Reservoir characterization study of the Cuitlahuac gas field in the Burgos basin, Northeastern Mexico

Abstract

A recent trend in reservoir studies is the integration of petrophysical geological and geophysical information in high‐resolution reservoir models. Success in integrated reservoir characterization depends on identifying seismic and petrophysical attributes that are well correlated to the properties being modeled e.g., lithofacies, porosity and fluid type. This study employed integrated petrophysical analysis, well‐based rock property study, acoustic and elastic seismic inversions, AVO modeling and attribute generation to characterize Oligocene gas reservoirs in the Cuitlahuac Field in the Burgos Basin of northeastern Mexico. Cuitlahuac Field has produced over 320 Bcf since its discovery in 1972. Current daily production is 28 MMcfd. Production is from thin‐bedded Tertiary fluvio‐deltaic clastics with complex reservoir geometry. Of nine well‐based seismic attributes generated from the petrophycial logs (Possion's Ratio, Acoustic Impedance, Shear Impedance, Lambda, Mu, Bulk Modulus, Lambda‐Rho, Mu‐Rho and Vp/Vs), acoustic impedance (AI) most effectively discriminates sandstone from shale ‐ but only in the shallower section. Amplitude versus offset (AVO) analysis shows Class I response in the shallower section and Class II response in the deeper section. On the other hand, fluid substitution study shows that Mu‐Rho and Lambda‐Rho are good discriminators for both lithology and fluid type. To capture detail in the thin gas reservoirs, high‐resolution stochastic inversion was performed on the 3D seismic volume. The resulting acoustic and shear impedance volumes show good correlation with well log data. The attributes Lambda‐Rho and Mu‐Rho were calculated from the acoustic impedance (Ip) and shear impedance (Is) volumes. The seismic‐derived Lambda‐Rho and fluid type at each well were integrated using sequential indicator simulation with collocated cokriging to obtain a reservoir model.