On the basis of stratigraphic correlation, the characteristics of reservoir rocks of the Kangcun Formation, origin, types and features of sand bodies, pore types and textures of reservoir rocks and distribution characteristics of the reservoir in the Dawanqi oilfield have been intensively studies. The Kangcun Formation of the Dawan oilfield belongs to a delta sedimentary system formed when a river with a low meandering curvature enters a very shallow lake, which determines that its main reservoir sand bodies are of deltaic sand body type. The sand bodies may be subdivided into delta plain distributary channel sand bodies, delta-front subaqueous distributary channel sand bodies and river mouth bar sand bodies. The main reservoir space types are residual primary intergranular pores and next come intergranular solution pores and micropores. The distributary channel sand bodies consist predominantly of medium and coarse sandstone, pebbly sandstone and fine sandstone, which are characterized by development of large pores and throats, high porosity and permeability and good accumulation properties, and the river mouth bar sand bodies are composed chiefly of fine sandstone and siltstone with a relatively fine grain size, a relatively low porosity, a high permeability and a relatively small pore diameter. Vertically, sand bodies are better developed in the middle and lower parts of the Kangcun Formation and less developed in the upper part, where arenaceous beds and argillaceous beds alternate with each other but generally the sandstone content is not high, commonly ranging from 15 to 30%. Laterally, due to the influence of factors such as provenance, the Kangcun Formation reservoir is thick in the northeast and thin in the northwest. The general distribution pattern of the physical properties of the reservoir is that:the porosity decreases from northeast to southwest and the permeability becomes poor from southeast to northwest.
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