Practical Aspects Of Foam Fracturing In The Devonian Shale
Authors: Komar C.A. , Yost A.B. , Sinclair A.R. 
Published: December 2007

Available data on foam frac treatments from DOE/industry cooperative ventures and the state-of-the-art in the formulation of foam fluids for hydraulically fracturing the Devonian shale are reviewed and discussed in light of an engineering measurement of factors affecting cleanup, induced geometry, production and cost. The benefits and limitations of foam as the fracturing fluid for the Devonian shale are discussed and evidence supporting the observations are exhibited. Special laboratory studies on formation damage and fracture conductivity impairment associated with fracture treatments using water based fluids and foam are reviewed as well Rationale for selection of parameters used in the development of foam frac designs are set forth and limitations affecting universal applicability of foam frac stimulations are identified.

Results of early well life production rates are reviewed in light of necessary costs for achievement of the limited foam frac stimulations conducted. Overall, these treatments appear to be quite suited for the Devonian shale since the formation is shallow exists at a low temperature and is composed of a low permeability rock that requires minimal contact time permeability rock that requires minimal contact time with fracturing fluids to avoid being damaged and to preclude interference with gas production from the preclude interference with gas production from the native fracture system. Prospects for development wherein foam fracturing may be likely to succeed in linking the reservoir capacity with the wellbore are identified based on the stress ratio concept.

Introduction

A recent innovation in the developing of hydraulic fracturing is the use of foam as a low-residual fracturing fluid. The fracturing fluid is composed of water, a foaming agent, and nitrogen that form a homogeneous gas-in-water emulsion when mixed at predetermined rates. Depending upon the quality of predetermined rates. Depending upon the quality of the emulsion, foam displays either Newtonian or Bingham plastic behavior and is a high viscosity fluid as well as an efficient fluid. The effective efficiency and viscosity of foam generate large surface area and good proppant placement with low injection rates. Moreover, the low volume of water required to compose the foam minimizes the amount of fracturing liquid exposed to the formation. The low liquid content is quickly returned to the surface by expansion of the nitrogen during flowback.

The properties that make foam ideal as a fracturing fluid in the water sensitive, low-pressure, low gas volume Devonian shale formation include the high efficiency due to low fluid loss coefficients, negligible sand-settling velocities, low friction loss in pipe, and high viscosity inside the induced fracture. In addition, the absence of chemical fluid loss additives to control leak off during treatment leaves both the formation face and proppant bed relatively clean. Accordingly, foam seems to fit the definition of a desirable fracturing fluid since it can hydraulically create a fracture, it can carry sand into the fracture, it minimizes formation permeability damage, and it cleans up quickly after permeability damage, and it cleans up quickly after the job.

Foam has been used quite widely in the oil and gas industry for the past five years. However, the advent of foam fracturing into the Devonian shale evolved from the Department of Energy research at Morgantown Energy Technology Center (METC) that was started in 1975 and was directed at improving gas productivity from new shale wells. Together with productivity from new shale wells. Together with independent gas producers and in cost sharing contracts with Kentucky West Virginia Gas Co., Consolidated Gas Co., and Columbia Gas System, DOE-METC has tested the effectiveness of both conventional-size foam treatments and large-volume treatments in stimulating gas production from different stratigraphic units within the Devonian shale Formation. Although replicated tests are only available to arrive at a statistically-derived conclusion of the foam fracturing concept in one geologically similar area, sufficient data has been accumulated to indicate a trend.