Analytical and numerical estimates of hydraulic fracture characteristics created by a wellbore pressure pulse

摘要

Hydraulic fractures are known to interact with natural fractures and other heterogeneities in rocks. When injection rates, fracture apertures and propagation pressures are low, natural discontinuities in the rock tend to arrest fractures, and fracture planes are deviated from the direction dictated by in-situ stress, forming local stepovers and pinchpoints. One conceptual possibility to radically increase propagation pressure and injection rate is to release energy and create a pressure pulse, generating motive force pushing fluid into the fracture, locally inside the wellbore. Compared to conventional injection using surface pumps, this allows the reduction of fluid friction losses inside the well, the release of energy at higher rates, and the containment of high pressure away from surface equipment and personnel. In this paper, we derive and discuss analytic estimates for the final extension of axisymmetric hydraulic fractures created by a local pressure pulse in the wellbore. Analytic equations explicitly specify the relationship between mechanical properties of the rock format ion, in-situ stress conditions, parameters of the wellbore energy source generating the pressure pulse and resulting size of the fracture. Analytic estimates are helpful for fast engineering estimates and preliminary feasibility assessments of fracturing systems based on wellbore pressure pulse. In the end, we illustrate analytic predictions with numerical modeling.