What's happening in exploration
Gravity: a force of attraction? Or maybe it sucksIt was billed as the last eclipse of the century. As the moon’s shadow made its way across a long path from England to the Indian Ocean, hundreds of scientists were hard at work, gleaning what they could from the event. This is also the eclipse that hopes to solve a 45-year-old gravitational mystery. To understand the enigma, one must begin at the 1851 World’s Fair. At the fair, Jean Bernard Leon Foucault showed that a pendulum could track the Earth’s rotation. The principle is simple: as the pendulum swings freely from a universal joint, the Earth continues to rotate beneath it. Today, there are more than 60 Foucault pendulums worldwide, located mostly in museums and atriums, some swinging from heights of more than 90 ft. Jump ahead 103 years. In an extraordinary feat, Maurice Allais, working at his Paris lab, recorded the angular rotation of a Foucault pendulum every 14 minutes for 30 days and nights — without missing a data point. His observations happened to overlap an eclipse. His findings were repeated five years later in an identical experiment: "During the total eclipses of the sun on June 30, 1954, and Oct. 22, 1959, quite anomalous deviations of the plane of oscillation of the (Foucault) pendulum were observed ..." Allais made this statement during his 1988 Nobel autobiographical lecture. The recorded deviations were relatively large and long (2.5 hr) duration. Only two scientific records of long-term Foucault pendulum movement have ever been published — both by subsequent Nobel prize winners, albeit not for their pendulum work. However, there have been many investigations into the Allais effect since it was first reported. The published Allais-effect scorecard thus far: six yeas, three nays and one maybe. Only four of these used Foucault pendulums, and those were all years. One of the confirmations, during a 1981 eclipse, was made without the observers’ knowledge of the Allais effect. The current effort. Because of an eclipse’s short duration, numerous tests can’t be conducted from a single location. Also, to eliminate the possibility that the Allais effect is due to local effects, such as seismic or temperature changes, a global effort was undertaken for the August 11 event. Dr. David Noever of NASA/Marshall coordinates a worldwide team on four continents, seven countries and 11 cities. The 12 Foucault-pendulum members consist of universities, museums, NASA and a monastery; while a dozen — mostly exploration service companies, such as LaCoste & Romberg and Edcon — comprise the gravimeter group. They will make observations both within and outside of the path of totality. Should the Allais effect hold, it would reinforce the inescapable fact that our knowledge of gravity, and much else, is tentative and incomplete. Absent systematic error or local effects, there is no theoretical framework that can explain the Allais effect. Nevertheless, that won’t stop speculative theories, which currently include focused gravity waves and space-time anisotropy (as if geophysicists don’t have enough anisotropy in their lives!). For more information, go to: http://science.msfc.nasa.gov/newhome/headlines/ast06aug99_1.htm. Comments, ideas or suggestions? Drop this editor a line at: fischerp@gulfpub.com. Gravity’s effect on reservoirs? Could a better understanding of the effect of tidal forces result in more oil produced? The National Petroleum Technology Office — a branch of the DOE — awarded $400,000 to the California-based Reservoir Engineering Research Institute to find out. The Institute and its 20-company members will contribute an additional $1.3 million for the three-year project. Hydrocarbon type, "wettability" of reservoir rock, and fracture type and thickness all play in role in hydrocarbon migration. The researchers will first concentrate on wettability, or affinity for a liquid to cling to a surface. Wettability has long been known to be a primary factor in capillarity. (Capillarity is that strange force that causes a liquid to defy gravity and draw itself up a slender tube — without having to suck.) In addition, capillarity depends on the precise spacing of interconnected pore spaces and ribbon-thin fractures. The research will first study how fracture geometry influences hydrocarbon movement in the reservoir. Next, they will focus on how / whether tidal forces affect fractures and thus hydrocarbon flow. It may turn out that tidal forces provide optimum times for production or well stimulation. Field data will be used from well-known oil producing formations, such as Austin Chalk and Ellenberg field. Smartwell seismic sensors. For the past 10 years, the Institut Francais du Petrole (IFP) and Gas de France (GdF) have been developing permanent seismic sensors. They can be used for repetitive seismic, microseismic and production monitoring. They have been installed on several wells at GdF’s underground storage facility for testing purposes. Results thus far suggest they will be very useful in reservoir monitoring, in particular for tracking the extension of a gas cap or an aquifer, or for optimizing secondary-recovery techniques. Using permanent seismic sensors to locate microseismic events can also allow a better understanding of the mechanisms in fractured reservoirs subject to subsidence. Geological modeling. In 1998, with support from nine major oil companies, IFP set up the Welgem consortium. Welgem addresses the problem of constraints on geostatistical models by dynamic well-test data. The basic idea is to invert the facies properties of the geostatistical model by matching results from digital simulations of well tests with field data. A beta version of the software has been delivered to participating oil companies for final
study. The next step is to establish a users group to monitor and support use of the code.
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