Frequently, the composition of petroleum-bearing formations includes certain minerals and clays, the swelling of which in contact with water-based drilling and completion fluids, may cause formation damage and adversely affect the wellbore stability. This paper presents a kinetic model for correlation and prediction of the water sensitivity and swelling characteristics of petroleum-bearing formations and its verification by experimental data.

The swelling of petroleum-bearing formations is perceived to occur via the absorption of water by a water-exposed surface hindered diffusion mechanism. Hence, a theory of swelling and alteration of petroleum-bearing clayey formations is developed and applied for correlation of various properties of practical importance, including water content, permeability, volume expansion or porosity, and basal spacing of clay. An analytical solution is derived and reformulated for convenient straight-line plotting of experimental data. It is demonstrated that this model accurately represents the swelling characteristics of petroleum-bearing formations, successfully correlates various experimental data, and allows for accurate determination of the swelling rate parameters.

The theoretical treatment provides insights into the mechanism of the swelling of petroleum-bearing formations and leads to the development of a practical and theoretically rigorous method for accurate straight-line correlation of experimental data and determination of the swelling rate parameters. This model can be used for accurate description of the swelling characteristics of petroleum-bearing formations, prediction of conditions causing wellbore stability problems, and development of optimal strategies for effective mitigation of the undesirable consequences of swelling in petroleum reservoirs.

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