Evaluation of Stimulation Treatments in Appalachian Tight Gas Sands

Abstract

ABSTRACT Hydraulic fracturing is the most common method used to improve production from wells drilled into "tight" formations. Accurate fracture design is essential in order to obtain highly conductive and deeply penetrating fractures. In the past, many stimulation treatments in the northeastern United States had little basis for design. Thousands of wells have been fractured and comparative analysis of different techniques was extremely difficult. This paper attempts to evaluate fracture design in relation to tight gas sands in the northeast. A review of the major variables affecting hydraulic fracture design is included and a discussion of three pressure transient methods used in the evaluation is presented. Pressure buildup analysis was used to determine effective reservoir permeability and pressure. Type curve matching was used to approximate fracture lengths and to predict production resulting from changes in fracture geometry. Computer reservoir simulation analysis helped in more accurately modeling the reservoir to support the production forecasting. A case history detailing this method of evaluation in the Medina Formation is discussed. Actual field data are compared to the predicted results. A field study is also presented which deals with the "Clinton" formations in Ohio. A number of wells were evaluated (after stimulation) with type curves and some ideas on job designs are suggested.