Abstract

Dynamic loading methods promise new modes for stimulating geological resources. In contrast to traditional fracturing methods (e.g. hydraulic fracturing) the stresses in the source region may be significantly larger than the in situ stress which helps creating fractures not oriented with the maximum in situ stress. This paper discusses simulation of dynamic fracture initiation and propagation using Lawrence Livermore’s GEODYN-E and GEODYN-L codes. These are massively-parallel multi-material codes developed for shock wave propagation in heavily jointed rock masses. The codes have been validated by modeling various underground explosions. Here, we focus on various mechanisms of dynamic fracture generation in a rock formation with pre-existing joints/cracks. Various source geometries and energy release rates are considered to optimize the enhancement of the fracture network, which could be stimulated later using traditional methods..

1. INTRODUCTION

Large-scale deployment of long lateral wells supporting the initiation of multiple hydraulic fractures has led to a surge in production from unconventional resources in North America. However, one limitation of such fracturing operations is that the induced fractures tend to be aligned with the maximum in-situ stress direction, which is not necessarily the optimal direction required to create the most permeable fracture network. Here, we investigate possible advantages of emerging technologies using explosives to dynamically fracture deeply buried shale formations as well as provide flexibility and control to design more efficient fracture networks and enhance permeability in tight formations at depths of a few kilometers. In this approach we rely on the ability of stress waves from an explosive charge to overcome the in-situ stresses and create fractures in many directions, in contrast to one stress-aligned fracture formed during hydraulic fracturing. Additional approaches are presented to create enhanced fracture networks by using multiple explosive charges, varying their geometries, and optimizing their initiation times. The massively parallel codes, GEODYN-L and GEODYN-E used in the current studies have been validated for underground explosions in rocks [1].

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