CEMENTING DESIGN FOR DEEP CARBON DIOXIDE (C02) INJECTION WELLS

Deep carbon dioxide injection is one of the latest studies in enhancing the oil recovery for deep
well around the globe. However, Carbon Dioxide (C02) has the tendency to corrode and react with the
Portland cement downhole. This eventually will cause severe leaking behind casing, reduce the
injectivity and shorten the life of the well. Meanwhile in deeper well, the high pressure and temperature
will offer problems in fluid loss rate, thickening lime and unstable cement development which will shrink
the potential of the cement to support the casing and seal fluids from flowing behind the casing. Due to
the relatively higher pressure (<10000 psi) and temperature (250aF to 350°F), an adequate thickening
time, sufficient fluid loss, faster development of compressive strength and better C02 resistance are
expecting from the system in order to suit the condition. This paper is mainly on determining the
composition of silica fume, !illite and superplasticizer that fit the provision as well as evaluating the
physical and chemical properties of the new system (thickening time, fluid loss, C02 corrosion rate and
compressive strength development). Introducing 3 new additives into the system explicitly silica fume,
!illite and superplasticizer is believe to give a better performance than the neat cement. Silica fume is a
common additive for deep well system and trusted to improve the strength of the sheath during the C02
attack. Meanwhile it is to say that filite has the potential to replace the water required in the system and
superplaticizer is added to help in reducing the water content of the cement. Cement class G is still used
instead to proof that the cement is feasible for the acidic environment which can last for more than 30
years downhole alongside in improving the injectivity performance of a well. After a series of intense
laboratory work, the new slurry system is proven to be better in reducing the water content which
contributed to higher resistance during C02 attack, superior fluid loss control and strength development
as well as longer thickening time that will allow deeper and longer pumping distance.