Dean Oliver

Papers that are published in SPEJ generally first appear in the proceedings of one of SPE’s many technical conferences. When I previously reviewed the sources of individual papers over an 18-month time span in 2005–2006, I found that the two largest sources of papers for SPEJ were the Annual Technical Conference and Exhibition (40%) and the Improved Oil Recovery Symposium (15%). Most of the remainder were originally presented at several symposia for specialists (Oilfield Scale, Formation Damage, and Reservoir Simulation) and an average of one paper per issue had never been presented at a meeting, but was submitted directly to the peer-review process (a so-called unsolicited manuscript).

As SPE President William Cobb pointed out in the January issue of JPT, the number of manuscripts submitted for peer review has increased substantially over the past several years. The increase of submitted manuscripts can almost entirely be attributed to the increase in number of SPE technical conferences (32 conferences in 2007). Despite these changes, however, this issue of SPEJ follows a somewhat familiar pattern—four of the papers were first presented at ATCE, four were first presented at the IOR Symposium, one came from the Reservoir Simulation Symposium, one from Europec, and one from the International Oil and Gas Exhibition (China). The final paper was submitted directly for peer review. Because four of the papers originated at that series of meetings, I will provide a brief introduction to those papers.

“Impact of Acid Additives on the Rheological Properties of a Viscoelastic Surfactant and Their Influence on Field Application,” by Nasr-El-Din et al., examines a class of viscoelastic surfactants that are used to enhance sweep efficiency during matrix acid treatments. The effects of acid additives, including corrosion inhibitors, an iron-control agent, a hydrogen-sulfide scavenger, an antisludge agent, and a nonionic surfactant on the rheological properties of these systems were examined over a wide range of parameters. Effects of mutual solvents and methanol on the apparent viscosity were also investigated. The authors observed that temperature, pH, shear conditions, and acid additives have a substantial influence on the apparent viscosity of the surfactant-acid system. The viscosity and related properties are very different from what were observed with both natural and synthetic polymers. The differences in these properties were characterized and correlated with the type and nature of the additives used. Optimum conditions for better fluid performance in the field were derived.

“An Experimental Study of Wetting Behavior and Surfactant EOR in Carbonates With Model Compounds,” by Wu et al., focuses on the mechanisms responsible for enhanced oil recovery (EOR) from fractured carbonate reservoirs by surfactant solutions, and methods to screen for effective chemical formulations quickly. One key to this EOR process is the surfactant solution reversing the wettability of the carbonate surfaces from less water-wet to more water-wet conditions. This effect allows the aqueous phase to imbibe into the matrix spontaneously and expel oil bypassed by a waterflood. This technology provides a new opportunity for EOR, especially for fractured carbonate, where waterflood response typically is poor and the matrix is a high oil-saturation target

“Approximate Pore-Level Modeling for Apparent Viscosity of Polymer-Enhanced Foam in Porous Media,” by Huh and Rossen, describes a pore-level modeling study whose objectives are, first, to develop an apparent viscosity expression for polymer enhanced foam (PEF) at fixed bubble size, as a step to interpret the available laboratory coreflood data; and second, to understand why PEF is not as effective in porous media as in bulk state. To derive the apparent viscosity, a pressure-drop calculation for gas bubbles in a circular tube is extended to include the effects of shear-thinning polymer in water. The authors report that the apparent rheology of the foam depends on the rheology of the liquid; the trapping and mobilization of gas as a function of pressure gradient; and capillary pressure, which affects the apparent viscosity of the flowing gas even at fixed bubble size.

“Favorable Attributes of Alkaline-Surfactant-Polymer Flooding,” by Liu et al., reports a laboratory study of the alkali-surfactant-polymer (ASP) process. For the experiments that the authors performed, including some with surfactant concentrations as low as 0.2 wt%, interfacial tensions were low over a wide salinity range, leading to high oil recoveries in both dolomite and silica sandpacks. They did find that it was necessary that sufficient polymer be present to provide adequate mobility control and that salinity must be below the value at which phase separation occurred in the polymer/surfactant solution. Comparisons between predictions from a numerical simulator and the sandpack results were very good.

Please take a moment to scan the other eight papers. There is great deal of interesting material in this issue. I will also take this opportunity to encourage you to attend the IOR Symposium. It is held every 2 years in Tulsa, Oklahoma. This year, it occurs 20–23 April.