Copyright 2012, AADE This paper was prepared for presentation at the 2012 AADE Fluids Technical Conference and Exhibition held at the Hilton Houston North Hotel, Houston, Texas, April 10-11, 2012. This conference was sponsored by the American Association of Drilling Engineers. The information presented in this paper does not reflect any position, claim or endorsement made or implied by the American Association of Drilling Engineers, their officers or members. Questions concerning the content of this paper should be directed to the individual(s) listed as author(s) of this work. Abstract Surfactants systems have been used in oil well drilling and completion fluids for several decades and have been used for numerous applications, including emulsification of brine for invert emulsion fluids, emulsion prevention in completion fluids, wellbore clean-up in spacer trains, flowback enhance- ment in drill-in fluids and numerous other applications. In recent years, the use of specialized designer surfactant blends to remove formation damage and dramatically improve production in cased hole and open hole completed wells has prompted field personnel to expand the range of target applications of this technology. The aforementioned specialized surfactant blends have several unique functional characteristics that make them ideal for multiple uses in the field. Generally, these systems solubilize oil, remove oil from surfaces, remove emulsions, water-wet and disperse solids, reduce interfacial tension and mobilize in-situ fluids. With a full understanding of the mechanistic ways that these surfactant blends function under downhole conditions and when confronted with various operational issues in the field, this technology was successfully used to free stuck pipe, to free blocked completion screens of heavy oil sediments and to prepare a well for water injection. This paper presents the technology associated with specialized designer surfactant blends and the case studies where the technology was applied in the field to enable project successes. Introduction Prevention of formation damage has been a major emphasis for fluid designs targeted for the reservoir drill-in and completion phases of drilling projects. 1-2 Similarly, surfactant systems for more effective displacements, drill-in fluid filter cake removal, and perforation damage remediation have been introduced to further enhance wellbore productivity and achieve project objectives. As the frequency and success of designer surfactant systems applied to a wide range of wellbore clean-up scenarios increased, an expanded understanding of their versatility by R&D departments began to emerge. Transferring this new technology to field personnel can be a painstakingly long process; however, once the basic fundamentals are fully understood, the scope and number of field applications expand, leading to a similar expansion of the technology to include markets not previously conceived by research personnel. One of the new surfactant system designs that enjoyed significant success is the removal of S/OBM filter cakes in open hole (OH) completions with microemulsion technology. 3 Likewise, in wellbore displacements and cased hole (CH) remediation applications, microemulsion technology has been successfully applied to clean oily debris from casing and to treat damaged perforation zones. As will be explained in more detail, these surfactant systems impart ultra-low interfacial tension (IFT) between in-situ fluids and the surfactant-based treatment fluids. The low IFT, in turn, is associated with high oil solubilization, increased diffusion rate, and enhanced fluid mobility and the dispersion of compacted oil-wet solids to achieve a wide range of downhole objectives. When field personnel began to more fully understand the value of low IFT, high diffusion coefficients, oil solubility, water-wetting phenomenon and fluid mobility alteration, they began to envision a rash of new field applications for microemulsion technology. This paper presents the process used to select and combine surfactants to design highly efficient microemulsion cleaning fluids not only targeted to improve reservoir production but also to improve other critical processes during the wellbore construction process. In addition, three field applications are presented that demonstrate the successful application of these specially designed surfactant systems. Selection of Surfactants for Treatment Fluids The process of selecting a formulation with surfactants for enhancing well injection or production needs be done systematically. Normally, this includes phase behavior studies as a function of the composition, and studies of interfacial tension, contact angle, fluids compatibility and permeability evaluation .4 These surface-active additive packages consist of a blend of surfactants and co-surfactants that are soluble in water. The selection of these additives is determined from systematic phase behavior studies in brine-oil-surfactant systems. Additional components, such as acid, are also included in the phase behavior studies. In general, the performance of the surface-active additive packages and phase behavior of the system is significantly influenced by temperature, salinity, oil/water ratio, and other factors. AADE-12-FTCE-53 Specialized Surfactant Technology Applications Enable Project Successes Patricia Ullauri, Carlos Toro, Cesar Guerra, Tom Jones and Lirio Quintero, Baker Hughes