The Secondary Logging Interpretation Of Chang 4+5 And Chang 6 Reservoirs In MJH Area And The Review Of Old Wells

The MJH Development Zone has long been developing the Chang4+5 and the Chang6 oil layers as its main oil producing layers,and each oil well has achieved considerable oil production.In recent years,the abundance of the remaining blocks is becoming lower and the difficulty of development is gradually increasing,facing the severe situation of resource shortage and the reserves are in short supply.Therefore,we must work hard in the old block to achieve sustainable development of the oilfield.This paper focuses on the study of the Chang4+5 and Chang6 reservoirs in the MJH area.Based on the collection,sorting,and analysis of a large number of rock identifications,physical tests,and laboratory analysis data,this paper studied the four-property relationship.Based on the analysis of key well data,the reservoir parameter calculation model was studied,the logging interpretation models of each reservoir parameter are established,and the reliability of the model is verified.At the same time,a comprehensive well logging interpretation method that uses the curve morphological characteristics and the curve overlap method for qualitative identification and the chart correction method to determine the effective layer lower limit standard as the quantitative evaluation index is determined.Finally,the above research results are applied to the review of old wells to provide the basis for the next step in the study area to find potential targets.In the research process,the following points are mainly obtained:(1)The lithology of the reservoir is mainly feldspathic sandstone,with fine-grained sandstone structure as the majority,followed by medium and fine-grained sandstone structures.Cements such as calcite and chlorite are more common in reservoir interstitials.The main reservoir space of the reservoir is the remaining intergranular pores,the pore throat structure is characterized by the “micro-throat throat”,the pore structure is more complex,and the physical properties of the reservoir are poor,mainly low porosity,low permeability and low permeability reservoirs.(2)There is a positive correlation between reservoir porosity and permeability,and there is a good positive correlation between interval transit time and porosity and permeability of reservoir.In the case of poor physical properties,the interval transit time appears to be lower.In the case of better physical properties,the interval transit time appears to be higher.Through the study of four-property relationship,using crossplot technique,the porosity and permeability logging interpretation models of Chang4+5~2,Chang6~1 and Chang6~2 are established.(3)For the selection of the shale content calculation method,the natural potential curve,natural gamma curve and resistivity curve are mainly used,take the low value of the three calculation results as the result value.(4)For the calculation of water(oil)saturation,Archie's formula is used.Because of the difference in pore throat structure at each layer,the difference in rock electrical parameters also varies.Finally,determined that the rock electrical parameters of the reservoir in the study area.Chang4+5~2: a=1.5826,m=1.8378,b=1.0105,n=1.6073;Chang6~1 and Chang6~2:a=0.8185,m=2.2493,b=0.8356,n=1.4597.(5)Based on the study of the four-property relationship of reservoirs,comprehensive application of test oil,core analysis,production results,and well logging data,etc.,using the statistical method and the intersection chart between the parameters to determine the lower effective limit of effective thickness of Chang 4+5~2,Chang 6~1 and Chang 6~2 reservoirs.(6)Reviewing more than 100 old wells in the study area,14 well-selected layers of 14 wells were selected as the proposed test section for the study area,which provided a theoretical basis for future potential exploration in the study area.