Study On Ultra-high Temperature Poly-sulfonated Drilling Fluid For Deep Coring Drilling In Well Songke 2

With the development of deep drilling projects,higher demands have been put forward for high-temperature drilling fluid.Compared with water-based drilling fluid,oil-based drilling is much more advantageous to be used in hot wells,considering the comprehensive effects of high temperature resistance,inhibition,lubrication and filtration.However,water-based drilling fluid is still unreplaceable in terms of environmental,logistical and cost effective.Domestic water-based drilling fluid temperature resistance is generally below 200 ?,higher-temperature drilling fluid technology is in urgent demand.Different from the conventional drilling fluid,the main technical difficulties of ultra-high temperature water-based drilling fluid including: a)wellbore stability under high temperature and pressure environment,b)rheological properties controlling,c)inhibition controlling,etc.In general,the deeper the well,the higher the risk of encountering the complex formations,and the more complicated factors should be considered,leading to more difficult to balance the contradictions between the various properties of the drilling fluid.Based on the Continental Scientific Drilling Project of Songliao Basin,we carried out the research of high-temperature drilling fluid suitable for 4th spud.On the basis of the formations to be drilled and the designed drilling technology,the key point of the drilling fluid design was to achieve the harmonization of the comprehensive properties,including rheology,filtration,and inhibition.Firstly,we summarized the research progress of high-temperature drilling fluid system at home and abroad,and clarified the mechanism of high temperature on rheology,filtration,and inhibition,etc.Attapulgite was compounded with sodium bentonite to increase the clay quantity limit in formulating high temperature drilling fluid.Drilling fluid additives of great salt resistance and thermal stability were optimized for colloid protection.Results shown that the addition of bentonite varies between 2% and 4% was suitable to formulate the drilling fluid at 230?.Compared with the chloride salt,the use of formate as inhibitor can improve the thermal stability of the drilling fluid.The high temperature drilling fluid developed has a good stable thermal stability,rheological property,lubrication,inhibition,and wall building property.A good effect of the high-temperature drilling fluid system was obtained in field application during the core drilling project.