Drilling Fluid Technology for Horizontal Well in Ecuador Tambococha Oilfield

Abstract

The Tambococha Block in Ecuador is an oil field with high porosity and high permeability reservoir characteristics, the lower formation is broken and micro-fractures are developed too. For this reason, utilizing Polyalcohol XCS-III and emulsified paraffin G325 as the main two agents, then optimizing other environmentally friendly agents, a strong plugging reservoir protection water-based drilling fluid is formed finally, which is suitable for the Tambococha oil field in Ecuador. The drilling fluid utilizes the synergistic plugging effect of emulsified droplets, cloud point effect, micron particles and rigid particles to reduce the oil-water interfacial tension and prevent the drilling fluid from entering the formation to finally achieve the purpose of anti-collapse plugging and reservoir protection. Laboratory experiments show that the drilling fluid has strong inhibitory properties, and the linear expansion rate of cuttings in it is reduced by 64.8% compared with that in clean water; the plugging performance is good, and its particle size distribution can fit the ideal filling curve better; the damage to reservoir is a little, with an average damage rate of 10.25% to the cores of the U layer of the Napo formation; the drilling fluid has good environmental performance, and the content of heavy metals meets the requirements of sewage discharge standards. The drilling fluid system has been successfully applied to 15 horizontal wells in the Tambochocha Oilfield. The main performance is with wellbore stability and smooth tripping. The average daily crude oil output of a single well neers 300 t, which is nearly 90% higher than that of offset wells, and the environmental indicators of drilling fluid and drilling cuttings meet the requirements of EPA1311 standards. The research results show that the water-based drilling fluid can meet the drilling safety and reservoir protection requirements of horizontal wells of the Tambococha oil field in Ecuador.