Identification of ichnofabrics and their geological significance based on core and electrical imaging logging

XIANG Wei; WANG Xiaofei; CUI Weiping; NIU Yongbin; WANG Shiyue; TANG Di; LI Pingjiu; CHENG Yigao; SHAO Weimeng

doi:10.16186/j.cnki.1673-9787.2023100059

Abstract：Objectives In order to ascertain the development characteristics of ichnofabric of Sanya Forma-tion in Songtao Uplift in Qiongdongnan Basin,and to explore the hydrocarbon geological significance of these ichnofabrics,Methods on the basis of detailed observation and description of the development charac-teristics of trace fossils and host sediments on the core of representative coring wells,ichnofabrics were iden-tified.By calibrating the depth of the core and electrical imaging logging,the calibration of electrical imag-ing log images with core was achieved.Then,the response characteristics of ichonfabrics to electrical imag-ing logging were carefully analyzed,and reference image templates for the identification of ichnofabrics us-ing electrical imaging log were established.Results(1)Five kinds of ichnofabrics were identified on the core and electrical imaging log images of the study area:Phycosiphon-Chondrites ichnofabric,Phycosiphon-Planolites ichnofabric,Planolites-Thalassionides ichnofabric,Palaeophycus ichnofabric and Ophiomorpha-Thalassionides ichnofabric.By synthesizing the sedimentological and ichnological properties of 5 types of ich-nofabrics,their sedimentary environment formed was interpreted.(2)According to the comparison between the ichnofabrics identified from the cores and the electrical imaging images of 112 horizons in 9 wells in Qiongdongnan Basin,104 horizons were completely consistent,and the identification accuracy could reach 92.9%,while 8 horizons were inconsistent due to poor electrical imaging quality.It was reliable and effective to identify ichnofabrics of Sanya Formation in Songtao Uplift of Qiongdongnan Basin based on core and elec-trical imaging logging images.Conclusions This study was of great significance for analyzing the deposi-tional environment and predicting the distribution pattern of reservoirs in the study area,revealing the modi-fying effect of ichnofabric on hydrocarbon reservoirs,and promoting increased hydrocarbon storage and pro-duction,as well as enhancing recovery in the study area.