Description Of Chang 6 Reservoir In Nan 212 Well Block In Ordos Basin

The Chang 6 reservoir group of the Upper Triassic Yanchang Formation in the Wellblock N212 is a typical low porosity and ultra-low permeability reservoir.It has great potential for exploration and development and is one of the main oil layers in the study area.However,due to the complex geological conditions in the study area,the reservoir characteristics are not clear,the stable production rate is low,and the development is difficult.Therefore,strengthening the fine description of Chang 6 reservoir in the study area,studying the sedimentary facies characteristics and reservoir distribution characteristics of each layer of Chang 6,can provide an important theoretical basis for improving oil and gas recovery and later exploration and development.In this study,logging data,core description data of coring wells and a large number of analysis and test data were used to conduct fine stratigraphic division and comparison research,structural characteristics research,sedimentary facies and reservoir characteristics research,secondary interpretation of logging data,reservoir distribution characteristics and main control factors and other geological characteristics of each layer of Chang 6 in the study area.Fine research,establish a logging interpretation model of reservoir parameters suitable for the area,and finally use petrel software to establish a structural model,lithofacies model and attribute model that can accurately characterize the three-dimensional spatial structure of the reservoir in the study area.The study shows that the Chang 6 reservoir group in the study area is delta plain deposition,and the sedimentary microfacies are mainly distributary channel microfacies and interchannel microfacies.The sand body connectivity is better along the source direction,and the sand body connectivity is relatively poor in the vertical source direction.The sandstone type of Chang 6 reservoir is mainly feldspar sandstone,followed by a small amount of lithic feldspar sandstone;the sorting was mainly good,accounting for 85.8 %;the rounding is mainly sub-angular,accounting for 97.5 %;the compositional maturity is low and the structural maturity is high.The interstitial material of Chang 6 reservoir in the study area is mainly cement,and the content of matrix is less.Cements mainly develop carbonate cements,silicate cements and clay minerals.Carbonate cements are dominated by calcite,with a calcite content of 5.2 %.Silicate cements are dominated by laumontite,with a content of 5.3 %.Clay minerals are dominated by chlorite,followed by illite,with contents of 3.5 % and 1.2 %,respectively..The reservoir belongs to low porosity and ultra-low permeability reservoir.Statistical comparison of the changes before and after the second interpretation of each well in each sub-layer of Chang 6,on the whole,after the second interpretation,the number of poor oil layers decreased,oil layers,oil-water layers and oil-bearing water layers increased,of which oil layers increased by 9 %,oil-water layers increased by 7 %,oil-bearing water layers increased by 14 %,water layers increased by 3 %,and poor oil layers decreased by 31 %.The Chang 6 reservoir in the study area is mainly distributed in the sand body with good connectivity and some high parts of the structure.The oil and water are often stored together,which belongs to the typical structural-lithologic reservoir.The structural model,lithofacies model and attribute model established by petrel software are in good agreement with geological research.