340 Optimal well performance is always associated with the creation of a clean and undamaged connection between wellbore and reservoir. However, it is apparent that the use of shaped-charge perforating tends to produce perforation-induced formation damage. This damage impairs fluid flow and decreases well productivity. To minimize and eliminate this damage, underbalance perforating should be considered. Underbalance perforating has been considered as one of the best means of providing a transient surge flow for tunnel cleanup. This paper introduces the formulation of super lightweight completion to achieve underbalance condition. The formulation was optimized using fractional factorial design. The result indicates that the experimental data and model predictions agreed well. The optimum formulation condition is able to produce a stable fluid with minimum and acceptable density and viscosity. INTRODUCTION In cased hole wells, perforation tunnels are the only passage that allows fluid formation flowing towards the wellbore. To create these flow pathways, the shaped-charge jet perforator is the most widely used method [1]. The aim is to create a clean and undamaged connection between wellbore and reservoir. However, as this jet travels at high velocity (~8000 m/sec), it carries impact pressures of several million psi when it enters the reservoir [2]. This pressure impact generally impairs the rock properties. This rock properties impairment is referred to “perforation-induced formation damage” or perforation damage. It is reported that about 20% of rock permeability is reduced after gun detonation [3]. The problem of perforation-induced formation damage could be minimized or reduced through acidizing, skin fracture, extreme overbalance, propellant-assisted perforating, and shock or surging techniques [2, 4-6]. Unfortunately, such treatments require additional works, time, and cost. Thus, one of the most attractive ways to minimize or overcome perforation damage is through underbalanced perforation [2, 3, 7-9]. The method has been widely proven to improve productivity of wells [10, 11]. However, the question remains as to how to effectively achieve the underbalance condition effectively, i.e., what degree of underbalance is needed, what surge-flow is needed, and whether the procedure is effective in all situations[12]. Chemistry and Technology of Fuels and Oils, Vol. 46, No.5, 2010 FRACTIONAL FACTORIAL DESIGN OPTIMIZATION OF NONTRADITIONAL COMPLETION FLUID FOR PERFORATION WITH UNDERBALANCE Munawar Khalil, Badrul Mohamed Jan, Abdul Aziz Abdul Raman ____________________________________________________________________________________________________ Department of Chemical Engineering, Faculty of Engineering, University of Malaya 50603 Lembah Pantai, Kuala Lumpur, Malaysia. Published in revised form in Khimiya i Tekhnologiya Topliv i Masel , No. 5, pp. 40 – 45, September – October, 2010. 0009-3092/10/4605–0340  2010 Springer Science+Business Media, Inc.