Geological Characteristics and Production Performance of a Sandstone-Fractured Basement Composite Reservoir

Abstract

A definition is given of the sandstone-fractured basement composite reservoir and its origin is analyzed at first; then take the SR oilfield as a case to describe its geological characteristics in terms of sand distribution, structural characteristics, oil-water contact, barrier distribution, and development degree of basement fractures; finally analyze the challenges of developing this type of reservoir and propose reasonable development strategy. The sandstone-fractured basement composite reservoir in Bongor Basin has a large thickness of sandstone but a limited horizontal distribution, a large reservoir structural relief, a unified oil-water system and the more developed fractures on the top of the basement. The challenges to face in the development include weak natural energy, high strata dip, extremely strong heterogeneity in basement reservoir, lack of stable barriers between sandstone and basement. This type of reservoirs requires prompt energy support through separated layer water flooding. An oil well should produce at a specific proration relative to the degree of fracture development, and at the same time, it is necessary to prevent the rapid breakthrough of injected water along the erosion surface of the basement.