셰일저류층의 다단계 수압파쇄에서 응력그림자 효과를 고려한 균열형태 분석

초록

During multi-stage fracturing in a low permeable shale formation, stress interfer�ence occurs between the stages which is called the “stress shadow effect(SSE)”. The effect may alter the fracture propagation direction and induce ununiform geometry. In this study, the stress shadow effect on the hydraulic fracture geometry and the well productivity were inves�tigated by the commercial full-3D fracture model, GOHFER. In a homogeneous reservoir mod�el, a multi-stage fracturing process was performed with or without the SSE. In addition, the fracturing was performed on two shale reservoirs with different geomechanical proper�ties(Young’s modulus and Poisson’s ratio) to analyze the stress shadow effect. In the simulation results, the stress change caused by the fracture created in the previous stage switched the maximum/minimum horizontal stress and the lower productivity L-direction fracture was more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than the relatively ductile Eagle Ford shale, the fracture width in the former was developed thicker, resulting in the larger fracture volume. And the Marcellus shale’s Young’s modulus is low, the stress effect is less significant than the Eagle Ford shale in the stage 2. The stress shadow effect strongly depends on not only the spacing between fractures but also the geomechanical properties. Therefore, the stress shad�ow effect needs to be taken into account for more accurate analysis of the fracture geometry and for more reliable prediction of the well productivity.

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