Fines migration

Unfortunately, not all scales are removable by chemical methods. For example, only calcium carbonate scale is readily removed by acid. Others, such as calcium sulfate, can be removed chemically, but inefficiently or only partially. Most scales require mechanical methods, such as milling, for complete removal. See chapter 14 for further discussion of scale removal. 

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Mechanical strain. When broken beads and fines migrate to the top of the resin bed during serviee, mechanieal strain is eaused whieh results in ehaimeling, inereased pressure drop, or premature breakthrough. The eombination of these resulting eonditions leads to a drop in eapaeity. 

R. N. Vaidya and H. S. Fogler. Formation damage due to colloidally induced fines migration. Colloids Surfaces, 50 215-229, 1990. 

Other minerals beside water-swelling clays have been found to undergo fines migration. The permeability damage caused by essentially non-swelling clays such as kaolinite and chlorite is a well-known phenomenon. Silica fines have been identified as a potential source of permeability damage in various poorly consolidated U.S. Gulf Coast formations (1). Other minerals identified as constituents of mobile fine particles include feldspar, calcite, dolomite, and siderite (4,5). 

Core floods were performed to determine if treatment polymers would prevent permeability damage caused by fines migration within consolidated rock and whether the adsorbed polymers would themselves reduce core permeability. The tests were performed using Hassler sleeve chambers. With the exception of the polymer... 

Fines production from untreated test sands and permeability damage observed in untreated cores indicated that the laboratory test flow rates were above the critical flow velocity required to initiate fines migration. 

Results indicated that swelling clay stabilizers such as poly (DMA-co-EPl) which do not possess a quaternary nitrogen atom in a pendant chain may not be very effective at preventing permeability damage due to fines migration in the absence of water-swelling clays. 

The purpose of this paper is to report on three fluid-related phenomena in particulate materials fines migration and formation clogging, particle drift in AC-electric fields, and mixed fluid conditions. Processes are analyzed at the microscale. 

Valdes, J.R. (2002) Fines Migration and Formation Damage - Microscale Studies Ph.D. Dissertation, Georgia Tech, Atlanta, Georgia... 

Fines Migration in Petroleum Reservoirs in Suspensions, Fundamentals and Applications in the Petroleum Industry, Schramm, L.L. (Ed.), American Chemical Society Washington,... 

Valdya, R.N., Fogler, H.S., 1992. Fines migration and formation damage influence of pH and ion exchange. SPEPE (November), 325-330. 

Chemical Factors. There are several mechanisms to damage a formation that involve chemical factors. The most important and well defined mechanisms are the following (1) fines migration and clay swelling, (2) mixing of incompatible waters, and (3) corrosion products. A brief discussion of each mechanism follows. 

The question now is why a change in salinity or pH can trigger fines migration This point has been extensively studied over the last few decades and is discussed in Chapter 7 of this book. However, a brief explanation of this phenomenon will be given here. A fine particle attached to another larger particle (Figure 2) is subjected to several colloidal forces, including London-van der Waals attraction force, Born... 

Permeability Reduction in Presence of Oil. Muecke (55) and Sarkar and Sharma (56) examined permeability reduction due to chemical fines migration in Berea core samples saturated with brine and at residual oil saturation. Liu and Civ an (49) modeled permeability impairment due to salinity shock with and without the presence of residual oil. In the first experiment, fresh water was injected into a Berea sandstone core saturated with 3 wt% sodium chloride. In the second experiment, the fresh water was injected into a similar core at residual oil saturation. Figure 4 shows that their model predicted the experimental data fairly... 

Figure 3. Permeability decline due to chemical fines migration. (Reproduced with permission from reference 29. Copyright 1983.)...

Mechanical Factors. The most important mechanisms of formation damage by mechanical factors are (1) mechanical fines migration and (2) invasion of foreign particles. 

Mechanical Fines Migration. A fine particle attached to the surface of the sand particle is subjected to several hydrodynamic forces (51, 65). The two major hydrodynamic forces that act on a fine particle are the lift force and the viscous-drag force (Figure 2). The lift force, Fl, acts in a direction normal to the flow direction ([/-direction) and its magnitude is (66)... 

Injection of low-salinity waters into sandstone reservoirs can trigger fines migration and clay swelling. Injection of water that is incompatible with the formation brine may cause precipitation of calcium, barium, and strontium sulfates, which can plug the formation. 

Production of petroleum is often hampered by damage to the permeability of reservoir rocks resulting from interaction of injected fluids with the porous rock formation. Fine particles of clays and other minerals are often found attached to the pore walls of reservoir rocks. The interaction between injected fluids and the rock can cause their movement by a combination of mechanical shear forces, colloid-chemical reactions and geochemical transformations. This chapter reviews several different aspects of the fines migration process. 

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