Interdependence of Hydraulic Parameters in Transient Induced Contaminant Intrusion in a Pipeline

Sensitivity Analysis of Hydraulic Parameters on Contaminant Intrusion in Transient Conditions

Volume of fluid-based CFD study of triggering and eruption in urban storm sewers

Geyser eruption in urban drainage is a high-velocity discharge of an air–water mixture driven by intense air–water interactions. It is sudden, destructive and strongly non-linear, and is often associated with air entrapment, surcharge flows during intense rainfall and transient hydraulic processes, posing risks to drainage assets and surface infrastructure. A representative horizontal main pipe–vertical riser configuration is modelled using a volume of fluid (VOF) two-phase framework and a systematic numerical study is conducted of the inlet pressure head, dimensionless initial entrapped air index, Ia0, and the initial water-column height. Results identify a distinct eruption threshold: under the fixed geometry and boundary conditions considered in this study and within the tested parameter range, geyser eruption is triggered when Hin/H0 ≥ 1.33 andIa0 ≥ 3.20. As the free surface enters the upper riser, pronounced pressure spikes at PT4 and PT5 can serve as precursors. For a given inlet pressure head and the initial entrapped air condition, increasing the initial water-column height leads to higher eruption velocities, highlighting its control over eruption intensity.

Water hammer study in rigid and viscoelastic pipelines with sensitivity analysis of overpressure and damping

Pressure transient analysis for detecting leakages along active and abandoned wells.

Leakage out of the target formation is a major risk associated with subsurface wellbores. This study explores feasibility of leakage detection with pressure transient analysis (PTA) in multiple potential leakage scenarios, including induced fractures and casing failures in active and legacy wells, which may become conductive from injection‑induced pressure buildup. A mechanistic well-reservoir model based on a representative offshore Norwegian sandstone reservoir was used in the study. The fluid flow simulation study for a single-phase, isothermal, low-compressible fluid (water) has two parts. The first addresses the mechanisms of induced fracturing and fracture propagation through caprocks, creating out-of-zone leakage risks. Then, it proposes an approach to model fracture propagation into cap-rocks and explores feasibility of early detection of the fracture leakage into cap-rocks with PTA of step-rate tests. The second part examines casing-cement-rock integrity failure mechanisms with focus on behind-casing leakage or crossflow detection with PTA. A dedicated modeling approach for behind-casing leakage resulted in revealing pressure derivative signatures associated with the leakage from the flow simulations, confirming feasibility of the leakage detection from PTA of shut-ins responses of active and abandoned wells. The monitoring approach considered in the study relies on real-time pressure data from permanent downhole gauges (PDGs) installed in active wells or wireless PDGs in abandoned wells, interpreted with the PTA methods evaluated. Results from the simulated cases have demonstrated the feasibility of the PTA methods to detect leakage with a possibility to approximately assess leakage rates in some cases, with the assessment accuracy decreasing with declining leakage rate. The feasibility study results are valid for the cases considered and the assumptions taken, and further testing and validation of the PTA methods using field data is a necessary next step in maturation of the interpretation methodology presented.

Hidden Risks to Sustainable Operation of Water Systems: Suffosion Process Triggered by Pipe Leakage

Failures and leakages in water distribution pipelines affect the sustainable operation of water supply systems. While water losses caused by leaks are widely recognized, their impact on soil stability and internal erosion processes remains insufficiently investigated. This study examines water flow velocity distributions in soil around leaking water pipes regarding suffosion risk. Numerical simulations were performed using the FEFLOW software for four scenarios combining two pipe diameters and two internal pressure levels. Each scenario assumed circumferential leakage with continuous water outflow into the surrounding soil. The numerical model was validated through field experiments conducted on four experimental setups. The simulation results showed that flow velocities near the pipe exceeded critical values in all scenarios, indicating a risk of suffosion. Although hydraulic pressure and leakage area significantly affected local flow velocities, their influence on the extent of the potential suffosion zone was negligible. In all cases, the zone where critical velocities were exceeded extended more than 1.5 m from the leakage location. The results highlight the importance of considering suffosion risk in the operation and risk assessment of sustainable water supply systems. They also indicate that this hazard should be taken into account during the design stage, particularly when selecting pipeline routes and assessing ground conditions.

Occurrence of severe slugging in oil production lines and mitigation methods: A numerical simulation approach using ALFAsim®

Severe slugging represents a major challenge in offshore production systems, potentially compromising operational stability and the integrity of installations. Although established simulators such as OLGA® are widely used for its analysis, there is a gap in the literature regarding the application of the one‐dimensional simulator ALFAsim® for modelling and mitigating this phenomenon. In this context, this study aims to evaluate ALFAsim's® capability to identify severe slugging and analyze mitigation strategies in a system composed of a well, flowline, and riser. The methodology was based on one‐dimensional transient numerical simulations, including domain discretization with a linear mesh (10 m segments), solution of the mass and momentum conservation equations, and identification of flow patterns using the unit cell model. Boundary conditions of flow rate, pressure, temperature, and gas–oil ratio were imposed, with parametric variation of the oil flow rate between 800 and 1400 m 3 /d. For mitigation analysis, a choke valve located at the top of the riser was modelled using a C v (flow coefficient) versus opening curve, and gas injection at the base of the riser was performed at different rates. The results indicated that ALFAsim® reproduced the main hydrodynamic characteristics of the phenomenon, including cyclic flow oscillations and pressure variations, with an approximate cycle period of 7000 s. A choke valve opening of 92.5% and a gas injection of 660,000 m 3 /d are found to be the most effective conditions for flow stabilization. These findings demonstrate that ALFAsim® is a suitable tool for the analysis and mitigation of severe slugging.