ABSTRACT
In recent years, exploration and development of gas hydrate in deep water has become more and more important. The problems encountered in gas hydrate cementing are low temperatures, short sealing segment, and large annulus. The strength of normal portland cement develops too slowly at low temperatures to support the wellhead.
With compounds of organic and inorganic materials, the reinforced agent is developed to improve the strength of portland cement. The expansion agent and low density lightening material were optimized to meet the low temperature requirement.
New type low density low temperature early strength cement slurry is designed based on high packing theory. PVF (packing volume fraction) of the five-element system is more than 0.80. The slurry density can be regulated between 1.30g/cm3 and 1.50g/cm3. When the thickening time of the cement slurry is more than 150 minutes at 30°C, the compressive strength of cement can reach 6.5MPa after 24h of curing at 4°C. The cement slurry has excellent comprehensive performance such as: good rheology and good stability.
Deepwater oil and gas resources have become an important source of oil and gas development, and seawater natural gas hydrates have become the frontier of future energy. Cementing technology is an important technology to ensure deep water gas hydrates exploration and development. Deep water gas hydrate cementing is facing difficulties such as low temperature, unconsolidated formation and shallow water flow (Romero, J., and Touboul, E.,1998; Calvert, D. G. and Griffin, T. J.,1998; Liu Zhengli, Hu Weijie.,2015). Strength of oil well cement develops slowly at low temperatures, prolonging the setting time of the well, and it is more prone to shallow water flow. Aiming at the problem of slow development of cement strength at low-temperature in deep water, a new type of low-temperature early-strength cement slurry was developed through the study of admixtures and the high-packing optimization design of the cement slurry system.
