The Influential Factors Analysis Of Oil-water Distribution In Continental Litho-stratigraphic Reservoir

Jiyuan Area is located in two tectonic units: Shanbei slope and Tianhuan depression. Chang4+52reservoir is one of main oil-producing formations in the Yanchang Group of Upper Triassic. According to the present situation of the complex oil-water distribution,the study choses two comparative work areas named Baoziwan and Hujianshan for anatomy and study,calculates the development scale of sand body,and analysizes the structure of it.And then,the study takes systematic research on the sedimentary characteristics, reservoir petrology characteristics, diagenesis and pore structure.Based on this,the paper analysize the influential factors of the complex oil-water distribution present.The following achievements were obtained by the research:Chang4+52reservoir in the area belongs to the meandering river delta sedimentary system.And it mainly belongs to the delta front subfacies. It has the typical sedimentary characteristics of shallow water dalta. The underwater distributary channel microfacies developed. And the mouth bar microfacies developed little. Hujianshan area is mainly controlled by the northeast provenance. The scale of sand body developed in4+523stage is the largest,and decreased rapidly in the late. Its main structural model of sandbody is the II type of low-energy washing and sand-shale contacting. So the complexity of oil-water distribution is higher. Baoziwan area is controlled by both northwest and northeast provenance. The scale of sand body developed is relatively stable. The scale of sand body developed in4+522stage is the largest, followed by4+523stage.That in4+521stage is the worst. It mainly includes two types of structural model of sandbody: Ⅰ type of high-energy washing and sand-sand contacting,and Ⅱ type of low-energy washing and sand-shale contacting. As the result,the complexity of oil-water distribution is lower.The rock type of reservoir is brown,grey or light grey feldspar and syrosem feldspar fine sandstone and siltite.The content of quartz is low. Alkali feldspar, biotite and kaolinite are the main minerals that affect the reservoir pore type and pore structure.Alkali feldspar is the material basis of high quality reservoir development. Kaolinite’s precipitation in situ can make the reservoir property become good or bad. Biotite’s expansion could destroy pore structure and reduce the reservoir permeability greatly. The area enriched biotite relatively always has higher degree of oil-water distribution complexity.Both of the two areas’ pore structure is not well.The two main pore structure types are ⅡB and ⅢA.The pore structure is divided into four categories according to actual situation. ⅡA—ⅡB low displacement pressure tupe and ⅡB middle displacement pressure—ⅢA low displacement pressure tupe are the two main types.The diagenetic stage of Chang4+52reservoirs still remain between the B phase of early diagenesis and A phase of middle diagenesis.In addition to the traditional types of diagenesis,abmormal diagenesis,such as feldspar large-scale dissolution, biotite’s strong deformation and swell,influenced on the reservoir’s pore structure evolution significantly.Through the study, the diagenetic facies can be divided into four types.Among them,the kaolinite cementation-feldspar dissolution facies is dominant. The pore structure type in the area of it develops is better relatively. But the reservoirs still have strong heterogeneity and oil-water distribution complexity.