Enhanced Oil Recovery by Repetitive Electrohydraulic Shock Waves: Fracturing and Enhanced-Permeability

Abstract

Owing to the inefficiency of the conventional recovery methods to yield the original oil in place, the production decrease of the oil well is an increasingly serious problem all over the world. The conventional enhanced oil recovery (EOR) methods are now facing the challenges such as high price, environmental unsafety, low efficiency, etc, the need for EOR techniques to recover a higher proportion of the oil has become imperative. Based on high-pulsed power technology, a novel enhanced oil recovery technology using repetitive electrohydraulic shock waves is proposed in this paper. The electrohydraulic shock wave is induced by the rapid expansion of plasma channel of the liquid pulsed discharge. Then the repetitive shock waves with steep fronts and high intensity are utilized to generate micro-cracks in rocks. In order to further evaluate the validity of such technology in the respect of oil well stimulation, the generation of electrohydraulic shock wave and the effect of fracturing the rocks and then enhancing the permeability are evaluated. Experiment results demonstrate that controlling the shapes of the plasma channels is a remarkable way to enhance the shock wave intensity. The FEM simulation and cement specimen test also show the evolution of the micro-cracks of the specimens. The specimens are fractured by the electrohydraulic shock waves. On-site experiment proves that micro-cracks contributed to a great reduction of the difficulty and energy consumption in the oil recovery process and confirms the potential of this technology to be a promising EOR method in low permeability reservoir.