The Research Of The Oil And Gas Reservoir Identification Characteristics Of Yan-chang Tormation In Zhiluo Oilfield–taking C2, C8 Reservoir As An Example

Fu xian exploration area of Zhi luo oilfield is located in the southeast of shan bei slope in the Ordos basin.Most of reservoirs are shallow oil and gas reservoir.Oil and gas are all distributed in the reservoir which is low porosity and permeability.Resistivity of some gas reservoir is close to oil reservoir.Based on the existing well logging data,the logging response characteristic of oil reservoir is weak.There are some difficulties in the identification of oil layer and gas layer.The paper is based on the petroleum geology,sedimentary petrology,geophysical well logging theory and experiment testing,etc.According to the principle of geological conditions restraining logging,core scale logging,based on the geological data,core data,well logging data and dynamic test data,firstly,do some research about the geological characteristics of reservoir in the study area,secondly complete the study of four-property relationship and establishing the corresponding well logging interpretation models,then According to demestic and overseas research status of oil and gas layer,we study the identification methods of oil layer and gas layer,and using the method of comprehensive identification of oil reservoir and gas reservoir to verify the application of the example in the study area.At last forecast gas reservoir distribution and estimate the natural gas resource.Research shows that the thickness of Chang 2 and Chang 8 formation is basically stable.The top structure of the sand body of these two reservoirs has a certain similarity and inheritance which has the characteristics of higher east and lower west and some areas presents low amplitude uplift like nose.The thickness of the sand body is NE-SW in banded distribution,the sedimentary microfacies are underwater distributary channel,distributary bay and distributary channel flank.The underwater distributary channel is relatively developed,Chang 8 is wide distributed than Chang 2,and extends far from Chang 2.The four-property relationship shows that the lithology controls the physical property,the physical property affect the oil and gas,the higher the oil level,the moreobvious the corresponding electrical characteristics.Then we summarized oil and gas reservoir identification methods.Common logging methods used in oil layer identification are standard water layer comparison method,radial resistivity comparison method,adjacent well curve comparison method,minimum oil resistivity method,logging parameter curve overlapping method,intersection graph method,etc.Common logging methods used in gas layer identification are three porosity curve overlapping method,the three porosity difference-ratio method,P-wave difference method,full wave logging method,visual fluid identification index method,elastic modulus coefficient method,nuclear magnetic resonance method,neutron gamma time lapse method and acoustic time-resistivity transformation method etc.We mainly use the three porosity difference-ratio method and acoustic time-resistivity transformation method to distinguish from oil layer and gas layer.Through comprehensive interpretation and case analysis the whole well,we find acoustic time-resistivity transformation method is suitable for the reservoir of high resistance,more air content.As for low porosity,low permeability,low resistance gas reservoir,adopt three porosity difference-ratio method.Finally,predict the favorable area of gas layer and obtain the composite gas area about 49.93 square kilometre,and estimate Chang2,Chang8 resource which is about 723 million cubic meters.