Abstract
A major challenge of a steamflooded field in Indonesia, one of the world's largest thermal recovery projects, is the short life of the well from the well integrity aspect. The outcome of a joint study group between the operator and the cementing service provider reveals that 77% of the injector wells drilled in a recent period of 5 years required remedial squeeze cementing operations. The operating expenditure of workover operations and the costs of the deferred production to the operator are significant; hence, a cementing solution is needed to improve the efficiency in managing the mature heavy oil reserve.
The current cementing practice calls for placing the API class G cement and silica flour blended system across unconsolidated sand bodies and exposing it to large temperature changes. Results of the stress modeling predict the conventional cement system failure under the anticipated conditions of injection and workover operations. An innovative steam-resilient cement system with tailored thermal and mechanical properties up to a temperature of at least 350° C [650° F], beyond the maximum steam injection temperature of the field, is maintaining the integrity.
Field trials in Indonesia confirm that this new system can be easily integrated into standard cementing operations using conventional equipment. Cement evaluation logs after cement operations prove that proper zonal isolation is achieved. All the candidate wells, first one since January 2011, are currently under the steam injection with no sign of wellbore integrity failure.
This novel cement system, by keeping adequate level of flexibility and optimum thermal properties, provides a long term well integrity solution for any well exposed to similar conditions, such as in fields exposed to steam injection. Operators can rely on cement sheath integrity exposed to thermal processes to produce heavy oils.
