Preparation of a High Temperature- and Salt-Resistant Styrene Butadiene Latex under the Action of Composite Emulsifiers and the Performance Evaluation Thereof

Styrene butadiene latex as a toughening agent in well cement slurries has some deficiencies such as poor thermal stability and salt resistance, and the styrene butadiene latex has to be used together with latex conditioners. To solve these problems, the styrene butadiene latex is modified with other monomers, such as sodium styrenesulfonate and itaconic acid as the functional monomers, and a composite emulsion system containing OP-10 and SDS to produce an SCMBR latex. The effects of different emulsifier formulation on the properties of the latex were investigated. The microstructure of the SCMBR latex was characterized with particle size, Zeta potential and transmission electron microscope. The thermal stability and salt resistance of the SCMBR latex was evaluated. Laboratory experimental results show that the SCMBR latex has good thermal stability, the thermal decomposition temperature is as high as above 400 ℃. The SCMBT latex also shows good salt resistance. TEM image shows that the SCMBT latex is evenly dispersed with no aggregate existed. The SCMBT latex can significantly improve the stability of cement slurries, it reduces the amount of free liquid to less than 1%, and the difference between the density of the top and the density of the bottom can be reduced to 0. The SCMBT latex can also be used to improve the rheology of the cement slurries and the flexural strength of set cement. A set cement modified with the SCMBR latex has 28 d flexural strength 20.5% higher than the flexural strength of the pure set cement. In deep and ultra-deep well cementing the SCMBR latex will have broad application prospect.