| A contradiction comes into being that whether keeping the hole and blocking the leakage or protecting the permeability of the formation. To solving this problem, we use polymers such as guar gam, konjaku flour and Na-CMC, combining with the chain scission and degradation in modern biology, and develop temporarily blocked drilling fluid, which is marking as self-degradated, harmless to the formation and can be widely used in oil, gas and water well drilling.In the past three years, to realize the task, the author took great attention in investigation and research work, the collection of reference information, and theoretical analysis. Based on these previous works, hundreds of lab performance tests of different compounding temporarily blocked drilling fluid have been done. The lab achievements have been used in water well drilling. At the meantime, the project group upon which the research work depended has cooperated with the local company the produce the fundamental materials of temporarily blocked drilling fluid.Based on the drilling engineering, by means of modern biology and connected with organic chemistry, high polymer chemistry, biochemistry, analytical chemistry and fluid mechanics, we developed temporarily blocked drilling fluid, which has great scientific and novelty meanings.Temporarily blocked drilling fluid can be auto-degradated and toxicless and harmless to the local environment. Distinguished from traditional temporarily blocked agents, it does not need additional unblocking technology such as pressure unblocking, acidizing, oil-solubl or broking gam, which elementarily improves the unblocking technology and the productive efficiency. The enzyme can effectively and thoroughly degradate the polymers, which avoiding the harm of polymer on the formation after drilling work.The present status of temporarily blocked drilling fluid and the related materials was introduced firstly. The performances and uses of polymers such as guar gum, konjac, Na-CMC, and HEC which make up of the main agent of temporarily blocked drilling fluid, are represented. In succession of this content, the characters, performance parameters and the main performance mechanics of polymer drilling fluids was compactly introduced. As a main part, the knowledge of enzyme was interpreted in detail which including the classification, the obvious characters of it as catalyst, the catalyst effect, the reaction mechanics, the dynamics and the influencing factors. At the ending of this chapter, the author talked about the application of enzyme in drilling industry.After introducing the temporarily blocked mechanics of conventional temporarily blocked agent, the author primarily analyzed the temporarily blocked mechanics of temporarily blocked drilling fluid. Used enzyme as the main agent to control the performance of it, the degradation of it can be man-controlled, which ensures the process of blocking to unblocking. Then the degradated principles of several polymers such as starch, CMC and guar gam were analyzed in detail.Hundreds of lab tests were preceded about the degradation of enzyme on polymer and composite polymers. Then plenty of tests were done on the temporarily blocked drilling fluidwhich was made up of bentonite, polymers and enzyme. Using the self-developed recovering testing apparatus of permeability, the author tested the recovering performance of permeability of the temporarily blocked drilling fluid and got the excellent and special compounding of it.When the temporarily blocked drilling fluid was used in water well drilling, the lab test demonstrated that the performance of drilling fluid can be artificially controlled. It can be auto-degradated and have no pollution or harm on the formation. The recovering ratio of the permeability of the formation is as high as 90%. At the same time, the general parameters of it such as viscosity, API fluid loss, stability, lubricating ability and rejection capability have meet up the technical standard of quality drilling fluid, especial the protection perfo...
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