Compatibility evaluation of modified seawater for EOR in carbonate reservoirs through the introduction of polyphosphate compound  

作　　者：Bisweswar Ghosh Liying Sun Nithin Chacko Thomas 

机构地区：[1]Petroleum Engineering Department,Khalifa University,Abu Dhabi,United Arab Emirates [2]College of Petroleum Engineering,China University of Petroleum(Beijing),Beijing 102249,China

出　　处：《Petroleum Science》2020年第2期393-408,共16页石油科学（英文版）

摘　　要：Waterflood-assisted oil recovery with sulfate-spiked seawater would cause incompatibility scaling in carbonate reservoirs and reduce economic benefits.This research investigated the benefits of polyphosphate compounds in reducing scaling potential as well as its effect on oil recovery when mixed in high sulfate flood water.Severity of scaling potential of sulfate-spiked water in a carbonate reservoir environment was measured,followed by systematic screening of a polyphosphate compound,which successfully inhibited the sulfate scale precipitation at concentration as low as 100 ppm.The new formulation(seawater with four times sulfate and phosphate,SW4 SP)was evaluated and compared with benchmark formulation(modified seawater with four times sulfate,SW4 S).Contact angle,ζ-potential and drainage studies show that SW4 SP changed the rock wettability from oil wet to water wet to a larger degree compared to SW4 S.Improved recovery efficiency of SW4 SP was confirmed through a set of core flooding studies in the tertiary and quaternary flood modes.Whereas SW4 S recovered 7.7%of original oil in place(OOIP),SW4 SP recovered about 8%of OOIP in the tertiary mode under approximately identical flow conditions.Flooding with SW4 SP in the quaternary mode following a tertiary flood with SW4 S on the same core resulted in 1.7%additional oil recovery,showing improved efficiency of the new flood water formulation.Waterflood-assisted oil recovery with sulfate-spiked seawater would cause incompatibility scaling in carbonate reservoirs and reduce economic benefits.This research investigated the benefits of polyphosphate compounds in reducing scaling potential as well as its effect on oil recovery when mixed in high sulfate flood water.Severity of scaling potential of sulfate-spiked water in a carbonate reservoir environment was measured,followed by systematic screening of a polyphosphate compound,which successfully inhibited the sulfate scale precipitation at concentration as low as 100 ppm.The new formulation(seawater with four times sulfate and phosphate,SW4 SP) was evaluated and compared with benchmark formulation(modified seawater with four times sulfate,SW4 S).Contact angle,ζ-potential and drainage studies show that SW4 SP changed the rock wettability from oil wet to water wet to a larger degree compared to SW4 S.Improved recovery efficiency of SW4 SP was confirmed through a set of core flooding studies in the tertiary and quaternary flood modes.Whereas SW4 S recovered 7.7%of original oil in place(OOIP),SW4 SP recovered about 8% of OOIP in the tertiary mode under approximately identical flow conditions.Flooding with SW4 SP in the quaternary mode following a tertiary flood with SW4 S on the same core resulted in 1.7% additional oil recovery,showing improved efficiency of the new flood water formulation.

关 键 词：INCOMPATIBILITY SCALING SODIUM trimetaphosphate(SHMP) Smart waterflood Scale INHIBITOR Water compatibility Enhanced oil recovery 

分 类 号：TE357.6[石油与天然气工程—油气田开发工程]