ABSTRACT
Revitalizing aging fields can be complicated when viewed through an outlook of economic viability versus the associated operational and design risks. However, workover campaigns may be deemed more economically efficient and lower risk with the continuous advancements in technology, especially applicable to smart well designs. Workover projects are becoming ever more viable, with production being optimized through the application of advanced well construction products such as Solid Expandables along with existing brownfield infrastructure.
The operator of the Hassi Messaoud field, one of the largest and oldest onshore oil producing fields in Algeria, embarked on a large scale workover campaign to revitalize this field and optimize oil production from wells which have been drilled over 40 years ago. The typical workover program targeted extending the open-hole below the 7-in. casing across the Cambrian reservoir and completing the wells with a 4-1/2-in liner. Challenges with various formations encountered and the depleted reservoir resulted in the viability of only a slim hole configuration restricting production.
Maximizing the wellbore diameter across the reservoir while isolating higher pressured shale's directly above and balancing the economic return on investment required the inclusion of multiple technologies to achieve the well and production objectives, all using the existing well infrastructure.
A total of 7 wells have been worked over to date since early 2010 which avoided slim-bore configurations through the inclusion of 939m of 5-1/2" expandable tubular maximizing reservoir diameter and serving as a permanent mechanical barrier. The campaign also incorporated underbalanced drilling operations as a tool for mitigating subsequent pressured formations and testing production as required. The actual campaign had a reduction in operational time of 40% while significantly increasing and optimizing production rates.
