Overview of Formation Damage 7 formation; and (5) Develop methodologies and strategies for formation damage control and remediation. This book reviews and systematically analyzes the previous studies, addressing their theoretical bases, assumptions and limitations, and pre- sents the state-of-the-art knowledge in formation damage in a systematic manner. The material is presented in seven parts: I. Characterization of the Reservoir Rock for Formation Damage— Mineralogy, Texture, Petrographies, Petrophysics, and Instrumen- tal Techniques II. Characterization of the Porous Media Processes for Formation Damage—Accountability of Phases and Species, Rock-Fluid- Particle Interactions, and Rate Processes III. Formation Damage by Particulate Processes—Fines Mobilization, Migration, and Deposition IV. Formation Damage by Inorganic and Organic Processes—Chemi- cal Reactions, Saturation Phenomena, Deposition, Dissolution V. Assessment of the Formation Damage Potential—Testing, Simu- lation, Analysis, and Interpretation VI. Drilling Mud Filtrate and Solids Invasion and Mudcake Formation VII. Diagnosis and Mitigation of Formation Damage—Measurement, Control, and Remediation References Amaefule, J. O., Ajufo, A., Peterson, E., & Durst, K., "Understanding Formation Damage Processes," SPE 16232 paper, Proceedings of the SPE Production Operations Symposium, Oklahoma City, Oklahoma, 1987. Amaefule, J. O., Kersey, D. G., Norman, D. L., & Shannon, P. M., "Ad- vances in Formation Damage Assessment and Control Strategies", CIM Paper No. 88-39-65, Proceedings of the 39th Annual Technical Meet- ing of Petroleum Society of CIM and Canadian Gas Processors Asso- ciation, Calgary, Alberta, June 12-16, 1988, 16 p. Barkman, J. H., & Davidson, D. H., "Measuring Water Quality and Pre- dicting Well Impairment," Journal of Petroleum Petroleum Technology, Vol. 253, July 1972, pp. 865-873. Bennion, D. B., Thomas, F. B., & Bennion, D. W., "Effective Labora- tory Coreflood Tests to Evaluate and Minimize Formation Damage in Horizontal Wells," presented at the Third International Conference on Horizontal Well Technology, November 1991, Houston, Texas. Bennion, D. B., & Thomas, F. B., "Underbalanced Drilling of Horizon- tal Wells: Does It Really Eliminate Formation Damage?," SPE 27352 8 Reservoir Formation Damage paper, SPE Formation Damage Control Symposium, February 1994, Lafayette, Louisiana. Bennion, D. F., Bietz, R. F, Thomas, F. B., & Cimolai, M. P., "Reduc- tions in the Productivity of Oil & Gas Reservoirs due to Aqueous Phase Trapping," presented at the CIM 1993 Annual Technical Conference, May 1993, Calgary. Bennion, B., "Formation Damage—The Impairment of the Invisible, by the Inevitable and Uncontrollable, Resulting in an Indeterminate Reduction of the Unquantifiable!" Journal of Canadian Petroleum Petroleum Technology, Vol, 38, No. 2, February 1999, pp. 11-17. Bishop, S. R., "The Experimental Investigation of Formation Damage Due to the Induced Flocculation of Clays Within a Sandstone Pore Struc- ture by a High Salinity Brine," SPE 38156 paper, presented at the 1997 SPE European Formation Damage Conference, The Hague, The Neth- erlands, June 2-3 1997, pp. 123-143. Civan, F, Predictability of Formation Damage: An Assessment Study and Generalized Models, Final Report, U.S. DOE Contract No. DE-AC22- 90-BC14658, April 1994. Civan, F., "A Multi-Purpose Formation Damage Model," SPE 31101 paper, Proceedings of the SPE Formation Damage Symposium, Feb- ruary 14-15, 1996, pp. 311-326, Lafayette, Louisiana. Duda, J. L., "A Random Walk in Porous Media," Chemical Engineering Education Journal, Summer 1990, pp. 136-144. Energy Highlights, "Formation Damage Control in Petroleum Reservoirs," article provided by F. Civan, The University of