Thermo-Hydraulic State Estimation and Robust Decision Support for Multiphase Kick Transients from Sparse Surface Measurements

• Juan Esteban Cárdenas

  Universidad de Pamplona, Calle 28B 14–67, Barrio Miraflores, Pamplona, Norte de Santander, Colombia

  Author

• Mateo Andrés Villalba

  Universidad Surcolombiana, Carrera 9A 22–41, Sector La Merced, Neiva, Huila, Colombia

  Author

• Santiago Ricardo Borrero

  Corporación Universitaria del Caribe (CECAR), Avenida Los Fundadores 5–118, Urbanización El Prado, Sincelejo, Sucre, Colombia

  Author

Early identification and characterization of gas influx events during drilling remains difficult because the most reliable measurements are typically available at the surface, while the hazardous dynamics occur along an extended, heterogeneous wellbore. Surface pressure and flow signals are continuously accessible, but they are often non-unique with respect to downhole states because multiphase slip, compressibility, dissolution, and evolving frictional losses can produce similar signatures for distinct influx scenarios. This paper develops a physics-first estimation and decision-support framework that converts sparse surface measurements into probabilistic downhole reconstructions suitable for real-time operational guidance. The core contribution is a coupled thermo-hydraulic model that accounts for gas compressibility, transient annular hydraulics, and pressure- and temperature-dependent gas solubility in non-aqueous drilling fluids, embedded within a constrained moving-horizon inference scheme. The estimator jointly reconstructs the latent state fields and an unknown influx boundary profile while enforcing mass conservation, momentum balance, and phase-equilibrium consistency. To improve robustness under model-form uncertainty and unmodeled flow-regime effects, the framework augments deterministic inversion with ensemble-based uncertainty propagation and risk-calibrated decision metrics that remain meaningful when the inverse problem is ill-conditioned. Numerical experiments spanning circulating and shut-in conditions demonstrate that the method can separate competing explanations for similar surface pressure traces by exploiting the joint evolution of pressure gradient, dissolved-gas inventory, and annular holdup. The resulting system offers a principled route to rapid, quantitatively interpretable kick assessment without relying on bespoke flow-pattern labels, while remaining compatible with data-driven components as optional accelerators rather than as primary arbiters of physical plausibility.

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