Zonal Isolation Modeling and Measurements - Past Myths and Today's Realities
- Simon G. James (Schlumberger) | Linda Boukhelifa (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- March 2008
- Document Type
- Journal Paper
- 68 - 75
- 2008. Society of Petroleum Engineers
- 1.6 Drilling Operations, 1.14.4 Cement and Bond Evaluation, 1.14.3 Cement Formulation (Chemistry, Properties), 4.3.4 Scale, 4.1.5 Processing Equipment, 5.4.6 Thermal Methods, 3 Production and Well Operations, 2.4.3 Sand/Solids Control, 2 Well Completion, 1.14 Casing and Cementing
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- 777 since 2007
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Over the past 10 years, several papers have been published discussing the long-term mechanical durability of the cement sheath. The customary procedure is to use a model to predict potential failure scenarios and to subsequently design a sealant material that will not fail under the expected conditions. The predictive models are either analytical or finite-element models. The analytical models can only be applied to relatively simple situations that require a simplified set of input data. In these cases, the results are consistent with those of finite-element models. More complex situations can be simulated with finite-element models, but the input data requirements are far greater. Typically in the modeling papers, little information is included on how the input data is obtained. Because of this, several papers have been published that have proposed ways to obtain the input data, in particular the mechanical parameters of the set cement. Because typically these papers have addressed only one or two parameters however, the proposed methods are inconsistent. This paper critically reviews the published information and highlights the strengths and weaknesses of the previous approaches. Subsequently, the paper presents new measurement methods and data analysis techniques to determine cement mechanical parameters in sufficient detail to allow them to be implemented in any laboratory with appropriate equipment. The predictions using data from the new measurement methods have been verified at the field level through evaluation of actual wells. Finally, the methods have been used to demonstrate the mechanical durability of flexible cement systems aged at high temperatures for one year; this is the first time that such data have been presented on these systems.
The effect of pressure and temperature changes on the integrity of the cement sheath was demonstrated experimentally many years ago (Goodwin and Crook 1992; Jackson and Murphey 1993). More recently, this behavior has been modeled by use of both analytical (Thiercelin et al. 1997) and finite-element (Bosma et al. 1999) models. Although finite-element models are capable of handling more complex situations, they are usually used with simplifying assumptions in which case they offer no advantages over analytical models. Indeed, Bosma et al. (1999) used the analytical model and results from Thiercelin et al. (1997) as a benchmark for their finite-element model and showed good agreement between the two models. Formation creep, which can potentially induce large strains in the cement sheath, was also discussed by Bosma et al. (1999), but this will not be addressed in this paper.
Both types of models assume a linear-elastic mechanical behavior. Therefore, the response of the cement sheath to strain is determined by the static Young's modulus and Poisson's ratio of the cement through Hooke's law. A correction of dynamic values of Young's modulus and Poisson's ratio is required to be used in Hooke's relationship. The failure point is given by either the tensile strength or the compressive strength of the cement (using the Mohr-Coulomb failure criterion for the latter), depending on the expected failure mechanism. In general, decreasing the Young's modulus or increasing the Poisson's ratio of the cement will decrease the stresses induced in the cement sheath and, for a given situation, will decrease the risk of failure.
In the modeling papers discussed above, there has been little discussion of how to determine the appropriate parameters that describe the cement mechanical behavior. Thiercelin et al. (1997) determined the Young's modulus in flexion and flexural strength (Mr) from three-point bending tests. The authors noted that the loading rate is a key parameter in determining the ultimate strength of the material: the lower the loading rate, the lower the flexural strength measured. They applied a safety factor of 50% to the flexural strength to obtain a tensile strength value more representative of downhole conditions. Because three-point bend tests were performed however, there was no way to determine the Poisson's ratio of the cement, so the value was estimated at 0.2. The model described was a linear thermo-elastic model, so the use of a single value of Young's modulus and Poisson's ratio was appropriate.
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Baumgarte, C., Thiercelin, M., and Klaus, D. 1999. Case Studies of Expanding Cement ToPrevent Microannular Formation. Paper SPE 56535 presented at the SPE AnnualTechnical Conference and Exhibition, Houston, 3-6 October. doi:10.2118/56535-MS
Bosma, M., Ravi, K., van Driel, W., Schreppers, G.J. 1999. Design Approach to Sealant Selectionfor the Life of the Well. Paper SPE 56536 presented at the SPE AnnualTechnical Conference and Exhibition, Houston, 3-6 October. doi:10.2118/56536-MS
Boukhelifa, L. et al. 2005. Evaluation of Cement Systems for Oil-and Gas-Well Zonal Isolation in a Full-Scale Annular Geometry. SPEDC20 (1): 44-53. SPE-87195-PA doi: 10.2118/87195-PA
C 190-85, Tensile Strength of Hydraulic Cement Mortars. 1985. WestConshohocken, Pennsylvania: ASTM.
C 348-86, Standard Test Method for Flexural Strength of Hydraulic CementMortars. 1986. West Conshohocken, Pennsylvania: ASTM.
C 39/C 39M-01, Standard Test Method for Compressive Strength ofCylindrical Concrete Specimens. 2001. West Conshohocken, Pennsylvania:ASTM.
