Casing Expansion as a Promising Solution for Microannular Gas Migration

Abstract

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.

Digital Cement Integrity: A Methodology for 3D Visualization of Cracks and Microannuli in Well Cement

“…Consequently, several laboratory experiments have been performed to study and understand these cement sheath failure modes and the resulting loss of zonal isolation [15,[18][19][20][21][22]. Furthermore, other authors have focused on studying microannuli formation and the resulting flow through these leakage pathways [23][24][25][26].…”

Systematic Experimental Investigation on In-Situ Self-Adaptive Sealing Property of Composite Pressure-Activated Sealant for Curing Minor Tubular Leaks

“…As the most traditional repair methods, mechanical repairs [1] and chemical sealants [2][3][4][5] have been extensively studied over the past few decades. Although these conventional methods have proven useful in curing leaks and restoring the integrity of the wellbore, there are various limitations to on-site operations.…”

Chemo-Physico-Mechanical Behavior of Class G Oil Well Cement Pastes

“…The fact that confined cement paste can withstand significant plastic deformation is a mechanism that is utilized by casing expansion technologies to close migration paths behind casing [273][274][275]. In the study by Kupresan et al…”

“…The annulus was subsequently compressed radially by using an expansion cone to expand the diameter of the inner pipe by 2 to 8%. The casing expansion was found to reduce the permeability by several orders of magnitude, and inspection of the compressed annulus cement suggested compaction due to pore collapse, displacement of pore fluid, and an apparent softening and rehydration of the cement [273]. More recently, a tool has been developed that performs local casing expansion by pressing hardened steel fingers into the wall of the inner casing [276].…”