塔河稠油高黏特性及其侵入钻井液治理探索OA北大核心CSTPCD

High viscosity heavy oil invasion in the Tahe block have caused serious damage to the properties of the drilling fluids.To deal with this problem,the key properties of the Tahe heavy oils and those of the typical poor quality heavy oils were compared,and the change of the viscosity of the Tahe heavy oil asphaltenes in toluene solution with the concentration of the heavy oils was studied.It was found that the high viscosity of the Tahe heavy oils comes from high asphaltene content and high aromaticity.Based on this finding,two programs were prepared;one is,at the time when there is only slight heavy oil invasion,a compound additive containing appropriate dispersants and aromatic fraction can be added into the contaminated drilling fluid to disperse the heavy oils.This treatment has been best done in the 5#drilling fluid.In drilling the well TH121155X,the dispersity of the heavy oils in the solids-free drilling fluid was more than 99%.The other treatment involves the contamination of drilling fluids by large amount of heavy oils.In this treatment the heavy oils are wrapped up by wrapping agents and therefore lose their adhesiveness.The adhesiveness of the wrapped heavy oils on the surfaces of the drilling tools is minimized and the heavy oils can thus be effectively and efficiently separated out by the shale shakers.Study results show that wrapping agent BGJ-2-4 has good wrapping capacity for the treatment of heavy oils found in the well TH12471H,and the adhesion rate on the walls of mud tanks is only 0.3%.