Executive Summary

Anil Ambastha, Chevron

Papers in this issue of SPE Res Eval & Eng focus primarily on enhanced oil recovery, CO2 sequestration, reservoir surveillance, and formation evaluation. The following is a brief outline of the papers in this issue:

Enhanced Oil Recovery

Upscaling of Miscible Floods in Heterogeneous Reservoirs Considering Reservoir Mixing shows how to estimate the level of mixing in a reservoir and how to incorporate mixing into the upscaling procedure. Heterogeneities are assumed to dominate the flow regime so that gravity effects are negligible. This paper shows how to determine a priori the maximum gridblock size allowed in both the x- and z-direction to predict the oil recovery from miscible gasfloods accurately. Using the method of characteristics and a newly developed mixing-cell method, A Practical Method for Minimum Miscibility Pressure Estimation of Contaminated CO2 Mixtures provides an easy and accurate way to determine impure CO2 minimum miscibility pressures (MMPs) for variable field solvent compositions based on just a few MMPs. The approach could alternatively be used to estimate the enrichment level required to lower the MMP to a desired pressure. The number of MMPs needed for the method is equal to the number of components in the injection gas. Experimental and Numerical Modeling of Three-Phase Flow under High-Pressure Air Injection presents numerical simulation of three-phase coreflood and combustion tube experiments. Analysis of the simulated data suggests that the reduction in gas-phase mobility encourages an early increase in the oil rate, which is more consistent with experimental data than that predicted by a model with conventional relative permeability. The improved characterization on relative permeability considering gas-phase hysteresis for simulating high-pressure air injection enhances the predictive capability of the available commercial simulators. MEOR Success in Southern Saskatchewan describes a successful pilot application of injection of a nutrient solution into several wells to stimulate indigenous microbes to grow, multiply, and help to release oil. This process achieved significant water-cut reduction and increased oil production from a mature waterflooded field in Saskatchewan.

CO2 Sequestration

Extraction of Dissolved Methane in Brines by CO2 Injection: Implication for CO2Sequestration discusses phase-behavior and numerical-simulation results for brine/methane/CO2 systems. Results of 1D and 3D compositional simulations are described around the issues of methane extraction and CO2 sequestration.

Reservoir Surveillance

Integrated Surveillance Enhancing Quality of Decisions and Reservoir Description in the Harding Field applies an array production log (PL) to improve reservoir characterization along a horizontal well. Improved characterization showed that initial insert string solution was inappropriate and pointed to a new infill target toward the toe of the horizontal well. This paper also highlights the need to take more PL measurements to calibrate the seismic response and improve the reservoir model.

Formation Evaluation

Net Pay: What Is It? What Does It Do? How Do We Quantify It? How Do We Use It? emphasizes the importance of net pay for the volumetric estimation of hydrocarbon resources and provides a data-driven path to ascertain net pay under various reservoir conditions. The Equations Archie Forgot: Anisotropy of the Rocks analyzes electrical flow through the intricate conductive paths of the rock in its quest to shed light on the role and quantification of anisotropy in relation to Archie’s equation. The author confirms his analysis with Archie's and Hamada's core datasets. The principles described in this paper can be applied in clean and complex formations (shaly sands, thin beds and vuggy and fractured carbonates) to get enhanced values of water saturation.

As you study your favorite paper(s) to enhance your own knowledge and/or apply in your work activities, please recognize that SPE welcomes further "discussion" of any of the papers published in any SPE journal, including this one. Therefore, please feel free to submit discussion of a paper either online or by mail to SPE.

Anil Ambastha, Chevron