Study On Oil-water Distribution Law Of Ordovician Fracture-cavity Carbonate Reservoir In Lungu Oilfield

The Ordovician reservoir in the Lungu oilfield is a typical fracture-cavity carbonate reservoir in ancient buried mountains.Yijianfang formation and Yingshan formation is the main oil-bearing series.After nearly fifteen years of development,the oilfield is currently in the stage of high-water production.Reservoir heterogeneity and complex oil-water distribution are the most important factors restricting reservoir development.In order to achieve efficient and sustainable development of oilfield,the paper has carried on the study of oil and water distribution in the study areas.Based on the production test data of each well,this paper analyzed the characteristics of water production,the characteristics of water rise and the source of water,and divided the four water types.By analyzing the relationship between the ion concentration and the salinity of the stratified water and the plane distribution characteristics of the localized combination parameters,four oil and gas accumulation zones were identified: the LG15 well area,the LG7 well area,the LG2 well area and the LG100 well area.The dynamic characteristics of formation water quality during reservoir development are analyzed.By identifying the longitudinal distribution of the oil and water layers in the single well profile and combining the reservoir space combination,this paper established five fluid distribution geologic models.Taking the typical fractured cavities as the research object,the original oil-water interface was calculated by means of production analysis,pressure gradient method and original oil pressure-density formula calculation method.It was concluded that different fractured cavities had different oil and gas systems.There is no uniform oil and water interface,but it overall shows from south to north gradually uplift characteristics,and the overall trend of the buried hill.Unconformity,tectonic fracture,tectonic traps,multi-stage reservoir formation and residual hill gully are the main factors controlling oil and water distribution.