Ideally, a reservoir drill-in fluid (RDF) possessing both an oil external phase for drilling and a water external phase for completion would provide the ideal solution for drilling and completing a well. Through the manipulation of surfactant chemistry, a novel reversible invert emulsion drilling system, which provides both attributes, has been developed. During drilling, an operator can utilize the reversible oil-based mud to take advantage of the commonly accepted properties that enhance the drilling efficiency and then convert this system to a water-based fluid to improve the completion efficiency.
The amine-based surfactants used in the reversible invert system are strong emulsifiers in an alkaline medium; however these same emulsifiers become more common direct oil-in-water emulsifiers in the presence of protonating agents such as acid. This process of protonation and deprotonation of emulsifiers controls the emulsion phase of this drilling system and thereby, the oil-wetting and water-wetting characteristics of the subsequent filtercake and entrained solids. As the bridging agents in filtercake are commonly calcium carbonate, once water-wet (in presence of acid) promote clean-up and thus, are readily consumed by common acids that may be utilized during the completion phase.
This system was field trialed with success for drilling and completing an injector in the first quarter of 2000. Since this initial application, numerous completions have utilized this reversible invert RDF system. This system has been successfully applied to a variety of completions, in particular: injectors and producers, openhole gravel-packs (OHGP), expandables and standalone as well as various environments and reservoirs. Theoretically, this system also provides advantages with respect to common cementing and environmental issues.
This paper presents the development of this multi-purpose drilling and completion system and discusses the application of this technology to adapt to the challenges of evolving global completion complexity.
Several case history examples are presented from selected completions. The paper includes the laboratory pre-planning and field data illustrating the concerns and the development of a solution with respect to drilling and clean-up.