THE CHARACTER OF UPPER PALEOZOIC RESERVOIR FRACTURES AND THE EVALUATION OF THEIR DISTRIBUTION IN TABAMIAO AREA OF ORDOS BASIN

According to core of well drilling,study in thin section fracture,and analysis of fracture explanation from well logging,combined with history of the regional tectonic stress and the isotope character of filling,from well logging the genesis of fracture is determined.That the fractures are typical regional fractures which have following characters:1)There are extension high-angle or vertical fractures in core,which appear in group;2)Both sandstone and shale,develop fractures,with the former better than the latter;3)The formation period of fracture coincides with active period of Yanshan tectonic movement;4)The attitude of fractures are stable and coincide with the principal stresses of Yanshan tectonic movement;5)The growth of fracture is not constricted by local deformation.Based on the summary of geological factors controlling the development of fractures,finite element technique is employed to simulate the structural stress field and the distribution characteristics of regional fractures is evaluated in line with the stratigraphic feature.