Characteristics And Comprehensive Evaluation Of Chang 6 Reservoir In Wangjiawan West Area,ordos Basin

The Chang 6 reservoir characteristics of Wangjiawan West in Ordos Basin,the study area of this paper,have been little studied and not deep enough,which seriously hinders the subsequent development work.Since the objective and practical understanding of reservoir properties will affect the development effect of low permeability oil and gas fields,the analysis results of the characteristics of Chang 6 reservoir and its influencing factors in the study area and the evaluation results of the reservoir are of great importance for the exploration and development of Chang 6 reservoir in Wangjiawan West area of Ordos Basin.In this paper,the author firstly divided the Chang 6 formation in the study area into 6 sublayers by establishing standard wells and comparing consecutive wells,and on this basis,then used logging and recording data as well as core observation,microscopic identification of common and cast thin sections,pore penetration test and other experimental testing methods to clarify the sedimentary characteristics and reservoir characteristics of the Chang 6 formation in the study area,based on this,then carried out the analysis of the main control factors of the reservoir,and finally then used the Based on this,the analysis of the main reservoir control factors was carried out,and finally the classification and evaluation of the reservoirs in the study area was completed using the gray correlation method and the inflection point method.The following results and insights were achieved.(1)The Chang 6 formation in the study area can be precisely divided into 6 sublayers,including Chang 611,Chang 612,Chang 621,Chang 622,Chang 63 and Chang 64,with no obvious undulations in the comparison of each sublayers with wells,and a relatively simple structure,which is consistent with the monoclinic structure of the Yishan slope as a whole,and has good inheritance,and nosing structure is developed locally due to differential compaction.(2)The depositional characteristics of the Chang 6 reservoir in the study area show that the submerged divergent channel micro-phase and the divergent interbay micro-phase are superimposed in the vertical direction,and the single-well phase characteristics show that the number and thickness of the submerged divergent channel sand bodies in the Chang 63 and Chang 64 sublevels are worse than those in the other four sublevels;the planar characteristics show that the scale of channel development and the thickness of the sand bodies are gradually increasing from the Chang 64 to the Chang 611 period.(3)The feldspathic sandstone is the main sandstone type of the Chang 6 reservoir in the study area,and it also contains part of rock chip feldspathic sandstone;the residual intergranular pore is its main storage space,which can account for about 54%of the total pore space,and the percentage of dissolution pore space is the second,which is about 35%;the core test results of the study area show that the average porosity of the best physical Chang 61 and Chang 62 sub-layers are 10.97%and 10.28%,and The average values of permeability are 1.79×10-3μm2 and 1.58×10-3μm2 respectively,while the physical inhomogeneity of the cores of the Chang 64 sub-layer is strong,and the difference between good and bad is large.(4)The diagenesis of the Chang 6 reservoir in the study area is strong and varied,among which dissolution has constructive positive significance on the reservoir properties,while compaction has mainly destructive negative significance on the reservoir properties,and the influence of cementation is more complicated,for example,chlorite and siliceous are good for resisting the damage of the reservoir space by compaction due to their hardness,but also destroying the reservoir properties due to their filling of cemented pores.The physical properties of the reservoir.(5)The reservoirs are divided into four categories according to the comprehensive evaluation score of the reservoirs.The comprehensive evaluation score of Class Ⅰ reservoirs is greater than 0.5,which are mainly located at the development of thick sand bodies in submerged diversion channels;the comprehensive evaluation score of Class Ⅱ reservoirs is between 0.33 and 0.5,which are the most common reservoirs in the study area and are located at the development of submerged diversion channels;the comprehensive evaluation score of Class Ⅲ reservoirs is between 0.23 and 0.33.The comprehensive evaluation score of Class Ⅲreservoir is between 0.23 and 0.33,which is located at the lateral edge between the submerged diversion channel and the inter-diversion bay;the comprehensive evaluation score of Class Ⅳreservoir is less than 0.23,and its reservoir characteristics are poor,with low test oil yield,high water content and low recovery value.