Effect of Droplet Size, Emulsifier Concentration, and Acid Volume Fraction on the Rheological Properties and Stability of Emulsified Acids
- Saleh Haif Al-Mutairi (Saudi Aramco) | Alfred Daniel Hill (Texas A&M University) | Hisham A. Nasr-El-Din (Texas A&M University)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- November 2008
- Document Type
- Journal Paper
- 484 - 497
- 2008. Society of Petroleum Engineers
- 2.2.3 Fluid Loss Control, 4.1.5 Processing Equipment, 5.8.7 Carbonate Reservoir, 3.2.4 Acidising, 4.2.3 Materials and Corrosion, 2.5.2 Fracturing Materials (Fluids, Proppant), 3.3.1 Production Logging, 4.3.4 Scale, 4.1.2 Separation and Treating, 1.8 Formation Damage
- emulsified acids
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- 729 since 2007
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Acid-in-diesel emulsions have been used extensively in matrix-acidizing and acid-fracturing treatments. This acid has several advantages, including lower corrosion rate, minimum number of additives, and deep acid penetration. For stimulation purposes, the most important properties of emulsified acid are reactivity, stability, and viscosity. The size distribution of the droplets of the emulsion affects these properties.
The purpose of this paper is to correlate the droplet size of the dispersed phase (acid) to the viscosity and stability of emulsified acids. Measurements of the droplet size were acquired with laser-diffraction techniques and analyzed by use of an advanced image-processing system. The apparent viscosity was measured with a Brookfield PVS rheometer at various temperatures. The stability of the emulsified acid was monitored by use of an HTHP see-through cell.
Steady shear viscosity was measured for emulsions with droplet sizes ranging in diameter from 1 to 20 µm. The viscosity covered a shear rate range from 10 to 750 s-1 and a temperature range from 25 to 80°C. All measurements were regenerated for emulsifier concentrations of 1, 5, and 10 gpt. It was noted that finer emulsions had higher viscosities. Likewise, similar measurements were performed with varying acid volume fractions.
The most stable emulsion was noted at an acid volume fraction of nearly 0.7. Other volume fractions were stable for a few hours before diesel was expelled as a separate layer above the emulsion. Eventually, the remaining emulsion stabilized at an acid volume fraction of 0.7.
This paper discusses the effects of the acid volume fraction, emulsifier concentration, and droplet size distribution on the rheological properties and stability of emulsified acids.
Perhaps the first introduction of emulsified acid to the oil industry was by a patent filed by de Groote (1933). According to de Groote, the aim of his invention was to remove formation damage from carbonate rocks with "an aqueous acid solution emulsified in a suitable vehicle that effectively protects the metallic parts of the well from injury by the acid in the solution while the solution is being introduced into the well". De Groote used hydrochloric acid (HCl), nitric acid, and a mixture of the two acids to prepare his emulsion. Crude oil and coal tar distillates, such as naphtha and carbon tetrachloride, were used as dispersing fluids. Sulfonic acid was used as the emulsifying agent, but he did mention the possibility of using asphalt. The procedure he described in the patent for preparing the emulsion is similar to today's practices. However, today's emulsifiers are more efficient. He added approximately 2 to 5% of the emulsifying agent to the continuous phase (crude oil, in his case), and then added the acid to the mixture in 33.3 acid/66.7 crude-oil volume ratio.
Interestingly, the objective that inspired the invention of emulsified acid was not to deepen the penetration of the acid, not to decrease the leakoff rate, nor to retard the acid reaction. The inventor objected to the old and previously known chemical treatment because according to him, the raw acid used as the treating agent attacks the metal parts of the well structure and its working parts, which limits the foreseen benefits from the whole treatment. From this point of view, the emulsified acid was invented to address corrosion of well tubulars much more than to be an improved stimulation fluid.
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Al-Anazi, H.A., Nasr-El-Din, H.A. and Mohamed, S.K. 1998. Stimulation of Tight CarbonateReservoirs Using Acid-in-Diesel Emulsions: Field Application. Paper SPE39418 presented at the SPE Formation Damage Control Conference, Lafayette,Louisiana, USA, 18-19 February. doi: 10.2118/39418-MS.
ASTM D 341, Standard Test Method for Viscosity-Temperature Charts forLiquid Petroleum Products. 2001. West Conshohocken, Pennsylvania: ASTMInternational.
