Acona’s process prioritises solutions to reduce P&A program costs. It involves a multi-disciplinary team with petroleum technology (for flow potential and understanding of annuli pressure history), geoscience (for overburden studies and identification of permeable zones and hydrocarbons), drilling engineers (for P&A plans) and risk analysis expertise.
Acona’s approach starts with a thorough mapping of the overburden and the key issues for effective barriers are:
- Barrier material and length. Calculations show that the shear strength and length of a barrier plug are non-critical for a good annular seal. A short section of creeping shale or a settled mud interval can provide an adequate seal. A leak off test through perforations below an assumed barrier or an inflow test above are alternative direct verification methods for this. A gas detection log to verify that the annulus is gas free can supplement the test.
- Shale capped repositories may store well fluids. Shallower permeable formations may accept large volumes leaked from deeper zones. Water has low mobility compared to gas. Required barrier quality is therefore lower against zones containing water.
- Cross-sectional plugs. Most exploration wells and many production wells have a low amount of internal corrosion or wear. External corrosion will not occur in a static environment. Many wells may therefore not need cross-sectional plug(s).
The project will give an updated status of the overburden and a plan for verification of assumptions made for reduction of uncertainties. The work can be simplified further as experience is gained by elimination of some verifications already proven valid for the whole field.
Our Well Engineering Services
Acona offer well engineering services for review and verification on how to solve the many P&A well integrity issues for a cost effective program. We can advise, facilitate, review and verify P&A well designs.