Research On The Mechanism Of Wellbore Instability And Technical Methods In Baonan Area

Oil Field data of Baonan area show that the complex downhole troubles have threatened drilling rate and the exploration and development. Wellbore instability is the bottleneck of the drilling speed of the block, so need to actively carry out the wellbore stability technology, improving drilling speed. Through the study of this thesis it is hoped that the reason for the complex downhole troubles like drill pipe sticking and bit balling of Baonan area can be found out, and excogitate a kind of anti-sloughing drilling fluids that can be well used in this area.In this thesis, it firstly analyzed the actual situation of Baonan oil field and researched on the reasons for the borehole instability; Secondly, it excogitated a kind of anti-sloughing drilling fluids that can be well used in this area. The physical and chemical characteristics of shales in the formations which were liable to collapse were studied. I used the drill core which was got during the borehole drilling in Baonan oil field to research on the technology of borehole stability, including the establishment of the three pressure profiles, composition analysis of clay mineral, dispersion test and so on. On the basis of the former research, the mechanism for borehole physical chemistry instability and pipe sticking were analyzed, and also the competent drilling fluids technology were putted forward, viz. enhancing the sealing and inhibitive ability.After finished the study of physical and chemical characteristics of shales, it researched on the configuration and performance of anti-sloughing drilling fluids.The research of anti-sloughing drilling fluids configuration included the selection and analysis of inhibitive agent, thinning agent, anti-sloughing agent, filtration control agent and plugging agent; The performance tests of drilling fluids included density, rheological and filtration control properties, viscosity, inhibitive character,anti-contamination property and lubricity;On the basis of optimized inhibitive agent,thinning agent, anti-sloughing agent, filtration control agent and plugging agent,excogitated a kind of anti-sloughing drilling fluids, and it was practice used in Baonan area.A lot of laboratory results and on site practice showed that this kind anti-sloughing drilling fluids exhibited favorable rheological and filtration control properties, as well as inhibitive character, anti-contamination property, and can effectively seal the micro-fractures and fracture zones in the formations, and the on-site maintenance is convenient.