In China, the drilling industry has had numerous environmental restrictions on some materials it uses and the methods of the disposal. Both the governors and the drilling engineers welcome the use of environmentally safe drilling fluid. However, there is a contradiction between maintaining borehole stability and protecting the permeability of the reservoir in water well drilling. The mud invades in the porosity in a large radius near the wellbore. With the flushing work, some of the invaded mud is cleaned. However, the majority of the mud remains in the porosity. The residual mud not only plugs the porosity but also is a kind of contamination to the aquifer. It becomes a barrier to recover the permeability of the promising aquifer and greatly decreases the yield of water. The paper proposes the use polymers such as Na-CMC, guar gum and HEC to develop temporarily plugging drilling fluid, combining with the bio-degradation principle in modern biology. This fluid is marked as self-degrading, harmless to the reservoir and can be widely used in oil, gas and water well drilling. Distinguishing from traditional temporarily plugged agents, it does not need additional unplugging technology which elementarily improves the unplugging technology. This paper analyses in detail the action mechanism of temporarily plugging drilling fluid and the enzyme degradation mechanics. Meanwhile, it presents the lab tests of viscosity and permeability recovery and the field trial in Zhangye city of Gansu province of North West China. The results of lab and field trial confirms the performance of temporarily plugging drilling fluid that it can be self-degrading, harmless to the reservoir, effectively maintains the borehole and plugs the leakage while remarkably recovers the permeability of the reservoir. Therefore, it has a promising future.

You can access this article if you purchase or spend a download.