Experimental Assessment of Casing Expansion as a Solution to Microannular Gas Migration

Abstract

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.

Reaction-driven casing expansion: potential for wellbore leakage mitigation

“…Constraints from casing burst studies provide similar values [39,64]. As such, the stresses that could potentially be induced, if a wellbore would be plugged with low-porosity CaO aggregate, are more than sufficient to bring about casing expansion leading to mechanical closure of annuli and fractures similar to that seen in the experiments of Kupresan et al [74,75]. However, whether these theoretical FoC stresses can be attained in practice depends on whether reaction can go to completion, and hence on the reaction kinetics, the supply of reactants, the reaction mechanism, and the effect of stress on reaction.…”

“…A performance study of squeeze cementing operations performed on wells in west Texas found that first-attempt remediation was successful in only 47 of 137 cases (34%), and that the success rate for multiple attempts (up to five per well) was \60% [25]. There is therefore substantial interest in alternative approaches to leakage mitigation, such as the casing expansion procedure recently proposed by Kupresan et al [74,75]. This involves permanent radial expansion of the casing pipe, thereby closing annuli, fractures and other voids outside the casing, while placing the cement there under compression.…”

“…This involves permanent radial expansion of the casing pipe, thereby closing annuli, fractures and other voids outside the casing, while placing the cement there under compression. Kupresan et al [74,75] tested this method in three laboratory experiments on composite samples consisting of two concentric steel cylinders (length 60 cm, diameter inner pipe *6 cm, diameter outer pipe *10.2 cm), where cement was injected in the annular region between these two pipes. After curing, sealing was poor due to the induction/presence of debonding defects at the inner pipe wall, producing apparent sample permeabilities of 1.4 9 10 -13 -7.1 9 10 -12 m 2 .…”

“…After curing, sealing was poor due to the induction/presence of debonding defects at the inner pipe wall, producing apparent sample permeabilities of 1.4 9 10 -13 -7.1 9 10 -12 m 2 . Subsequent expansion of the inner pipe, by 2-8% via internal pressurisation or swaging, caused significant reduction in permeability, reducing this to *3 9 10 -19 m 2 in the initially most permeable sample and to values below detection in the other two samples [74,75]. These findings are promising, especially since increased confinement may help maintain the mechanical stability of the cement, i.e.…”

“…A potential limitation to the method proposed by Kupresan et al [74,75], is that the casing diameter must be plastically expanded. In their experiments, this was achieved using (ductile) expandable casing tube technology [18,88], swaged open with a pull-through mandrel and internal expansion cones.…”