Characterization of Natural Discontinuities in Tight Sandstone and Gas Shale Unconventional Reservoir Rocks of Thrace Region in Turkey with DFN Method

Abstract

ABSTRACT: The gas shales of the Mezardere formation and the tight sandstones of the Teslimköy unit in this formation in Thrace region have been considered for many years to be some of the remarkable sources of hydrocarbon production from unconventional reservoir rocks in Turkey. Design of a hydraulic fracturing (HF) operation is the only way for oil and gas recovery from such unconventional reservoirs. As hydraulic fractures induced by HF operations are likely to interact with natural ones, geometrical characterization of natural discontinuities gains importance to be able to build a more realistic reservoir model including structural geological components before an operation. This may reduce operational costs as well as increase production efficiency. Discrete fracture network (DFN) modeling of natural discontinuities (e.g., fractures, joints, faults, bedding, planes etc.) is quite a strong tool for this kind of purpose. In this study, preliminary results of an ongoing study on the development of DFN models in FracMan from outcrop data of natural discontinuities of tight sandstone and gas shale unconventional reservoir rocks of Thrace region are presented. These models can serve as unique database in reservoir modeling prior to potential HF operations probable to be performed in Thrace region in the future. 1. INTRODUCTION Unconventional reservoirs are becoming more important in natural gas and petroleum industry in Turkey as well as in the world. Especially, Thrace Region, in NW Turkey, has a big potential to produce oil-gas from unconventional reservoirs. While Hamitabat Formation and Ceylan Formation have been defined as host rock for natural gas and limited oil (Soylu et al., 1992), Mezardere Formation is defined as good host rock for gas and oil (Bürkan, 1992 and Soylu et al., 1992). A DFN model is essential for the reservoirs to run processes. Traditional data in structural geology from natural discontinuities, which are location, orientation and position, are used to create a DFN model. The originality of this study is that it is the first DFN modelling attempt being carried out on aforementioned unconventional reservoir rocks of Thrace region in Turkey. The DFN models defined through this study can serve as valuable database in terms of reservoir modelling studies prior to potential HF operations probable to be performed in the study area in the future.