Second-Generation Synthetic Drilling Fluids

Abstract

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Summary At the start of the 1990's, three synthetic materials were introduced:esters, ethers, and polyalphaolefins (PAO's). Now heading toward the last half of this decade, a new generation of synthetics is gaining popularity - linearalpha oletins (LAO's), internal or isomerized olefins (IO's), and linearparaffins (LP's). While similar, they also have differences, both as base fluids and as formulated drilling muds. These second-generation synthetic-based fluids (SBF's) have benefits over their predecessors in that they have lowerkinematic viscosity and are less expensive. As drilling fluids, these technical advantages give rise to a more flexible fluid to meet greater drilling demands for high-temperature/high-pressure (HTHP) applications, extended-reach-drilling projects, and deepwater drilling. As with the first-generation materials, environmental issues are the drivers for the development and use of these second-generation synthetics. Introduction Drilling with synthetic-based muds (SBM's) or pseudo-oil-based muds (OBM's)has become commonplace in both the Gulf of Mexico and North Sea areas. Synthetics also are in use or their implementation is planned in numerous other regions, such as the Far East, Australia, Mexico, Continental Europe, South America, and Russia. Because of the evolving marketplace, the view is that the industry has moved to at least the second generation of synthetics or pseudos. The boundary that separates first- from second-generation SBM's is arguably arbitrary but generally is delineated by both the cost and kinematic viscosity of the base fluid. Typically, second-generation synthetics are cheaper and thinner. Even considering these factors, second-generation SBM's have not totally replaced first-generation ones, although the use of the former flourishes while the latter wanes in areas where they coexist. Therefore, the first-generation SBM's can be considered to be based on the ester, ether, and PAO, while in the subsequent generation, the LAO's, IO's, and LP's are the base materials. Table 1 gives a more complete listing of first- and second-generation synthetics.