| This paper made in-depth research of remaining oil distribution regularity and controlling factors of the extra low permeability reservoir of chang6 in Xiqu Oilfield,by closely combined with the actual exploration,with multidisciplinary geological theory and technology for guidance,made full use of drilling,well logging and logging display,experimenta1 analysis,the production test results and all dynamic monitoring data,etc.,combined the theoretical analysis and dynamic verification,macro contrasting and local dissecting,and the method of multifactor composite analysis.Set up the regional stratigraphic framework through fine stratigraphic division and correlation of the objective interval strata;found out the characteristics of current tectonic and the sedimentary microfacies distribution;Summarizes the characteristics of reservoir lithology and properties,and counted its development status of interlayer insulation,analysized the reservoir heterogeneity and seepage characteristics comprehensively;calculated the oil reserves of chang6 reservoir too.Evaluated comprehensively its development effecting from the present situation,the injection-production corresponding rate,water cut changes and reserves producing degree;analysized respectively the controlling factors that sedimentary rhythm,local micro-structure and interlayer of the oil and water remigration in the waterflooding process based on the above result;find out the rule of oil-water movement and reservoir water flooding condition currently.Analysized qualitatively the possible enrichment area of residual oil;calculated quantitatively the residual oil saturation and its distribution characteristics.Discussed detailedly the controlling and influencing factors of residual oil distribution from the sedimentary,structure,heterogeneity and injection-production system,summarized the distribution regularity of residual oil,and foretasted its advantageous area.Study results show that the chang6 reservoirs is the low porosity and ultra low permeability structure-lithologic reservoir,the low-amplitude structures are developed widely the oil-layer is lenticular and multi-layer type distribution,and relative developmenting in local high structure;reserves distributed mainly in chang 62-1 and chang 61-3 layers on the longitudinal and northern block on the plane.Due to poor injection-production correspondence,injection-production pressure unbalanced,different stress level in space,adding the widely developed interlayer and mutil-mining and mixed injection;leading to dash water absorption,single output,water flooding control degree and sweep efficiency is low,reserves producing degree is small,production decline is fast,recovery degree is low and remaining reserves is big.The remaining oil distributed still mainly in northern block and chang 62-1 and chang 61-3 layer.Local changes in the roof surface of the reservoir not only control the direction of the advantage of injection water,but also increasing the redistribution of oil-water in local space.The interlining of the interconnection between the well is not only modified the reservoir property,but also has certain restriction effect.Injected water extremely easily along the effective channels which is between the parts of connected interlayer and relatively good property and relatively low structure seeped displacement preferentially,and the some zone that flank of main body facies,strong heterogeneity and micro high structure is usually the remaining oil enriched relatively in the process of water injection development of ultra low permeability reservoir.It is the remaining oil enrichment region that has imperfectly injection-production system and low natural energy and lowly reserves producing scale,especially in the early stages of development.Currently,the remaining oil distribution of chang6 reservoir is largely affected by injection-production system;however,the remaining oil distribution is mainly comprehensive controled by sedimentary microfacies,micro structures and reservoir heterogeneity in some wellblock where injection-production system is perfect. |