Oklahoma Energy Center, Vol. 1, No. 2, p. 5, Summer 1990. Mungan, N., "Discussion of An Overview of Formation Damage," Jour- nal of Petroleum Technology, Vol. 41, No. 11, Nov. 1989, p. 1224. Piot, B. M., & Lietard, O. M., "Nature of Formation Damage in Reservoir Stimulation, in Economides," M. J. and Nolte, K. S. (eds.), Reservoir Stimulation, Schlumberger Education Services, Houston, Texas, 1987. Porter, K. E., "An Overview of Formation Damage," JPT, Vol. 41, No. 8, 1989, pp. 780-786. Part I Characterization of the Reservoir Rock for Formation Damage Mineralogy, Texture, Petrographies, Petrophysics, and Instrumental Techniques Chapter 2 Mineralogy and Mineral Sensitivity of Petroleum-Bearing Formations* Summary The origin, mineralogy, and mineral sensitivity of petroleum-bearing for- mations are reviewed. The mechanisms of mineral swelling, alteration, and fines generation are described. The models for mineral sensitive properties of rock and the methods for interpretation of experimental data are presented. Introduction Among others, Ohen and Civan (1993) point out that fines migration and clay swelling are the primary reasons for formation damage measured as permeability impairment. Poorly lithified and tightly packed formations having large quantities of authigenic, pore filling clays sensitive to aque- ous solutions, such as kaolinite, illite, smectite, chlorite, and mixed-layer clay minerals, are especially susceptible to formation damage (Amaefule et al., 1988). Formation damage also occurs as a result of the invasion of drilling mud, cements, and other debris during production, hydraulic fracturing, and workover operations (Amaefule et al., 1988). This chapter describes the mineral content and sensitivity of typical sedi- mentary formations, and the relevant formation damage mechanisms involv- ing clay alteration and migration. Analytical models for interpretation and correlation of the effects of clay swelling on the permeability and porosity of clayey porous rocks are presented (Civan, 1999). The parameters of the * Parts of this chapter have been reprinted with permission of the Society of Petroleum Engineers from Civan (1999). 10 Mineralogy and Mineral Sensitivity of Petroleum-Bearing Formations 11 models, including the swelling rate constants, and terminal porosity and permeability that will be attained at saturation, are determined by corre- lating the experimental data with these models. The swelling of clayey rocks is essentially controlled by absorption of water by a water-exposed surface hindered diffusion process and the swelling-dependent properties of clayey rocks vary proportionally with their values relative to their satu- ration limits and the water absorption rate. These models lead to proper means of correlating and representing clayey rock properties. Origin of Petroleum-Bearing Formations As described by Sahimi (1995), sedimentary porous formations are formed through two primary phenomena: (1) deposition of sediments, fol- lowed by (2) various compaction and alteration processes. Sahimi (1995) states that the sediments in subsurface reservoirs have undergone four types of diagenetic processes under the prevailing in-situ stress, thermal, and flow conditions over a very long period of geological times: (1) mechanical deformation of grains, (2) solution of grain minerals, (3) alteration of grains, and (4) precipitation of pore-filling minerals, clays, cements, and other materials. These processes are inherent in de- termining the characteristics and formation damage potential of petroleum- bearing formations. Constituents of Sedimentary Rocks Many investigators, including Neasham (1977), Amaefule et al. (1988), Macini (1990), and Ezzat (1990), present detailed descriptions