The Study Of Remaining Oil Distribution For Thick Oil Layer’ High Water-Cut Stage In North-Three-West Western Area Of Saertu Oil Field

Main contents of development and adjustment of oil field in high water cut stage is "understanding and exploitation of remaining oil". And there are many ways to study the formation and distribution of remaining oil, which research the remaining the oil from different aspects and different angles. But a variety of methods have their own limitations of application, which also show the difficulty and importance of the remaining oil in the formation and distribution study.The aimed district is located in the western end of the anticline in the northern part of the Saertu Oil Field. And clastic develop in the reservoirs which deposited in the huge river—delta depositional system, where on vertical, three sets of oil layer—Saertu, Putaohua and Gaotaizi sediment. In the area, the average number of single well drilled single sand in pure reservoirs is74.1. The thickness of sandstone is98.78m, effective thickness is55.68m, and thick oil layers commonly develop in the district. Since the main reservoirs of Saertu, putaohua were put into development in1964, the area has undergone three major adjustments. Currently there are seven sets of well network. By the end of December2009, the region’s cumulative water injection and cumulative oil production had been up to24738.41×104m3and4583.61×104t separately. And the recovery level of the area is34.99%, the oil production rate is0.61%. The area has a cumulative injection-production ratio of1.02, year-injection-production ratio of0.94, composite water cut of92.04%and the formation pressure10.76MPa. To sum up, the district has entered the high water cut stage.Stepping into the late development of high water cut stage, the development contradictions of Saertu Oil Field are as follows:"integrated with high moisture content","high degree of recovery","high oil production rate","a low reserve-production ratio","low recovery". But there are also a large quantities of oil can’t be recovered in the reseriovrs. And because the large area of the reservoir plane has been flooded influnced by injecting water and the distribution of remaining oil is extremely complecated, analysis of the remaining oil becomes difficult. Besides, the development of the target of this area has turned from the oil layers sets in early stage to layer the mid, even to single-layer, single sand body now. And the principal contradiction of exploitation convert from the inter-layer contradiction to contradiction of the inner-layer even to the building structure within the sand body. Therefore, in this paper the author combinte the static data and dynamic data, qualitative and quantitative method, with the application of geological modeling, in the way of dynamic analysis and numerical reservoir simulation technology, and conclude distribution characteristics of remaining oil of thick reservoir section in the high water cut. The specific main several researches are as follows:1Based on the facies analysis, the distridution of sandbodies is maken clear and the geological model is also set up.Through the facies study of the reservoirs,the influence to the formation and distribution of remaining oil from the difference of reservoirs structures is maken clear of. And we set up the geologic model to characterize the petroleum pool feature and supply the foundation to the numerical simulation.2Study the distribution of remaining oil qualificatively by means of dynamical analysis, from the angle of the forming factors of remaining oil, based on the results of fine geological discription and according to the statistical results of inspection wells and logging flooded layers data, the remaining oil distribution characteristics of majior reserveiors are studied by means of dynamical analysis.3Discribbing the motion law of oil and water quantitatively and the distribution of oil in different stages. On basis of fruit of dynamical analysis,with the numerical simulation of the oil reservoirs, we play back the production process and the distribution of oil in different stages. The distribution of remaining oil in typical layers was discribed quantitatively and potential place of remaining oil was also figured out.From the above, we include the main types, main controls and distribution of remaining oil in the area in high water cut stage. Based on the dynamical analysis, the main types of remaining oil are in included as follows:well pattern imbalance type, voidage-injection imbalance type, nook of oil sandbody type,retained region type and intraformational unwatered out reservoirs type. Then combining the controls of remaining oil, with the fruit of geological model, the characteristics of remaining oil are as follows:(1) in the area between the two adjacent injection well or production well the remaining oil zone of enrichment.(2) in the area where the facies types are complicated, the low permeability layers are the main zone of enrichment.(3) in the area where the well pattern are not imbalenced.(4) relatively poor oil reserveoirs.