Simultaneous Multifracture Treatments: Fully Coupled Fluid Flow and Fracture Mechanics for Horizontal Wells

Abstract

Successfully creating multiple hydraulic fractures in horizontal wells is critical for unconventional gas production economically. Optimizing the stimulation of these wells will require models that can account for the simultaneous propagation of multiple, potentially nonplanar, fractures.In this paper, a novel fracture-propagation model (FPM) is described that can simulate multiple-hydraulic-fracture propagation from a horizontal wellbore. The model couples fracture deformation with fluid flow in the fractures and the horizontal wellbore. The displacement discontinuity method (DDM) is used to represent the mechanics of the fractures and their opening, including interaction effects between closely spaced fractures. Fluid flow in the fractures is determined by the lubrication theory. Frictional pressure drop in the wellbore and perforation zones is taken into account by applying Kirchoff's first and second laws. The fluid-flow rates and pressure compatibility are maintained between the wellbore and the multiple fractures with Newton's numerical method. The model generates physically realistic multiple-fracture geometries and nonplanar-fracture trajectories that are consistent with physical-laboratory results and inferences drawn from microseismic diagnostic interpretations.One can use the simulation results of the FPM for sensitivity analysis of in-situ and fracture treatment parameters for shale-gas stimulation design. They provide a physics-based complex fracture network that one can import into reservoir-simulation models for production analysis. Furthermore, the results from the model can highlight conditions under which restricted width occurs that could lead to proppant screenout.

Numerical Analysis on the Optimization of Hydraulic Fracture Networks

“…We refer for comparison to the model of Wu and Olson [8] for the fracture configurations of a single horizontal wellbore with two initial fractures (Figure 6a) and two horizontal wellbores with one fractures each (Figure 6b). These are the most classic configurations and have been simulated in many works [3,8,32,37,40,41].…”

“…These are the most classic configurations and have been simulated in many works [3,8,32,37,40,41]. The correct simulation of these configurations requires the precisely solving of the stress field and fluid pressure, and the correct calculating of the stress intensity factors of fracture tips.…”

“…Numerical models can be established according to field conditions and all the details can be exported for analysis. Therefore, numerical modeling is an important tool for engineers to predict the geometry of fracture networks [8].…”

“…Zhang et al [30] investigated the stability of hydraulic fracture network propagation and found that the localization instability can be suppressed by fluid viscosity. To sum up, the DDM-based models are appropriate for the simulation of complex fracture networks and have been used by more and more researchers [3,7,8,[28][29][30][31][32][33].…”

“…With the distributions of fracture length, orientation, aperture, etc., and the fracture density, random NF networks can be created [20]. The DFN model has been used by many researchers [3,7,8,20,32]. For example, Riahi and Damjanac [20] investigated the effects of NF connectivity, injection pressure, etc., on the complexity of hydraulic fracture network.…”