The comb-type salt-resistant polycarboxylate dispersant (CSPD) was developed to solve the shortcomings of the poor dispersibility of the current dispersant in saline cement slurry. CSPD has salt-to-saturation resistance, poor thixotropy, and the use in saturated saline water prepared slurry can still meet the requirements of the standard for dispersant in freshwater systems. It can effectively disperse salt-containing high-density cement slurry, conventional density and low-density cement slurry. CSPD has successfully solved the problem that the slurry cannot be prepared and cannot be constructed due to the rapid hydration of the saline slurry which was prepared with NaCl in the high-temperature environment. It also solved the core problem in the nano-based low-density cement slurry. Besides the application in anti-channeling cement slurry led to good dispersion performance. It has been successfully applied in Halfaya Oilfield, Missan Oilfield, Dagang Oilfield and Tarim Oilfield, effectively improving the fluidity of cement slurry, ensuring the displacement efficiency, improving the cementing quality, and ensuring the cement ring sealing ability.
During the drilling process, complex formations such as high-pressure saline formations, large salt paste formations, or water-sensitive formations were encountered (Chang, 2013; Gao, 2014; Hou, 2013; Wei, 2014) both in China and overseas in Iraq, Kazakhstan, Uzbekistan, Indonesia and other countries (Chen, 2015; Gai, 2011; Zhou, 2011; Zou, 2015). In addition, in sea and coast operations, it is often attempted to directly prepare cement slurry with seawater (Chen, 2013; Lu, 2014). Due to the high solid content and high salt content, salt/seawater cement slurry exhibits poor fluidity, strong thixotropy and high initial consistency.
Comb-type polycarboxylate dispersant is a kind of high performance dispersant which is used to help modify slurry rheology for easier mixing and placement. Rheology is a measure of both the resistance to flow and a reduction in the resistance to flow under pressure. Adding comb-type polycarboxylate dispersant can reduce friction and pressure during pumping, enhance turbulent flow with reduced pumping rate, and allow operators to mix densified cement slurries. Comb-type polycarboxylate dispersant can also be used to reduce the pressure exerted when cement passes through unconsolidated sands, depleted or weak formations, which may prevent leakage circulation.
