The Impact of Oriented Perforations on Fracture Propagation and Complexity in Hydraulic Fracturing

Abstract

To better understand the interaction between hydraulic fracture and oriented perforation, a fully coupled finite element method (FEM)-based hydraulic-geomechanical fracture model accommodating gas sorption and damage has been developed. Damage conforms to a maximum stress criterion in tension and to Mohr-Coulomb limits in shear with heterogeneity represented by a Weibull distribution. Fracturing fluid flow, rock deformation and damage, and fracture propagation are collectively represented to study the complexity of hydraulic fracture initiation with perforations present in the near-wellbore region. The model is rigorously validated against experimental observations replicating failure stresses and styles during uniaxial compression and then hydraulic fracturing. The influences of perforation angle, in situ stress state, initial pore pressure, and properties of the fracturing fluid are fully explored. The numerical results show good agreement with experimental observations and the main features of the hydraulic fracturing process in heterogeneous rock are successfully captured. A larger perforation azimuth (angle) from the direction of the maximum principal stress induces a relatively larger curvature of the fracture during hydraulic fracture reorientation. Hydraulic fractures do not always initiate at the oriented perforations and the fractures induced in hydraulic fracturing are not always even and regular. Hydraulic fractures would initiate both around the wellbore and the oriented perforations when the perforation angle is >75 • . For the liquid-based hydraulic fracturing, the critical perforation angle increases from 70 • to 80 • , with an increase in liquid viscosity from 10 −3 Pa·s to 1 Pa·s. While for the gas fracturing, the critical perforation angle remains 62 • to 63 • . This study is of great significance in further understanding the near-wellbore impacts on hydraulic fracture propagation and complexity. failure [3][4][5]. Implicit in this is understanding fracture initiation and propagation in the near-wellbore region as of great significance for hydraulic fracture treatment and injectivity test interpretation [6][7][8].Since most wells are cased and require to be perforated to access the reservoir, the majority of hydraulic fracturing treatments are conducted through perforations. Perforations play a vital role in the origin of complex fracture geometries [6,[9][10][11][12]. In fractured reservoirs, perforations are often the sole hydraulic connection between the fractured reservoir and the wellbore. Hydraulic fractures initiated from preexisting perforations will reorient themselves normal to the direction of the minimum far-field stress as they propagate out from the wellbore [2,4,[13][14][15][16]. Near the wellbore, multiple sub-parallel fractures may be generated due to fracture initiation processes such as perforations and natural flaws located at the open-hole wellbore wall. Hydraulic fractures commonly initiate either from perforations located at the cased wellbore or from preexisting natural ...

An open-access stress magnitude database for Germany and adjacent regions

“…In such cases, σ 3 should not be equated with S hmin , as it might actually be S V which has been determined. Liu et al (2018) showed that the FBP decreases with increasing stress ratio S Hmax /S hmin . They also investigated the implications of oriented perforations varying from S Hmax orientation, suggesting increasing FBP with higher orientation discrepancies.…”

Research and Application of Radial Borehole Fracturing Based on Numerical Simulation

“…During fracturing in the wells of perforation completion, the dual-wing fracture propagating along the maximum principal stress is always formed, and the fracture network is not likely to occur [1][2][3][4]. Moreover, when not being distributed along the maximum principal stress, the remaining oil is not able to be connected by the conventional dual-wing fracture, significantly reducing the effect of stimulation [5].…”

Discrete Element Simulation of Interaction between Hydraulic Fracturing and a Single Natural Fracture

“…Their results displayed before the HF reaches a NF, and the fracture re-initiation across the NF and with an offset is probable. Liu et al [21] presented a fully coupled finite-element method (FEM)-based hydraulic-geomechanical fracture model accommodating gas sorption and damage to better understand the interaction between hydraulic fracture and oriented perforation. Liu et al [22] developed a hybrid finite volume and XFEM for simulating hydro-fracture propagation in quasi-brittle materials.…”

“…In order to understand the interaction mechanism and the importance of each parameter, it is necessary These interaction modes depend on the in situ stresses, the orientation of induced fracture with respect to the NF, mechanical properties of the rock, properties of NF, and the HF treatment parameters, including fracturing fluid properties and injection rate. In this regard, several works have been published in three categories of experimental [5][6][7][8][9][10][11][12], analytical [13][14][15][16], and numerical methods [17][18][19][20][21][22][23].…”