A Step by Step Approach to Hydraulic Fracture Treatment Design, Implementation, and Analysis for Tight Gas Sands

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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 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

A synthesis of treatment design parameters, treatment procedures in the field, quality control, and analysis of procedures in the field, quality control, and analysis of created fracture parameters is essential to improve and optimize hydraulic fracture treatments in a particular field. This paper provides a step-by-step approach to treatment design optimization that combines laboratory, field and analytical efforts. The laboratory program includes measurements of porosity, absolute and relative permeability, capillary pressure, elastic moduli, matrix permeability, capillary pressure, elastic moduli, matrix permeability and proppant bed sensitivity to fluid (reservoir permeability and proppant bed sensitivity to fluid (reservoir and treatment) all at simulated in-situ conditions and appropriate petrographic study. The field test program involves in-situ stress measurements (mini-fracs in the pay and surrounding formations), fracture orientation pay and surrounding formations), fracture orientation determination and transient pressure tests. Successful implementation of the optimized design is then carried out by monitoring of flow rate and bottom hole pressure during the job and change of design parameters as necessary to tailor the fracture geometry. This must be coordinated with a quality control program for both the equipment and materials used in the job. A brief review of the state-of-the-art of transient pressure analyses of fractured wells is also included in the paper to inform the practicing engineer of the advantages, disadvantages and limitations of each technique. Finally, a field example is presented that illustrates the step-by-step approach. Designed and created fracture parameters are critically compared to demonstrate the effectiveness of the procedure and show how such information can be used to further improve results.

We gratefully acknowledge the Gas Research Institute (GRI) and the U.S. Department of Energy, which have funded some of the work presented here.

Introduction

Since the early mid-century, hydraulic fracturing has been proposed as the solution to economically increase oil/gas proposed as the solution to economically increase oil/gas production from the relatively low pressure, low permeability production from the relatively low pressure, low permeability reservoirs. Results to date of hydraulic fracturing treatments, however, vary from extremely successful to extremely disappointing failures. The disappointing failures and the recent global energy crisis have raised the need to critically understand the stimulation process and devise means of optimizing the effectiveness of these treatments.

The study presented by Fast, et al. following their hydraulic fracturing experience at the Wattenberg Field was one of the first papers to critically outline some of the basic important parameters papers to critically outline some of the basic important parameters controlling the success of hydraulic fracturing. They emphasized pre-job planning and pre-stimulation well testing and noted a pre-job planning and pre-stimulation well testing and noted a requirement for further research and development. Since then, the data and tests needed for stimulation design have become more clearly defined. Simonson, et al., first defined the conditions needed for fracture containment and which since have been detailed by Cleary and Ahmed, et al.. Ahmed, et al. described tests that evaluate fracturing fluid damage to the reservoir matrix permeability and fracture conductivity and showed the importance of these tests when designing hydraulic fracturing treatments. Meanwhile, fracturing fluid proppant developments have greatly enhanced the opportunity of improving stimulation design.

Recent literature contains increasing evidence of enhanced production and improved economics with better pre-job evaluation production and improved economics with better pre-job evaluation and planning. Besides the Wattenberg Field, job locations have included the Cotton Valley, the Anadarko Basin, the North Douglas Creek Arch, the North Sea, and the Fort Union Formation in the Green River Basin in Wyoming. The pre-job testing and evaluation was different for each of the projects listed; however, there was emphasis on the selection of fracturing fluid (to minimize residue accumulation and matrix permeability damage) and quantifying the fracture conductivity required to economically optimize treatments.

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