of the vari- ous constituents of oil and gas bearing rocks. Based on these studies, the constituents of the subsurface formations can be classified in two broad categories: (1) indigenous and (2) extraneous or foreign materials. There are two groups of indigenous materials: (1) detrital materials, which originate during the formation of rocks and have restricted forma- tion damage potential, because they exist as tightly packed and blended minerals within the rock matrix; and (2) diagenetic (or authigenic) mate- rials, which are formed by various rock-fluid interactions in an existing pack of sediments, and located inside the pore space as loosely attached pore-filling, pore-lining, and pore-bridging deposits, and have greater for- mation damage potential because of their direct exposure to the pore flu- ids. Extraneous materials are externally introduced through the wells completed in petroleum reservoirs, during drilling and workover opera- tions and improved recovery processes applied for reservoir exploitation. A schematic, pictorial description of typical clastic deposits is given in Figure 2-1 by Pittman and Thomas (1979). 12 Reservoir Formation Damage !LY PACKED AUTHIGENIC CLAY IN PORES. DETUTM ClAY AGGREGATE GRAIN! TIGHTIY DETKITAL CUV MATRIX NILS PORES Figure 2-1. Disposition of the clay minerals in typical sandstone (after Pittman and Thomas, ©1979 SPE; reprinted by permission of the Society of Petro- leum Engineers). Composition of Petroleum-Bearing Formations The studies of the composition of the subsurface formations by many, including Bucke and Mankin (1971) and Ezzat (1990), have revealed that these formations basically contain: (1) various mineral oxides such as SiO 2 , A1 2 O 3 , FeO, Fe 2 O 3 , MgO, K 2 O, CaO, P 2 O 5 , MnO, TiO 2 , Cl, Na 2 O, which are detrital and form the porous matrix, and (2) various swelling and nonswelling clays, some of which are detrital, and the others are authigenic clays. The detrital clays form the skeleton of the porous ma- trix and are of interest from the point of mechanical formation damage. The authigenic clays are loosely attached to pore surface and of interest from the point of chemical and physico-chemical formation damage. Typical clay minerals are described in Table 2-1 (Ezzat, 1990). However, the near-wellbore formation may also contain other sub- stances, such as mud, cement, and debris, which may be introduced dur- ing drilling, completion, and workover operations, as depicted by Mancini (1991) in Figure 2-2. "Clay" is a generic term, referring to various types of crystalline min- erals described as hydrous aluminum silicates. Clay minerals occupy a large fraction of sedimentary formations (Weaver and Pollard, 1973). Clay minerals are extremely small, platy-shaped materials that may be present in sedimentary rocks as packs of crystals (Grim, 1942; Hughes, 1951). The maximum dimension of a typical clay particle is less than 0.005 mm (Hughes, 1951). The clay minerals can be classified into three main groups (Grim, 1942, 1953; Hughes, 1951): (1) Kaolinite group, (2) Smectite (or Mineralogy and Mineral Sensitivity of Petroleum-Bearing Formations 13 Table 2-1 Description of the Authigenic Clay Minerals* Mineral Kaolinite Chlorite Chemical Elements* f Al 4 [Si 4 0 10 ](OH) 8 (Mg,Al,Fe) 12 [(Si,Al) 8 0 20 ](OH) 16 Morphology Stacked plate or sheets. Plates, honeycomb, Illite Smectite Mixed Layer (|Ca, NA) 07 (A1, Mg, Fe) 4 [(Si, Al) g 0 20 ] • nH 2 0 Illite-Smectite Chlorite-Smectite cabbagehead rosette or fan. Irregular with elongated spines or granules. Irregular, wavy, wrinkled sheets, webby or honeycomb. Ribbons substantiated by filamentous morphology. * After Ezzat, ©1990 SPE; reprinted by permission of the Society of Petroleum Engineers. t After J. E. Welton (1984). ISOPACHOUS RIM CEMENT INTERGRANULAR PORES DEFORMED _ MUD FRAGMENT INTERGRANULAR PRESSURE - SOLUTION INTERGRANULAR PORE BODY SAND-SIZE RITAL GRAIN PORE THROAT CEMENT MICROPOROSITY IN CLAY Figure 2-2. Description of the constituents in typical sandstone (after Mancini, 1991; reprinted by permission of the U.S. Department of Energy). 