Enhanced Productivity of Carbonate Reservoir by Cross-Dipole Shear-wave Logging in the Bakr/Amer Field, Gulf of Suez, Egypt
Taher El-ZefZaf1, Maher Omara1, Theodore Klimentos2
(1) General Petroleum Company (GPC), Cairo, Egypt (2) Schlumberger, Cairo, Egypt
Earth stress patterns give a general indication of the most likely fracture orientation or maximum stress trend. Nonetheless, local variations and the effects of localized structures, such as large faults, can modify the stress pattern, counteracting or adding to the regional stress. Thus, such a local stress and fracture profile information can be very meaningful to many petroleum exploration and development related aspects, such as, selecting perforation intervals and strategy, planning hydraulic fracturing operations, optimum well placement, wellbore stability, sand production, and hydrocarbon migration.
In this study, cross-dipole shear-wave anisotropy logs, acquired in several wells of the Bakr/Amer field (Gulf of Suez), were used to enhance the productivity of the Nullipore carbonate reservoir by determining the orientation and magnitude of the principal horizontal stresses and detecting major fractured intervals. Currently, the Bakr/Amer field accounts for 55% of the General Petroleum Company’s (GPC) daily oil production. Approximately, 40% of this amount is solely produced from the uppermost reservoir known as the “Nullipore”. The cross-dipole shear sonic data was processed to obtain oriented fast and slow shear waves. This information was then used to determine the direction and magnitude of the in-situ earth stresses, and the orientation of fractures. Zones showing significant shear-wave anisotropy were detected as open fracture systems, using the shear-wave anisotropy data in conjunction with the Stoneley-wave chevron patterns and other available logs. These intervals were subsequently perforated and produced significant amounts of hydrocarbons. Further application of this technique in several wells of the Bakr/Amer field proved that the Nullipore reservoir productivity is primarily controlled by the flow contribution from natural fractures. New highly deviated wells were completed over the Nullipore on the basis of the newly acquired information and excellent results were obtained. Moreover, older wells were restudied and recompleted on the same basis and a large increase of production was attained.