THE CHARACTERISTICS AND EVALUATION OF FRACTURES DISTRIBUTION IN XUJIAHE FORMATION IN THE WESTERN DEPRESSION OF THE SICHUAN BASIN

The sandstone reservoir of Xujiahe Formation in the Western Depression of the Sichuan Basin,is the main gas producing zone of the West Sichuan district.The porosities and permeability of the reservoirs are very poor.The fractures are the major filtration passages in the reservoirs and play an important role in gas containing capability of reservoir.So the feature recognition and distribution of fractures is critical to evaluation of re-servoirs.The author sums up the features of fractures through the analysis of rock core and well log information,and concludes that fractures in the reservoirs are mainly diagonal fractures.The width of fractures mainly is from 0.5 to 2.0 mm and the length of fractures mainly is from 5 to 50 cm.There are two main kinds of fractures in this areas: tectoclase and regional fractures.Taking Fenggu Structure as an example,the author makes the distribution evaluation of tectoclase by the means of distortional stress simulation,structure curvature and structure filtration and distribution evaluation of regional fractures,which has some guide contribution on exploration and exploitation in the areas.