Expro is an energy services provider headquartered in Houston, Texas, United States.
The Vaca Muerta formation ranks among the most productive formations in the Neuquén Basin and plays a key role in regional energy economy, during well development of tight formations, casing deformation events are frequently detected, with high impact due to fracturing processes (Vítolo et al.,2025). In order to properly address these events, a thorough understanding of their characteristics is required. One of the main challenges lies in accessing the horizontal section of the well, where wireline services—commonly used to convey logging tools—are unable to reach the required horizontal depth. In such cases, alternative conveyance methods, such as coiled tubing or tractor, must be employed. Coiled tubing was used in the three wells analyzed in this study. Characterizing a deformation represents the first step toward determining an effective solution, allows the definition of the new drift diameter in the affected section of the downhole completion, with the ultimate objective of designing a new tool string capable of reaching the target zone and enabling a redesign of the well completion. It is well known that casing deformation events limit reservoir accessibility and, in many cases, prevent well completion and subsequent production stage. Moreover, the strategies and attempts to address these issues may lead to ambiguous outcomes if they are not supported by accurate diagnostic information. A detailed understanding of the preparation procedures for the Multifinger Caliper (MFC), aimed at acquiring high-quality data, in accordance with data validation mechanisms, tool string design—which may vary depending on whether a Pipe Analysis Deformation (PDA) is planned—and operational considerations derived from experience in conveying the caliper via coiled tubing to pass through deformed intervals, provides invaluable guidance when addressing these operational challenges.
Abstract This paper examines the application of Distributed Fiber Optic Sensing (DFOS) for well integrity evaluation in support of plug and abandonment (P&A) planning. The study focuses on the use of distributed temperature sensing (DTS) and low-frequency distributed acoustic sensing (LF-DAS) to detect and characterize subtle flow behavior, including micro-leakage, intermittent flow, and behind-casing communication, in a multistring well configuration. A distributed fiber optic cable was deployed inside the well to acquire continuous temperature and acoustic measurements along the wellbore. LF-DAS was applied to enhance sensitivity to low-rate and transient flow phenomena that may not be detectable using conventional acoustic frequency ranges. Data were acquired over an approximately eight-hour period following a structured three-stage operational sequence comprising baseline monitoring, annulus bleed-off, and injection to full choke opening at 100% while bleed-off. DTS and DAS responses were analyzed across acquisition stages to isolate flow-induced signatures and evaluate behind-casing fluid movement in a multistring environment. Analysis of the DFOS data identified several flow-related features relevant to well integrity assessment. A localized near-surface anomaly, characterized by subtle temperature variations coincident with elevated low-frequency acoustic response, was interpreted as micro-leakage. The anomaly was transient and observed only during specific acquisition stages, demonstrating the capability of LF-DAS to detect short-duration and intermittent leakage events that may not be evident under steady-state conditions. LF-DAS measurements also enabled discrimination of flow direction and relative flow intensity, indicating predominantly downward behind-tubing flow along the wellbore. In addition, distributed responses identified behind-casing fluid movement within a cemented interval, interpreted as crossflow between multiple reservoir sections. Differences in acoustic response magnitude and direction between reservoir intervals A–B and C–D suggest pressure communication and complex behind-casing connectivity. The resolution provided by LF-DAS allowed accurate localization of flow anomalies and identification of multiple contributing sources. This level of accuracy is particularly important for sustained casing pressure (SCP) remediation during plug and abandonment operations, where misidentification of leak location may lead to ineffective barrier placement. Overall, the results demonstrate that integrated DTS and LF-DAS measurements provide enhanced sensitivity for characterizing low-rate, transient, and multisource flow behavior relevant to P&A planning. This paper adds to existing literature by presenting field-based evidence of the advantages of LF-DAS for well integrity evaluation. The study demonstrates the ability of LF-DAS to detect very small and intermittent leaks, determine flow direction and relative magnitude, and localize multiple leak sources in a multistring well. These findings provide practical guidance for users assessing well integrity prior to abandonment.
