Frac-and-pack stimulation. Application design, and field experience

A relatively short, highly conductive fracture created in a reservoir of moderate to high permeability will breach near-wellbore damage, reduce the drawdown and near-wellbore flow velocity and stresses, and increase the effective wellbore radius. Fracturing treatments of this type have two stages: fracture created, terminated by tip screenout, and fracture inflation and packing. Such a two-stage treatment is the basis of a number of new well-completion methods, collectively known as ″frac-and-pack.″ This technique has been successfully applied, with a range of fracture sizes, to stimulate wells in various reservoirs worldwide. This paper discusses the criteria for selecting wells to be frac-and-packed. We show how a systematic study of the inflow performance can be used to assess the potential of frac-and-packed wells, to identify the controlling factors, and to optimize design parameters. We also show that fracture conductivity is often the key to successful treatment. This conductivity depends largely on proppant size: formation permeability damage around the created fracture has less effect. Appropriate allowance needs to be made for flow restrictions caused by the presence of the perforations, partial penetration, and non-Darcy effects. We describe the application of the overpressure-calibrated hydraulic fracture model in frac-and-pack treatment design, and discuss some operational considerations with reference to field examples. The full potential of this promising new completion method can be achieved only if the design is tailored to the individual well. This demands high-quality input data, which can be obtained only from a calibration test. This paper presents our strategy for frac-and-pack design, drawing on examples from field experience. We also point out several areas that the industry needs to address, such as the sizing of proppant in soft formations and the interaction between fracturing fluids and resin in resin-coated proppant.