Natural Fracture Modeling in Unconventional Dadas-I Member for 3D Seismic Survey in the Southeastern Turkey

Abstract

Abstract Silurian age Dadas-I shale exhibit low porosity and extremely low matrix permeability. Acting as one of the main source rocks in South-East Turkey, it represents a self-sourced unconventional play. This study aims at using an approach spanning from seismic to image log data analysis and 3D geomechanics to develop a discrete fracture network model (DFN) to provide new insights into distribution of hydrocarbons since only developed natural fractures make this reservoir producible. The study uses borehole image log data acquired in the Dada»-I interval of 3 exploration wells: X-1, X-6, X-9, 3D seismic and 3D geomechanical model. The main steps of the workflow are: 1).to use interpreted image logs and classify the fractures by fracture sets, 2).to evaluate possible fracture drivers, defined as any 3D properties that can be sensitive to fracture intensity information in the inter-well space, 3).to review this analysis in the context of the seismic structural interpretation and regional tectonic framework, 4).to employ geomechanical model for likelihood of local reactivation. The analysis of natural fracture properties, together with petrophysical data, seismic interpretation, and stress regime enable to build a 3D DFN model, predicts fractures occurrence in the Dada»-I interval and used this output for dynamic reservoir modeling. The seismic attributes together with regional geology reveals two major sets of fractures: strike in ESE-WNW that relates to the first extensional tectonic event and the second with a strike NNE-SSW after paleo-stress rotation from E-W to N-S. Application of geomechanical model discloses that not all fractures should be considered as point of weakness. Only discontinuities that are favorably oriented to in-situ stress more likely to be hydraulically conductive. The result of this interpretation were used to predict hydrocarbon flowing zones. Accordingly, the selection of testing intervals on the basis of the highest density of fractures only is not a valid approach to determine prospective zones. In the current strike-slip/compressional regime, the fracture direction and dip is the main control to hydrocarbon flow with the best contribution from natural fractures oriented close to the present day maximum horizontal stress.