C 469-02, Standard Test Method for Static Modulus of Elasticity andPoisson's Ratio of Concrete in Compression. 2002. West Conshohocken,Pennsylvania: ASTM.
di Lullo, G. and Rae, P. 2000. Cements for Long Term Isolation—Design Optimization by ComputerModelling and Prediction. Paper SPE 62745 presented at the IADC/SPE AsiaPacific Drilling Technology Conference, Kuala Lumpur, 11-13 September. doi:10.2118/62745-MS
Dillenbeck, R.L., GoBoncan, V. and Rogers, M.J. 2005. Testing Static Tensile Behavior UnderDownhole Conditions. Paper SPE 97967 presented at the SPE Eastern RegionalMeeting, Morgantown, West Virginia, 14-16 September. doi: 10.2118/97967-MS
Goodwin, K.J. and Crook, R.J. 1992. Cement Sheath Strength Failure.SPEDE 7 (4): 291-296. SPE-20453-PA doi: 10.2118/20453-PA
Haimson, B.C. and Tharp, T.M. 1974. Stresses Around Boreholes in BilinearElastic Rock. SPEJ 14 (2): 145-151. SPE-4241-PA doi:10.2118/4241-PA
Handin, J. 1965. Strength of OilWell Cements at Downhole Pressure-Temperature, Conditions. SPEJ5 (4): 341-347; Trans., SPE 234. SPE-1300-PA doi:10.2118/1300-PA
Heinhold, T., Dillenbeck, R.L., and Rogers, M.J. 2002. The Effect of Key Cement Additives onthe Mechanical Properties of Normal Density Oil and Gas Well CementSystems. Paper SPE 77867 presented at the SPE Asia Pacific Oil and GasConference and Exhibition, Melbourne, Australia, 8-10 October. doi:10.2118/77867-MS
Heinhold, T., Dillenbeck, R.L., Bray, W.S., and Rogers, M.J. 2003. Analysis of Tensile StrengthMethodologies for Evaluating Oil and Gas Well Cement Systems. Paper SPE84565 presented at the SPE Annual Technical Conference and Exhibition, Denver,5-8 October. doi: 10.2118/84565-MS
ISRM Commission on Standardization of Laboratory and Field Tests. 1978. Suggested Methods forDetermining Tensile Strength of Rock. Int. J. Rock Mech. Min. Sci. &Geomech. Abstr. 15 (3): 99-103. doi:10.1016/0148-9062(78)90003-7.
Jackson, P.B. and Murphey, C.E. 1993. Effect of Casing Pressure on Gas FlowThrough a Sheath of Set Cement. Paper SPE 25698 presented at the SPE/IADCDrilling Conference, Amsterdam, 23-25 February. doi: 10.2118/25698-MS
Le Roy-Delage, S., Baumgarte, C., Thiercelin, M., and Vidick, B. 2000. New Cement Systems for Durable ZonalIsolation. Paper SPE 59132 presented at the IADC/SPE Drilling Conference,New Orleans, 23-25 February. doi: 10.2118/59132-MS
Moroni, N., Vallorani, F., Johnson, C., Perez, D., and Bilic, J. 2005. Achieving Long-Term Isolation forThin Gas Zones in the Adriatic Sea Region. Paper SPE 92193 presented at theSPE Western Regional Meeting, Irvine, California, 30 March-1 April. doi:10.2118/92193-MS
Mueller, D.T., et al. 2004. CharacterizingCasing-Cement-Formation Interactions Under Stress Conditions: Impact onLong-Term Zonal Isolation. Paper SPE 90450 presented at the SPE AnnualTechnical Conference and Exhibition, Houston, 26-29 September. doi:10.2118/90450-MS
Nelson, E.B. and Guillot, D. ed. 2006. Well Cementing. Sugar Land,Texas: Schlumberger.
Pedersen, R.O., et al. 2006. Cementing of an Offshore DisposalWell Using a Novel Sealant That Withstands Pressure and Temperature Cycles.Paper SPE 98891 presented at the IADC/SPE Drilling Conference, Miami, Florida,21-23 February. doi: 10.2118/98891-MS
Ravi, K., McMechan, D.E., Reddy, B.R., and Crook, R. 2007. A Comparative Study of MechanicalProperties of Density-Reduced Cement Compositions. SPEDC 22(2): 119-126. SPE-90068-PA doi: 10.2118/90068-PA
Reddy, B.R. et al. 2007. CementMechanical-Property Measurement Under Wellbore Conditions. SPEDC22 (1): 33-38. SPE-95921-PA doi: 10.2118/95921-PA
Thiercelin, M., Baumgarte, C., and Guillot, D. 1998. A Soil Mechanics Approach To PredictCement Sheath Behavior. Paper SPE 47375 presented at the SPE/ISRM RockMechanics in Petroleum Engineering, Trondheim, Norway, 8-10 July. doi:10.2118/47375-MS
Thiercelin, M.J., Dargaud, B., Baret, J.F., and Rodriguez, W.J. 1997. Cement Design Based on CementMechanical Response. Paper SPE 38598 presented at the SPE Annual TechnicalConference and Exhibition, San Antonio, Texas, 5-8 October. doi:10.2118/38598-MS