Abstract

The Staged Field Experiment (SFE) Well No. 2 is the second of four wells funded by the Gas Research Institute (GRI) for the advancement of research in fracturing and completion technology. This tight gas well is located in a lease owned by Amoco, in the North Appleby Field, Nacogdoches County of East Texas. The well is completed in the Travis Peak Formation which is a sequence of sand shale layers found from 8,000 to 10,000 ft. The permeability and porosity average approximately 0.05 to 0.08 md and 5 porosity average approximately 0.05 to 0.08 md and 5 to 9 %, respectively.

Extensive pre- and post-fracturing tests were conducted by a consortium of academic and industry participants under the direction of a main GRI participants under the direction of a main GRI contractor. These include the stress testing of 25 zones and two mini-fracturing treatments ranging in volumes up to 6550 bbls. This paper derives a closure stress profile and possible variations using these data and related field experience, and simulates the main fracture treatment using a three dimensional fracture simulator. The simulations suggest fracture width reduction (pinching) at the perforations because of the presence of a low stress perforations because of the presence of a low stress zone below and unsymmetric fracture height growth. Significant fracture height is indicated by both field data analysis and simulations. Fracture treatment design strategy is significantly affected by this occurrence, which suggests changes to common fracture design practices of many operators in the area. The simulations are compared with post-fracturing field data analysis to assess post-fracturing field data analysis to assess the resulting fracture geometry and the predictive capabilities of the simulations. Fracture design strategies are suggested for the area resulting from the experience gained from the SFE No. 2 well.

Introduction

This paper presents the authors' evaluation of the data obtained from the Staged Field Experiment (SFE) Well No. 2, in the East Texas, North Appleby Field, in Nacogdoches County (Figure 1). It addresses the evaluation of stress profiling techniques, problems encountered in the complex Travis Peak sand shale sequences, and three dimensional Peak sand shale sequences, and three dimensional (3D) simulations of fracture geometry for these profiles using Terra Tek's Terra Frac simulator. profiles using Terra Tek's Terra Frac simulator. The SFE No. 2 well is the second in a series of four research wells to be drilled and funded by the Gas Research Institute (GRI) for the advancement of fracturing and completion technology in tight gas sands. The North Appleby Field includes a small number of wells on 640 acre spacing which generally produce gas at low rates with 50–100 bbls of water produce gas at low rates with 50–100 bbls of water per day. per day. The SFE No. 2 was spudded July 7, 1987 and reached a total depth of approximately 10,160 ft on August 27, 1987. The Travis Peak Formation is a tight gas sand formation with the Upper Travis Peak, which is the subject of this analysis, found from 8,000 to 9,000 ft. Pertinent data for the Upper Travis Peak are in Table 1.

Following the drilling and casing of the SFE No. 2, twenty five intervals were stress tested and a number of geophysical and micro-seismic experiments were conducted. Two mini-fracture treatments and a main fracture treatment were performed on the Upper Travis Peak beginning April 28, 1988 and concluding September 16, 1988.

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