Water-flooded Layer Logging Evaluation Of Ultra-high Water Cut Reservoir Of Neogene In Yang-erzhuang Oilfield,Dagang Oil Province

Waterflood development is an important means of increasing and stabilizing oil production in most oilfield of China,most of which have entered high or even extra-high water cut stage.In these oilfields,seriously flooded oil-reservoirs and complex residual oil distribution lead to increasingly prominent production conflicts.It is of great significance to carry out logging evaluation research on water-flooded layers in extra-high water cut reservoirs for the further tapping of remaining oil.First of all,take neogene ultra-high water cut reservoir in Yang-Erzhuang oilfield of Dagang oilfield as the main object,logging,core analysis and relevant geologic data are used to establish the relationships among lithology,physical property,electric property and hydrocarbon-bearing to recalculate the reservoir parameters.In the meantime,combined with data of core CT scan and production performance,it is analyzed that the changes of characteristics in lithology,physical properties,pore structure and oil-bearing after waterflooding,and the qualitative identification methods for water-flooded zones applicable to this area are summarized.Then,seepage discrepancy was revealed based on the six flow units due to strong reservoir heterogeneity.And the water cut model of various flow units is set up respectively to realize the fine evaluation of flooding levels.Finally,logging interpretation results,production dynamics,isotopic tracer data and relevant geologic data are used to investigate the influencing factors and laws of waterflooding in the study area.The main conclusions of this thesis are listed as follows:(1)After prolonged waterflood development in Yang-Erzhuang oilfield,the lithology,physical properties,and pore structure after waterflooding not simply tends to be getting better,but instead present bidirectional evolutionary features.The final evolutionary state of reservoir is controlled by the combined effects of water-drive strength,reservoir sensitivity,wettability,clay minerals type and content.(2)Based on reservoir physical properties changes after waterflooding,there are several methods,can be used to qualitatively identify water-flooded layer,such as the migration of spontaneous potential,the comparison of transverse resistivity curves,contrastive analysis of neighboring well on resistivity,the correspondence of resistivity curve and self-potential curve and so on.(3)Considering the strong heterogeneity of target strata,six kinds of flow units were identified,and the seepage discrepancy of six flow units was revealed by numerical simulation and relative permeability curves.The water cut model is set up respectively on the basis of flow unit division,and fine evaluation of flooding levels is realized.(4)Major reservoirs in study area have been watered-out seriously,and the distribution of remaining oil presents a highly disperse state.In the plane,the remaining oil distribution is affected by sedimentary facies,structure,and oil recovery mode.Remaining oil is relatively enriched in the high point of structures close to faults,the incompletion areas of injection-production pattern,and the facies with relatively poor physical properties(including non major facies and the thin reservoirs or sand edge of major facies).In vertical section,the remaining oil distribution is controlled by the deposition rhythm,configuration interface,physical property changes and so on.And there are large differences in waterflooding pattern,which leads to complex residual oil distribution.