Executive Summary

It is my great pleasure to serve along with Knut-Andreas Lie as Executive Editor of SPE Journal. I hope to perform as well as our two esteemed predecessors, Mustafa Onur and Yucel Akkutlu.

Enhanced Oil Recovery. For my first issue of SPEJ, I have selected 25 papers—11 of which focus on enhanced oil recovery. The first paper demonstrates that too much association between hydrophobic associating polymers can limit their utility for polymer flooding—especially with respect to penetration into less-permeable rock and if polymer concentration exceeds a certain limit. In the second paper, use of ammonia as an alkaline agent is argued to save weight and space during offshore ASP floods. However, use of ammonia may require simultaneous addition of sodium carbonate to precipitate calcium when calcium-intolerant surfactants are used. The third paper introduces alkali metal silicides for generating heat and alkali silicates during recovery of heavy oils. The fourth and fifth papers describe the coupling of a geochemical package, called IPhreeqc, with the chemical-flooding reservoir simulator, UTCHEM. The sixth paper models displacement of 5,000-cp oil by combining electric heating, horizontal wells, and alkali/cosolvent/polymer flood. The seventh paper simulates electric Joule heating of heavy-oil reservoirs, with an emphasis on the effects of water-saturated fractures (which are beneficial) and water vaporization (which is detrimental).

In the eighth paper, computed tomography (CT) images are reported for surfactant imbibition into oil-wet limestones, and a new scaling group is proposed to model gravity-dominated surfactant imbibition. In the ninth paper, CT images are used to argue that diffusion can be a feasible oil-recovery mechanism during CO2 floods in highly fractured reservoirs. The tenth paper presents a laboratory study of foams that were stabilized by use of nanoparticles. The ability to propagate effectively through porous media remains an important uncertainty for these materials. In the eleventh paper, laboratory pressure-decay experiments are used to determine diffusion coefficients for CO2, propane, and butane when contacting a heavy Canadian oil. Diffusion coefficients for CO2 were approximately three times higher than for propane and approximately six times higher than for butane.

Multiphase Flow and Phase Behavior. I have placed five papers under this heading, the first of which applies mode decomposition and interpolatory projection methods to speed up simulations of two-phase flows in heterogeneous porous media. The second paper simulates three-phase capillary pressure curves and fluid configurations in 2D rock images during gas flow to displace oil and water under mixed-wet conditions. The third paper examines the effect of temperature on gas/oil relative permeability for Orinoco Belt foamy oil. Increased temperature was found to significantly increase gas relative permeability, with minor effect on oil relative permeability. The gas relative permeability behavior was tied to the resin and asphaltene composition of the oil. The fourth paper measures and models methane solubility and density and viscosity of Athabasca bitumen at temperatures from 50 to 190°C. The relative impact of methane on bitumen viscosity was substantially greater at 50°C than at 100°C or higher temperatures. The fifth paper argues that molecular modeling must be used (in place of conventional equations of state) to describe phase behavior in pores less than 10 nm in size (i.e., in shale).

Fracture Inducement and Characterization. Five papers are also included in this category. The first paper uses numerical and analytical studies to determine when, where, and how microseismicity is generated in natural fractures during hydraulic fracturing. The paper shows that both fluid leakoff and stress changes can induce local slip along natural fractures. The second paper describes an automated method to make discrete fracture networks on the basis of microseismic data. The method uses a Hough-transform technique and fracture plane orientations derived from moment-tensor analysis. In the third paper, flowback-salinity data from three multifractured horizontal wells were analyzed. A model was developed to estimate the distribution of fracture aperture sizes. The fourth paper discusses the principles and application of applying nodal analysis to evaluate production from unconventional reservoirs. The fifth paper develops a model for fracture height growth and containment for multiple induced fractures in horizontal wells as a function of fracturing-fluid pressure, fracture spacing, and modulus contrast.

Acidizing. There are two papers included that deal with acidizing. The first examines phosphonic-based hydrofluoric acid and its effects on four clays and flow in sandstone. The paper concludes that this acid performs better than regular mud acids in Berea sandstone at 300°F. The second paper presents a thermal-fracturing-acidizing model that uses the lattice Boltzmann method to simulate reactive transport.

Drilling. In the final category, two papers deal with drilling. The first paper examines how the design of push-the-bit rotary-steerable systems affects the tendency to drill spiraled boreholes. The paper found that as pad stiffness increases, perturbations in the borehole geometry can trigger self-excited oscillations. The final paper uses a mechanical-specific-energy model to analyze the rate of penetration for pulsed-jet drilling. Both laboratory and field data were analyzed.

Randy Seright, New Mexico Institute of Mining and Technology