ISIP Analysis is a novel analytical method that calculates the hydraulic height of induced fractures and the in-situ horizontal stress anisotropy from the evolution of instantaneous shut-in pressures during a multi-stage horizontal completion. The fracture height calculated will be smaller than what is measured through microseismic measurement, but larger than the propped and effective fracture height.
Because every frac stage contributes to increase minimum horizontal stress and reduce the formation's horizontal stress anisotropy, ISIP Analysis may be a useful tool to guide the spacing design of perforation clusters. Increased characterization of hydraulic fracture dimensions from ISIP Analysis also makes it a useful addition to any workflow looking to optimize well spacing and stacking in unconventional plays. Multiple formulations of the stress escalation equation were derived, as well as type-curves that relate hydraulic-fracture height to the parameters of the equation. ISIP Analysis consists in finding the unique combination of parameters of the stress escalation equation that best matches field ISIP data. Application of ISIP Analysis is illustrated in the paper using field data taken from wells in various shale formations across North America. It addresses key uncertainties in the design of unconventional field development and is being proposed as an inexpensive alternative to other stress/fracture diagnostic techniques. In addition, the method has been successfully used to design the number of perforation clusters and their spacing to reach a desired magnitude of stress interference during horizontal-well stimulation.
While other techniques such as microseismic monitoring, tracers, downhole tiltmeters, pressure gauges, may be utilized to characterize fracture dimensions, the main advantage of ISIP Analysis is the ability to be applied to a vast majority of wells, without additional hardware, operational delay, or any modification to the well or completion design. As a result of its simplicity, ISIP Analysis takes a trained completion engineer only a few minutes to complete.