The Study On Architecture Analysis And Remaining Oil Distribution Patterns Of Meandering River Reservoir

Many major oilfields in China including Gudao oilfield which were discovered in 1960s and 1970s, have been at high water-cut stage, but oil recovery is comparatively low, about 30 percent. And prolific remaining oil with different scale and form distributes in the long term water flooded reservoirs. The remaining oil generally distributed with accumulation in certain areas, controlled by the reservoir architecture that mainly is the lateral accretion sandwich in the point bar, so the study of reservoir architecture and the remaining oil distribution pattern controlled by architecture are very significant. In this paper, taking the Guantao formation of Gudao oilfield as a case, using the method of scale analysis and model fitting, the architecture of the meandering river reservoir is precisely anatomized, the systemic analyzing method of fluvial reservoir inner architecture is established, and the remaining oil distribution patterns controlled by the different hierarchy architecture are summarized, which will help to study the characteristics of the simillar reservoir in the other oil fields. Not only is the study significant to the remaining oil forecasting of the middle and later production stage, but also it is important for the theory development of reservoir geology.With the knowledge of high-resolution sequence stratigraphy, taking many factors into account, such as isochronous slice, degradation of stream, sand bodies stacking and lateral alternation of micro-facies, an accurate sequence frame was established. On the basis of high-resolution stratigraphic correlation, single layer and oil sand body are correlated within this frame, taking modern deposition and outcrop study as a guidance, four architecture hierarchies, composite channel, single channels, point bars and lateral accretion sandbody are identified, The result indicates that No.3 and No.4 sand group in upper Guantao Formation of Gangdao oilfield are dominated by meandering river deposition, including three types of sand bodies,single channel, anabranched channel and flaky sand body, and each of them has different characteristics of facies variation laterally.In the stacked channel sand, abandoned channel is identified by adopting the method of relative depth of sand top, the scale of single channel sand is recognized by using log data of dense spacing wells. Then, guided by the spatial combination model of the single channel, the four kinds of single channel boundary is reasonably combined using " adjacent is similar "rule. According to Satellite pictures of meander river, Yueliang Pao, Nenjiang River, the relation between the length of point bar and bankfull width is calculated, which is first presented in the world. According to the shape of abandoned channel, the trend of sand body thickness and vertical sequence, the point bar is recognized. Based on empirical formula, horizontal well, numerical simulation of concept model and data of dense spacing wells, scale and dip strike of lateral accretion sandbody are ascertained, reservoir architecture of the point bar in key well area is anatomized, and three-dimensional reservoir architecture model is set up precisely.On the basis of architecture anatomy and dynamic data analysis, remaining oil distribution patterns controlled by different hierarchy architecture units, stacked channel, single channel and inner architecture of point bar, are summarized. With the study of numerical reservoir simulation of practical and conceptual model, muddy lateral accretion sandwich, as a controlling factor of remaining oil distribution, is analyzed in detail.