Determination of Optimum Parameters of Aphron Fluid Using Design of Experiments with Taguchi Method and Laboratory Investigation of its Rheological Properties and Formation Damage

Recently, in consequence of the decrease in easy access to crude oil reservoirs, oil and gas industry has fouced on production from heavy oil and exhausted reservoirs (low pressure reservoirs). Drilling in low pressure reservoirs is associated with many technical and economical problems that occasionally make these fields economically unprofitable. Most of the problems include uncontrollable lost in fracture and formation damage in production zone. Drilling fluid plays a significant role in achieving the appropriate drilling technology as penetration of the drilling fluid in formation results in reducing the productivity of the well especially in depleted reservoirs. Multi-layer micro-bubble fluids or aphrons have been used in recent years as a part of water base and oil base drilling fluids. Their effect on reducing the formation damage has been observed in application. It should be noted that these fluids are suitable for drilling of depleted reservoirs because of their bridging properties. In this study, in order to determine the optimal stability conditions of factors such as: type of polymer, polymer concentration, surfactant concentration, pH, salinity, mixing time and RPM using Taguchi experimental design with L36 array (two parameters in two levels and five parameters in three levels) Were optimized. Then, the effect of the concentration of polymer and surfactant on rheological properties was studied and the optimal fluid was selected for damage testing, and the return permeability of the micro-bubble fluid was compared with the base polymeric fluid. A micro-bubble fluid with a concentration of 3 pounds per barrel of XG and 1 pound per barrel of SDBS showed the most stablilty and most stable rheological properties.Micro-buble fluid also showed a better performance in evaluating pressures in formation damage test in comparison with polymer base fluid both return permability wise and shut-off wise.