Reservoir Architecture And Remaining Oil Distribution Analysis Of Delta Front

Hai26block is located at the south of Liaohe faulted’s central uplift, which is the main block of Hai wai he oil field, the main oil bearing development series is Neogene Dongying formation (Ed1、Ed2). Through30-years of development, the research area has stepped into the exploiting stage of high water cut(92%)and low recovery of reservoir(19%).The distribution of remaining oil becomes increasingly complex, and a appreciable amount of remaining oil is distributed in long-term water flooding oil deposit withong different scales and forms. In order to enhance the oil recovery efficiency,detailed study on remaining oil distribution and controlling factors of which at middle-later stage of water flooding is urgently developed.In this paper, the factors which control the formation and distribution of residual oil are studied accurately by anatomizing reservoir architecture based on delta front depositional characteristics and conceptual models, reservoir geology, well logging geology,development geology and correlative theories.In accordance with the primary marker beds of contrast in region, stratigraphic classification and correlation of study area were devised.At the top of d2,"Jagged" low resistance mudstone was identified,which is boundaries of d1and d2’s;"Folder nose" low resistance mudstone, at the top of d3,which is boundaries of d2and d3, lithology is composition of gray green mudstone with siltstone and pelitic siltstone."V" mudstone, at the top of d2I, lithology is gray green mudstone, apparent resistivity curves and curves of both sensors "V"-shaped;"W"-shaped mudstone, at the bottom of d2Ⅱ,which is boundaries of62Ⅱ and d2Ⅲ, lithology is composition of gray green mudstone with thin pelitic siltstone. Based on this, the generally developmental single sand body in the work area are selected to complete the stratigraphic correlation skeleton profile of the single sand bodies.Based on the analysis of sedimentary facies symbol such as lithology, texture, sedimentary structure and paleontology,the result indicated that reservoir of Hai26-section is mainly delta front depositional system,microfacies can be divided into subaqueous distributary channel, estuary dams, interdistributary channel, distal bar,front sheet sand and lake mud. The channel frequently crisscrossed with strong water dynamic and consistent extending direction.The integrated application of different scales of geological and geophysical data carried out on the reservoir layer, interlayer, flat and micro-heterogeneity analysis and evaluation. Studies have shown that the degree of innerbeded heterogeneity is strong while the in-layer heterogeneity and alreal heterogeneity of which is medium-low. The third and fourth-order surfaces of subaqueous distributary channel in research area systemically analysed according to the theory of Miall hierarchy interfaces. Compared with Miall six-order surfaces, the top and bottom boundary surfaces of single channel were defined as the fourth-order and the interlayer of the subaqueous distributary channel bodies were defined as the third-order surfaces. Guided by the concept of "model fitting, dynamic validation", the subaqueous distributary channel sand reservoir of H26-section was analyzed to examine the spatial distribution and identification marks of the architectures within the reservoir. Results indicated that the single channel sand body can be identified by such marks as sand elevation difference between wells,argillaceous sedimentary break section and difference of channel sand thickness;5superimposed patterns of complex sand bodies were summaried including vertically superimposing,laterally lapped,lapped crossed superimposing and isolated distribution.The factors influencing the formation and distribution of remain oil was reviewed with5respects as faults, reservoir engineering, sedimentary rhythms,micro tectonic and spatial contact of sand bodies.The reservoir architecture research and the production of dynamic data was combined for carrying out the study on the relation between reservoir architecture and remaining oil formation and distribution, which suggested that the spatial contacted of the architecture elements is an important controlling factor for the remain oil formation.Summaried2types of spatial contact style of single sand body as adjacent and separate which including8contacted styles:HH.HL,LL&HHH,HLH,LHL,HLL,LLL(H respects flow units with good physical property as L respects poor one). Style of LH has negatiave impact on water injection to some extent,take channel contacted with overbank sand for example,the injected water is difficult flowed into overbank sand which in poor physical property thus cause the accumulation of remaining oil; The water-absorbing and fluid folwing capacity of style LL is not well which indicated that injected water can hardly to flow towards to any architecture element; Because there is a architecture element of low permeability between H and H of style HLH,the injected water of H cannot flowed towards another H;style LHL,the injected water of H is difficult flow into the2sides of L.Further pointed out that there are2types of remain oil distribution,inlaid and isolate in H26-section,the spatial contact parts of single sandbody always be the remaining oil enriching area due to difficult water injection and poor physical property.