New Insights into Propagation of Emulsified Acids in Vuggy Dolomitic Rocks
- Ahmed S. Zakaria (Texas A&M University) | Mohammed Sayed (Texas A&M University) | Hisham A. Nasr-El-Din (Texas A&M University)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- February 2014
- Document Type
- Journal Paper
- 150 - 160
- 2013. Society of Petroleum Engineers
- 5.6.5 Tracers, 4.1.2 Separation and Treating, 4.3.4 Scale, 3.2.4 Acidising
- 2 in the last 30 days
- 450 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 10.00|
|SPE Non-Member Price:||USD 30.00|
Carbonate formations are very complex in their pore structure and exhibit a wide variety of pore classes, such as interparticle porosity, moldic porosity, vuggy porosity, intercrystalline porosity, and microporosity. Understanding the role of pore class in the performance of emulsified-acid treatments and characterizing the physics of the flow in the acid propagation are the objectives of our study.
The study was performed by use of vuggy-dolomite cores that represent mainly the vuggy-porosity-dominated structure, whereas the homogenous cores used represent the intercrystalline pore structure. Coreflood experiments were conducted on 6 x 1.5-in. cores by use of emulsified acid formulated at 1 vol% emulsifier and 0.7 acid volume fraction. The objective of this set of experiments is to determine the acid pore volume (PV) to breakthrough for each carbonate pore class at different injection flow rates.
In this paper, we examine whether the heterogeneities observable at the thin-section scale have a significant influence on the results of the emulsified-acid coreflood experiments. The heterogeneities were characterized using thin-section observations, tracer experiments, scanning electronmicroscopy (SEM), and resistivity measurements. Thin-section observations provide means to study the size of vugs and their distribution and connectivity, and to explain the contribution of the pore class in the acid propagation. Also, the rotating-disk experiments of emulsified acid with dolomite were related to our coreflood experimental results.
The acid PV to breakthrough for vuggy-porosity-dominated rocks, ranging from0.1 to 0.3, was observed to be low when compared with homogenous carbonates (intercrystalline pore structure) with PVbt ranging from 2.5to 3.5. Also, the wormhole dissolution pattern was found to be significantly different in vuggy rocks than that in homogenous ones. Thin-section observations, tracer results, and the coreflood experiments indicate that the vugs are distributed in a manner that creates a preferential flow path, which can cause a rapid acid breakthrough and effective wormholing rather than those with a uniform pore structure. The rotating-disk results also showed that the reaction kinetics played a role in determining the wormhole pattern.
|File Size||1 MB||Number of Pages||11|
Arbogast, T., Brunson, D.S., Bryant, S.L. et al. 2004. A PreliminaryComputational Investigation of a Macro Model for Vuggy Porous Media. InComputational Methods in Water Resources XV, ed. C.T. Miller et al. NewYork: Elsevier.
Batycky, J.P., Maini, B.B., and Fisher, D.B. 1982. Simulation of MiscibleDisplacement in Full Diameter Carbonate Cores. SPE J. 22(5): 647-657. http://dx.doi.org/10.2118/9233-PA.
Buijse, M.A. and Van Domelen, M.S. 2000. Novel Application of EmulsifiedAcids to Matrix Stimulation of Heterogeneous Formations. SPE Prod &Fac 15 (3): 208-213. http://dx.doi.org/10.2118/65355-PA.
Coats, K.H. and Smith, B.D. 1964. Dead-End Pore Volume and Dispersion inPorous Media. SPE J. 4 (1): 73-84. http://dx.doi.org/10.2118/647-PA.
Daccord, G. and Lenormand, R. 1987. Fractal Patterns From ChemicalDissolution. Nature 325: 41-43.
Garrocuh, A.A. and Gharbi, R.B. 2006. A Novel Model for Viscoelastic FluidFlow in Porous Media. Paper SPE 102015 presented at the SPE Annual TechnicalConference and Exhibition, San Antonio, Texas, 24-27 September. http://dx.doi.org/10.2118/102015-MS.
