Analysis On Reservoir Hierarchical Structure And Remaining Oil Pattern In The West Part Of The 7^th Block In Gudong Oilfield

In the middle-later development period of oilfield, a large number of oil and gas has been produced, with a considerable number left in the reservoir. Most of the main oilfields exploited in the 1960s and 1970s in our country have been in high or extra-high water cut and production decline stages. Recovery is about 34%.But after long-term waterflooding, bulks of residual oil still distributes in the reservoir in different scales and different forms.A lot of influential factors can be concluded for the distribution of the remaining oil, roughly divided into two types: geofactor and development engineering factor. Heterogeneity is the main geofactor, which is composed of reservoir heterogeneity, microtectonics and fluid heterogeneity. The development engineering factors consist of well pattern, injection-production factor and so on.Reservoir heterogeneity is an important factor influencing the distribution of the residual oil. We have studied the macro- sand body morphology and the microtectonics many times and benefited from these techniques. Then with the development of gas-oil exploitation, the remaining oil inside the sandbody becomes the target, therefore, inner anisotropy in this sandbody(like the interface between the genetic units inside the compounding sand body, the barrier and the interbed etc.) and its impacts on distribution of the residual oil seem more and more important. However, the researches about internal configuration of the sand (including the geometric shape,size,direction,distribution and overriding correlation) are few ,we should do more to improve it.River facies is the main reservoir containing oil in most oilfields in our country. The upper of Guantao formation in Gudong oilfield is river facies reservoir. The formation above Ng53 is meandering river deposit while the parts below is anastomosed stream deposit. Until recently, Meticulous reservoir description has been taken several times on upper of Guantao formation in the west 7th block of Gudong oilfield, and initiative effects on development of the field have been brought out, but systematic reservoir structure research hasn't been carried out yet. This project analyzes the internal structure of river facies reservoir anatomically, developing a method interpreting and predicting the internal structure of the reservoir ,with a case study of Guantao formation, the west 7th block of Gudong oilfield .Its directory effect on the fine investigation of other similar oil fields not only helps to forecast the distribution of the remaining oil at the later stage of the development, but also contributes to the development of the theory of reservoir geology.