Technology Based Formation Damage Control & Mitigation Measures in the SINCOR Zuata Field, Venezuela

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe poor productivity and abnormal productivity decline in some SINCOR horizontal wells in the Faja field could be traced back to drilling and well completion practices.The wells were drilled with solid-free XCD mud and completed with slotted liners. Drilling operation is characterized by severe mud losses. The wells were brought into production without wellbore cleanout to remove the drilling mud induced damage. The wells produce Extra Heavy Oil (EHO). The observed trends since the start-up of production was indicative of the skin damage magnitude. An in-house review in 2005 adopted an approach that included acquiring and extending information derived from cores and reservoir fluids, laboratory analysis data, drilling, well completion/well test results, and production data. X-ray diffraction studies show that the formation contains about 8% of clay minerals which comprise mostly kaolinite (~85%) with traces of illite and smectite. The damage mechanisms identified included fines migration, the swelling of reactive clay minerals, physical blockage by unremoved filter-cake masses, water-block resulting from massive leakoff of aqueous mud filtrate, the wax crystallization and asphaltene precipitation blockage. Engineering work and technology-based solution which encompass diagnosis of damage mechanism, laboratory testing, formulation and optimization of treatment fluids, job design and field execution procedure were carried out to mitigate the formation damage. The surfactant-diesel based (SDB) treatment design and application has yielded great successes in removal of formation damage, resulting in a high incremental oil production with job payback time of 3 -24 days. Evaluation of the two SDB treatment campaigns conducted in 2005/2006 revealed that water-block with its associated high Interfacial Tension against the EHO constitutes a serious impediment to oil productivity.

Protocols for Slotted Liner Design for Optimum SAGD Operation

“…This program was, in part, motivated by the relatively poor historic performance of many straight and keystone cut type slotted liners where either high liner generated differential pressures (sometimes exceeding 1000 kPa) or significant physical production of sand was occurring. The motivation of this study was to investigate the mechanisms of why slotted liners tend to plug, and to provide potential solutions and optimum completion geometries for practical field application in active and future SAGD projects (6)(7)(8)(9)(10) .…”