1. Research progress of cementing additives

In the past 30 years, cementing admixtures have developed rapidly abroad, and their varieties have been updated rapidly. At present, there are 15 functional classifications, and there are more than 100 varieties in total. On the basis of absorbing and digesting foreign advanced technology, China has also established an additive system and corresponding products suitable for domestic oilfield cementing, which can basically meet the cementing needs of most domestic wells. Limited by space, this paper only introduces the research progress of the two most important and most studied admixtures, fluid loss additive and retarder.

1.1 research progress of fluid loss additive

Fluid loss additive products can be divided into two categories: granular materials and water-soluble polymers and organic materials. In granular materials, latex has become a research hotspot at home and abroad because of its good filtration loss reduction, gas channeling prevention, toughening and other advantages, and its research progress will be listed separately below. At present, most of fluid loss additive products are water-soluble polymers and organic materials, which can be divided into modified natural products and synthetic polymers. In addition, many researches have been made on the environmentally friendly fluid loss additive abroad.

1.1.1 modified natural product fluid loss additive

Modified cellulose is a kind of fluid loss additive widely used in water-soluble natural products. CMC (carboxymethyl cellulose), HEC (hydroxyethyl cellulose) and cmhec (carboxymethyl hydroxyethyl cellulose) can be used as fluid loss additive. CMC makes cement slurry flocculate and has strong retarding property, so it is not used now. HEC's comprehensive performance is acceptable and has a few applications. CMHEC is widely used abroad, but rarely produced in China. The common disadvantages of modified cellulose are poor water solubility, high viscosity, poor temperature resistance and delayed development of cement strength. It is a better way to improve the properties of cellulose by chemical graft copolymerization and introducing other functional monomers. Modified cellulose products developed abroad plus ZOC-52 and ZOC-54 developed by ZORANOC company. ZOC-52 can be used at 149 ℃ and ZOC-54 can be used at 176 ℃ in dry fresh water and brine cement slurry. The domestic modified cellulose products are ZOC-BF1 of ZORANOC.