Petrological Characteristics And Lithologic Logging Model Of Buried Hill Formation In Bohai Sea Area

Buried hill oil and gas reservoirs are an important part of oil and gas exPoration in Bohai Bay Basin.The buried hill strata in the Bohai Sea area are mainly the Archean,Mesoproterozoic,Paleozoic and Mesozoic strata.The types of rocks are sedimentary rocks,igneous rocks and metamorphic rocks,which can be subdivided into Carbonate rocks,clastic rocks,volcanic rocks,volcanic clastic rocks,intrusive rocks,and regional metamorphic rocks.The comPex lithologic composition brings difficulties to the logging lithology identification in the study area.Under the guidance of the theory of petrology and logging geology,based on the petrological identification of 141 drilling core and cuttings(475)systems,the rock-electrical relationship qualitative interpretation temPate,And the quantitative discriminant model of Fisher function,a comprehensive discriminant model of lithologic logging suitable for the buried hilly seam in the Bohai Sea is established,which lays a solid foundation for the accurate description of the lithologic distribution of the buried hills in Bohai Sea.The geological characteristics of buried hill strata in the study area are described by core observation,flake identification and combined with existing geological data.Based on the logging data,the logging response characteristics of each lithology in the study area are summarized,and the qualitative interpretation temPate of rock-electricity relationship is established.The sedimentary rocks(microcrystalline limestone,bio-limestone,Rocks,microcrystalline dolomites,gray dolomites,mudstones,sandstones),volcanic rocks(rhyolite,slender rock,jelly rock,rough rock,andesite,Ansan basalt,basaltic andesite,basalt,Rock,Ansanitic tuff,middle tuff,altered basalt,basaltic breccia,basaltic tuff),metamorphic rocks(mixed rock,carbonate mixed rock,gneiss,carbonate Rock).Using the technique of rendezvous mapping,the samPe set of logging response suitable for the study area was selected,and a semi-quantitative intersection graph model with different lithologies was established.The GR-RD diagram and GR-DEN map were used to identify the three rocks.The sedimentary rocks(dolomite,mudstone,mudstone,limestone and rock)were recorded by GR-RD,CN-RD and CN-ZDEN The authors have identified the volcanic rocks(andesite,illite tuff,breccia,black cloud monzonite,rough rock,tuff,basalt)by using GR-ZDEN map and CN-ZDEN map.The metamorphic rocks(gneiss,shale porphyry,slate)were identified using the GR-ZDEN map and the CN-ZDEN map.According to the same lithology in different wells,the distribution of logging data is scattered and can not establish an effective crossPot to identify the lithology.The normalized rendezvous graph model is established.The GRI-RDI diagram is used to analyze the lithology,The grape rocks and basalts were identified by GRI-ZDENI map.The GRI-RDI diagram was used to identify the granulite and gneiss.Based on the multivariate statistical pattern recognition lithology,the Fisher discriminant coefficient of the 10 lithologies in the study area was calculated by Fisher discriminant analysis.The Fisher function model of logging lithology was established,and the dolomite,Feldspar sandstone,debris mudstone limestone,mudstone,andesite,black cloud monzon granite,rough rock,gneiss,slate,granite porphyry automatic identification.For the study of comPex lithology,a single use of a lithology identification method can not be accurately identified.The logging curve of the rock-electrical relationship temPate is less,but the human error is large.The intersection graph model requires less logging curve,but the intersection point is more comPicated.The Fisher discriminant method can realize the lithology automatic in the logging software But it requires more than the number of logging curves.Based on the characteristics of Fisher discriminant recognition,the Fisher discriminant method is used to identify the lithology.For the special section re-combination of the rock-electrical relationship model,the intersection graph model is assisted to achieve high efficiency,High accuracy of lithology identification,and then to the study area lithology system to carry out logging interpretation.