Partially hydrolyzed polyacrylamide with high molecular weight is designed to inhibit clays and clay shales by means of clay particles encapsulation. Furthermore, the reagent may serve as a drilling mud thickener, flocculent, fluid loss reducer, and it has low lubricating properties. The reagent may be used in different types of water-based drilling muds, including clayless and thin clay drilling systems, weighted fluids, seawater-based drilling muds.
Range of applications
It has exclusive encapsulating properties providing high well bore stability. Normal drilling mud concentration ranges from 2 to 8 kg/m3. The reagent is efficient in potassium chloride and salt-saturated drilling muds (although it may be necessary to increase the reagent concentration slightly). In thin clay systems it is often used as a thickener and flocculent to increase bentonite return. When the reagent is used in weighted drilling muds, it provides an improvement of clay cake quality and reduction of fluid loss. When drilling large-size wells, it is often used for making sand bridges to remove coarse grains of drilled cuttings. To prepare such sand bridges, sometimes it is enough to put 3-4 liters of concentrated (30%) polymer solution in the drilling strings during RIH/POOH or extension operations. The most effective way is to inject aqueous solution of polymer in thin jet into the active mud tank during circulation.