Executive Summary

Anthony R. Kovscek, Stanford University

This issue of SPE Journal contains a broad range of topics related to carbon dioxide, gas injection and production, and reservoir geomechanics, as well as reactions in porous media. The concept for an issue with a focus on CO2-related topics emerged more than a year ago. While SPE Journal  has published manuscripts related to CO2-enhanced oil recovery (EOR) and gas injection on a regular basis, there has been a steady uptick in submissions with different focuses. In this issue, papers range from EOR, CO2sequestration, experimental measurement of relative permeability, CO2-induced mineralization, well cements in CO2-rich environments, salt deposition around wells, and similar topics.

With respect to CO2, it seems that members of the Society, through their research, have embraced CO2 in the subsurface nearly in its entirety. Given the current and growing importance of CO2 EOR as well as the potential importance of carbon sequestration in geological structures and enhanced gas recovery, this is an important undertaking of the research community. Of note in this issue are the six manuscripts relating to chemical reactions in porous media. While some of these manuscripts are traditional in the sense that they are concerned with formation acidizing, the remainder relate to the interaction of CO2-laden brine with well cements and mineralization within the formation. The complete cycle of CO2 from injection to migration within a geological structure to immobilization and to mineralization is under consideration.

What I find interesting on a personal level is the nonconventional spectrum of topics investigated. Some of the papers that readers will find in this issue examine the transport behavior and the very nature of CO2 and natural gas within tight rocks such as shales and coal. Shale gas and its host shale porous medium have been the source of much interest lately. For geological carbon sequestration, this medium has been virtually ignored until the very recent past. We have spoken of depleted oil and gas reservoirs, saline aquifers, and unmineable coal beds as geological storage sites. Sequestration capacity of these geological settings alone has been estimated, through with a great range of variability. Of course, much more work is needed; however, it may well be shown that the potential for CO2 storage in shale is vast. Coupled with this sequestration potential is the reality that the recovery factors for natural gas from shale are rather low to date. It is not difficult to envision a recovery process that injects CO2 into gas shale as a means of enhancing gas recovery with a byproduct of CO2 storage. The research and engineering effort will be significant to realize such a vision, but the task has begun, as reported in this issue.

In closing this final issue of 2011, I would like to extend my sincere thanks to the Associate Editors (AEs) of SPE Journal. You will find their names at the front of the print version and also online, listed on the mainSPE Journal page. Your AEs do the hard work of soliciting reviews, making sure that high-quality reviews get delivered, and synthesizing a recommendation from those reviews. Without their efforts, SPE Journalwould not turn around the first reviews and decisions on manuscripts in roughly 100 days as we do now. The service of AEs is invaluable to this journal, and has not gone unnoticed.

Thank you for reading. I hope that you enjoy this issue and its 25 papers.