Research on low oil-water ratio of oil-based drilling fluid system
At present,the oil-water ratio of oil-based drilling fluid system widely used in China remains high,and due to the poor performance of some treatment agents,the amount used in some drilling fluid systems is too large.The combination of the two poses great diffi-culties in reducing the comprehensive cost of oil-based drilling fluid system.To this end,a design concept for a low oil-water ratio of drilling fluid system was proposed,and based on this,key treatment agents for oil-based drilling fluid system were selected.Through compat-ibility experiments,a low oil-water ratio of drilling fluid system formula was constructed,and on-site applications were carried out.The overall idea is to effectively reduce the oil-water ratio on the basis of ensuring good emulsification stability,rheological properties,and strong plugging while drilling,a new type of emulsifier with multiple active points has been devel-oped,which increases the number of active adsorption groups within the molecule and ex-hibits good emulsification stability and rheological properties under low oil-water ratio.A low oil-water ratio diesel based drilling fluid system was constructed with three treatment agents as the core,including organic soil with good viscosity increasing and shear reducing effects,filter loss reducing agents with good filter loss reducing effects,and flow pattern regulators with improved rheological properties and emulsion stability.The system has a demulsification voltage greater than 1 000 V before and after aging under an oil-water ratio of 70/30,and greater than 500 V before and after aging under an oil-water ratio of 60/40.The ratio of yield stress to plastic viscosities greater than 0.40,indicating good emulsification stability and rhe-ological properties.Low oil-water ratio of oil-based drilling fluid system has been applied on-site in 12 shale horizontal wells.The drilling fluid system has stable performance,good well-bore purification effect,and controllable emulsification stability,leading to greatly saving the amount of base oil and significantly reducing the cost of oil-based drilling fluid system.
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