The paper was presented at the SPE/DOE Unconventional Gas Recovery Symposium of the Society of Petroleum Engineers held in Pittsburgh, PA, May 16–18, 1982. The material is subject to correction by the author. Permission to copy is restricted to an abstract of not more than 300 words. Write: 6200 N. Central Expwy., Dallas, TX 75206.

Abstract

Stimulation of the Upper Devonian Benson Formation of Central West Virginia has lead to the use of various types of treatments. The following is an investigation of one of the more recent techniques, Foam/Nitrogen Fracturing, as it compares to the conventional Water Frac methods. The Benson is a shallow water turbodite deposit with thicknesses variable up to 30 feet. It is a brown siltstone which characteristically becomes commercially productive only after stimulation. Over the past three years stimulation of Union Drilling Benson wells in Upshur and Barbour Counties has been exclusively Foam Frac or Water Frac, with few exceptions. Foam Fracs were used initially for three reasons:

  1. to keep large volumes of water out of the formation in order to prevent clay swelling,

  2. to aid in well clean-up,

  3. to allow better sand placement through increased carrying quality of foamed Nitrogen.

The ultimate goal of the Foam treatment is to increase gas flow from the wells. Methods of investigation include records kept of (1) volumes of water used for treatments, (2) cleanup and service rig time and efficiency (3) open flows from foam frac and water frac treated wells, an indication of the sand placement abilities. Conclusions based on open flow results indicate that lower volumes of water, quicker well clean-up, and improved sand placement are desirable for the Benson Formation.

Introduction

Beginning in 1979, Union Drilling, Inc. embarked upon a foam fracturing program for the Benson "sand" in Central West Virginia. Historically, Benson treatments have involved only water fracturing methods. The foam fracturing program was instituted for three basic reasons:

  1. To keep large volumes of water out of the formation in order to prevent clay swelling;

  2. To aid in well clean-up; and

  3. To allow better sand placement through increased carrying quality of foamed Nitrogen. The ultimate goal of the foam fracturing program, of course, was to increase gas flow from the wells.

A total of twenty-nine wells were fractured using foam between June of 1979 and October, 1981. Each was perforated and fractured in the Benson "sand". Several wells were completed in both the Benson and Riley but, for the purposes of this report, only single stage Benson stimulations are investigated. This paper will examine the results of the foamed wells verses the results of basic water fracturing methods used on forty-nine single stage Benson wells completed by Union Drilling between August of 1969 and June of 1978. The investigation was conducted in the following manner:

  1. General Geology of the Benson "sand" –– a description of the Benson and its characteristics.

  2. General Procedures –– a summary of the stimulation and testing procedures used for both types of wells.

  3. Open Flow Analysis –– statistical analysis of the resulting openflows after frac.

  4. Production Analysis –– preliminary analysis of in line production.

  5. Economic Analysis –– comparison of average cost of the two treatments.

  6. Conclusions and Summary –– conclusions based on data presented, including a discussion of parameters which cannot be measured, and pitfalls associated with each analysis.

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