Reasearch On The Feature Of Yanchang Formation Of Wayaobao Oilfield

Ultra-low permeability clastic reservoirs of Yanchang Formation in Ordos Basin developnatural fractures with different levels, and the majority of high-yield wells are related toreservoir fractures. Making proper understanding and evaluation in reservoir fracture,finding outthe distribution of cracks, is important for oil exploration and development of Wayaobaooilfield.Based on outcrop and core observation and description in the study area, combined withregional tectonic setting, conducting some questions which are reservoir characteristics of thestudy area, natural fracture characteristics, artificial fracture characteristics, fracturecharacteristics and effects on development by the the data of casting thin, particle size images,capillary pressure and the analysis of physical properties, Determine the reservoir characteristicsof Yanchang reservoir; natural fracture characteristics and the features、hape、direction ofmicro-cracks; the features、hape、direction of crack cracking after rock fracturing;to discuss theinfluence of the cracks on remaining oiland water injection.Research shows that,intergranular pore and dissolution porereservoir is the main pore typein the reservoir of Chang4+5and Chang6. The pore structure can be divided into three types,middle-small aperture and middle-little throat, small aperture and little throat, tiny aperture andtiny throat.The characteristic of Natural fractures: the fracture density is vertical fracture and itsdrilling rate is20%, the drilling rate of horizontal fracture or meshy fracture is100%; The depthof cut is about30cm, The width is less than1mm; The angle of vertical fracture is more than80°,and the angle of horizontal fracture is less than10°; The straight fracture in the Fracture surfaceis filling by calcium carbonate. The main form are irregular meshy fracture, nearly flat fractureand granular fracture; The direction of micro fractures is mainly northeast.Determine the direction of artificial fracturing fracture: the cracks about west east-northsouth direction is most development, at the same time appears the north east, north westdirection cracks. This is the same with the direction the of the core-cracks, which is broadly inline with the derection of fracture with fracturing monitoring on field.When the direction of the first fracturing overall is NNE, The secondary fracturing makecracks in NE or NEE direction, in this way the region of residual oil able to developed. Influence on affusion development of fractures is mainly for injection water generally wouldoccur Interporosity flow along the fracture, on the direction of fractures Production well watercycle is short, the moisture content rise faster or occur acceleration flooded.