3. The improvement of the dispersant of ZOC-F44S on the water loss reducing agent

The dispersing agent can eliminate the agglomerated cement particles, and make the cement paste have better homogeneity, thus improving the water loss control of the cement slurry. This effect must be based on the compatibility of dispersant and water reducing agent. For the membrane-forming water reducer widely used at present, because the polymer dissolves slowly or only partially expands, it is often mixed in cement and it controls the water loss mechanism by the complexation of inorganic salt with water-soluble functional groups on the polymer molecular chain to form macromolecular cross-linking, thus preventing the filtrate from penetrating in the cement slurry. The disadvantage of this water loss reducing agent system is that the control reproducibility of the water loss is poor when the temperature is low. Because of the change of raw materials or cement, the water loss can not be controlled, which increases many commissioning and repeated work. In this case, even the introduction of ketaldehyde dispersant can only disperse cement particles and improve the pulping performance, and the control of water loss of cement slurry is less improved. At present, the developed dispersion agent of zoc-f44s can effectively improve the pulping performance of cement slurry, but also make film-forming loss reducing agent have good water loss control ability under very loose conditions (including the change of raw materials and cement varieties and batches). The experimental results of the water loss control ability of the slurry system with the addition of the ZOC-F44S dispersant in the film-forming water loss reducing agent system are shown in Table 4. 

Table 4 Effect of ZOC-F44S dispersant on film forming fluid loss additive at 30 ℃   

 No.   Fluid Loss Additive(%) ZOC-F44S Dispersant(%)  API water loss(mL/6.9MPa,30min)

 1                                                           ---                                         560

 2                                                          1.6                                        295  

 3          0.5                                           2.0                                        200

 4                                                          2.5                                         80

Table 4 clearly shows that according to the API water loss test method, when the test temperature and the amount of film-forming fluid loss reducer are low, the water loss control ability of cement slurry is poor, and there is basically no water loss control effect. With the addition of ZOC-F44S dispersant, the dispersion loss is obvious. 

The higher the dosage of ZOC-F44S dispersant, the more significant the effect of reducing water loss. The experiment shows that the cement slurry with high content of ZOC-F44S dispersant is stable, which indicates that the control of water loss is not caused by settlement. This shows that ZOC-F44S dispersant can be compatible with film-forming  fluid loss reducing additive, which not only improves the fluidity of cement slurry, but also improves the function of fluid loss reducer and enhances the function of water loss control. Therefore, it is not necessary to control the water loss by increasing the expensive dosage of fluid loss reducing additive (generally speaking, increasing the dosage of  fluid loss reducing additive will increase the consistency of cement slurry, so it is necessary to add dispersant at the same time The agent. So as to reduce the cost of cement slurry. Effect of 4f dispersant on temperature resistance of film forming fluid loss reducing additive and retarder.

For many years, fluid loss reducing additive is one of the conventional admixtures that must be used in the cement slurry of deep wells and target formations. In recent ten years, the fluid loss additive used in many oilfields in China is film-forming, which has the characteristics of strong water loss control ability and little influence on the strength development of cement paste. Since its compatible ketone aldehyde dispersant was successfully applied, the application scope of the fluid loss additive has been greatly expanded. However, the difficulty of this system for many years lies in the complexity of the retarding system, the small selection space of retarder, and the poor compatibility of hydroxy Carboxylates with good retarding ability in cement. When carboxylates are added into the system, it is easy to cause "bulge" phenomenon, resulting in the thickening of cement slurry. In order to improve the thickening property of the cement slurry of the film-forming fluid loss reducer, the developed ZOC-F44S dispersant has the function of eliminating "bulge", so that the hydroxycarboxylate can be compatible with the fluid loss reducer at low dosage, thus reducing the complexity of the retarder. The experimental results are shown in Table 5.

The retarding properties of hydroxycarboxylate at different temperatures after adding ZOC-F44S dispersant into the film-forming fluid loss additive system were investigated in Table 5. The results show that the retarding effect of film-forming fluid loss additive system is obviously improved due to the addition of ZOC-F44S dispersant. When the temperature is low, a small amount of retarder can prolong the thickening time. With the increase of temperature, the thickening time of cement slurry can be adjusted by appropriately increasing the dosage of retarder, and there is a good consistency between the thickening time of cement slurry and the dosage of Retarder in the range of temperature blind zone (100-120 ℃).

Table 5 Effect of ZOC-F44S dispersant on retarding and temperature resistance of film-forming fluid loss additive

No.  Fluid loss Additve Dispersant Retarder TT(min)     TT(min)      TT(min)      TT(min)

      (%)             (%)       (%)  80℃40MPa 100℃52MPa 110℃55MPa120℃60MPa

1                                 0.05       137         188                     221

2                                 0.1         214         278                    333

3    0.7              2        0.15                                                216

4                                 0.21                                               280

 Note: 1. Pure cement at 80 ℃, 2, 100 ℃, 110 ℃ and 120 ℃ are cement and 35% silica powder; 3. Retarder is hydroxycarboxylate. 

Conclusion. 

Through the study of ZOC-F44S oil well cement dispersant, the results show that: 1. The results show that: 1.ZOC-F44S dispersant has good cationic reducing effect and can effectively improve the fluidity of cement slurry

2. ZOC-F44S dispersant has good compatibility with film-forming fluid loss reducer, which can better improve its low-temperature water loss control ability, so as to broaden the dependence of fluid loss reducer on the selection of raw materials, reduce the amount of expensive polymer materials, save the cost, and reduce the repetitive work in cement slurry design.

3. The addition of ZOC-F44S dispersant makes the design of film-forming fluid loss reducer cement slurry system more convenient, reduces the dependence on retarder, expands the selection range of retarder, and makes the retarder system of film-forming fluid loss reducer simpler. ZOC-F44S dispersant also has the advantages of no dusting and rapid dissolution, thus reducing the impact on human body.