The objective of this research was to investigate the potential impact of expandable casing technology on the remediation of Sustained Casing Pressure (SCP). Varying magnitudes of SCP exist in the Gulf of Mexico (GOM), where over 80% of casing strings exhibiting SCP are production and surface casings, representing a great technical, economic, and environmental risk. Situations in which SCP is observed usually result in costly and frequently unsuccessful remediation efforts. The technique proposed in this project with expandable casing can be done during drilling, producing, or during the abandonment process. A unique bench-scale physical model was used to simulate expansion of a previously-cemented casing under field-like conditions. Experimental measurements obtained during low-percentage casing expansion exhibited improvement of cement integrity with significant changes in the cement sheath. Successful multi-rate flow-through experiments with nitrogen gas showed the effectiveness of this technique in complete closure of microannular gas leakage pathways, providing ideal cement remediation. If implemented, this technology has potential to become a cement remediation technique for leaks behind the casing.
Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe (casing), and protects metal components from corrosive fluids. These are essential for uncompromised wellbore integrity. Cements can undergo multiple forms of failure, such as debonding at the cement/rock and cement/metal interfaces, fracturing, and defects within the cement matrix. Failures and defects within the cement will ultimately lead to fluid migration, resulting in inter-zonal fluid migration and premature well abandonment. Currently, there are over 1.8 million operating wells worldwide and over one third of these wells have leak related problems defined as Sustained Casing Pressure (SCP)The focus of this research was to develop an experimental setup at bench-scale to explore the effect of mechanical manipulation of wellbore casing-cement composite samples as a potential technology for the remediation of gas leaks.The experimental methodology utilized in this study enabled formation of an impermeable seal at the pipe/cement interface in a simulated wellbore system. Successful nitrogen gas flow-through measurements demonstrated that an existing microannulus was sealed at laboratory experimental conditions and fluid flow prevented by mechanical manipulation of the metal/cement composite sample. Furthermore, this methodology can be applied not only for the remediation of leaky wellbores, but also in plugging and abandonment procedures as well as wellbore completions technology, and potentially preventing negative impacts of wellbores on subsurface and surface environments. Video LinkThe video component of this article can be found at
Summary The objective of this research was to investigate the potential effect of expandable-casing technology on the cement sheath and remediation of sustained casing pressure (SCP) caused by microannular gas migration. Varying magnitudes of SCP exist in the Gulf of Mexico, where more than 80% of casing strings exhibiting SCP are production and surface casings, representing a great technical, economic, and environmental risk. Situations in which SCP is observed usually result in costly and frequently unsuccessful remediation efforts. A unique bench-scale physical model was used to simulate expansion of a previously cemented casing under field-like conditions. Experimental measurements obtained before and after low-percentage pipe expansion exhibited improvement of cement/pipe interface. Successful multirate flow-through experiments with nitrogen gas showed the effectiveness of this technique in sealing of microannular-gas-leakage pathways, providing ideal remediation of SCP immediately post-expansion; and after up to 60 days of post-expansion, the seal integrity was intact.
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