Hidajat, I., Mohanty, K.K., Flaum, M. et al. 2004. Study of Vuggy CarbonatesUsing NMR and X-Ray CT Scanning. SPE Res Eval & Eng 7(5): 365-377. http://dx.doi.org/10.2118/88995-PA.
Hoeffner, M.L. and Fogler, H.S. 1988. Pore Evolution and Channel FormationDuring Flow and Reaction in Porous Media. AICHE J. 34 (1):45-54. http://dx.doi.org/10.1002/aic.690340107.
Izgec, O., Zhu, D., and Hill, A.D. 2010. Numerical and ExperimentalInvestigation of Acid Wormholing During Acidization of Vuggy CarbonateRocks. J. Petrol. Sci. Eng. 74 (2): 51-66. http://dx.doi.org/10.1016/j.petrol.2010.08.006.
Lucia, F.J. 1983. Petrophysical Parameters Estimated From VisualDescriptions of Carbonate Rocks: A Field Classification of Carbonate PoreSpace. J. Pet Tech 35 (3): 626-637. http://dx.doi.org/10.2118/10073-PA.
Lynn, J.D. and Nasr-El-Din, H.A. 2001. A Core Based Comparison of theReaction Characteristics of Emulsified and In-situ Gelled Acids in LowPermeability, High Temperature, Gas Bearing Carbonates. Paper SPE 65386presented at the SPE International Symposium on Oilfield Chemistry, Houston,Texas, 13-16 February. http://dx.doi.org/10.2118/65386-MS.
Moctezuma-Berthier, A. and Fleury, M. 2000. Permeability Mapping on VuggyCore Samples Using Tracer Experiments and Streamline Simulations. Paper SPE58992 presented at the SPE Annual Technical Conference, Villahermosa, Mexico,1-3 February. http://dx.doi.org/10.2118/58992-MS.
Myers, M.T. 1991. Pore Combination Modeling: A Technique for Modeling thePermeability and Resistivity Properties of Complex Pore Systems. Paper SPE22662 presented at the SPE Annual Technical Conference and Exhibition, Dallas,Texas, 6-9 October. http://dx.doi.org/10.2118/22662-MS.
Sayed, M.A. and Nasr El-Din, H.A. 2012. Reaction Rate of Emulsified Acidsand Dolomite. Paper SPE 151815 presented at the SPE International Symposium onFormation Damage, Lafayette, Louisiana, 15-17 February. http://dx.doi.org/10.2118/151815-MS.
Xu, B., Kamath, J., Lee, S.H. et al. 1998. Use of Pore Network Models toInterpret Laboratory Experiments on Vugular Rocks. J. Petrol. Sci. Eng. 4 (3): 179-186.
Zakaria, A.S., Hafez, M.M., Ochi, J. et al. 2011. Application of GeneticAlgorithms to the Optimization of Pressure Transient Analysis of WaterInjectors Using Type Curves. Paper SPE 143386 presented at the SPE EuropeanFormation Damage Conference, Noordwijk, The Netherlands, 7-10 June. http://dx.doi.org/10.2118/143386-MS.
Zhang, L., Bryant, S.L., Jennings, J.W. et al. 2004. Multi-scale Flow andTransport in Highly Heterogeneous Carbonates. Paper SPE 90336 presented at theSPE Annual Technical Conference, Houston, Texas, 26-29 September. http://dx.doi.org/10.2118/90336-MS.
Zhang, L., Nair, N., Jennings, J.W. et al. 2005. Models and Methods forDetermining Transport Properties of Touching-Vug Carbonates. Paper SPE 96027presented at the SPE Annual Technical Conference, Dallas, Texas, 9-12 October.http://dx.doi.org/10.2118/96027-MS.
Ziauddin, M. and Bize, E. 2007. The Effect of Pore-Scale Heterogeneities onCarbonate Stimulation Treatments. Paper SPE 104627 presented at the SPE MiddleEast Oil & Gas Show and Conference, Bahrain, Kingdom of Bahrain, 11-14March. http://dx.doi.org/10.2118/104627-MS.