture is shown to grow as a square root of time. The asymptotic fracture propagation regimes at small and large time are constructed and the transient solution is computed by solving a nonlinear system of algebraic equations formulated in terms of the fracture aperture. At early time, the fracture is hydraulically invisible and the injection pressure increases with time 𝑡 as log 𝑡, while at late time, leak-off from the borehole is negligible and the injection pressure decreases as 𝑡 −1∕4 . According to this model, the peak injection pressure observed when injecting fluid in weak, poorly consolidated rocks should not be interpreted as indicating a breakdown of the formation, but rather as marking the transition between two asymptotic flow regimes. The timescale that legislates the transition between the small and large time asymptotic regimes is shown to be a strongly nonlinear function of a dimensionless injection rate.

Physicochemical Effect on Coal Pores of Hydrocarbon Chain Length and Mixing of Viscoelastic Surfactants in Clean Fracturing Fluids

“…Coalbed methane (CBM) extraction can effectively alleviate energy shortages, improve mine safety, and reduce greenhouse gas emissions. In recent years, measures such as hydraulic slotting, hydraulic cavitating, chemical stimulation to promote the exploitation of CBM have been applied. − The strong heterogeneity and low permeability of coal reservoirs make it difficult to effectively exploit CBM by conventional methods. − Hydraulic fracturing is an effective method to improve the permeability of rock masses − and, in recent years, has been increasingly used in coal reservoirs. − Hydraulic fracturing involves the injection of high-pressure fracturing fluids into a rock mass to produce fractures, thus increasing permeability. The fracturing fluid is the core component of the hydraulic fracturing process.…”

Spatial and temporal constraints of the cohesive modeling: A unified criterion for fluid‐driven fracture

“…As a classical fracture problem, the fluid-driven fracture, which couples the solid deformation and fluid flow, has a wide range of applications in engineering, such as hydraulic fracturing [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] for the exploitation of hydrocarbons like oil, gas and so on, underground CO 2 storage, 48,49 and mining. 50 During the fracture propagation, the fracture process zone is too large compared with the fracture length to be neglected at the crack tip of the quasi-brittle materials.…”

A bi‐fidelity model for hydraulic fracturing

“…[9] the extended FEM approach, in Ref. [10] the unstructured mesh algorithm, the isogeometric analysis, 11 and the implicit level set algorithm (ILSA). [4][5][6][7]12 Broadly speaking, high-fidelity models can produce accurate and reliable predictions.…”

“…[9] the extended FEM approach, in Ref. [10] the unstructured mesh algorithm, the isogeometric analysis, 11 and the implicit level set algorithm (ILSA) 4–7,12 …”