An Organosoluble Polymer for Outstanding Fluid Loss Control With Minimum Formation Damage

Abstract

Abstract Complex well configurations with long openhole sections are often left unprotected for a long time under various conditions. Oil-based and synthetic-based drilling fluids are very well suited for drilling these long sections down to reservoir formations, providing high rates of penetration, excellent lubrication properties, and wellbore stability. The enhancement in wellbore stability and lubricity as well as reduction in differential sticking, mud losses, and formation damage can be directly influenced by fluid-loss control and filtercake properties. As an example, formation damage is largely caused by solid invasion occurring during the first step of filtration, perhaps adversely affecting the porous media permeability/stability, and consequently, reservoir productivity. Both good fluid-loss control and minimum formation damage are required for drilling and completion fluids. A synthetic polymer, based on a unique microgel structure, has been designed to provide excellent fluid-loss control and low formation damage in OBM/SBM. Optimization of polymer morphology and fluid solubility gives a very versatile and cost-effective fluid-loss additive. The unique microgel structure allows the polymer particles to swell and stack up, forming a thin and efficient filter cake. The ability of the microgel particles to deform under shear stress allows them to be back-produced from the formation more effectively than non-deformable additives, thus reducing risks of formation damage in the pay zone. The polymer also may contribute to the rheology of the mud by providing low shear viscosity under demanding conditions. This paper reviews the effectiveness of the organosoluble polymer by presenting evidence of low formation damage illustrated by good return permeability data from both field and laboratory applications. Finally, data will be presented on new developments based on similar chemistry, allowing applications into more extreme conditions of temperature.