Natural Fracture and Cleat Patterns in Coalbed and Shale Gas Reservoirs of the Donets Basin (Ukraine)

The Donets Basin (Ukraine/Russia) is one of the major coalfields in the Europe, which contains a number of conventional gas accumulations and has the potential to host significant quantities of unconventional gas. Right now the interest to unconventional gas potential of the Donets Basin is critical, because most of potential operators are standing on the threshold of starting wide-scale industrial exploitation. The main focus of this contribution is to get insight into style and structural trends of natural fracture and cleat patterns in the basin to ensure proper technical decisions for mitigation of mining safety problems and efficient exploitation of coalbed methane and shale gas reservoirs. The extensive database of digital maps of underground mining operations, structural mine-scale maps and sections, combined with results of underground surveys have been used to delineate fracture and cleat networks in the Donetsk-Makeevka region and Zasydko coal mine. The inferred tectonic zones, discrete fractures and tectonically induced cleat patterns clearly possess features of self-similarity and usually align with directional stresses, more specifically, of strike-slip-transpressional regime governed by NW-SE or NNW-SSE trending maximum stress axis.