You're a petroleum engineer confronting that dreadful question, “Where to drill that next infill well?” Desperation sets in. Production has fallen big time. Management is unhappy. Shareholders are furious. A few months ago, the Wall Street Journal reported that, through 2017, one operator had spaced its wells 330 ft apart, then increased this to 500 ft (see “A Fracking Experiment Fails to Pump as Predicted, B. Olson, July 4, 2019). But the Journal ofPetroleum Technology recently gave different numbers, now “450 ft or 600 ft” (see “Simple Well Spacing Calculations are Inaccurate and Costly,” T. Jacobs, November 2019). Sometime back, the present author recalls a smaller 200 ft. Or something like that. Whatever the specifics, the consensus is clear - too close a spacing may be too bad and too late. <...>

Russia has increasingly become one of the most important centres for the activities on raw commodity assessments in the recent years due to its enormous resources spread out over a huge territory. As Russia is rapidly closing the gap between the requirements of the internationally accepted codes and its own resource assessment standard, the practical reality is that the legacy of the Soviet Union for the assessment of resources is still active and alive today. However, this does not mean the requirements of the old Soviet system, now the Russian system, are redundant or unacceptable to the codes seen in the international scenery; but it is rather a descriptive and useful tool which guides the competent persons and practitioners in a well prescribed way when they are assessing the mineral resources in Russia. As the old Soviet standard has also been adopted into the national legislations in the other former Soviet Union countries similar to the current Russian system, the Russian code has become an important element in reconciliation of the resources in accordance with the criteria defined in the internationally recognised codes for Reporting Mineral Resources and Ore Reserves such as JORC. This article reviews the experience of IMC in resource estimation in both Russia and neighbouring CIS countries in compliance with both the national code and international codes, and the related issues and obstacles faced and dealt by the competent persons <...>

Precious and base metal mineralization has long been known to occur in the El Indio area of central Chile. This mineralization occurs as veins containing very high grade Au and Ag, which was the main target for the majority of subsequent exploration. This exploration usually employed the use of remote sensing techniques to highlight color anomalies related to hydrothermal alteration, and local prospectors and geologists to follow up these anomalies. The recent discovery of significant disseminated Au mineralization south of El Indio in both Chile and Argentina has shown that the El Indio belt of rocks is probably under explored. Exploration techniques which can detect a variety of styles of mineralization in a single pass, and which are economically viable, must be introduced to the Andean exploration community. One of these techniques is stream sediment geochemical sampling; a well used exploration method in many parts of the world, but apparently only recently used in the Andes in a systematic fashion. <...>

When discussing the stability of iron oxides, one must invariably deal with oxygen fugacity as a variable. To many geophysicists the importance of this variable in determining the stability and composition of oxides is not immediately apparent. Indeed, even within the petrologic community there are many misconceptions about what oxygen fugacity is and how it applies to rocks. The purpose of this chapter is to introduce the concept of oxygen fugacity so that later discussions within this book that use oxygen fugacity as a variable will be more comprehensible. <...>