New Correlations of Acid-Fracture Conductivity at Low Closure Stress Based on the Spatial Distributions of Formation Properties
- Jianye Mou (China University of Petroleum) | Ding Zhu (Texas A&M University) | Alfred D. Hill (Texas A&M University)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- May 2011
- Document Type
- Journal Paper
- 195 - 202
- 2011. Society of Petroleum Engineers
- 5.1.5 Geologic Modeling, 3.2.4 Acidising, 4.3.4 Scale
- 8 in the last 30 days
- 734 since 2007
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Because of irregular fracture surfaces caused by heterogeneities such as variations in local mineralogy and variations in leakoff behavior, we use a correlation to calculate fracture conductivity in acid fracturing. An acid-fracture-conductivity correlation consists of two parts: conductivity at zero closure stress and the rate of conductivity change with closure stress. Existing correlations do not consider the effect of variations in formation properties and were developed on the basis of laboratory experiments that use core samples with dimensions of only a few inches. On the other hand, acid-fracture simulators have grid sizes of several feet to tens of feet. Therefore, correlations should be scaled up properly when used in a fracture simulator. This paper presents new correlations to obtain the conductivity at zero closure stress. This conductivity can then be incorporated in acid-fracture-conductivity models that consider the effect of closure stress.
In this study, an extensive numerical study was performed using an intermediate-scale acid-fracture model with total dimensions comparable to a gridblock size in an acid-fracturing simulator and grid sizes comparable to core-sample sizes used in laboratory acid-fracture-conductivity tests. In this model, the distributions of permeability and mineralogy along the fracture faces are geostatistically generated. The model generates fracture-surface-etching profiles as a function of acid contact time, from which we can obtain fracture-width distributions when the fracture surfaces have come in contact at low closure stress. We then calculate the fracture conductivity by solving for the flow rate through this irregular domain for a fixed dp across the domain. By analyzing the relationship between the fracture conductivity created and statistical properties of the permeability and mineralogy distributions, we developed new acid-fracture-conductivity correlations for low closure stress. These correlations can be used directly to better predict the primary coefficient in the widely used Nierode-Kruk (Nierode and Kruk 1973) correlation of acid-fracture conductivity. This work allows the Nierode-Kruk (N-K) correlation to be scaled up to the dimensions appropriate for use in an acid-fracturing simulator.
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Beg, M.S., Kunak, A., Oguz, G., Ming, Z.D., and Hill, A.D. 1996. ASystematic Experimental Study of Acid Fracture Conductivity. Paper SPE 31098presented at the SPE Formation Damage Control Symposium, Lafayette, Louisiana,USA, 14-15 February. doi:10.2118/31098-MS.
Blatt, H., Middleton, G., and Murray, R. 1980. Origin of SedimentaryRocks, second edition. Englewood Cliffs, New Jersey: Prentice Hall.
Coulter, A.W., Alderman, E.N., Cloud, J.E., and Crowe, C.W. 1974.Mathematical Model Simulates Actual Well Conditions in Fracture AcidizingTreatment Design. Paper SPE 5004 presented at the Fall Meeting of the Societyof Petroleum Engineers of AIME, Houston, 6-9 October. doi: 10.2118/5004-MS.
Economides, M.J. and Nolte, K.G. 2000. Reservoir Stimulation, thirdedition. Chichester, UK: John Wiley & Sons.
Gong, M. 1997. Mechanical and Hydraulic Behavior of AcidFractures--Experimental Studies and Mathematical Modeling. PhD dissertation,University of Texas at Austin, Austin, Texas.
Mou, J., Zhu, D., and Hill, A.D. 2010a. A New Acid Fracture ConductivityModel Based on the Spatial Distributions of Formation Properties. Paper SPE127935 presented at the SPE International Symposium and Exhibition on FormationDamage Control, Lafayette, Louisiana, USA, 10-12 February. doi:10.2118/127935-MS.
Mou, J., Zhu, D., and Hill, A.D. 2010b. Acid-Etched Channels inHeterogeneous Carbonates--a Newly Discovered Mechanism for CreatingAcid-Fracture Conductivity. SPE J. 15 (2): 404-416.SPE-119619-PA. doi:10.2118/119619-PA.
Newman, M.S. and Rahman, M.M. 2009. A New Efficiency Criterion for AcidFracturing in Carbonate Reservoirs. Paper SPE 122630 presented at the AsiaPacific Oil and Gas Conference & Exhibition, Jakarta, 4-6 August. doi: 10.2118/22393-MS.
Nierode, C.E., Williams, B.B, and Bombardieri, C.C. 1972. Prediction ofStimulation from Acid Fracture Treatments. J Can Pet Technol 11 (4): 1-11. JCPT Paper No. 72-04-04. doi: 10.2118/72-04-04.
Nierode, D.E. and Kruk, K.F. 1973. An Evaluation of Acid Fluid LossAdditives, Retarded Acids, and Acidized Fracture Conductivity. Paper SPE 4549presented at the Fall Meeting of the Society of Petroleum Engineers of AIME,Las Vegas, Nevada, USA, 30 September-3 October. doi: 10.2118/4549-MS.
Roberts, L.D. and Guin, J.A. 1974. The Effect of Surface Kinetics inFracture Acidizing. SPE J. 14 (4): 385-395; Trans.,AIME, 257. SPE-4349-PA. doi:10.2118/4349-PA.
Van Domelen, M.S. 1992. Optimizing Fracture Acidizing Treatment Design byIntegrating Core Testing, Field Testing, and Computer Simulation. Paper SPE22393 presented at the International Meeting on Petroleum Engineering, Beijing,24-27 March. doi:10.2118/22393-MS.
van Domselaar, H.R., Schols, R.S., and Visser, W. 1973. An Analysis of theAcidizing Process in Acid Fracturing. SPE J. 13 (4):239-250; Trans, AIME, 255. SPE-3748-PA. doi: 10.2118/3748-PA.
Walsh, J.B. 1981. Effect of pore pressure and confining pressure on fracturepermeability. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 18 (5): 429-435. doi:10.1016/0148-9062(81)90006-1.
Williams, B.B. and Nierode, D.E. 1972. Design of Acid Fracturing Treatments.J Pet Technol 24 (7): 849-859; Trans., AIME,253. SPE-3720-PA. doi:10.2118/3720-PA.
Williams, B.B., Gidley, J.L., and Schechter, R.S. 1979. AcidizingFundamentals. Richardson, Texas: SPE.
Witherspoon, P.A., Wang, J.S.Y., Iwai, K., and Gale, J.E. 1980. Validity ofCubic Law for Fluid Flow in a Deformable Rock Fracture. Water Resour.Res. 16 (6): 1016-1024. doi:10.1029/WR016i006p01016.