Effect of Oilfield Scale Deposition on Mobility Ratio

Abstract

Scaling phenomenon is a major problem that occurs when water is injected for oil displacement and pressure maintenance in oilfields. This phenomenon of precipitation and accumulation of oilfield scale due to incompatibility between formation and injected water is induced around the well bore after water breakthrough at reduced reservoir pressure. The effect results in formation damage which may negatively impact on reservoir performance well bore performance and the success of water flooding project that depends on mobility ratio. This paper presents an analytical model based on existing thermodynamic models for predicting brine mobility, hydrocarbon mobility and mobility ratio of water flooded reservoir with possible incidence of scale precipitation and accumulation. The key operational and reservoir/brine parameters which influence the mobility ratio such as salt concentration in the brine, produced water rate, pressure drawdown, reservoir temperature were identified using this model. Results of the study shows that the mobility ratio of a water flooded reservoir remains constant until water breakthrough and achieves an increasing local maximum at 10% pore volume injected water as the flow rate of produced water increases with a significant jump beyond the critical flow rate observed at mobility ratio of 1. Similar results corroborating above were obtained with variation in skin factor. This model therefore can be used to diagnose, evaluate and simulate mobility ratio and skin factor in a water flood scheme enabling production engineers plan an economically efficient water flood scheme.

Endpoint Mobility Ratios for Vertical and Horizontal Wells with Incidence of Scale Deposition

“…Pressure gradient due to the presence of scale in the flow path as follows [3,4]. Instantaneous local porosity is defined as the difference between the initial porosity and the damaged fraction of the pore spaces i.e.…”

“…Scaling phenomenon is a major problem that occurs when water is injected for oil displacement and pressure maintenance in oilfields [1][2][3]. This phenomenon of precipitation and accumulation of oilfield scale is due to incompartibility between formation and the injected water induced around the wellbore after water breakthrough at reduced reservoir pressure [4,5].…”

Predicción del daño a la formación por acumulación de CaCO3 durante el flujo constante de salmueras en el medio poroso

“…Para el caso de daño por CaCO 3 se asigna la concentración de Ca ++ en los percentiles 10, 50 y 90 de una distribución homogénea que provee un Scale Tendency (ST) para los pozos del campo para tomar acciones de remediación y control. Además, Fadairo et al, (2008) investiga el efecto que tiene la depositación de escamas en la relación de movilidad. El estudio muestra un modelo basado en modelos termodinámicos para predecir la movilidad de la salmuera, de los hidrocarburos con la posible precipitación y acumulación, lo relevante de este estudio es que tiene en cuenta las condiciones operacionales, las concentraciones de la salmuera, la tasa de agua producida, el diferencial de presión y la temperatura del yacimiento.…”

Effect of Temperature on Scale Formation Around the Wellbore and Hole Cleanup For Reconditioned Drilling Mud

“…This paper presents a Solution [X] (based on experimental analysis) for effective wellbore and open hole clean up of a producing well at different temperatures, especially at offshore locations where seawater is mostly injected. An analytical model for the prediction of BaSO4 scale build up rate under an idealized flow condition as derived by Fadairo et al (2008) was used for prediction of scale formation. We observe technical issues that influence the impact of BaSO4 scale deposition on inflow performance and also identify key parameters that influence the magnitude of BaSO4 scale deposition.…”