A Fully Coupled Numerical Poroelastic Model to Investigate Interaction between Induced Hydraulic Fracture and Pre-Existing Natural Fracture in a Naturally Fractured Reservoir: Potential Application in Tight Gas and Geothermal Reservoirs

Abstract

This paper investigates interaction of induced and pre-existing fracture by coupling wellbore, induced fracture and natural fracture in a poroelastic reservoir. Possibilities of fracture crossing, bending, arrest and shear dilation for various angles of approach are investigated under different scenarios: in-situ stress state, reservoir rock and fluid properties and characteristics of natural fracture. The fully coupled poroelastic model and results of this study in particular have a beneficial application in the design and optimization of hydraulic fracture treatments in naturally fractured reservoirs, therefore tight gas reservoirs and enhanced geothermal systems. The model can be extended to design stimulation of naturally fractured reservoirs based on shear dilation (high pressure low injection rate). In this paper we have demonstrated that natural fractures, faults and other discontinuities severely restrict propagation of an induced fracture. In-situ stress state, orientation and shear strength of pre-existing fracture prove to be most significant factors that influence the fracture propagation trajectory:–Because of the poro-elastic formulation it was possible to investigate the change in stress state ahead of the fracture tip and evaluate whether the fracture is going to be attracted or rejected by the interface. It was observed that high leak off influences dilation of natural fracture ahead of the arrival of the induced fracture tip.–Possibilities of fracture arrest increases with increase in high differential stress state and shear strength of pre-existing fractures.–Fracture crossing is another dominating behaviour for natural fracture with small aperture while fracture dilating for natural fracture with larger aperture. Fully coupled poroelastic modelling allowed us to gain new knowledge on interaction between induced and pre-existing fractures. This methodology and knowledge base will significantly improve our current approach to design and implement hydraulic fracture treatment in naturally fractured reservoirs.

A Review of Numerical Simulation Strategies for Hydraulic Fracturing, Natural Fracture Reactivation and Induced Microseismicity Prediction

“…The fluid flow and geomechanical deformations are coupled based on Biot's poro-elastic theory [38,39] and fracture propagation is modeled using linear elastic fracture mechanics (LEFM). Technical literature shows a number of applications of the FEM method to study the restriction of hydraulic fracture propagation by natural fractures and discontinuities [40,41]. Fig.…”

“…The DFN approach has been applied widely and successfully in different investigation domains: geothermal reservoirs [85,86], interaction between natural and induced fractures [40] and microseismicity [86]. In particular, Kohl and Mégel [86], employed statistical fractures in a discrete fracture network, in order to honor the available data of the Soultz geothermal site.…”

Numerical Simulation of Artificial Fracture Propagation in Shale Gas Reservoirs Based on FPS-Cohesive Finite Element Method

“…Many scholars have studied the propagation pattern of an artificial fracture intersecting with a single natural fracture by physical modeling and numerical modeling [5,6]. It is generally believed that there are three situations of the intersection between an artificial fracture and a single natural fracture [7][8][9][10][11]: the artificial fracture intersects with the natural fracture, the natural fracture intercepts, and the artificial fracture is deflected into the natural fracture. Rock samples from shale gas reservoirs were scanned by microseismic monitoring technology, and the results showed that there are multi-intersected natural fractures in the rock samples [12][13][14].…”

Modeling Shear Dominated Hydraulic Fracturing as a Coupled Fluid-solid Interaction

“…The problem of interaction between the hydraulic and natural fractures has been studied by many authors as the main reason causing the cloud of failed zone around the treated wellbore (Dahi-Taleghani and Olson 2009;Rahman and Rahman 2009;Tao et al 2009). Rahman et al (2009) have developed a fully coupled numerical poroelastic model to investigate the interaction between the induced fracture and pre-existing natural fractures in hydraulic fracturing modeling.…”

“…Rahman et al (2009) have developed a fully coupled numerical poroelastic model to investigate the interaction between the induced fracture and pre-existing natural fractures in hydraulic fracturing modeling. In their study rock tensile failure criterion was implemented to simulate the induction and propagation of new fractures.…”