Bioturbation plays an important role in enhancing the reservoir capacity of tight reservoirs.This study aims to understand the alteration mechanism and effects of bioturbation on oil and gas reservoirs,to clarify the key control factors and constraints influencing the production of bioturbation.The petrophysical characteristics of bioturbation and host sediments in carbonate rocks,such as mineral composition,pore spaces,porosity and permeability,were studied based on the detailed observation and description of the Ordovician cores from the Tahe oilfield.The effect of bioturbation on petrophysical properties of carbonate rocks were carefully analyzed.The results show:(1)Two types of bioturbation,Thalassinoides-like burrows and Planolites-like burrows,mainly occur in the Ordovician cores of the Tahe oilfield,ranging from the Lower-Middle Ordovician Yingshan Formation to the Middle Ordovician Yijianfang Formation.The burrow-fills are mainly composed of dolomite with subhedral and euhedral crystals.The host sediments mainly consist of micrite.(2)The pores in the host sediments are poorly developed and are incapable of forming effective reservoir spaces.However,well-developed intercrystalline pores among dolomites and microfractures in bioturbated sediments with better connectivity can form effective pore spaces.The results of porosity and permeability show that the host sediments without bioturbation are characterized by poor porosity and permeability.However,with the increase of bioturbation intensity,the porosity of the bioturbated sediments firstly increases and then decreases,whereas the permeability increases all the time.(3)Multiple burrows overprinted in the Ordovician carbonate rocks,forming a large-scale bioturbated carbonate rocks with lateral continuity and vertical connectivity,due to the suitable sedimentary setting,ecological conditions,favorable spatiotemporal sediment matching,and abundant organism-substrate interaction.Subsequently,diagenesis(particularly dolomitization and dissolution)has played a positive role in altering the rock fabric and improving the petrophysical properties of bioturbated carbonates.

Yong-Bin Niu;Meng-Yuan Cheng;Li-Jun Zhang;Jian-Hua Zhong;Sheng-Xin Liu;Duan Wei;Zi-Lu Xu;Pei-Jun Wang

Key Laboratory of Biogenic Traces and Sedimentary Minerals of Henan Province,Jiaozuo 454003,Henan Province,China;Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region,Henan Polytechnic University,Jiaozuo 454003,Henan Province,China;School of Geoscience,China University of Petroleum(East China),Qingdao 266580,Shandong Province,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;School of Energy Resource,China University of Geosciences(Beijing),Beijing 100083,China;Development Affairs of Tarim Oilfield,PetroChina,Korla 841000,Xinjiang Uygur Autonomous Region,China

古地理学报（英文版）

[1]Yong-Bin Niu;Meng-Yuan Cheng;Li-Jun Zhang;Jian-Hua Zhong;Sheng-Xin Liu;Duan Wei;Zi-Lu Xu;Pei-Jun Wang-.Bioturbation enhanced petrophysical properties in the Ordovician carbonate reservoir of the Tahe oilfield,Tarim Basin,NW China)[J].古地理学报（英文版）,2022(01):31-51

Bioturbation,Tahe,Thalassinoides,burrows,Yingshan,Yijianfang,burrow,micrite,dolomites,bioturbated,dolomitization

enhanced,petrophysical,properties,Ordovician,oilfield,Tarim,Basin,NW,China,plays,important,role,enhancing,capacity,tight,reservoirs,This,study,aims,understand,alteration,mechanism,effects,bioturbation,gas,clarify,key,control,factors,constraints,influencing,production,characteristics,host,sediments,rocks,such,mineral,composition,spaces,porosity,permeability,were,studied,detailed,observation,description,cores,from,carefully,analyzed,results,show,Two,types,like,Planolites,mainly,occur,ranging,Lower,Middle,Formation,fills,composed,subhedral,euhedral,crystals,consist,pores,poorly,developed,incapable,forming,effective,However,well,intercrystalline,among,microfractures,better,connectivity,can,that,without,characterized,by,intensity,firstly,increases,then,decreases,whereas,Multiple,overprinted,large,scale,lateral,continuity,vertical,due,suitable,sedimentary,setting,ecological,conditions,favorable,spatiotemporal,matching,abundant,organism,substrate,interaction,Subsequently,diagenesis,particularly,dissolution,has,played,positive,altering,fabric,improving,carbonates

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