A review and phenomenological modeling of the various processes causing reservoir formation damage are presented. The mechanisms involved in the migration, deposition, and mobilization of the fine particles and inorganic and organic precipitates are described physically and mathematically. The various problems created by fine particles at the pore surface, clogging and dislodgment of the pore throats, aggregation, and interface particle transfer processes in multi-phase fluid systems flowing through porous media are described. The implications of the various mechanical, chemical, and thermal processes on the behavior of the particles are discussed. The various types of shock phenomena and their effects on the particulate processes are explained. The alteration of the pore connectivity, preferential hydraulic paths, permeability and porosity of porous media as a result of the various particulate processes are formulated. The phenomenological modeling of the particulate processes in single- and multiple-porosity reservoir formations is presented. The applications may concern with the damage by particles, injectivity decline in waterflooding wells, formation damage by drilling mud invasion, formation damage in naturally fractured reservoirs, asphaltene deposition, and sand production and gravel pack damage.
Formation damage is a terminology used to delineate the undesirable reduction of permeability by various processes occurring in geological porous formations, and therefore reducing the productivity and injectivity of the wells involving the oil and gas production systems. It should not be confused with the completions damage, delineating the loss of well performance by other affects, including deposition of particulate matter, fluid mobility reduction, and fluid flow conditions owing to the hindering features of the specific completion techniques at and around the wellbore (Butler et al., 2000). Frequently, formation damage occurs in the production and injection wells near-wellbore region, where conditions vary significantly compared to the rest of the reservoir owing to the convective acceleration and deceleration, and change of the fluid conditions. However, formation damage can also occur throughout the reservoir formation eventually as the reservoir production continues, especially when the asphaltene and scale formation conditions are attained (Wang and Civan, 2005abc).
The reservoir formation generally contains various types of mineral oxides and swelling and non-swelling types of clays. However, other substances, such as drilling mud, hydraulic fracturing fluids, cement, various debris, may also invade the reservoir formation as a result of the practices required for petroleum recovery from subsurface reservoirs. Examples of these include the materials used for fluid loss control, mud weighting, and pore blocking/bridging, particulates present in injection water, drill cuttings, and various corrosion products (Bennion and Thomas, 1994, Bennion, 2002). Ordinarily, the mineral matter loosely attached at the pore surface is not free to interact with the other minerals. When the conditions are disturbed, the various ionic and particulate species generated from various minerals may be unleashed into the flowing pore fluid system, creating conditions similar to a bowl of soup, where they can interact in difficult-to-control complicated ways with each other and the pore structure (Civan, 2007).
The processes governing the fine particle behavior during the flow of oil, gas, and brine through the reservoir formation and well completion system are very complicated in nature and affected by various factors. The rates of these processes strongly depend on the local conditions, including the chemical state, flow, temperature, pressure, stress, and other relevant factors. Consequently, the adverse affects may be controlled by controlling such conditions in view of the damaging process time scales relative to the injection and production time scales at the wells. The best option in avoiding formation damage is to prevent disturbing the existing in situ equilibrium conditions. However, this requires a scientific insight and practical understanding of these processes. From the practical point of view, the primary objective is obtaining simplified mathematical models for the complicated particle transport processes and their interactions with the reservoir formation. Such models may be instrumental in designing optimal strategies for prevention of formation damage in petroleum reservoirs.