DRILLING FLUIDS TECHNOLOGY FOR PROTECTION HEAVY OIL RESERVOIR

The heavy oil reservoir have the characters of high porosity and high permeability,the serious formation damage will be caused by the drilling fluids loss during the drilling.Recognizing the pore structure and designing the reasonable drilling fluid system for protection reservoir are prerequisite for efficient development of the heavy oil reservoirs.The experiment results of original drilling fluid showed that the drilling fluid had the features of the poor filter cake,and the low permeability flow back effect.According to the reservoir damage characteristics of drilling fluid,the temporary plugging drilling fluid system for protection reservoirs have been developed,and the experiment results were very good,the mud cake could be formed in few minutes after the fluid contaminate core,and the temporary blocking rate could be up to 99% in a short time,the flowback recovery rate could reach 90%.