Proper Design Criteria of Microemulsion Treatment Fluids for Enhancing Well Production

Abstract When newly drilled oil and gas wells fail to reach the expected production levels, near-wellbore damage may have resulted from fluid incompatibility, poor fluid/rock interaction and/or mechanical damage. These problems may also occur during remediation or stimulation operations, if the treatment fluid is not properly designed. The principal formation damage mechanisms that lead to these problems are in-situ emulsions, wettability changes, water blocks and scale formation. It is recognized that such reservoir damage can be removed or prevented using microemulsion technology that leads to more productive oil and gas wells. The challenge is to design and select an optimized microemulsion system based on the reservoir conditions, such as the bottomhole temperature and the individual compositions of the crude oil, formation water, and the drilling and completion fluids. A well-designed treatment fluid should provide ultra-low interfacial tension, high oil solubilization and total compatibility with all fluids it encounters. The selection of the optimum formulation for a specific application requires a systematic study of the phase behavior of brine-surfactant-oil systems as a function of temperature and its final composition, including the salt, surfactants, co-surfactants and an optional acid. This paper provides a comprehensive discussion of the phase behavior obtained with the brine/surfactant/oil systems used in microemulsion formulations for formation damage prevention and removal. Laboratory tests results and field applications in openhole and cased-hole completed wells have proven that the microemulsion treatment fluids are successful in the field, if there is a systematic analysis of phase behavior that identifies and defines the treatment fluid phase boundaries.