Abstract

This study focuses on how the fracturing treatment design parameters such as the volumes of liquid injected, size and amount of proppant influence the Estimated Ultimate Recovery (EUR), in Upper Devonian formations in the Appalachian Basin. An extensive database containing completion, stimulation, and production data from the Benson formation was utilized in this study. The selection criteria for wells which were ultimately used in the study included wells with single zone completion and long production history with adequate completion data. These criteria eliminated the major uncertainty caused by multiple zone completions or inconsistent production data. The total proppant placed during stimulation treatments was found to be the major variable that influenced EUR. Increasing the total proppant not only increases EUR but also to decreases the number of wells required to effectively drain the reservoir. Subsequent economic analysis provided the basic guidelines to achieve economic recovery from the Upper Devonian formations in the Appalachian Basin.

Introduction

The Upper Devonian play in the Appalachian Basin is underdeveloped and EUR for the wells producing from these zones have been inconsistent and vary from poor (20 MMcf) to excellent (>1.0 Bcf). Most gas wells which are completed in low permeability formations of the Appalachian Basin, such as Benson, require stimulation to achieve commercial production. Hydraulic fracturing treatments have become a common practice for enhancing the production from the wells of various potential. The ability of a fracture to achieve increased production depends on the size and areal extent of fracture. It is often difficult to determine the fracture shape, dimensions, conductivity and the manner the fracture propagate in the subsurface strata due to lack of in-situ rock properties and stress field. As a result, the ability to optimize treatment designs and economics is often limited to selecting the appropriate types of fluids and additives, total volume of fluids, amount and size of the proppant, and injection schedule.1

Although the stimulation treatments have enhanced the production from the low permeability formations in the Appalachian Basin, it is uncertain that the treatments represent the optimum designs. Our previous investigations 2 have revealed that the optimization of treatment designs can further improve economic production. It is therefore necessary to evaluate the impact of the stimulation treatments on EUR and the degree of improvement that can be achieved through optimization. More specifically, the objective of this study was to identify the stimulation treatment parameters that had the greatest impact on production and EUR and to place an economic value on them.

Study Area

Most wells that produce from the Upper Devonian section in the Appalachian Basin have multi-zone completion and comingled production. As a result, it is difficult to find a good study group. The focus of this study is the Benson Sandstone which is productive in North Central West Virginian as illustrated in Figure 1. Dominion E&P has over 3500 wells completed in the Benson formation, out of which it was possible to identify 500+ wells that were completed only in Benson. To keep reservoir properties more consistent, four groups of wells were selected namely area I, area II, area III and area IV as illustrated in Figure 2.

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