Sedimentary Facies Analysis And Hydrocarbon Distributio N In Western District Of N3W Area Of Saertu Oil Field

As one of the main fields in daqing, after years of high-speed water flooding produ ction, Saertu oil field is in matural production phase with extreme high water cut. It is a key problem to locate the distribution of remaining oil in order to improve recovery and maitain ouput volume. Research shows that the reservoir is mainly distributary channel sandbody and front sheetlike sand body. After years of development, there is a large diff erence in the various types of sand body output and remaining oil distribution. In this pa per a new method was induced to quantify the original hydrocarbon in place and remaining oil volumes in different microfacies sandbodies based on reservoir modeling and reservoir stimulation, which may give some advice for the reservoir adjustment.Located in the west of the northern anticline Saertu oilfield, tectonicly it is relatively gentle, with a stratigraphic dip of2-30°, and only one normal fault iis found in the southwestern corner of the study area.Three sets of sandbodies Sa,Pu,Gao, were developed in the reservoir in early stage of Middle Cretaceous middle as a part of a large river-delta depositional in northern songliao basin. Mainly reservoir of Sa,Pu were put into production from1964,three main adjustment has under gone,and seven sets of well nets were used in the water flooding development and part of the reservoir is polymer flooded.Taking usage of cores and well logging data, facies were analysized for Sa,Pu,Gao reservoir sedimentary period. Five main micro-facies were recognized, including water distributary channel, underwater distributary channel, fine sand, the main sheet sand and subordination sheet sand. With very gentle slope, open and shallow water, wave energy is weak relative to the energy of the river, which made distributary channel well deposited in the plain and front of delta. Facies statistics of321Wells in the78deposition unit, the reservoir was grouped into Ⅰ, Ⅱ, Ⅲ, Ⅳ four types of reservoir architecture, in which type Ⅰ,Ⅱ with a high ratio of distributary channel and Ⅲ,Ⅳ is mainly consisting of sheet like sand bodies of delta front.In the similar hydrocarbon accumulation conditions, oil distribution in the same set of sandbody is mainly controlled by reservoirs architecture and heterogeneity. Oil volume was calculated for the microfacies and layers based on geologic model, which give a clue for the controlling factors on oil accumulation in the reservoir. It shows that the main river channel and main sheet sand is the main area for oil to accumulate, among which76.52%of the volume is in river channel control, and4.19%in fine sand, and13.97%in the main sheet sand,5.32%in the subordination sheet sand. In typical layers of type Ⅰ and Ⅱ, volumes in river channel is94.17%and75.7%respectively, while in typical layers of Ⅲ, IV the number is63.68%and52.81%.Finally, based on the reservoir numerical simulation, select four different time points in the geological model:second oil production (1993,1997) and three mining stage (2007,2010) of oil saturation, and count the different time points remaining reserves that controlled by the sedimentary facies in fine geologic model, analyzes remaining oil potential characteristics in different microfacies, analyze recovery of different the facies from four typical reservoir architecture, finaly find out the main object for the the reservoir adjustment.1. Remaining oil potential analysis of different microfacies:recovery percentage of1993,1997are belong to the secondary explioitation, in which the river reserves oil displacement efficiency is highst than other microfacies, to43.13%. since2007, recovery percentage is at the Tertiary Oil Recovery section, in this stage,river recovery degree slow rise less than50%, the main sheet sand and subordination sheet sand recovery degree increase quickly of40%or so, which shows that in the late stage of Tertiary Oil Recovery, the displacement efficiency is higher in two kinds of sheet sand.2. Remaining oil potential features of typical layer:from the recovery degree of typical layers, layer I have a high recovery degree:river is59.17%, fine sand as high as78.39%, shows that the remaining oil potential is general of this kind layer. In second layer, river and the subordination sheet sand recovery degree both about35%, subordination sheet sand a little higher than river channel sand, and the main sheet sand at less than20%, and the recovery degree is lower than layer Ⅰ, and the phase constitute complexer, so the remaining oil potential bigger, layers Ⅲ are main sheet sand and subordination sheet sand, its recovery degree are less than30%, and the remaining oil potential focus mainly on main sheet sand, layer Ⅳ because of its own reserves smaller, and this layer of remaining oil potential is poorer.