1 INTRODUCTION
The ability to predict the mechanical response of rock in three dimensions over the spatial and time scales of geologic interest would give the oil and gas industry the ability to reduce risk on prospects, improve pre-project initial reserve estimates, and lower operating costs. A program has recently been initiated, under the auspices the Advanced Computational Technology Initiative (ACTI), to achieve such a computational technology breakthrough by adapting the unique advanced quasistatic finite element technology developed by Sandia to the mechanics applications important to exploration and production activities within the oil and gas industry. As a pre-cursor to that program, in an effort to evaluate the feasibility of the approach, several complex geologic structures of interest were analyzed with the existing two-dimensional quasistatic finite element code, SANTOS, developed at Sandia. Some examples will be presented and discussed in this paper.
The ability to predict the mechanical response of rock in three dimensions over the spatial and time scales of geologic interest would give the oil and gas industry the ability to reduce risk on prospects, improve pre-project initial reserve estimates, and lower operating costs. A program has recently been initiated, under the auspices the Advanced Computational Technology Initiative (ACTI), to achieve such a computational technology breakthrough by adapting the unique advanced quasistatic finite element technology developed by Sandia to the mechanics applications important to exploration and production (E&P) activities within the oil and gas industry. The need for such a program arose from the demand for new tools which can contribute to the exploration of petroleum by better understanding the geological processes. The interpretation of seismic data, on which exploration is mainly based, allows the industry to identify potential traps that can enable the accumulation of hydrocarbons. This is possible because seismic data can provide a picture of geologic structures as they are encountered in the present. The kinematic reconstructions try to trace back encountered cross sections by relying solely on conservation of mass. As Plischke, et al. (1991) have noted, although some of these methods may also incorporate compaction laws and have gained a professional degree of functionality, they do not account for equilibrium as required in mechanics: they simply try to trace back the encountered cross-sections more or less by purely geometrical operations. Although a limited amount of work has been done using continuum mechanics to improve the under- standing of geologic structures through the use of the finite element method in 2D, currently available commercial finite element technology does not efficiently treat the non-linearities associated with large deformation and fracture and cannot handle the size of problems needed for E&P applications. Further- more, 2D analysis does not accurately describe complex 3D geometries in oil fields. Consequently, techniques that can handle hundreds of thousands of elements are needed to solve typical geomechanics problems encountered by industry. However, because of the nature of the techniques used in commercial finite element technology, practical limits of around ten thousand elements are more common.
