Solvable model of gas production decline from hydrofractured networks

Abstract

We address questions that arose from studying gas and oil production from hydrofractured wells. Does past production predict the future? This depends on deducing from production as much as possible about the plausible geometries of the fracture network. We address the problem through a solvable model and use kinetic Monte Carlo and Green's function techniques to solve it. We have three main findings. First, at sufficiently long times, the production from all compact fracture networks is described by a universal function with two scaling parameters, one of which is the diffusivity of unbroken rock α and the second of which is a parameter V ext with units of volume. Second, for fracture networks where the power-law distribution of fracture spacings falls below a critical value (and this appears to be the case in practice), early-time production always scales as one over the square root of time. Third, the diffusivity α that sets the scale for late-time production is inherently difficult to estimate from production data, but the methods here provide the best hope of obtaining it and thus can determine the physics that will govern the decline of unconventional gas and oil wells.

Mechanism and Model Analysis of Ultralow-Temperature Fluid Fracturing in Low-Permeability Reservoir: Insights from Liquid Nitrogen Fracturing

“…Since the successful implementation of hydraulic fracturing in the Klepper well in Grant County, Kansas, the United States, in 1947, hydraulic fracturing has evolved over half a century to become the predominant reservoir reconstruction technology. Once the fracture pressure threshold of a reservoir is surpassed, high-pressure water injection triggers the activation and expansion of the natural fractures surrounding the wellbore, leading to the formation of an interconnected fracture network that enhances the reservoir's permeability [5][6][7][8]. However, the transformation of the coal seams via hydraulic fracturing is accompanied by a series of challenges.…”