シェールガス・オイル開発におけるジオメカニクス

Abstract

It is well known that horizontal drilling and hydraulic fracturing are key technologies to carry the shale gas revolution forward to success. Efforts in enlarging reservoir contact are needed to realize commercial production from shale reservoir whose permeability is supposed to be in the order of nano-Dary to micro-Darcy. To design mud system, to keep wellbore stability and/or to optimize hydraulic fracturing fluid and pumping schedule, knowledge about rock mechanics and stress environment is quite important. A technical area of analyzing, integrating and interpreting such knowledge is called “geomechanics”.In this paper, we describe geomechanics from various aspects by focusing application to hydraulic fracturing technology. We review mechanical property of shale and some important parameters such as Young's modulus, Poisson's ratio, UCS, hardness and brittleness. Then, we show how those parameters impact hydraulic fracturing. A geomecanical models which consist of mechanical faces, mechanical properties and stress information is briefly explained. A case study of microseismic monitoring in Barnet shale field is introduced to reveal created hydraulic fracture patterns and those relationship to production that are significantly affected by pre-existing natural fracture system.