关键词: 松软煤层,    ,  , 生物酶,    ,  聚合物,    ,  , 护壁,    ,  , 解堵

Abstract: The effective degradation of bioenzymatic can make the polymer changed from longchain to shortchain and the viscosity will be decreased, and the mud cake can be well cleared up. For this purpose, the viscosity exhaustion method was used, the bioenzymatic corresponding to different polymer were preferred, and four recipes of biodegradable drilling fluid were settled. The properties of drilling fluid have been obtained through the filter cake removal experiments and the permeability recovery experiments. The results show that the different kinds of polymers correspond to different optimal biological enzymes, X1, X6, X3 and X6 are the optimal enzyme corresponds to CMC, PACLV, HEC and guar gum drilling fluid respectively; Four recipes of enzyme biodegradable drilling fluid preferred are of higher practical value, which could clean up the mud cake after drilling process, and the degree of injury of the reservoirs is smaller.

Key words: Soft coal seam,    , Enzyme,    ,  Polymer,    , Stable borehole,    ,  Effective degradation