Abstract Expro's Octopoda® annulus intervention technology was deployed to remediate sustained casing pressure (SCP) in the C annulus of a Petroleum Development Oman (PDO) well. SCP originated from a shallow aquifer and, under Omani regulations, required isolation or well abandonment. The rig-less intervention established a circulation path for placement of kill-weight brine to restore hydrostatic overbalance without inducing losses. A wellhead survey confirmed access for the Octopoda® system, and a 6.9 mm OD hose was deployed to 230 m within the C annulus. A total of 32 m3 of 1.39 SG calcium chloride brine was circulated to displace degraded annulus fluid and re-establish overbalance. To prevent aquifer flow during circulation and maintain displacement efficiency, backpressure was applied via an in-line choke to achieve balanced circulation. Establishing circulation at depth in a live annulus was critical to the success of the intervention. Monitoring returns density and annulus pressure allowed pump rate and choke settings to be adjusted in real time, maximizing operational efficiency while avoiding losses to a known weak formation. C annulus pressure was reduced to 0 psi following placement of 32 m3 of brine, and the full operation was completed in under two weeks, including mobilization and demobilization. Subsequent monitoring confirmed the annulus remained at 0-psi surface pressure 22 months later, allowing PDO to remove the dispensation and continue production without a workover or abandonment. This case demonstrates that annulus intervention enables controlled fluid circulation in a pressurized annulus and provides a more predictable and lower-risk alternative to conventional SCP remediation methods.
Abstract Lateral vibrations in drill strings reduce drilling efficiency, accelerate component wear, and increase the likelihood of nonproductive time. Although various downhole vibration mitigation devices are used in practice, their performance is often evaluated qualitatively or inferred from field trends without rigorous physical characterization. This work develops a scientific, physics-based modeling approach for a vibration mitigation tool that introduces a controlled pivot point in the bottom-hole assembly (BHA) and employs viscoelastic elements to dissipate energy through damping. A comprehensive workflow is presented that quantifies the tool's behavior through controlled laboratory testing, dynamic modeling, and field-level validation. A structured laboratory program was conducted across all tool sizes using impulse loading tests to measure the dynamic response of the assembly with and without the tool installed. Deflection and damping characteristics were extracted from both static and dynamic measurements, revealing significant differences between the two methods and highlighting the importance of dynamic calibration for elastomer based damping systems. Numerical simulations were then used to reproduce the experimental results, enabling calibration of the tool's deflection and damping coefficients. These coefficients were integrated into a BHA dynamics model for evaluation in a representative field case. The calibrated model was applied to a drilling interval with both surface and downhole vibration measurements recorded near the bit and at two locations surrounding the tool's pivot point. The dynamic model was iteratively refined until the simulated response converged with measured field data. A comparative simulation, in which the tool was replaced with a standard stabilizer of equal dimensions, was then performed while holding all other conditions constant. The presence of the tool reduced lateral acceleration by an average of 29% along the modeled drill string and by 50% below the reamer. Bending stress decreased by 10% along the full interval and by 30% below the reamer. Frequency-domain analysis confirmed broad-spectrum suppression of lateral and torsional vibration modes at all monitored locations. The combined laboratory and field validated simulations demonstrate that the calibrated parameters reliably characterize the tool's behavior and provide a predictive framework for optimizing BHA configurations. This methodology enables quantitative pre-job assessment of tool placement, expected vibration reduction, changes in critical speeds, and system-level dynamic response, supporting data-driven integration of vibration-mitigation strategies into modern drilling system designs.
The concept of utilizing an expandable liner is presented to restore casing integrity when unexpected casing damage occurs during well stimulation. This solution allows the operator to continue with additional planned frac stages with little downtime or changes to the overall operational plan. A solid expandable liner is a specially designed casing string that is cold-worked downhole to plastically deform the casing and make it larger than its run-in-hole OD. It has metal seals on the OD of the casing that provide a pressure seal and anchor the new casing string/patch into the existing casing to isolate casing damage. The planning and preparation process is discussed including boundary conditions, diagnostic procedures such as cased-hole logging and wellbore cleanout, followed by the installation process of expanding the liner at the given setting depth. The expandable liner solution is compared to more traditional solutions for addressing casing damage during well stimulation, such as cement or resin squeezes and conventional liners. Six field case studies are presented showing different scenarios where unexpected casing damage occurred during fracturing operations and an expandable liner was used to restore casing integrity and allowed the frac operation to continue. Expandable liners are an innovative solution that can help save operators rig time and money while providing a permanent repair that still has a large enough pass-through ID and high enough pressure ratings to allow the well stimulation and completion to be executed as planned without deviation to pressures or equipment sizing.
