Abstract: Study on dehydration pattern in dense oil with high wa- ter content and the matching techniques was made in the de- velopment stage when the dense oil development is at the stage of high water content,with difficulty to be dehydrated and high energy consumption.The designed four-phase (oil,gas,water and sand) separator of HNS type can be used to reach less than 3.0% water content in crude oil for the dense oil with 85% about water content and less than 1000 mg/L oil content in sewage.The device is of compact conformation,large treatment amount,reliable operation, high availability,high separation effect and high automation, thus greatly simplifying the flow of dehydration,gathering and treatment.