Three-dimensional representations of salt-dome margins at four active strategic petroleum reserve sites.

Abstract

3 SAND2003-3300Unlimited A new modeling algorithm has been developed to overcome limitations of many standard geological modeling software packages in order to deal with structurally overhanging salt margins that are typical of many salt domes. This algorithm, and the implementing computer program, make use of the existing interpretive modeling conducted manually using professional geological judgement and presented in two dimensions in the original site characterization reports as structure contour maps on the top of salt. The algorithm makes use of concepts of finite-element meshes of general engineering usage. Although the specific implementation of the algorithm described in this report and the resulting output files are tailored to the modeling and visualization software used to construct the figures contained herein, the algorithm itself is generic and other implementations and output formats are possible.The graphical visualizations of the salt domes at the four Strategic Petroleum Reserve sites are believed to be major improvements over the previously available two-dimensional representations of the domes via conventional geologic drawings (cross sections and contour maps). Additionally, the numerical mesh files produced by this modeling activity are available for import into and display by other software routines. The mesh data are not explicitly tabulated in this report; however an electronic version in simple ASCII format is included on a PC-based compact disk.

Conversion of the West Hackberry geological site characterization report to a three-dimensional model.

“…These two representations of the salt geometry were converted to 3-D MVS models. The method used to generate the 3-D representation of the salt dome margin is documented in a separate report (Rautman and Stein, 2003).…”

“…For the full set of digitized contours, corresponding 3-D points on successively deeper and shallower contour rings are connected using the external software code, ctr2evs (Rautman and Stein, 2003), to form a mesh comprised of quadralateral and triangular elements, similar to those used in finite-element models. This process is shown conceptually in Figure 2.…”

Conversion of the Bayou Choctaw geological site characterization report to a three-dimensional model.

“…The methodology used to convert the paper site characterization model of the Bayou Choctaw salt dome margin is documented in a separate report (Rautman and Stein, 2003). The approach involves digitizing in calibrated x-and y-state plane coordinate space the various structure contours drawn of the top of salt.…”

“…For the full set of digitized contours, comsponding 3-D points on successively deeper or shallower contour "rings" are connected using the external software code ctrleva (Rautman and Stein, 2003) to form an approximation of a finiteelement mesh. This process is shown conceptually in figure 3.…”

“…Second, capturing the inferred faulting shown in figure 26 is quite difticult and beyond the capabilities of the ctr2.v. program (Rautman and Stein, 2003) at its current state of development. This limitation will be addressed in future development of the modeling code.…”