Evaluation of Cement Systems for Oil and Gas Well Zonal Isolation in a Full-Scale Annular Geometry
- Linda Boukhelifa (Heriot-Watt U.) | Nevio Moroni (ENI S.P.A.) | Simon James (Schlumberger) | Sylvaine Le Roy-Delage (Schlumberger) | Marc J. Thiercelin (Schlumberger) | Guillaume Lemaire (National Inst - Applied Sciences)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- March 2005
- Document Type
- Journal Paper
- 44 - 53
- 2005. SPE/IADC Drilling Conference
- 5.3.9 Steam Assisted Gravity Drainage, 1.2.3 Rock properties, 1.6.9 Coring, Fishing, 2.7.1 Completion Fluids, 4.1.2 Separation and Treating, 3 Production and Well Operations, 5.2 Reservoir Fluid Dynamics, 1.6 Drilling Operations, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 4.3.4 Scale, 1.14.3 Cement Formulation (Chemistry, Properties), 1.14 Casing and Cementing, 1.11 Drilling Fluids and Materials
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Loss of zonal isolation in a wellbore can be caused by mechanical failure ofthe cement or by development of a microannulus. However, behavior of thesealant is driven by specific boundary conditions such as rock properties.Large-scale laboratory testing of the cement sheath in an annular geometry anda confined situation was performed to simulate various downhole stressconditions and evaluate the behavior of several sealants. Failure modes of thecement sheath were determined as a function of cement mechanical properties,loading parameters, and boundary conditions. Results were used to validate ananalytical model that predicts cement-sheath failure.
Interzonal communication in a wellbore may lead to loss of reserves,contamination of zones, production of unwanted fluids, or safety andenvironmental issues. Remedial solutions exist to repair the problems, but fortechnical or economic reasons, the well may be shut in or abandoned.
To maximize well life, the cement sheath must be chemically and mechanicallydurable. Sealants resistant to aggressive formation fluids should also bedesigned to withstand stresses exerted during production and well operations,such as casing-pressure tests, stimulation treatments, or temperature changesduring production cycles. To achieve this design goal, a better understandingof the mechanical behavior of different sealants under downhole conditions isrequired.1,2
According to Thiercelin et al.,3 changes in downhole conditions can causemechanical damage (e.g., mechanical failure or creation of microannuli) to thecemented annulus, which may lead to loss of zonal isolation. Thiercelin etal.'s paper3 concludes that the complete mechanical system formed by the steelcasing, cemented annulus, and formation should be considered, rather thansealant strength alone.
Increase of pressure and temperature in the wellbore first expands the innersteel casing, which instantly imposes this deformation on the surroundingcement sheath. This applies imposed displacements, rather than imposedstresses, to the cement inner diameter (ID). Over the lifetime of the well, thecement sheath must withstand multiple displacement cycles. Several authors4,5have proposed numerical models to simulate sealant mechanical behavior andpredict initiation of failures according to known mechanical properties of thecomplete system (i.e., steel, cement, and rock).
A large-scale laboratory test for sealants in an annular geometry has beendeveloped. This test simulates changes in well conditions that causecontraction or expansion of the inner casing. It can also evaluate theconfining role of the formation or outer casing. Such an experiment enables theevaluation of sealant mechanical responses under wellbore conditions. Thetensile and compressive stresses generated in the annulus are similar to thosethe sealant must withstand in a real wellbore. Loading simulated in thefull-scale annular sealing test is close to real field conditions.
Several cement systems exhibiting different mechanical behaviors have beentested, and the experimental results have been compared with predictions of anumerical model.
|File Size||2 MB||Number of Pages||10|
1.Thiercelin, M., Baumgarte, C., and Guillot, D.: "A Soil Mechanics Approach To Predict Cement Sheath Behavior," paper SPE 47375 presented at the 1998 SPE/ISRM Rock Mechanics in Petroleum Engineering Conference, Trondheim, Norway, 8-10 July.
2.Ravi, K., Bosma, M., and Hunter, L.: "Optimizing the Cement Sheath Design in HPHT Shearwater Field," paper SPE/IADC 79905 presented at the 2003 SPE/IADC Drilling Conference, Amsterdam, 19-21 February.
3.Thiercelin, M. et al.: "Cement Design Based on Cement Mechanical Response," paper SPE 52890 presented at the 1997 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 5-8 October.
4.Le Roy-Delage, S. et al.: "New Cement Systems for Durable Zonal Isolation," paper SPE/IADC 59132 presented at the 2000 IADC/SPE Drilling Conference, New Orleans, 23-25 February.
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8.Kopp, K. et al.: "Foamed Cement vs. Conventional Cement for Zonal Isolation—Case Histories," paper SPE 62895 presented at the 2000 SPE Annual Technical Conference and Exhibition, Dallas, 1-4 October.
9.Ravi, K., Bosma, M., and Gastebled, O.: "Improve the Economics of Oil and Gas Wells by Reducing the Risk of Cement Failure," paper IADC/SPE 74497 presented at the 2002 IADC/SPE Drilling Conference, Dallas, 26-28 February.