| The XingⅥgroup of Block Du 84 in Shuguang Oilfield is a thick-layered block-edge,bottom-water ultra-heavy oil reservoir.The steam oil production was implemented in the early stage of the reservoir,and the steam-assisted gravity drainage（SAGD）development mode was changed in the later stage to realize high-speed and high-efficiency reservoirs.After more than 20 years of high-speed mining of the reservoir,the stage recovery rate reached 43.1%,and it has entered the later stage of development,mainly in tapping the remaining oil.In order to further clarify the potential of remaining oil distribution,this article comprehensively adopts multidisciplinary basic theories and research methods such as sedimentary petrology,high-resolution sequence stratigraphy,geophysical logging,and reservoir engineering,and uses cores,logging,and development trends.Data that carried out research on fine geological characteristics,established a three-dimensional geological model of the reservoir,characterized the distribution law of remaining oil,analyzed the adaptability of the development of bottom water reservoirs,and formulated countermeasures for tapping the remaining oil potential of the reservoir.The main research results have the following four points:1.The stratum of the XingⅥgroup in Block Du 84 is divided into two medium-term and eight short-term base-level cycles,of which the medium-term base-level cycles correspond to two sandstone groups,and the short-term base-level cycles correspond to eight small layers.The total thickness of the sand body of XingⅥgroup is 112.2m,and the stratum gradually becomes thinner from northeast to southwest as a whole,and the thickness of each small layer from bottom to top becomes thinner layer by layer.Affected by strata uplifting and denudation,each small layer has been denuded to different extents at the edge of the block,and the two upper layers,Xing VI1-1 and Xing VI1-2,are almost completely ablated.2.The XingⅥgroup is a gravity flow turbidite fan deposition,which mainly develops the fan root main channel,the side edge of the main channel,the discriminating channel in the fan,the side edge of the braided channel,and the fan-side matting sand and the shallow lake mud six types of sedimentary microfacies.On the whole,the microfacies of the main channel of the fan root and the microfacies of the braided channel in the fan are the most developed.From the bottom to the top,the scale of the fan roots is shrinking,and the scales of the fan and the fan ends are expanding.3.Bottom water is widely developed in oil reservoirs,and the buried depth of the oil-water interface is-810m～-890m.The oil-water transition zone with a thickness of 1.5m to 32.6 is developed in most areas,with an average thickness of 12.7m.4.Residual oil research results show that the reservoirs are used more evenly.The bottom-avoiding oil layers and oil-water transition zones below the current wells are the main target intervals for the remaining oil potential.By implementing steam wells in horizontal wells and carrying out the SAGD conversion mode at the later stage of the wells,the bottom unused reservoir can be effectively used. |
