| Autor: |
Douglas Wilson, W. W. Fleckenstein, A. W. Eustes |
| Rok vydání: |
2018 |
| Předmět: |
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| Zdroj: |
Day 3 Tue, April 24, 2018. |
| DOI: |
10.2118/190031-ms |
| Popis: |
The Cohesive Zone Experiment (CZE), captured the effect of time, temperature, and pressure on the behavior of adhesive bonding between oilwell cements and casing. The CZE captured the behavior of bond failure as a function of displacement, showing the degree of compliance in the bond. Interpretation of the compliance behavior suggests an appropriate material property model of bond failure, suitable for mechanical FE analysis. The two failure models considered are the critical fracture energy (maximum area-specific energy) and the critical shear strength (maximum area-specific force). Two Class G cement compositions were tested: a 15.8 ppg neat cement (Class G neat) and a 14.2 ppg gelled cement (Class G with 7% bentonite). The testing was done at temperature and pressure regimes designed to conform to environments typical to onshore surface casing shoe conditions, both shallow and deep. The neat cement is tested at conditions typically assumed at shallower surface casing setting depth (~600’ TVD): 92°F and 262 psi. The gelled cement was tested at conditions typically assumed at deeper setting depths (~1800’ TVD): 101°F and 786 psi. Each composition was tested at two hydration times: an early time of 4 to 6 hours and a late time of 22 to 24 hours. The CZE results suggest cement at early hydration time (~5 hours) has a compliant bond. The adhesive bond of such an immature cement does not fail acutely when stressed to failure; the bond fails "intermittently" and retains some strength through displacement past the initial fracture. However, cements at late hydration time (~23 hours) do not show this compliance. The bond at late times fails acutely; displacement sufficient to initiate fracture is sufficient to fail the bond. The compliant bond behavior observed at early hydration times should be modeled with a specific energy value: the critical fracture energy. The non-compliant bond observed at late hydration times should be modeled with a specific force value: the critical shear strength. Values for each property are reported from mean values observed in the CZE. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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