Quantifying the Effects of Well Type and Hydraulic Fracture Selection on Recovery for Various Reservoir Permeability Using a Numerical Reservoir Simulator

Abstract

The industry is faced with the task of producing hydrocarbons from increasingly tighter reservoir rock including ultra low permeability sand and shale. As a consequence, the selection of an appropriate well type and fracture stimulation design is becoming even more critical to project success. The purpose of this paper is to provide some clarity by providing a general understanding about the effects of well type selection and hydraulic fracturing on hydrocarbon recovery for various reservoir permeability scenarios. Well types modeled include vertical, stimulated vertical, horizontal, axial stimulated horizontal and transverse stimulated horizontal with variations in compartment length and effective fracture length. This information has proven useful in the evaluation and planning of moderate to low to ultra low permeability well projects. The summaries that will be presented in this paper are a compilation of the results from numerous simulator runs for gas, black oil and gas condensate cases. These simulator runs included sensitivities on well type and permeability in order to compare recovery and production. Important conclusions pertaining to the recovery of hydrocarbons from ultra low permeability reservoirs and shale are made. In addition the obvious conclusion about the increasing difficulty of recovering hydrocarbons from lower permeability rock, a primary conclusion is that as reservoir permeability decreases, proper well type selection and effective hydraulic fracture stimulation design become much more crucial. The conclusions also show that for a given permeability, obtaining significant recovery of oil can be a much more difficult problem than with that of dry gas. These conclusions are supported by Bakken and Barnett Shale case histories which are included in this publication.

High-Resolution Numerical Modeling of Complex and Irregular Fracture Patterns in Shale-Gas Reservoirs and Tight Gas Reservoirs

“…Table 1 shows the reservoir and completion parameters used in this study. These parameters are representative of the Barnett shale, and were extracted from Shelley et al (2010), Houze et al (2010), andMiller et al (2010). The matrix permeability (1.0 Â 10 À19 m 2 ¼ 1.0 Â 10 À4 md) used in this study is at the upper range of permeability values for a Barnett shale.…”