The New Geophysics

Recent advances in understanding in situ fluid-rock deformation show that the stress-aligned fluid-saturated microcracks in almost all rocks in the Earth’s crust and upper mantle are so closely spaced that they verge on fracture-criticality and failure by fracturing. This means the microcracked rocks are critical systems with the “butterfly wing’s ” sensitivity of all critical systems. We suggest that the ‘crack-critical ’ crust has such profound effects on the behaviour, calculability, predictability, and even possibly controllability, of in situ rock and hydrocarbon reservoirs that it is a New Geophysics, where much conventional geophysics is invalid or inappropriate. We suggest that this New Geophysics has major implications for hydrocarbon recovery (and many other geo-engineering operations), and could change many aspects of oil-related geophysics in the future. Note that much of the evidence for the New Geophysics comes from earthquake rather than exploration seismology. But rock is rock. Almost all rocks are saturated with fluids, and the only difference between hydrocarbon reservoirs and other rocks is that the saturating fluid is a hydrocarbon rather than a water-based salt solution. The fundamentals of fluid-rock deformation remain the same. 1