QUANTITATIVE PREDICTION OF THE DISTRIBUTION OF TECTONIC FRACTURES RELATED TO FLEXURAL DEFORMATION IN UPPER PALEOZOIC TIGHT SAND RESERVOIRS IN THE TABAMIAO AREA, NORTHERN ORDOS BASIN

The Tabamiao area is located in the Yishaan slope tectonic belt in the north of the Ordos basin.The structure is gentle and it is commonly thought that there are no conditions for fracture growth.However,many regional tectonic fractures in upper Paleozoic reservoirs and local tectonic fractures related to localized flexural deformation of strata have been found in the study area through core observations,thin-section analysis,measurements of physical properties and well tests and logging.This paper mainly introduces the method of estimating tectonic fractures related to low-amplitude flexural deformation of strata and the sites and degrees of development of fractures and their attitudes in the target horizons.The research results show that flexural deformation mainly occurred in the Yanshanian and Himalayan periods and modified the strata to some extent.Tectonic fractures are of little significance for the accumulation performance of tight reservoirs but they apparently improve the permeability of the tight reservoirs.