Barnes, H.A. 1994. Rheology of Emulsions--AReview. Colloids and Surfaces A: Physicochemical and EngineeringAspects 91 (3 November 1994) 89-95.doi:10.1016/0927-7757(93)02719-U.
Barnes, H.A. 2004. Rheology of emulsions. In Emulsions: StructureStability and Interactions, ed. D.N. Petsev, Chap. 18, 744. Amsterdam:Elsevier B.V.
Bartko, K.M., Conway, M.W., Krawietz, T.E., Marquez, R.B., and Oba, R.G.M.1992. Field and LaboratoryExperience in Closed Fracture Acidizing the Lisburne Field, Prudhoe Bay,Alaska. Paper SPE 24855 presented at the SPE Annual Technical Conference,Washington, DC, 4-7 October. doi: 10.2118/24855-MS.
Bazin, B. and Abdulahad, G. 1999. Experimental Investigation of SomeProperties of Emulsified Acid Systems for Stimulation of CarbonateFormations. Paper SPE 53237 presented at the Middle East Oil Show andConference, Bahrain, 20-23 February. doi: 10.2118/53237-MS.
Bird, R., Steward, W., and Lightfoot, E. 1960. Transport Phenomena.New York: Wiley.
Buijse, M.A. and van Domelen, M.S. 1998. Novel Application of Emulsified Acidsto Matrix Stimulation of Heterogeneous Formations. Paper SPE 39583presented at the SPE Formation Damage Control Conference, Lafayette, Louisiana,USA, 18-19 February. doi: 10.2118/39583-MS.
Chong, J.S., Christiansen, E.B., and Baer, A.D. 1971. Rheology of concentratedsuspensions. J. Applied Polymer Science 15 (8): 2007-2021.doi:10.1002/app.1971.070150818.
Crenshaw, P.L. and Flippen, F.F. 1968. Stimulation of the Deep Ellenburger inthe Delaware Basin. JPT 20 (12): 1361-1370. SPE-2075-PA. doi:10.2118/2075-PA.
Davis, J.J., Mancillas, G., and Melnyk, J.D. 1965. Improved Acid Treatments by Use of theSpearhead Film Technique. Paper SPE 1164 presented at the SPE RockyMountains Regional Meeting, Billings, Montana, USA, 10-11 June. doi:10.2118/1164-MS.
de Groote, M. 1933. Process for Increasing the Output of Oil Wells. U.S.Patent No. 1,922,154.
de Rozieres, J. 1994. MeasuringDiffusion Coefficients in Acid Fracturing Fluids and Their Application toGelled and Emulsified Acids. Paper SPE 28552 presented at the SPE AnnualTechnical Conference and Exhibition, New Orleans, 25-28 September. doi:10.2118/28552-MS.
Dill, W.R. 1961. Reaction Times of Hydrochloric-Acetic Acid Solutions on Limestone. PaperSPE 211 presented at the Southwest Regional Meeting of the American ChemicalSociety, Oklahoma City, Oklahoma, USA, 1-3 December.
Farah, M.A., Oliveira, R.C., Caldas, J.N., and Rajagopal, K. 2005. Viscosity of water-in-oilemulsions: Variation with temperature and water volume fraction. J.Petroleum Science and Engineering 48 (3-4): 169-184.doi:10.1016/j.petrol.2005.06.014.
Fredrickson, A.G. 1964. Principles and Applications of Rheology.Englewood Cliffs, New Jersey: Prentice-Hall.
Guidry, G.S., Ruiz, G.A., and Saxon, A. 1989. SXE/N2 Matrix Acidizing. PaperSPE 17951 presented at the Middle East Oil Show, Bahrain, 11-14 March. doi:10.2118/17951-MS.
Gupta, R.K. and Seshadri, S.G. 1986. Maximum loading levels in filledliquid systems. Journal of Rheology 30 (3): 503-508.doi:10.1122/1.549856.
Kasza, P., Dziadkiewicz, M., and Czupski, M. 2006. From Laboratory Research toSuccessful Practice: A Case Study of Carbonate Formation Emulsified AcidTreatments. Paper SPE 98261 presented at the International Symposium andExhibition on Formation Damage Control, Lafayette, Louisiana, USA, 15-17February. doi: 10.2118/98261-MS.
