Abstract
Studies of hydraulic fracturing in fractured porous medium have commonly been made using in-situ fracture pressure upon the fracture (wing-crack) surfaces. Here we propose a novel technique, which may provide advantages such as increasing the rate of crude oil production from shallow to deep high pressure/high temperature reservoirs. More specifically, we show the results of numerical and experimental pulse power fracturing study in which the fracture propagation can be controlled, with application to unconventional reservoirs. In the experimental setup 1KJ energy is produced during electric discharge. In the experiments, the pressure rose up to more than 100 Kpsi (690 MPa), high enough for generating numerous new fractures. We have run several tests on cylindrical specimens of limestone and shale, each specimen being 15 cm in length and 5 cm in diameter. The results show that the measured fracture propagation rate using this method is considerably higher than we using conventional quasi static fracture propagation methods. Further field scale tests on this method are required to determine maximum fracture lengths.
1. INTRODUCTION
Hydraulic fracturing is one of the well-known standard operations after perforation in oil and gas wells, especially for unconventional reservoirs. One idea might be to use high injection pressure to create a simple two wings hydraulic fracture. However, such a method requires the use great volumes of fluid and increases the risk of propagation into underground water sources.
Such disadvantages have led researchers to try to find novel methods for hydraulic fracture operations by joining several new ideas derived from basic solid mechanics and fluid dynamics. One of the most important and novel methods in this context is hydropulse pressure fracturing. This is a dynamic fracture propagation method in which the excessive pressure is produced using an electrical discharge. In fact, unlike the traditional quasi-static fracture propagation, this method has the advantage of creating a two-wing planar hydraulic fracture. It is a dynamic fracture propagation method and is applicable in naturally fractured reservoirs. Creating multiple fractures is also possible with this method based on the power which was used.
