A m e r i c a
Pore-pressure prediction and wellbore stability in the deep Mexican Gulf of Mexico
JORGE MENDOZA-AMUCHÁSTEGUI, GABRIELVÁZQUEZ-JIMÉNEZ, MANUEL ESPINOSA-ORTEGA, CELESTINO VALLE-MOLINA, ESTEBAN ALVARADO-HERNÁNDEZ, MARIO GERARDO GARCIA-HERRERA, and RUBÉN NICOLÁS-LÓPEZ, Instituto Mexicano del Petroleo (IMP)
afe andeconomical exploration drilling largely relies on appropriate analyses and estimation of the overpressures in the subsurface. In contrast, incorrect predictions of these abnormal pressures can cause delaysand increase costs due to failures of rock formations, lack of drilling mud circulation, collapse of the casing, and closures for diﬀerential pressures. The main advantage of the integral methodologyfor the pore-pressure prediction presented in this article is modeling at two diﬀerent levels, regional modeling based on the basin model, and local modeling by means of geomechanical models applied tothe wellbore stability. Figure 1 illustrates the overall integration of the pore-pressure methodology. The combination of the 3D formation velocities and well-log information allow modeling basins andgeomechanics for wellbore stability. This study also addresses the local modeling for wellbore stability.
Figure 1. Diagram of the pore-pressure methodology.
Methodology Our methodology topredict pore pressure consists of ﬁve steps: (1) initial model of migration velocities, (2) automatic, high-density velocity analyses based on maximum amplitude semblance spectra, (3) smoothing ofvelocity analyses, (4) calibration of seismic velocities with well-log velocities, and (5) eﬀective stress calculation based on Eaton’s equation (Zoback, 2007). Prediction of pore pressure was performed at asite in deep waters of the Mexican Gulf of Mexico. Figure 2 shows the process to evaluate the velocities obtained at the site (steps 1 and 2). The seismic information used for velocity analyses...