Sensitivity Studies of Horizontal Wells with Hydraulic Fractures in Shale Gas Reservoirs

Abstract

TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractProducing natural gas from shale gas reservoirs has gained momentum over the past few years in North America and will become an increasingly important component of the world's energy supply. A shale gas reservoir is characterized as an organic-rich deposition with extremely low matrix permeability and clusters of mineral-filled "natural" fractures. Shale gas storage capacity is defined by the adsorbed gas on the organic material within the shale matrix and free gas in the limited pore space of the shale rocks. Horizontal drilling and hydraulic fracturing are the primary enabling technologies to obtain economical production from the shale gas reservoir. This paper presents a comprehensive reservoir simulation model to study the impact of reservoir and hydraulic fracturing parameters on production performance of a shale gas reservoir. The simulation model was constructed as a multi porosity system with matrix sub-grids to account for transient gas flow from the matrix to the fracture. The extended Langmuir isotherm was used to model the desorption process of multiple components during the production. Primary hydraulic fractures perpendicular to the horizontal wellbore were modeled explicitly with thin grid cells that preserved the finite conductivity. The hydraulically-induced fracture network around the horizontal well was characterized by the matrix-fracture coupling factor (sigma) and permeability of the fractures.The study was aimed to quantify the influence of the reservoir and hydraulic fracture parameters using experimental design, including porosity and permeability of the reservoir matrix and fracture, matrix-fracture sigma factor, matrix subdivisions and, primary hydraulic fracture half-length, height, spacing and conductivity, rock compaction, non-Darcy flow coefficient, as well as gas content. Sensitivity tests were performed to identify the most influential reservoir and hydraulic fracture parameters and provided important insights into the impact of uncertainties on shale gas production forecasts, which can be critical for fracture treatment design and production scheme optimization.

The Optimal Design of Hydraulic Fracture Parameters in Fractured Gas Reservoirs with Low Porosity

“…It can be confirmed from oilfield production. The gas production of field is higher when NF is well developed in reservoir [5] . In composite model, natural gas flows into wellbore from matrix and fracture simultaneously at the inner part.…”

“…Dual porosity (DP) models/ dual porosity and dual permeability (DPDK) models [1][2][3][4][5][6][7] , single porosity models [8] , and discrete models [9][10][11] are the most commonly used methods for naturally fractured reservoirs. Single porosity models cannot represent the interaction between the fracture and the matrix, and discrete models are time-consuming in setting up hydraulic and natural fractures and of high computational cost.…”

Temperature-Prediction Model for a Horizontal Well With Multiple Fractures in a Shale Reservoir

“…Several shape factors of the fluid flow and heat transfer were proposed by several researchers (Coats, 1989;Heel et al, 2008;Kazemi et al, 1976;Warren and Root, 1963). Zhang et al (2009) applied the dual porosity model for shale gas reservoir with the explicit expression of the primary hydraulic fractures as fine grid cells perpendicular to a horizontal well and fracture network in the vicinity of the hydraulic fractures was characterized by the shape factor and permeability of the fractures. They concluded the treatment provides an accurate response.…”

“…Originally, a dual porosity approach, one of the multiple porosity models, is used for the expression of naturally fractured reservoir. In dual porosity model, each reservoir grid contains matrix and fracture, and the flow and heat transfer between the matrix and fracture is controlled by shape factor, and this is the upscaling of the properties such as fracture permeability and porosity from the discrete fracture network model to the dual porosity system taking into account the complex fracture system and connectivity (Zhang et al, 2009) (Fig. 3.3a).…”

Numerical Simulation of Fluid Flow through Fractal-Based Discrete Fractured Network

“…By using the commercial simulator CMG, Odunuga [10] studied the self-similar reservoir fracture network fractal pattern and calculated the production capacity and drainage area of the fractured shale gas well with representative fractal patterns. The dual-porosity model is also used to shed light on the flow characteristics in shale gas reservoirs [11][12][13]. In the continuum media dual medium-based model, the fracture property is averaged and then assigned to each grid node, and it is generally reflected in the concept of the matrix and fracture, in which it is difficult to accurately characterize every detail of the complex fracture system.…”