Various admixtures to mitigate the long-term strength retrogression of Portland cement cured under high pressure and high temperature conditions  

作　　者：Jiankun Qin Xueyu Pang Ashok Santra Guodong Cheng Hailong Li 

机构地区：[1]School of Petroleum Engineering,China University of Petroleum(East China),Qingdao,266580,China [2]Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)),Ministry of Education,Qingdao,266580,China [3]Drilling Technology Team,Aramco Americas:Aramco Research Center,16300 Park Row Drive,Houston,TX,77084,USA

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2023年第1期191-203,共13页岩石力学与岩土工程学报（英文版）

基　　金：Financial support comes from China National Natural Science Foundation(Grant No.51974352);as well as from China University of Petroleum(East China)(Grant Nos.2018000025 and 2019000011)。

摘　　要：In order to investigate the problem of long-term strength retrogression in oil well cement systems exposed to high pressure and high temperature(HPHT)curing conditions,various influencing factors,including cement sources,particle sizes of silica flour,and additions of silica fume,alumina,colloidal iron oxide and nano-graphene,were investigated.To simulate the environment of cementing geothermal wells and deep wells,cement slurries were directly cured at 50 MPa and 200?C.Mineral compositions(as determined by X-ray diffraction Rietveld refinement),water permeability,compressive strength and Young’s modulus were used to evaluate the qualities of the set cement.Short-term curing(2e30 d)test results indicated that the adoption of 6 m m ultrafine crystalline silica played the most important role in stabilizing the mechanical properties of oil well cement systems,while the addition of silica fume had a detrimental effect on strength stability.Long-term curing(2e180 d)test results indicated that nano-graphene could stabilize the Young’s modulus of oil well cement systems.However,none of the ad-mixtures studied here can completely prevent the strength retrogression phenomenon due to their inability to stop the conversion of amorphous to crystalline phases.

关 键 词：High pressure and high temperature(HPHT) Strength retrogression Young’s modulus Water permeability Rietveld method 

分 类 号：TU45[建筑科学—岩土工程]