Summary

This paper describes a systematic approach to analyzing hydraulically fractured horizontal wells (HFHW) in the Permian Wolfcamp shale. With increased shale development via multiple transverse fractures in horizontal wells, it becomes imperative to develop techniques to better characterize well performance which ultimately improve our understanding for well spacing and completions optimization. The workflow presented here integrates fracture treatment analysis (FTA), rate transient analysis (RTA) and numerical simulation to analyze well performance data. Neither FTA nor RTA can be used alone to analyze well performance due to complex flow regimes, multiphase flow effects, and reservoir compaction. However, they are important building blocks in developing numerical simulation models for understanding the quality of stimulation and the effectiveness of reservoir drainage. By studying flow characteristics using RTA, we can obtain useful estimates of the effective fracture surface area and effective permeability of the stimulated volume that effectively contributes to production. These fracture properties and dimensions are used to constrain inputs for numerical simulation, which additionally accounts for complex phase-behavior, multi-phase flow, and rock compaction effects. Production history-matching is used to additionally estimate the effective properties of the complex fracture network, namely the width of the enhanced zone (Wenh) and the associated permeability within it (Kenh) that was created by stimulation processes. In this paper, we present a field case study in which we have successfully used this approach to characterize well performance. The method demonstrates how analytical techniques can be used before undertaking detailed numerical simulation in order to constrain the ranges of fracture dimensions that explain observed performance.

Introduction

With technological advances in well design and stimulation techniques, numerous shale plays have become profitable to develop in recent years. This has been demonstrated in the Bakken, Eagleford and Woodford shales. The latest addition to these plays are the Wolfcamp shales located in the Permian Basin of West Texas. The Wolfcamp formation lies beneath the Spraberry and Dean formations which form the Spraberry Trend field, and which until recently had been the principal target for reservoir development in the Permian Basin. Within the last 2 decades development had been extended to the Wolfcamp (and deeper) formations via vertical wells completed in up to 10 different zones. Pioneer Natural Resources is the largest acreage holder in the Spraberry field, and operates approximately 900,000 gross acres with a current producing well count over 7000 vertical wells. The majority of the acreage appears prospective for the Wolfcamp Shale. To accelerate production and maximize economic recovery, Pioneer recently drilled a number of horizontal wells targeting the Wolfcamp with tremendous success.

URTeC 1579514

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