Gas production from underground storage reservoirs is sometimes associated with solid particles eroded from the rock matrix. This phenomenon often called sand production can cause damage to the storage equipments, leading the operator to choke the wells and prevent them from producing at full capacity. Colloid release is often associated as a precursor of larger solid production. Indeed, in sandstone storage sites, clay release induced by the presence of condensed water associated with the gas production in the near-wellbore region can be a forecast of intergranular cement erosion. The objective of this work is twofold: firstly to experimentally investigate colloidal particle detachment through ionic strength reduction (absence of salinity of the condensed water) in porous media and secondly to determine its evolution with time and to model it. Laboratory experiments with model systems are developed to reproduce the particle generation and their transport in porous media. The model porous medium is a packed column of two powders: silicon carbide particles of 50 µm and silica particles of 0.5 µm (3% by weight) initially mixed together. Brine flows at different concentrations are imposed through the porous sample and, at very low salt concentration, colloid silica particles are massively released from the medium. Experimental evolutions of the particle concentration with time are compared to solutions of the advection-dispersion equation including first-order source terms for colloid release. The dispersion coefficients of the porous medium have been determined with tracer tests. The experimental results exhibit a different behaviour at short-and long-time intervals and a model has been built to predict the colloid production evolution with the introduction of two different time scales for the eroded rate. The model can be used in a core test to evaluate the amount of detachable fines and the rate of erosion.

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Gas production from gas wells or storage reservoirs is sometimes associated with solid particles eroded from the rock matrix. This phenomenon often called sand production can cause damages to the equipments, leading to choke the wells under their full capacity. Colloid release is often associated as a precursor of larger solid production and clay release can be a forecast of inter-granular cement erosion. Injections of dilute polymer/microgel solutions form a small part of the techniques employed today to deal with sand production in gas and oil wells. Nevertheless they could be used more often as a remedy against starting sand production problems as shown through recent field applications. The paper presents laboratory experiments carried out with model systems to reproduce particle generation and their transport in porous media. The approach consists in following the evolution of the colloidal particle detachment after ionic strength reduction and in defining the key parameters for release rate prediction. A different behaviour is highlighted at short and long time and the model, built to predict the colloid production evolution, is based on the introduction of two different time scales of the eroded rate.The laboratory experiments demonstrate the great efficiency of polymer/microgel treatments. The proportion of fines produced decreases drastically when the surface coverage related to the adsorption rate increases. The use of the model to describe the effect of the chemical treatment helps to show that this one does not modify the mode of production of fines but significantly reduces the quantity of fines likely to be carried away from the pore surface.

Two-phase internal flow is present in many piping system components. Although two-phase damping is known to be a significant constituent of the total damping, the energy dissipation mechanisms that govern two-phase damping are not well understood. In this paper, damping of vertical clamped-clamped tubes subjected to two-phase air-water internal flow is investigated. Experimental data is reported, showing no dependence of two-phase damping on tube natural frequency, and a strong dependence on void fraction, flow velocity and flow regime. Two-phase damping increases with void fraction, reaches a maximum, and decreases beyond that point. The maximum damping ratio is roughly 3% for all flow velocities. It is reached at around 50% void fraction for high velocities, and 25% void fraction for low velocities. Data points plotted on two-phase flow pattern maps indicate that damping is greater in a bubbly flow regime than it is in a slug or churn regime. The maximum two-phase damping is reached at the highest void fraction before the transition to a slug or churn flow regime. It appears that two-phase damping may depend on the interface surface area between phases.