Unconventional play development continues to expand quickly around the globe. The first unconventional play to be rapidly developed has been the Barnett Shale in North Central Texas. As of July 2012, the Barnett Shale has more than 13,000 multi-fractured horizontal wells (MFHW) with approximately 2,500 being five years or older. This gives the Barnett Shale a significant production database from which to perform production analysis.
Well spacing is a key value driver for field development and needs to be addressed early in the appraisal process. The extensive public production database was used to gain insights as to appropriate well spacing in two counties of the Barnett Shale, Denton and Wise. This paper demonstrates a workflow to understand appropriate spacing for future development based on infill production performance. Initial peak production and one-year cumulative gas production from infill and non-infill wells are used as key performance indexes. An important assumption of this work is that well spacing should be as close as possible where infill well results are as good as non-infill wells. When the infill well performance is poorer than the non-infill wells, the spacing is too close.
Forty MFHW spacing pilots were identified and analyzed, with 34 of these pilots meeting criteria for use in the study. This paper will review the workflow, the results, provide a recommended spacing based upon the performance data and also highlight other factors that may need to be considered. Currently, this paper is believed to be the first to utilize field performance in a simple and objective yet robust manner to generate a recommended spacing for a given area.
The Barnett is a Mississippian-age formation consisting of organic rich mudstone (shale), marls, and limestone. Pay shales in the Barnett formation were deposited in a deep, dysoxic to anoxic basinal environment. Deposition of the pay facies was primarily pelagic (sediments and organic material settling out of the water column). Non-pay facies are either clay-rich pelagic shales, or detrital carbonate gravity flow deposits (turbidites and debris flows).
In the study area, the Barnett Formation is divided into the Upper Barnett Shale and a Lower Barnett Shale, which are separated by the Forestburg Limestone member (Fig. 1). In the northeastern part of the Newark East Barnett field, the Barnett is underlain by the Ordovician-age Viola Limestone, a dense, non-porous limestone that acts as an effective fracture barrier, separating it from the underlying Ellenberger aquifer. To the south and west, the Viola has been eroded and removed, and the Barnett lies directly on the Ellenberger aquifer. The Barnett Formation is overlain by the Pennsylvanian-age (Morrowan) Marble Falls Formation, consisting of shales, marl and limestone, which also provide an effective fracture barrier.