THE FRACTURES PATTERNS AND TECTONIC STRESS FIELDS IN SHANSHAN OIL FIELD, XINGJIANG

Based on the investigation of field joints and cracks in the field paleomagnetic orientation of cracks in cores, and identification of cracks in dip logging curve, we have analyzed the tectonic stress field in Shanshan oil field.Xinjiang N30-40E-and N30-50 Wtrending conjugate shear fractures are well developed in the reservoir rocks.And high-angle, especially vertical fractures are predominant.
The structures in the Shanshan oil field were formed by a nearly N-S compression at the Yanshanian movement in Late Jurassic.The structures comprise the N-S-trending normal faults and the NE-NW conjugate fractures.
The present maximum horizontal principal stress determined from an analysis of the changes of the diameter of the drilling holes by dip logging is about 140° which is consistent with equivalent to the direction of fractures that would be artificially produced in the oil field.