| According to the analysis and study of the components of oil based cement slurry and its water plugging mechanism and seepage regulars,the mathematical model of it seeping through the fracture in the carbonate rock under the protection of pad fluid was formed.This mathematical model can show the relationship among the maximum depth of seepage,viscosity,fracture width,differential pressure and grouting speed.Optimize the composition of the oil based cement slurry while considering both its stability and fluidity.Then we got an oil based cement slurry with its displacement efficiency of 77.76% and its apparent viscosity of 1550mPa·s and an oil based superfine cement slurry with its displacement of 51.29% and its apparent viscosity of 456mPa·s.By adding glycerol into the slurry,the hydration depth and the utilization rate of the slurry was apparently raised.The hydration depth can be raised by 50% with the addition of glycerol whose weight is 0.2% of the cement’s while the viscosity and displacement efficiency is not apparently affected.The model of the carbonate rock fracture was formed by two pieces of marble slabs.The process of oil based cement slurry seeping through the fracture was simulated by pumping it into the model.Combining the consequences of the mathematical model and the physical model,it shows that the seepage pressure of oil based cement slurry seeping through the fracture is not high before it contacts with water and the seepage pressure of oil based superfine cement slurry is even lower.But after the slurry contact with water,its seepage pressure raised fast.At first,the seepage pressure of oil based superfine cement slurry is still lower that normal slurry’s.But because the hydration rate of superfine cement is much faster than ordinary cement,the seepage pressure of oil based superfine cement slurry grows much faster.It grows bigger than that of the ordinary oil based cement slurry after 15 minutes under normal temperature. |
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