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Basic Knowledge
7.5 Unti-fluid channeling cement slurry system
  • Detailed description
The formation reasons and solution measures of fluid channeling
1) The interface bond theory. The theory is that the fluid channeling is caused by poor cementation interface. The main reason is the existence of the mud cake leading to poor cementation of two interfaces, and cause fluid channeling. This theory makes people doing a lot of research work on replace mechanism and process, and suggests measures of the turbulent replacement, casing centralization, using scraper etc. and in the additives aspect, the dispersant and expensive agent are suggested to use.
2) The weightlessness theory. This theory is that the fluid channeling is caused by the weightlessness in the cement hydration process. It includes two aspects: ① Bridge blinding weightlessness: this theory makes the research and application of fluid loss additive a great progress.  ② Gelatinization weightlessness: this theory suggests the measures of increasing the cement slurry and multiple stage cementing.
3) Micro-crack—micro-fissure theory. In the last ten years, people at the conclusion of the front two kinds of the basis theory put forward a new unti-fluid channeling theory -- micro-crack—micro-fissure theory. The micro-crack is due to cement ring are not good cement with casing, and the micro-fissure is the tiny channels between cement ring and the strata or in cement ring. The main reasons of micro-cracks formation are ① the inherent characteristics of cement ②the existence of the mud cake ③grid structure strength formed in the early stage is low, can not bear the upper hydrostatic pressure, cause water gathered phenomenon, and this area can form micro-cracks after final set.
Based on the above understanding, there are appeared a lot of the channeling additives at home. The use temperature range of these additives is very wide. they can be used together with a variety of the additive materials and makes a variety of different density slurry, still can be used  together with expansion agent and foaming agent, that has better prevent channeling effect.