As an ex-USGS man and an ex-President of AAPG, may I recall the first words of the conference when Dr. McKelvey said that, for many years, we have watched cooperative efforts of these two the successful fruition of one such effort. Let me relate a few personal impressions I have had about this meeting, with the hope that they may be helpful at the next meeting 18 months from now.3 I am sure that Dr. McKelvey is absolutely right when he says that underground spac3e involves the discovery of an entirely new resource in the realm of environmental management. As was said by Dr. Greenfield at the dinner last night, we have passed the time when we can go high enough in the air to throw away our wastes, nor can we go deep enough in the sea to deposit our wastes.
There is a serious question as to whether our understanding of all the repercussions that may result from disposal of waste into the crust of the earth is sufficient to allow us to proceed without a great deal more concern than we have right now. In the early part of our meeting, there was far more claim to lack of knowledge about the characteristics of that very intricate dynamic system which is the crust of the earth than there was confident knowledge about what is there. Yet, from one of the first papers of the meeting, it become evident that the pace of establishing regulations is outstripping our real knowledge of what we are regulating.
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This publication consists of papers based on oral presentations at a symposium of the same name co-sponsored by the United States Geological Survey and the American Association of Petroleum Geologists. A wide range of technical issues are covered, as well as regulatory and liability concerns. Documentation of two areas in Colorado where earthquakes had resulted from subsurface fluid injection set the stage for modern debates regarding possible similar results elsewhere. A wide range of fluid compositions are subject to subsurface waste disposal. The largest volumes are brines separated during the production of oil and gas wells, but acid-water and industrial wastes of all types can be disposed in significant quantities in local areas. Large hydraulic fracture treatments never recover all of the injected fluids, and the chemical additives in the fluid that remains underground can be a concern. The subsurface injection of radioactive waste is a topic for three of the papers. The possible need for sequestration of carbon dioxide was not a significant concern at the time and was not covered, but many of the papers provide insight into the issues related to modern proposals. When fluids are injected under pressure into subsurface aquifers, they interact in numerous ways. The fluids can potentially migrate for long distances and potentially interfere with other uses for the native aquifer fluids. If the aquifer cannot transport all of the fluids away, the buildup in pressure can cause fracturing of the rock. Differences in composition between the injected and native fluids can cause chemical reactions to occur; in some cases these can be desirable in that they can immobilize certain solutes in mineral form. The long-term environmental consequences are a common theme in many of the papers because of the recognition that the disposed fluids would become a permanent fixture in subsurface aquifers and could have long-term consequences for their future utilization.