Knox, J.A. and Lasater, R.M. 1964. A New Concept in Acidizing UtilizingChemical Retardation. Paper SPE 975 presented at the Fall Meeting of theSociety of Petroleum Engineers of AIME, Houston, 11-14 October. doi:10.2118/975-MS.
Knox, J.A., Pollock, R.W., and Beecroft, W.H. 1965. The chemical retardationof acid and how it can be utilized. Journal of Canadian PetroleumTechnology (January-March): 5.
Li, Y., Sullivan, R.B., de Rozieres, J., Gaz, G.L., and Hinkel, J.J. 1993.An Overview of Current AcidFracturing Technology With Recent Implications for Emulsified Acids. PaperSPE 26581 presented at the SPE Annual Technical Conference and Exhibition,Houston, 3-6 October. doi: 10.2118/26581-MS.
Nasr-El-Din, H.A., Al-Anazi, H.A., and Mohamed, S.K. 2000. Stimulation of Water-Disposal WellsUsing Acid-in-Diesel Emulsions: Case Histories. SPEPF 15 (3):176-182. SPE-65069-PA. doi: 10.2118/65069-PA.
Nasr-El-Din, H.A., Solares, J.R., Al-Mutairi, S.H., and Mahoney, M.D. 2001.Field Application of EmulsifiedAcid-Based System To Stimulate Deep Sour Gas Reservoirs in Saudi Arabia.Paper SPE 71693 presented at the SPE Annual Technical Conference andExhibition, New Orleans, 30 September-3 October. doi: 10.2118/71693-MS.
Navarrete, R.C., Miller, M.J., and Gordon, J.E. 1998. Laboratory and Theoretical Studiesfor Optimization of Acid Fracture Stimulation. Paper SPE 39776 presented atthe SPE Permian Basin Oil and Gas Recovery Conference, Midland, Texas, USA,23-26 March. doi: 10.2118/39776-MS.
Nierode, D.E. and Kruk, K.F. 1973. An Evaluation of Acid Fluid LossAdditives, Retarded Acids, and Acidized Fracture Conductivity. Paper SPE4549 presented at the Fall Meeting of the Society of Petroleum Engineers ofAIME, Las Vegas, Nevada, USA, 30 September-3 October. doi: 10.2118/4549-MS.
Pal, R. 1996. Effect ofdroplet size on the rheology of emulsions. AIChE Journal 42(11): 3181-3190. doi:10.1002/aic.690421119.
Pal, R., Yan, Y., and Masliyah, J. 1992. Rheology of emulsions. InEmulsions: Fundamentals and Applications in the Petroleum Industry, ed.L.L. Schramm, Chap. 4, 131-170. Washington, DC: Advances in Chemistry Series,ACS.
Parkinson, C., Matsumoto, S., and Sherman, P. 1970. The influence ofparticle-size distribution on the apparent viscosity of non-Newtonian dispersedsystems. J. Colloid and Interface Science 33 (1): 150-160.doi:10.1016/0021-9797(70)90082-2.
Rodriguez, B.E., Kaler, E.W., and Wolfe, M.S. 1992. Binary mixtures of monodisperselatex dispersions: 2. Viscosity. Langmuir 8 (10): 2382-2389.doi:10.1021/la00046a008.
Ronningsen, H.P. 1995. Correlations for Predicting Viscosityof W/O Emulsions Based on North Sea Crude Oils. Paper SPE 28968 presentedat the SPE International Symposium on Oilfield Chemistry, San Antonio, Texas,USA, 14-17 February. doi: 10.2118/28968-MS.
Roscoe, R. 1952. Theviscosity of suspensions of rigid spheres. British Journal of AppliedPhysics 3: 267-269. doi:10.1088/0508-3443/3/8/306.
Sisko, A.W. 1958. The flowof lubricating greases. Industrial and Engineering Chemistry50 (12): 1789-1792. doi:10.1021/ie50588a042.
Taylor, G.I. 1932. Theviscosity of a fluid containing small drops of another fluid. Proc. R.Soc. A 138 (834): 41-48. doi:10.1098/rspa.1932.0169.
Ward, S.G. and Whitmore, R.L. 1950. Studies of the viscosityand sedimentation of suspensions Part 1.--The viscosity of suspension ofspherical particles. British Journal of Applied Physics 1:286-290. doi:10.1088/0508-3443/1/11/303.
Williams, B.B., Gidley, J.L., and Schechter, R.S. 1979. AcidizingFundamentals. Richardson, Texas: SPE.