Research On Borehole Stability Techniques In Tanan Block Of Haita Basin

The geological structure is very complex in Tanan Block of Haita Basin,circulation loss and borehole collapse is easy to happen during drilling process.Evaluating the formation stability of Tanan Block effectively and taking reasonable measures to control borehole collapsewhich are always the major problems that constrain exploration and development of Haita Basin to ensure high-quality,fast drilling.Based on the analysis of physico-chemical performance parameters of the mineral in Tanan Block,using Fuzzy Comprehensive Evaluation Method to access the stability of the clay shale,and found that this area is located in unstable level on the whole.Combined with the geological characteristics and construction in Tanan Block,the most effective measures are found out currently to prevent the region stratum collapsed--optimizing drilling fluid system.Based on the research of the reservoir geological characteristics in Tanan Block,the rheological property,rejection capability and reservoir protection effect of micro foam drilling fluid system which is used in Tanan Oil Field are evaluated.And find that the rejection capability and the ability of resistance lock water damage of the micro foam drilling fluid system are unsatisfactory.Aimed at the problems founded in evaluation process,we have optimized treating chemicals and their appropriate dosage according to the indoor experiment,optimized the micro foam drilling fluid system applied in the field.The optimized drilling fluid system has better rejection capability and effect of prevent the collapse.The application results show that the drilling fluid system can plug the micro pore of formation and control the accident of borehole enlargement and collapse effectively.