Geomechanics Aspects of the Oriente Basin, Ecuador, South America
Abstract
The Oriente Basin of Ecuador is one of the most productive of the South American Sub-Andean Basins and it contains a sedimentary fill between Paleozoic to Recent age. Major commercial interest is confined to the Cretaceous depositional cycle and all the significant production comes from fluvio- deltaic and marine sandstones of the Hollin and Napo Formations. To reach prospective targets, the oil companies have to drill tertiary continental and transitional sedimentary formations, i.e Chalcana, Orteguaza, Tiyuyacu, Tena. The challenges to overcome could be summarized in formations reactive to the drilling fluids, tertiary overpressure clay stones, volcanic inter bedding layers, hard conglomerate intervals, limestone rocks, sand production in the reservoirs, cretaceous overpressure shales and magma type intrusions. The objective of this paper is to illustrate the geomechanic behavior of the wells drilled in Oriente Basin at a regional scale based on the geological framework model of several fields that have been drilled or stimulated by using 1D or 3D mechanical earth models- MEM, (Plumb,R.A, 2000).
A compilation of data from drilling and sanding prediction analysis, open hole logs, rock mechanical data by integrating rock strength characterization at the laboratory, borehole images, and formation pressure measurements are analyzed to assist in well planning and field development and to understand the problems already encountered in the existing vertical, deviated and horizontal wells. A complete characterization of formation stresses is included using traditional techniques of estimation derived from microfracs, mini-fracs, leak-off tests, hydraulic fracture data, poroelastic strain calibration, or derived from advanced sonic stress estimation using the induced anisotropy in the presence of variation of the three shear modulus crossing dipole dispersions obtained from near-wellbore stress concentrations.
