2. Experimental method

A series of oil well cement performance tester produced by Chandler company of America was used to measure the parameters of cement slurry according to the test method of apispec10.

Influence of ZOC-F44S dispersant on properties of cement slurry and its compatibility with other admixtures

1. The pulping of cement slurry mixed with ZOC-F44S dispersant

1.1 pulping and cement paste stability with single addition of dispersant ZOC-F44S

Adding dispersant into cement can effectively improve the pulping performance of cement slurry, greatly increase the fluidity of cement slurry, eliminate the agglomeration of cement particles, and improve the dynamic fluidity of cement slurry. However, the addition of dispersant also easily leads to excessive dispersion of cement paste, resulting in the separation between cement particles and liquid. The typical case is that adding dispersant will cause the settlement of cement particles and produce free liquid, which will turn the cement slurry into an unstable system. By adding ZOC-F44S dispersant, the pulping of cement slurry and the stability of cement slurry after heating are shown in Table 1.

Table 1 pulping and slurry stability after single addition of ZOC-F44S dispersant

 ZOC-F44S dispersant Fluidity               After pulping

No. Dosage (%) (cm)   Keep for 2min       Keep for 10min       After 20 minutes at 60 ℃

1   1.6       26  Thin Slury no settlement  Slight thixotropy, no settlement Thin Slurry, no settlement in the bottom of barrel

2   2.0       29  Thin Slury no settlement  Week thixotropy, no settlement Thin Slurry, no settlement in the bottom of barrel

The study of adding ZOC-F44S dispersing agent in cement shows that the developed dispersing agent has good pulping performance, reducing resistance and improving fluidity of cement slurry. In addition, the prepared cement slurry also has a weak thixotropic property, which can eliminate the settlement of particles in the cement slurry caused by excessive drag reduction, and make the cement slurry in a homogeneous state. Moreover, the cement slurry mixed with ZOC-F44S dispersant can still make the cement slurry in a homogeneous system in a high flow state after heating

1.2 pulping and slurry stability when fluid loss additive and dispersant are mixed together

In the cement paste mixed with film-forming fluid loss reducer, ZOC-F44S dispersant was added to observe the pulping condition of the cement paste, including the wetting condition, fluidity, settlement of the cement particles and the change of the cement paste after standing. The experimental results are shown in Table 2.

Table 2 ZOC-F44S pulping performance of dispersant and fluid loss reducer

No. Fluid Loss Additive  Dispersant  Wettability Mobility  Keep for 2min       Keep for 5min

Dosage(%)    Dosage(%)             (cm)   Thixotropic structure  Slurry change

1     0.6           1.0       Fast     24      Small  No settlement, a little structure

2     0.6           1.4       Fast     26       No               a stir on thin

3     0.6           2.0       Fast     26       No  

4     0.8           1.4       Fast     24      Slight

5     0.6           0.5       Fast     24 Slightly stronger  No settlement, Strong structure   

                                                                                               still thick after stirring 

Note: the dispersant in No.5 is ketone aldehyde.

The results show that the dispersing agent ZOC-F44S has a good dispersing effect and can reduce the friction

The viscosity increasing and thixotropic structure caused by the weak addition of fluid loss reducer, especially the ability of cement slurry to maintain good flow after standing for a long time. The advantage of this feature is: when the pump stops working for a period of time, the structural force of the cement slurry is still small, which can reduce the starting pressure of the pump, so as to ensure the construction safety.