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Sealing Wellbores at the end of their lifecycle to restore subsurface seal integrity and prevent offshore wellbore leakage
  • Sai Vamsi Krishna Vissa,
  • Mileva Radonjic,
  • Yanyao Li
Sai Vamsi Krishna Vissa
Oklahoma State University Main Campus

Corresponding Author:vamsikrishna.vissa@okstate.edu

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Mileva Radonjic
Oklahoma State University
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Yanyao Li
Oklahoma State University Main Campus
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As we approach 2020, there are more well bores that require abandonment than well bores waiting to be drilled. The USA alone has ~1.7 Million well bores with an API number indicating that they are not permanently plugged, therefore will be in need of Plugging and Abandonment (P&A) at some point in the future. Some of these well bores are located in fragile ecosystems, such as the Gulf of Mexico, where it is estimated that 9,000 idle well bores are waiting permanent plugging and abandonment. The numbers of future P&As suggest requirement for an urgent improvement of current technology as many governments are preparing standards that require assurance for zero leakage over thousands of years. This paper/talk will present knowledge gaps we identified during literature review and the data obtained during first two terms of the ongoing project , under NASEM-GRP funding. Extensive literature review points to the following issues: 1) Portland-cement based materials, with their pH ~13, are geochemically incompatible with the reservoir conditions in the GoM. 2) Weak interfaces between and contamination with drilling fluids in well bore structures present high risk for Hydrocarbon leakage, which currently cannot be mitigated successfully. Placement and accessibility of well bore in offshore environment adds to technological complexity and increases the risk of leakage. 3) Monitoring and verification is currently not available for long-term assessment offshore. Some of our preliminary data suggests the following: 1) Plugging materials are impacted by contamination form drilling fluids and other well bore materials, such as fragment of dehydrated clays, oily rock fragments. 2) Casing corrosion might lead to deterioration of primary well bore cement, which can be difficult to locate and re mediate prior to plugging. 3) Geo-mimicry is a potential path forward in designing and developing barrier materials capable of serving over thousands of years.