14 Reservoir Formation Damage Montmorillonite) group, and (3) Illite group. In addition, there are mixed- layer clay minerals formed from several of these three basic groups (Weaver and Pollard, 1973). The description of the various clay minerals of the sedimentary for- mations is given by Degens (1965, p. 16). The morphology and the major reservoir problems of the various clay minerals is described in Table 2-2 by Ezzat (1990). Readers are referred to Chilingarian and Vorabutr (1981), Chapters 5 and 8, for a detailed review of the clays and their reactivity with aque- ous solutions. Mineral Sensitivity of Sedimentary Formations Among other factors, the interactions of the clay minerals with aque- ous solutions is the primary culprit for the damage of petroleum-bearing formations. Amaefule et al. (1988) state that rock-fluid interactions in sedimentary formations can be classified in two groups: (1) chemical reactions resulting from the contact of rock minerals with incompatible fluids, and (2) physical processes caused by excessive flow rates and pressure gradients. Table 2-2 Typical Problems Caused by the Authigenic Clay Mineral Mineral Surface Area m 2 /gm* Major Reservoir Problems Kaolinite Chlorite Illite Smectite Mixed Layer 20 Breaks apart, migrates and concentrates at the pore throat causing severe plugging and loss of permeability. 100 Extremely sensitive to acid and oxygenated waters. Will precipitate gelatineous Fe(OH) 3 which will not pass through pore throats. 100 Plugs pore throats with other migrating fines. Leaching of potassium ions will change it to expandable clay. 700 Water sensitive, 100% expandable. Causes loss of microporosity and permeability. 100-700 Breaks apart in clumps and bridges across pores reducing permeability. t After Ezzat, ©1990 SPE; reprinted by permission of the Society of Petroleum Engineers. * After David K. Davies—Sandstone Reservoirs—Ezzat (1990). Mineralogy and Mineral Sensitivity of Petroleum-Bearing Formations 15 Amaefule et al. (1988) point out that there are five primary factors affecting the mineralogical sensitivity of sedimentary formations: 1. Mineralogy and chemical composition determine the a. dissolution of minerals, b. swelling of minerals, and c. precipitation of new minerals. 2. Mineral abundance prevails the quantity of sensitive minerals. 3. Mineral size plays an important role, because a. mineral sensitivity is proportional to the surface area of miner- als, and b. mineral size determines the surface area to volume ratio of particles. 4. Mineral morphology is important, because a. mineral morphology determines the grain shape, and therefore the surface area to volume ratio, and b. minerals with platy, foliated, acicular, filiform, or bladed shapes, such as clay minerals, have high surface area to volume ratio. 5. Location of minerals is important from the point of their role in for- mation damage. The authigenic minerals are especially susceptible to alteration because they are present in the pore space as pore-lining, pore-filling, and pore-bridging deposits and they can be exposed directly to the fluids injected into the near-wellbore formation. Mungan (1989) states that clay damage depends on (1) the type and the amount of the exchangeable cations, such as K + , Na + , Ca 2+ , and (2) the layered structure existing in the clay minerals. Mungan (1989) describes the properties and damage processes of the three clay groups as following: 1. Kaolinite has a two-layer structure (see Figure 2-3), K + exchange cation, and a small base exchange capacity, and is basically a nonswelling clay but will easily disperse and move. 2. Montmorillonite has a three-layer structure (see Figure 2-4), a large base exchange capacity of 90 to 150 meq/lOOg and will readily adsorb Na + , all leading to a high degree of swelling and dispersion. 