In this paper,microscopic pore structure and movable fluid saturation characteristics of Chang 6 ultra-low permeability reservoir in Ansai Oilfield are studied by means of casting thin slices,scanning electron microscopy,constant pressure mercury intrusion,nuclear magnetic resonance,and real sandstone microscopic model.The results show that the content of intergranular pores has a good contribution to the saturation of the movable fluid,while the content of the dissolved pores is unfavorable to the occurrence of the movable fluid;throat size,pore throat ratio,sorting coefficient have a great influence on mobile fluid saturation,otherwise reservoir physical properties,porosity,pore radius do less.Real sandstone micro-displacement experiment shows that the displacement path and oil displacement efficiency of the samples with different physical properties are obviously different.The samples with permeability greater than 1.0× 10-3 μm2 are of pores-intergranular pore type and the type of displacement is net-uniform displacement with final flooding efficiency 69.3％.The samples with permeability from 0.5×10-3 to 1.0×10-3 μm2,the type of pores are dissolved pores-intergranular pore type,the displacement type is finger-net displacement with displacement efficiency 43.8％.The samples with permeability less than 0.5 ×10-3 μm-2 have micropore-dissolution pore type and displacement type are fingerdisplacement with final displacement efficiency 32.9％.

The conventional thin sections,casting thin sections,cathodoluminescence and scanning electron microscopy (SEM) and X ray diffraction experiment were used to study the reservoir diagenesis of Chang 7 tight iol reservoir in Heshui area,Ordos Basin,and to identifyits diagenetic facies types and establish the criteria for the classification of well logging response,while "dominant facies" method was used to predict the distribution of diagenetic facies.Research shows that the 7 diagenesis of the reservoir development district mainly includes compaction,cementation and dissolution.The occupation of compaction in the primary pores worsens the reservoir property which is in turn influenced by,while the dissolution of secondary pores favors the reservoir physical properties.The study area can be divided into strong corrosion dissolution pore facies,weak cementation residual intergranular pore facies,clay mineral inter-crystal glue facies,carbonate cementation facies and strong compaction facies.The first two facies,dissolution pore facies and intergranular pore facies are often developed in the middle of turbidity water channel in a wide distribution.This extensive development may lead to the formation of high quality reservoirs.In contrast,the other three facies,inter-crystal glue pore facies,carbonate cementation facies and coampaction facies,are more developed on both flanks of the water channel or in the middle of the channel,with poor physical properties,poor reservoir or non-reservoir.

The real sandstone micromodel was used to perform an experiment of microscopic waterflooding in Chang-6 reservoir with low permeability in Ansai oilfield,Ordos Basin.Based on the experiment and the in-depth analysis of thin section observation,physical property,SEM,relative permeability and mercury injection data,we studied the relationship between pore structure and micro-flow characteristics of waterflooding,which provide a scientific basis for effective oil exploitation in the future.The study shows that the lithology of reservoir is mainly fine-grained arkose with low compositional maturity;there are three major pore types including resid-ual intergranular pore,dissolved pore and dual pore+fracture,of which the residual intergranular pore is dom-inant;Dissolved pore and fracture are the key factors influencing the micro-heterogeneity.The experiment results indicate that there are homogeneous,reticular and finger-like micro-flows.Pore structure is closely related with micro-flow features.Reservoirs with different pore types show different micro-flow features.Flow paths of injected water depend on the relative permeability of pores and fractures in zones with well-developed fractures.Pore structure heterogeneity and wettability are the two main factors influencing displacement efficiency.

Aim To research the physical property and influence elements of Chang 6 Formation of Yanchang in Ansai Oil Field to suppling scientific and valid foundation of exploitation. Methods A synthesis analysis by using the cast slices,scanning electron microscope,porosity and permeability analysis,log interpretation,and mercury in-jection test. Results The research presents that the lithologic character of reservoir mainly includes fine arkose. The pore space of reservoir mainly includes the primary residual intergranular pores and emposieu. Fine pore-tiny throat and medium to fine pore-microscopic throat are the main pore configuration. Mercury intrusion method shows that micro heterogeneity of pore configuration is high. The role of the microfracture in improving the petrophysical property of reservoir and connectivity of pore throat of Chang 6 sandstone reservoir is very weak thus its belongs to low permeability and porosity oil reservoir. Conclusion The characteristics of reservoir are affected by deposition and diagenesis,and underwater distributary channel is the main favorable microfacie. The physical property was declined obviously for the intensive compaction in Xingbei area. Chlorite is the mainly clay mineral,which has constructive affect in keeping the pore space of reservoir. The composition of adelforsit is intense,whose composition pore is the important pore space for Chang 6 sandstone reservoir in Xingbei region. The development degree of emposieu is one of the important parameter in finding the beneficial reservoir.

