Reservoir compartmentalization can seriously compromise a project’s economics if left undetected during appraisal. Its early identification is made more likely if maximum use is made of available fluid appraisal data. This involves making a critical comparison of time-scales for various fluid properties to equilibrate compared with the actual time since those properties were initially disturbed. Spatially varying fluid properties indicate compartmentalization if they have existed for longer than the time needed for them to equilibrate.
Here we use data from appraisal wells and reservoir mixing time-scales to investigate vertical and horizontal compartmentalization in the Horn Mountain Field (Gulf of Mexico) and to quantify the properties of the baffles/barriers identified. We compare our results with earlier work using time-lapse geochemistry and mud gas isotope logging. Present fluid compositional variations in the field are shown not to be diagnostic of horizontal compartmentalization as the mixing time-scales by molecular diffusion are longer than the time since the reservoir filled. In contrast, pressure shifts and density differences are diagnostic. They indicate that faults within the Horn Mountain Field are relatively impermeable and would act as barriers during oil production. They also confirm that a shale-filled channel acts as a barrier to vertical flow.
Instability [Farley, 1963; Buneman, 1963] in the equatorial electrojet current system in the E~region of the ionosphere has been identified as&e cause of the observed Type I electron density irregularities. While the linear instability has been understood for nearly three decades, the effects of the nonlinear behavior remain unclear. One of the first calculations of the evolution of this instability in the nonlinear domain was due to Sudan [1983]. More recently, Machida and Goertz [1988] studied the instability numerically with an explicit particle (PIC) simulation method. They calculate electron heating in the the polar ionosphere in agreement with Sudan [1983], but it is not clear how good or complete the match is. Also, more complete parametric evaluation by such explicit methods would be limited, because the electrons must be treated as particles, while the instability occurs on the ion fluid time scale. The implicit ANTHEM code [Mason, 1993] can use particle electrons with a time step many times the plasma period, so that by implicit simulation a complete and parametric study of the instability should be feasible. The results of such a program would have important bearing on the understanding of electron heating by low-frequency turbulence in the ionosphere.Our present goal is to study the instability in the equatorial region. This region was ignored by Machida and Goertz. We seek to determine the cause of saturation, the velocity of the waves in the saturated state (do they travel at the sound speed) and any other nonlinear phenomena. The significance of this work derives from the large number of unanswered questions about Type I waves. These include, among others, the observation of vertically propagating two-stream waves (perpendicular to the current), the constant phase velocity of Type I waves at any angle with respect to the current and the details of the observed wave number spectra [Ke21ey,1989]. Much of the detailed observational data about these waves was-and still is-gathered by Cornell University researchers. This gives us the ability to closely correlate our results with the experimental data,We originally planned to evaluate the nonlinear behavior of the Farley-Buneman Instability solely with the ANTHEM implicit plasma mode. This model can treat electron kinetic influences on instability's long time scale evolution. However, Meers Oppenheim has developed two newer models, which allow for speedier electron fluidic treatments. The first is a two-fluid simulation, which also incorporates linear ion kinetic damping. This enables us to evaluate quickly the wave behavior assuming that kinetic effects are negligible. The second is an explicit particle code that uses particle ions and fluid electrons. This enables us to determine whether ion kinetic effects are substantially modi$ing the ion fluid behavior.Both the two-fluid and the ion particle simulators have been written and tested. Initial results of the fluid simulation show three nonlinear effects: (1) saturation, (2) nonlinear rotation of th...
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