Using Cloud Based Well Engineering Data and Wellbore Integrity Analysis to Reduce Risk in Niger Delta Workovers

Abstract

The Niger Delta is a prolific oil and gas province with almost 160 oilfields and 1,500 wells put on production since the 1960s. Many of these wells have been producing for decades and now find themselves in hands of new operating companies of limited resources. There are strong commercial drivers to keep these wells in production through rapidly planned workover operations. The historical records for these wells are poor and in many instances nonexistent, often being no more than a very simplistic A4 completion diagram lacking in details and summary. The basis for design and the history of numerous interventions has long been lost and the focus of new operators is often on only the production casing and the tubing strings. However, it is imperative to consider the full well architecture and construction history because some were design optimized with minimal casing setting 13 3/8" shallow and completing in 9 5/8". Worst case consequence of this design approach is well blowout and cratering if the production casing fails with a gas column to surface. A generic case is presented to emphasize the reality of this risk. The risks of extending well life, compounded by change of use in late life are discussed in the context of design validation. The causes and challenge of poor well engineering data are reviewed, to establish the historical norms in not only the Niger Delta but globally. The importance of tracking down data in the well Intervention planning process is emphasized. It is further proposed that controlled, as-built drawings of all wells, which do not omit casing details, lithology, and critical component features such as wellheads casing hanger seals and Xmas tree should be electronically created, cloud stored and used as a basis for well bore integrity analysis prior to undertaking interventions/workovers. An example from a North Sea Development Project is presented. Such a system should also be used to establish which critical barriers exist during the intervention, how they will be validated, and how is evidence captured in order to address the typical human factors which are fundamental in many blowouts. Critically the system should produce accurate well integrity reports during operations to track compliance with the plan. A generic example for a typical Niger delta dual bore completion well is presented.