Analytical models of suture formation in salt canopies for safer well planning

• Visualization of suture formation in coalescing salt sheets
• Templates of vertical sections and map views for seismic interpreters
• Diagnostic rules for kinematic conditions for suture shapes

The development of suture zones between salt sheets issued from nested feeder stocks is visualized here as the salt sheets grow and coalesce into a canopy. The analytical models are based on complex potentials, which provide exact solutions for multiple source flows as they compete for space when spreading into a viscous continuum (a salt canopy). Vertical cross-sections and base-of-salt maps, both rendered from seismic images, have previously revealed the existence of suture zones inside major salt sheets. A better understanding of the sutures is required to safely drill hydrocarbon reservoirs located below such salt bodies. The suture zones are potential drilling hazards due to anomalous pressure behavior of entrapped sediments. A large range of suture shapes and overriding structures are seen in seismic sections of salt canopies; an even larger range of suture shapes is modeled here by systematically varying the key parameters responsible for their formation. A better understanding of the structural evolution of sutures improves their early detection and reduces the risk of drilling hazards.

Shaded relief of the Central Gulf of Mexico seafloor bathymetry. Hummocky terrain is underlain by the allochtonous Sigsbee salt canopy which expands toward the leading edge down the continental shelf (courtesy: Google Earth). Inset graph shows petroleum exploration progressively moves outward from the shallow shelf area to deeper water, followed by production wells after a certain time lag (Δt). Source: Chevron investor presentation.Figure optionsDownload as PowerPoint slide