Abstract: Fault and Fracture Control of Fluid Flow and Diagenesis Around the Iberia Salt Dome, Iberia Parish, Louisiana

W. Lee Esch, Jeffrey S. Hanor

The pathways that channel kilometer-scale vertical fluid movement around salt domes are critical to understand because of the implications they have on petroleum migration and injection-well disposal. It is hypothesized that vertical flow is accommodated in fractures, faults, porosity developed in the margin of the salt, and through complexly interconnected sands. By means of geochemical and petrographic techniques, we are identifying specific fluid migration pathways on the southwest flank of the Iberia salt dome, Iberia Parish, Louisiana.

Brine samples from the Iberia field have been analyzed by ICP-AES for dissolved Na, K, Mg, Ca, Sr, Ba, Mn, Fe, Cu, Pb, Zn, Al, Si, and B. The concentration data have been contoured on a cross-section developed from well logs to identity spatial correspondence between structures or sand bodies, and compositional gradients of solutes within the pore fluids. Contour lines for Ba, B, Ca, Fe, and Sr deflect from sub-parallel with formation dip to sub-parallel with high-angle faults. This suggests that the faults either directly accommodate vertical fluid movement, or serve to partially juxtapose permeable sands in sand/shale successions, thus forming vertical pathways of complexly interconnected sands.

SEM-EDS inspection of well cuttings reveals the presence of diagenetic calcite, pyrite, vermiform kaolinite, barite, and sphalerite in pore spaces. In some samples, mineralization in dilated micro-fractures reveals that fracture porosity also contributes to pore-fluid movement in the Iberia flank sediments.

Thus, faults and fractures contribute to vertical fluid flow and solute transport over a wide range of dimensional scales at the Iberia salt dome.

AAPG Search and Discovery Article #90955©1995 GCAGS 45th Annual Meeting and Gulf Section SEPM, Baton Rouge, Louisiana