This paper presents the results of using a shale-specific, finite-difference reservoir simulation model to history match and forecast production data from the Barnett Shale reservoir. The paper will illustrate the many uses of the model for vertical and horizontal wells including determining gas in place, re-covery factors, optimal well spacing, drainage areas and drainage shapes, optimal fracture half-lengths and conductivi-ties, infill evaluations, horizontal well modeling and optimal number of stimulation treatments, analysis of microseismic data, and compression evaluations. The model was developed in the early 1990s to incorporate all of the production mecha-nisms inherent in shales including matrix gas porosity, gas desorption isotherm, single- or two-phase flow of gas and wa-ter in the natural fractures, layers, complex hydraulic fractures, and variable flowing bottomhole pressures. The paper will discuss the methodology to incorporate all field data into the simulator including core, logs, well test, completion, stimula-tion, microseismic, and production data. Examples will be given using public datasets. We also show production com-parisons between vertical and horizontal wells since this is of topical interest in the play's development history. Further-more, we discuss the various types of data to collect, their importance to proper stimulation design, and the integration methodology to evaluate and complete shale reservoirs.
The Barnett Shale is currently one of the most prolific gas reservoirs in the United States. Activity continues to increase with over 90 rigs drilling as shown in Fig. 1. Starting after 2000 when Devon acquired Mitchell Energy, the number of wells drilled has increased steadily. Numerous operators are actively expanding the play from its original area in Wise and Denton Counties to the north, south, and west. In addition, horizontal well drilling has opened up areas west of the Viola limestone formation. The Viola is a boundary to contain the stimulation treatment from entering the deeper, water producing Ellenburger.
Fig. 2 shows the total production from the Barnett shale. Fig. 2 is not completely up to date and current production is estimated to be approximately 1.25 Bscf/D with over 3,700 producing wells. They are also currently over 300 horizontal wells producing out of the 450 drilled to date. The volume from the horizontal wells is estimated at over 300 MMscf/D. Over 80% of the vertical wells have been drilled since 2000 and greater than 97% of the horizontal wells have been drilled since 2003, thus this is a very young growth play. Since 1981, the total gas produced from the field is estimated at over 1.4 Tscf. In 2004 alone, it produced 365 Bscf making it the largest gas field in Texas.