Over past few years, diagenesis researchers have made major progress in evaluating large empirical data sets and as a result, have begun to provide better assessments of major reservoir quality trends than were previously available. However, as the reader of this review may also infer, there have been no major breakthroughs in the resolution of many longstanding technical issues. One factor in these trends may be the decrease in basic diagenesis research in the petroleum industry. In the mid to late 1980's, many industry research programs still contained a range of projects that addressed fundamental diagenetic processes. Most of these programs now have very little explicit diagenesis research, and the research that remains is often focused on specific case studies. With oil prices expected to remain at moderate levels for the next several years, there is no reason to suspect the focus to change soon.
Even if research staffs were increased, one might still wonder how they would make major breakthroughs, given that most of the key technical issues have been around for decades. In my opinion, new breakthroughs in the field of reservoir quality prediction will come from continued emphasis on the three fundamental areas that typify most complex geologic systems: (1) adequate characterization of the critical components of the ``system,'' (2) a good understanding of interactions between individual components, and (3) quantitative modeling of the system's behavior as a whole. Diagenesis researchers are now addressing the right controversies and developing the right tools to make long-term progress in the above areas. The quartz cement controversy provides a good illustration. Over the past decade or so, presumed sources of quartz cement have covered the spectrum of scales from entirely local, i.e. intergranular pressure solution, to entirely regional, i.e. large-scale fluid flow. Neither end of the scale completely explained the observed cement trends, and current research efforts now reflect the realization that a truly predictive model for quartz cement will have to involve a range of local and larger-scale controls and their interactions. I believe we are now at the stage where the major controls are recognized, and we are correctly working on quantifying their interactions, as evidenced by recent analyses undertaken to quantify the role of shales as sources and sinks of cement. This seems a promising evolution and one likely to lead in the long term to more adequate predictions. In fact, the increased emphasis on shallow, groundwater-related diagenetic studies will undoubtedly help promote breakthroughs in our understanding of diagenesis in petroleum reservoirs by driving development of the tools required to predict complex, kinetically-controlled reactions in near-surface environments. As a final note, one message is clear: only through a carefully integrated mix of basic and applied research will it be possible to make needed technical advances. If our research focus is too narrow, we will lose opportunities to make those advances.
Acknowledgments. The experiences of a single researcher are largely inadequate to address all of the topics included in a subject as complex as sedimentary diagenesis. I am grateful to my colleagues at Exxon Production Research Company for discussions and insights, in particular, Joanna Ajdukiewicz, David Awwiller, Jon Kaufman, Kathy Nagy, Stan Paxton, Dave Pevear, Bob Pottorf, Peter Vrolijk, and Ray Wright. Careful reviews by two anonymous reviewers also improved the quality of the manuscript. Exxon Production Research Company is acknowledged for providing the time and resources to complete the review.