Abstract Hydraulic fracturing is the most common me used to improve production from wells drilled "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 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 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.
Introduction Due to their composition, "tight" formations are characterized by very low permeability. Thus, wells drilled into gas-bearing formations of this type generally produce at very low rates and must be hydraulically fractured to be commercial. Hydraulic fracturing increases the effective wellbore radius and greatly increases the production rate.
To obtain highly conductive and deeply penetrating fractures, accurate fracture design is penetrating fractures, accurate fracture design is imperative. The application of pressure transient analysis techniques to fracture design allows evaluation of current stimulation methods, nd past completion and stimulation practices, and leads to the better design and application of future treatments.
Optimization of stimulation design is one of the main objectives associated with tight gas production. Because of the generally low production rates production. Because of the generally low production rates from these reservoirs, the most cost-effective use of stimulation techniques and materials needs to be determined and then applied to achieve desired production results. production results. This paper describes a field study which was performed in an effort to optimize fracture treatment performed in an effort to optimize fracture treatment design in the "tight" Medina Sandstone formation in northwestern Pennsylvania. It lists the necessary reservoir and production data required, along with pressure transient analysis methods and shows how pressure transient analysis methods and shows how these are used in conjunction with one another. Calculation and comparison of the major stimulation design parameters are also mentioned.
Discussion Probably the most difficult task in an evaluation of this nature is gathering and computing the necessary information. These necessary data include the following information.Geophysical
Reservoir
Production
Well Completion
Stimulation
The required geophysical information includes an accurate determination of lithology, porosity (phi), zone thickness (h), reservoir fluid saturations (SW, So, Sg) and any structural trends.
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