3. Illites are interlayered (see Figure 2-5). Therefore, illites combine the worst characteristics of the dispersible and the swellable clays. The illites are most difficult to stabilize. Sodium-montmorillonite swells more than calcium-montmorillonite because the calcium cation is strongly adsorbed compared to the sodium cat- ions (Rogers, 1963). Therefore, when the clays are hydrated in aqueous 16 Reservoir Formation Damage SILICON -OXY6EN TETRAHEDRA SHEET GIBBSITE SHEET SILICON-OXYGEN TETRAHEDRA SHEET O) «<OH) v x 6® DO© . b-AXIS KAOLINITE (OH), Al, SI 4 0 IO Figure 2-3. Schematic description of the crystal structure of kaolinite (after Gruner-Grim, 1942, and Hughes, 1951; reprinted courtesy of the Ameri- can Petroleum Institute, 1220 L St., NW, Washington, DC 20005, Hughes, R. V., "The Application of Modern Clay Concepts to Oil Field Development," pp. 151-167, in Drilling and Production Practice 1950, American Petroleum Institute, New York, NY, 1951, 344 p.). SILICON - OXV8EN TETRAHEDRA SHEET T i H 2 O 9.6 - 21.4 A * SILICON-OXYGEN TETRAHEDRA SHEET GIBBSITE SHEET SILICON -OXYGEN TETRAHEDRA SHEET MONTMORILLONITE (OH), Al, SI, O K • n H : 0 Figure 2-4. Schematic description of the crystal structure of montmorillonite (after Hoffman, Endell, and Wilm Grim, 1942, and Hughes, 1951; reprinted courtesy of the American Petroleum Institute, 1220 L St., NW, Washington, DC 20005, Hughes, R. V., "The Application of Modern Clay Concepts to Oil Field Development," pp. 151-167, in Drilling and Production Practice 1950, American Petroleum Institute, New York, NY, 1951, 344 p.). [...]... migrate (Mohan and Fogler, 19 97) 0 .16 _ CORE WEIGHT - 33.6 yn 3 1U 0 .14 5 O 0 . 12 P 20 .3 s tc t0 .10 £ 0 .2 < 0 .1 0.04 0. 02 3 0.00 2 3 4 5 6 7 8 VOLUME 3.7* KCI THROUGHPUT (literj) 10 Figure 2 -11 Carbonate leaching from a field core by flowing a potassium chloride brine (after Reed, 19 77 SPE; reprinted by permission of the Society of Petroleum Engineers) 22 Reservoir Formation Damage 3 Also, fines attached... Petroleum) * After Civan, 19 99 SPE; reprinted by permission of the Society of Petrolem Engineers from SPE 5 21 3 4 paper 26 Reservoir Formation Damage Montmorillonite, NaCl/KCl mixed Crystalline Swelling o.: o.oi Formation Damage Zone 0.0 010 o.ooi 0. 01 NaCl(N) Figure 2 -16 Swelling chart for montmorillonite exposed to sodium and potassium chloride brines (after Zhou et al., 19 96; reprinted by permission... 0.0 10 Figure 2 -13 Swelling of montmorillonite in sodium chloride brine (after Mohan, K K., and Fogler, H S., 19 97; reprinted by permission of the AlChE, 19 97 AlChE All rights reserved) 10 0.0 ' 0 (2- 8) and, therefore, an analytical solution of Eqs 2- 2, 3, 8, and 5 according to Crank (19 56) yields . Fogler, 19 97). 20 .3 s 0 .2 < 0 .1 CORE WEIGHT - 33.6 yn 0 .16 _ 3 1U 0 .14 5 O 0 . 12 P tc t- 0 .10 £ 0.04 0. 02 3 0.00 23 45678 VOLUME 3.7* KCI THROUGHPUT (literj) 10 Figure 2 -11 . Carbonate . DE-AC 22- 90-BC14658, April 19 94. Civan, F., "A Multi-Purpose Formation Damage Model," SPE 311 01 paper, Proceedings of the SPE Formation Damage Symposium, Feb- ruary 14 -15 , 19 96, . of Formation Damage, " Jour- nal of Petroleum Technology, Vol. 41, No. 11 , Nov. 19 89, p. 12 24. Piot, B. M., & Lietard, O. M., "Nature of Formation Damage in Reservoir Stimulation,