Rock-Fluid Interaction: Predictable and Preventable Causes of Formation Damage

J. D. Kantorowicz

Numerous types of formation damage can occur during hydrocarbon reservoir development. Case studies reveal that the most common cause of formation damage is the rock-fluid interaction that occurs when introduced fluids upset the equilibrium that exists between a formation's pore fluids and minerals such as clays, carbonates, and anhydrite.

Clay minerals are particularly sensitive to changes in pore-fluid chemistry. Minerals may swell and disperse during injection of fresh water, whereas during stream injection they typically react to form smectites. Both effects reduce permeability. Clays also may adsorb surfactants or Na⁺ and reduce tertiary flooding efficiency. Finally, clays and other fines can be physically mobilized during production, plug pore throats, and reduce permeability.

Carbonate minerals are soluble during acid stimulation. Dissolution is advantageous if permeability increases, but damaging if previously cemented swelling clays are released, the rock's framework collapses, or dissolved minerals interact and reprecipitate. Carbonate and anhydrite dissolution during surfactant flooding may reduce recovery if Ca²⁺ complexes and precipitates the surfactants. Iron-rich siderite, hematite, or chlorite are soluble in acids or dilute injection waters from which iron gel or complexed polymers can precipitate, causing plugging.

Combined laboratory core flooding and petrographic investigations of exploration and appraisal core are required to predict the damage that may occur during field development. Criteria should be established enabling drilling, completion, injection, and stimulation program design to minimize or avoid damage during field development. Successful predictions on this basis may have an immediate and beneficial impact, reducing development costs and improving recovery efficiency.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.