2.  Development of cementing isolation fluid and materials

2.1. High temperature resistant isolation fluid

The key of high temperature resistant isolation fluid is to develop suspension with good performance. Through polymer modification, the temperature resistance and salt resistance of the isolation liquid were improved; the high temperature resistant suspension agent, together with weighting agent and auxiliary agent, was developed, and a 180℃ isolation liquid with good compatibility and stability was developed. The system has strong temperature resistance, can maintain stable suspension performance under high temperature conditions, and effectively solve the contradiction between suspension and rheology.

2.2. High efficiency flushing isolation fluid

Aiming at the problem of low displacement efficiency in high temperature deep well and long sealing section under complex well bore conditions, the suspension stabilizer of isolation fluid, oil-based drilling fluid flushing fluid and special weighting materials are developed; the high-efficiency flushing isolation fluid system is developed, which overcomes the problems of poor flushing effect and low displacement efficiency in the cementing process of ultra long sealing section, and creates conditions for good cement slurry cementation. High efficiency flushing isolation fluid has been successfully applied in gas storage, deep well, ultra deep well and shale gas well.

2. 3. Oil displacement type high density isolation fluid

In order to deal with the complex salt gypsum layer and the instability of shale gas well wall, high-density oil-based drilling fluid is generally used. By optimizing high-performance wetting reversal agent, a high-density oil displacement type isolation fluid was developed, which solved the cementing problem under the condition of oil-based drilling fluid. Laboratory experiments show that the developed oil displacement type high-density isolation fluid can completely dissolve the oil-based drilling fluid and achieve wetting reversal, which has a good effect of displacement and cleaning the oil-based drilling fluid, and creates conditions for improving the cementing quality under the condition of high-density oil-based drilling fluid.