The Importance of Well Construction and Well Integrity for Reservoir Management -- A Mature Field Experience in Sudan

Tewari, R.D. (GNPOC) | Raub, M.R.B.A. (GNPOC) | Omar, M.I. (QP) | Fenghan, B. (GNPOC) | Moris, M. (GNPOC) | Jelani, J. (PRSS) | Ramachandran, S. (AWT) | Fooks, A.L. (AWT) | Peden, J.M. (AWT) | Montague, Eamonn T. (Brunei Shell Petr. Sdn. Bhd.)


This paper describes the importance of well construction & well integrity and its relationship to reservoir management. Productivity enhancement studies in combination with reservoir simulation modeling on the Greater Heglig fields have revealed that well performances and production related problems were largely related to poorly designed wells and poor cementing practices.  As a result, water channeling and cross flow across wellbore dominated true well performance characteristics contributing to very high water cuts in the majority of the producers in Greater Heglig fields. Separating the mechanically induced well behaviour from reservoir behaviour helped history matching the wells greatly, findings of which were subsequently validated during the study through running of ultra sonic imaging tool.  The ultra sonic logging campaign proved the existence of channels, micro annuli's and cross flow across the wellbore causing a "water channeling phenomena" of up to 90% water cut across majority of the wells.  As part of the productivity enhancement program for the Greater Heglig fields, a total of 23 sidetrack candidates have now been identified to capture the remaining developed reserves of ca.  30.0 MMstb, which will otherwise remain unproducible from the existing wellbore's.  In addition to this, fit for purpose sidetrack well designs and construction together with good cementing practices will be required to ensure well integrity to improve reservoir management of the Greater Heglig fields.