Diagnosing Well Integrity in Oilfield with Corrosive Aquifer with Pulse Electromagnetic and Chorus Acoustic Technologies

Abstract This paper discusses the approach of through-barrier diagnostics to direct Plug and Abandonment (PnA) and sidetracking operations in one of the fields in Libya. PnA before sidetracking is a critical procedure in the lifecycle of a well, involving the secure sealing of mother wellbore to prevent hydrocarbon leaks and ensure environmental and safety compliance. Proper PnA confirms the integrity of the new sidetrack wellbore. The initial plan to revive the well involved abandoning the main borehole by isolating the perforated interval below and then drilling a sidetrack. Traditional evaluation methods revealed moderate corrosion in the 9 5/8″ production casing. To gain a comprehensive understanding of the well's condition, Pulse electromagnetic and Chorus acoustics technologies were employed, uncovering more extensive issues: approximately 200 feet of severe external metal loss in the 9 5/8″ casing and around 1200 feet in the 13 3/8″ casing, primarily due to a shallow aquifer and H2S / CO2 presence. Understanding and mitigating the effects of corrosive aquifers are essential for maintaining the integrity, safety, and productivity of wells. Therefore, Pulse electromagnetic survey was performed on a nearby well to evaluate the impact of the aquifer. This assessment revealed similar metal loss in the external casing, attributed to the active aquifer. However, the extent of the metal loss was less severe due to the younger age of the well. To address and manage these risks effectively, a time-lapse monitoring approach was proposed. This approach involves continuous or periodic monitoring over time to track the progression of corrosion and implement timely interventions. Such proactive measures are crucial for ensuring the long-term sustainability and operational efficiency of the wells, as well as for preventing potential environmental and safety hazards associated with corrosive aquifer interactions.