Study On Remaining Oil Distribution Pattern For Meandering Fluvial Channels In Lasaxing Oilfield

Being developed with waterflooding for more than 4 decades, the water cut in Daqing Oilfield is extra high now, mostly greater than 90%. But the remaining oil still exists, and is in a status of scattering entirely and concentrating locally. Meanwhile, researches indicate that the remaining reserve in channel sands covers 70% of all the waterflooding reserves, and 50% of the channel sands reserve is left in the meandering fluvial channel sand reservoir. In order to develop the filed further, study of the remaining oil distribution in thick reservoir, especially in the meandering fluvial channel sand is now a burning question. The question of effective developing and the EOR problem of thick reservoir have become an important research aspect, and it’s also a critical problem concerning the long-term development of the Daqing Oilfield.The geological architecture and remaining oil distribution pattern in the meandering fluvial channels are mainly discussed in this paper. Considering the researches in Daqing Oilfield, the method of architecture analysis in meandering fluvial channel is firstly summarized, which is "Predicting with Mode and Controlling in Step". On the basis of fine geological stratigraphic correlation, the reservoir unit of SII1+2a, SII1+2b, SII 7+8a, SII 7+8b, PI2a, PI 2b in Sabei block and the reservoir unit of PI2 in Sazhong block, which are meandering fluvial channel sand, are systematically analyzed with the method. The distribution of single fluvial channel and point bar in each channel is fixed, and the architecture parameter of each point bar is also given. And a new kind of all-in-one method of modeling and numerical simulation in the meandering fluvial channel sand is prompted in the paper, and it’s been implemented in the Sazhong block, which indicates a good result.The dynamic characteristic of watered-out behavior in meandering fluvial channel sand is studied in this paper based on the core sample data of 109 well and 886 single reservoir layers in Daqing Oilfield. By the analysis of every one of the 200 single channel reservoir layers, which belong to 32 wells that are drilled after the year 2000, the geological and developing factors that determine the remaining oil distribution in the reservoir are studied systematically, and the quantitative relationship between the factors and remaining oil is given in the paper. And such factors include the following: sedimentary microfacies, contact relation in the plane, accretion interlayer, permeability rhythm and etc. The remaining oil distribution pattern in meandering fluvial channel is also given in this paper: mainly the blocking type and small-scale sandbody type in the plane. Blocking type is the major one in compound meander belt, which includes the blocking of abandoned channel, interchannel, fault, poor area of the river edge, interface between channels, crevasse and etc.; and distribution pattern among meander bars is the type of inter-point-bar type while the one in the bar is the type of water injected perpendicular to the interlayer tendency. The remaining oil distribution pattern in the layer could be classified as the type of poor injecting-production relation locally and the type of poor physical property region in the layer according to the origin of remaining oil, while be classified as interlayer-controlling and permeability-rhythm-controlling type according to the existing form of the remaining oil.