A油田C区长6油藏属于典型的低孔特低渗透率油藏,经过近7年的开发,目前存在着油层非均质性强,油井见效程度差异大,注水井吸水不均,无效注水情况严重,水驱油效果较差等问题.为了有效控制含水率上升和提高采收率,在动态分析基础上,利用数值模拟技术对开发过程中存在的主要问题进行综合分析研究,提出了合理的调整方案,为高效开发该区块提供了技术支持和决策依据.

Aim Reservoir modeling technology controlled by sedimentary facies is a practical new technology which can improve the accuracy of geological modeling greatly.The key point is to establish an accurate digital model for spatial distribution of reservoir depositional micro-facies.Furthermore,to simulate the spatial distribution patterns of reservoir parameters,laying a solid foundation for reservoir simulation and remaining oil prediction.Methods modeling for fluvial facies reservoir of the Chang 2 group,Yanchang Formation of the upper triassic in Ordos basin constrained by the temporal and spatial distribution of depositional facies is studied in this paper.On the basis of the depositional facies model constructed by toughly consideration of the facies formation and origin,based upon application of multi-parameter coordination and on different level constraint approach.Results show that reservoir model controlled by depositional facies can truly reflect heterogeneity of the reservoir characteristics and connectivity of the sand bodies.Furthermore,depositional facies controlled reservoir model can simulate underground distribution of hydrocarbon-bearing reservoir properties more accurately and precisely,at the same time,it can provide a reliable basis for oil-pool digital simulation,residual oil prediction,adjustment and exploitation.

Aim To estimate the micro and macro heterogeneity of Chang 6 reservoir in Xingbei area of Ansai oilfield,and reseach the relationship of the heterogeneity of inner layer,interlayer and horizons and hydrocarbon distribution.Methods Based on the studies of reservoir sedimentary facies,using the result of well data of cores,digital pressing achievement,logging interpretation extra.Results The result indicates that the connectivity of the horizontal sandbodies and physical properties of the reservoir are important factors that influence the hydrocarbon distribution.Reservoirs have the character of Rhythm of grain-size,heterogeneity of permeability in vertical direction,which control the distribution of hydrocarbon.The finer in grain size and the better in physical properties the reservoir has,the wider the oil-bearing properties distribute.The thicker and distributed narrowers the barriers and interlayers are,the easier the hydrocarbon migrate in vertical derection.This exerts influence on the distribution of hydrocarbon vertically too.The heterogeneities in microcosmic pore structure control the full degree of hydrocarbon flowing in reservoirs.Conclusion The result indicates that the oil-contained in Xingbei area is controlled by the anisotrope in distribution of sands,lithology of interlayer and physical property and so on.The systemic reseaches of relationship on heterogeneities of reservoir and distribution of hydrocarbon are useful for understanding and estimating oil or gas reservoir correctly,designing reasonable well pattern,compartmentalizing pay zones,making suitable plan for enhanced oil recovery.

安塞油田塞431区块是坪桥区块长2油藏开发的重要组成部分,伴随着注水开发,油藏近年来一直表现为含水上升,油量下降的开发趋势,2008年初综合含水率达到92.1%,进入了特高含水开发阶段。通过对塞431区块在不同开发条件下表现出的不同开发特征进行研究,发现保持合理注采比,并进行合理的油水井措施,是提高塞431的油井利用率的关键,也是提高最终采收率的具体手段。

In the migration process of oil and gas,the liquid's features may change because of oxidation-deterioration and thermal-deterioration and the change of the hydrodynamic force.So the information about the migration and preservation of oil and gas can be learned from the features of the liquids in formation.The results indicate that the fault can act as a passage for the liquid flowing,including oil and gas's migration and water's permeating.The flowing includes horizontal way along the formation.The permeating water obstructs the oil and gas migrating and disappearing.The Cainan North Fault and Cainan Fault in Jurassic Xishanyao Formation are not belong to one hydrodynamic force system,and the hydrodynamic force is weaker in the west of the Cainan North Fault than in other areas.The weaker hydrodynamic force is good for the hydrocarbon preservation.The Jurassic Badaowan Formation is one hydrodynamic force system in the west of the Cainan North Fault and the Cainan Fault,and the higher water salinity is good for the preservation of oil and gas.