The Guandu Constructed Sandstone Reservoir Fractures,

GuanDu structure lies in Guandu tectonic zone of ChiShui valley in southern SiChuan basin. This tectonic zone distributes in the direction of north-north -west, which is a part of eastern-SiChuan complete folded zone extending to southwest on the shape of brush. There is extensive foreground in marine formation of JiaLingjing group,continental formation of Xujiahe group and lake formation of Jurassic system, we forecast fracture by the analog calculation of palaeotectonic stress field and rock bursting approach degree, and then forecast and evaluate fracture growth degree and distribution scope by rock mechanics fracture theory.Target formations in this research are Xjiahe sandstone formation of Upper Triassic and under sandstone formation of Lower ShaXimiao group of Jurassic, which are all nonmarine clastic reservoirs, but their matrix physical property is bad. The formation of good reservoir need following conditions: fractures (especially tectonic fracture) develop well; corrosion reworking of groundwater along the fracture. Good reservoir can not be formed without these two conditions, which has been proved by sandstone reservoir exploratory development in SiChuan basin. But groundwater corrosion is on the base of fracture growth, so fracture growth is the key to evaluate sandstone reservoir in XJiahe.Using well drilling,well logging,well testing,core testing and core observation data of new wells, on the base of tectonic data and geophysical data of XuJiahe reservoir, guided by tectonic geology,rock mechanics,geomechanics, we comprehensive evaluate sandstone reservoir of Xujiahe and lower ShaXimiao in fracture growth degree,distribution law,contributing factor,type and bearing of trend using technical methods such as structural interpretation,numeric analysis and mathematical statistics.Through comprehensive analysis of GuanDu structure in ChiShui, we get following conclusions: fractures develop well in sandstone of Xuyi,Xuer and lower ShaXimiao in nouth-middle and southern Guandu structure. Positions that fracture grows best is near the prominent and southern prominent. In southern GuanDu structure, fractures grow well in prominent,saddle and naeal pit. Fracture has three types: one is high angle shear fracture, which transverse to rock stratum. The second is low angle shear fracture, whose included angle with stratum is about 30 degree, distribute the core of middle-southern and southern GuanDu structure. The third is high angle tension fracture, which nearly transverse to rock stratum, distribute in high curvature position of northern GuanDu structure. Reservoir in tectonic zone is best in vertical, then is middle GuanDu structure, worst reservoirs lies in northern GuanDu structure. Horizontally, reservoirs in southern GuanDu structure is best, middle GuanDu structure is worse, and worst reservoirs lies in northern GuanDu structure.