Experimental Investigation of Crack Extension Patterns in Hydraulic Fracturing with Shale, Sandstone and Granite Cores

Jianming He,Chong Lin,Xiaole Wan,Xiao Li

doi:10.3390/en9121018

Abstract

Hydraulic fracturing is an important method of reservoir stimulation in the exploitation of geothermal resources, and conventional and unconventional oil and gas resources. In this article, hydraulic fracturing experiments with shale, sandstone cores (from southern Sichuan Basin), and granite cores (from Inner Mongolia) were conducted to investigate the different hydraulic fracture extension patterns in these three reservoir rocks. The different reactions between reservoir lithology and pump pressure can be reflected by the pump pressure monitoring curves of hydraulic fracture experiments. An X-ray computer tomography (CT) scanner was employed to obtain the spatial distribution of hydraulic fractures in fractured shale, sandstone, and granite cores. From the microscopic and macroscopic observation of hydraulic fractures, different extension patterns of the hydraulic fracture can be analyzed. In fractured sandstone, symmetrical hydraulic fracture morphology could be formed, while some micro cracks were also induced near the injection hole. Although the macroscopic cracks in fractured granite cores are barely observed by naked eye, the results of X-ray CT scanning obviously show the morphology of hydraulic fractures. It is indicated that the typical bedding planes well developed in shale formation play an important role in the propagation of hydraulic fractures in shale cores. The results also demonstrated that heterogeneity influenced the pathway of the hydraulic fracture in granite cores.

Highlights

Compared with other fossil fuels, shale gas is a cleaner and more sufficient resource
In fracturing experiments experiments were sandstone, shale, and and granite cores cores to investigate the differences of crack extension were conducted conductedwith with sandstone, shale, granite to investigate the differences of crack patterns in these three reservoir rocks
The results provide a novel insight into the crack extension crack extension patterns in sandstone, shale, and granite cores were analyzed

Summary

Introduction

Compared with other fossil fuels, shale gas is a cleaner and more sufficient resource. Enhanced Geothermal System (EGS)—formerly known as Hot Dry Rock (HDR)—is a technology used to exploit geological heat resources in non-volcanic regions where the natural permeability of rock formations is extremely low. It provides inspiring prospects in terms of producing large quantities of energy from deep underground rocks [1]. Hydraulic fracturing is a key technology in the exploitation and stimulation of tight sand gas, shale gas, and geothermal resources. The mechanisms of generating complex fracture networks are of vital importance for hydraulic fracturing treatment

Methods

Results

Conclusion