A Workflow for Integrated Barnett Shale Gas Reservoir Modeling and Simulation

Abstract

The Mississippian Barnett Shale reservoirs have opened a new era for US gas production. Many reservoir characterization efforts have been made and completion practices established to help understand the Barnett Shale reservoirs. The borehole image interpretation, drilling-induced fractures and conductive/healed fractures, reveals stress regime orientation, fracture morphology and their orientations. The interpreted results guide the design of horizontal wells to control hydraulic fracture directions and intensities. Conventional logs and cores have been used to classify lithofacies and estimate petrophysical and geomechanical properties for well positioning and reserve calculations. The seismic survey is not only interpreted for structure horizons and faults, but also analyzed for 3D property evaluations such as lithofacies distribution, discrete fracture network, and stress field. On the operation side, longer horizontal wells are drilled and massive multistage, multicluster hydraulic fracturing treatments (HFT) are executed. Various well placement and HFT schemes are performed. The microseismic (MS) has played an important role in understanding the estimation of hydraulic fracturing stimulated reservoir volume (ESV) and fracture intensities. In spite of this tremendous effort and progress, a systematic methodology appears lacking in the literature to integrate the variety of information and obtain accurate reservoir characterizations. In this paper, we present an integration workflow that incorporates seismic interpretations and attributes, borehole image and log interpretations, core analysis, HFT, and microseimic data to construct reservoir models and discrete fracture networks that are then upscaled to dual-porosity reservoir models for numerical simulation. The application of this workflow in field studies has revealed important observations and provided better understanding of the reservoirs. This integration workflow demonstrates an effective methodology for capturing the essential characteristics of Barnett Shale gas reservoirs, and offers a quantitative means and platform for optimizing shale gas production. Introduction Driven by gas consumption demand and rising oil and gas prices in the past several years, Barnett Shale gas production has gained momentum. The characteristics of the Barnett Shale reservoir can be typically described as extremely low permeability (100-600 nano-Darcys), low porosity (2-6%), and moderate gas adsorption (gas content 50-150 scf/ton). The general Barnett Shale reservoir deposition settings, lithofacies, natural fracture characterization, and production evaluation can be found in Louks et al. (2007), Gale et al. (2007), and Frantz et al. (2005). In order to achieve economical production and enhance productivity, a large number of horizontal wells have been drilled and massive multistage HFT jobs have been performed. Due to the complex nature of the Barnett reservoirs which is vastly different than that of conventional or other types of unconventional reservoirs, it is difficult to obtain a clear understanding and an accurate description of the reservoir. To quickly acquire knowledge and guide imminent placement (well spacing and pattern) designs, various well spacing pilots (e.g., 500 ft, 1,000 ft, and 1,500 ft, etc.) were drilled and various hydraulic fracturing operation schemes such as "zipper-frac" and "simul-frac" have been invented and tested (Waters et al., 2009).

Understanding Gas Production Mechanism and Effectiveness of Well Stimulation in the Haynesville Shale Through Reservoir Simulation

“…Past reservoir evaluations have focused on the Barnett shale play of north central Texas (Cipolla et al 2009a(Cipolla et al , 2009bZhang et al 2009;Du et al 2009), since there are thousands of wellbores and the production trends are well defined. These cases ranged from a lateral drilled as a single openhole completion to the current multistage transverse hydraulic fracture stimulations.…”

Using a Calibrated 3D Fracturing Simulator to Optimize Completions of Future Wells in the Eagle Ford Shale

“…Prior approaches relied on simplification or approximation of the detailed description the created complex fracture geometries (Du et al 2009(Du et al , 2010Ejofodomi et al 2011;Mongalvy et al 2011). However, modeling advancement made has enabled the explicit gridding of the complex hydraulic fracture geometries in reservoir simulation models, and this now provides the necessary detail to properly evaluate fracture treatment designs and well performance.…”

An Integrated Workflow for Reservoir Modeling and Flow Simulation of the Nikanassin Tight Gas Reservoir in the Western Canada Sedimentary Basin

“…There is also an automatic technique for translating fracture analysis into a reservoir simulator by setting the fracture grid properties automatically (Lolon et al 2007). Case studies of full field models integrating dynamic data have demonstrated that hydraulic fracture modeling is a key component for tight gas reservoir simulation (Iwere et al 2004;Frantz et al 2005;Du et al 2009). The method presented in this paper modifies both the connection factors and transmissibility multipliers for regions surrounding the well that hosts the fracture.…”