A feasibility Study Using Wells and CSEM Modeling in Miocene Sand Reservoirs, Offshore Mexico

Paola Vera de Newton, Amanda Geck Alvarez, Humberto Salazar, and Marco Vázquez
[email protected]

Joint modeling of rock and fluid properties reduces the number of false positives that occur during unilateral analysis of seismic and CSEM data. Because rock physics models explain log responses from underlying petrophysical properties, we tie an EM anomaly to rock properties by generating 1D CSEM models for three Gulf of Mexico Miocene reservoirs. Rock physics models help predict well log responses at insitu and fluid-substituted conditions in elastic and electrical domains. Seismic feasibility is assessed using synthetics, whereas CSEM feasibility is achieved by calculating synthetic amplitudes. Upper Miocene reservoir exhibits significant separation in the resistivity domain. In contrast, wet, commercial and non-commercial gas sands overlap in Poisson's ratio versus AI cross-plots, as do Middle and Lower Miocene sediment. Below the Middle Miocene boundary, sediments become highly laminated resulting in an increase in vertical resistivity. Similarly, fluid cases show that vertical resistivity is a good discriminator for the Upper Miocene pay, whereas deeper sands behave like anisotropic background. Seismic sensitivity is maximized in the Upper Miocene pay, but also in the underlying residual gas saturated sections. CSEM modeling shows good sensitivity for several frequencies in the Upper Miocene target. Marginal to limited sensitivity exists for detecting the Middle Miocene and stacked Lower Miocene reservoirs at offset ranges and frequencies typically associated with CSEM surveys. Sensitivity to stacked Lower Miocene targets is further decreased when Upper Miocene is present. This sensitivity analysis allows for an improved understanding of data requirements for higher-dimensional analysis, and demonstrates the value of rock physics, seismic and EM integration.

AAPG Search and Discovery Article #90167©2013 GCAGS and GCSSEPM 63^rd Annual Convention, New Orleans, Louisiana, October 6-8, 2013