A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
CO2-induced changes in oilwell cements under downhole conditions: First experimental results
One of the major technological issues for CO2 injection (for EOR, CCS, etc.) is the long-term behavior of cement-based materials used to ensure the overall sealing performance of the storage wells. When water is present, the CO2 after injection can react chemically with the cement (i.e. carbonation). How do the CO2-enriched formation fluids changes the cement's chemistry and properties? Could the sealing efficiency of the wells be affected by these changes? The objectives of this experimental program are to assess the kinetics and phenomenology of the changes that occur in different class-G Portland cements exposed to CO2-enriched aqueous fluids at 8 MPa and two different temperatures. The experimental program presented in this paper consists of: a first carbonation test (Test 1) using neat G cement, at a temperature of 90 deg C (194 F) and a pressure (supercritical CO2 above water) of 8 MPa (1160 psi); a second carbonation test (Test 2) using G cement with silica flour (to prevent strength retrogression), at a temperature of 140 deg C (284 F) and at the same CO2 pressure of 8 Mpa. Finally, coupled chemo-mechanical tests (dynamic tests) are underway on similar class-G cement and similar CO2-rich water. All the samples were prepared according to ISO/API specifications. The experimental set-up simulates downhole 'static' conditions: the samples were immersed in water in a cell thermally regulated and pressurized by CO2. Cement samples were exposed to CO2-saturated water for various lengths of time (from one week to 3 months) and were characterized using advanced methods for chemical and mineralogical analysis (X-ray tomography, SEM, XRD, TGA-TDA...) and mechanical testing. The main preliminary results show a reactive front (characterized by carbonation) progressing from the fluid-sample interface towards the sample centre. The carbonation front moves faster during Test 2 (at higher temperature) than during Test 1 (at lower temperature). SEM images of Test 2 also show a thin layer of dissolved carbonate at the sample's surface. The carbonated cement areas exhibit increased density and greater compressive strength. The results of coupled chemo-mechanical tests with injection of CO2-enriched water in samples under deviatoric stress show that the CO2 flow rate in the cement rapidly decreases, finally resulting in carbonation clogging of the cement sample. These results seem consistent with reported field observations.
CO2-induced changes in oilwell cements under downhole conditions: First experimental results
One of the major technological issues for CO2 injection (for EOR, CCS, etc.) is the long-term behavior of cement-based materials used to ensure the overall sealing performance of the storage wells. When water is present, the CO2 after injection can react chemically with the cement (i.e. carbonation). How do the CO2-enriched formation fluids changes the cement's chemistry and properties? Could the sealing efficiency of the wells be affected by these changes? The objectives of this experimental program are to assess the kinetics and phenomenology of the changes that occur in different class-G Portland cements exposed to CO2-enriched aqueous fluids at 8 MPa and two different temperatures. The experimental program presented in this paper consists of: a first carbonation test (Test 1) using neat G cement, at a temperature of 90 deg C (194 F) and a pressure (supercritical CO2 above water) of 8 MPa (1160 psi); a second carbonation test (Test 2) using G cement with silica flour (to prevent strength retrogression), at a temperature of 140 deg C (284 F) and at the same CO2 pressure of 8 Mpa. Finally, coupled chemo-mechanical tests (dynamic tests) are underway on similar class-G cement and similar CO2-rich water. All the samples were prepared according to ISO/API specifications. The experimental set-up simulates downhole 'static' conditions: the samples were immersed in water in a cell thermally regulated and pressurized by CO2. Cement samples were exposed to CO2-saturated water for various lengths of time (from one week to 3 months) and were characterized using advanced methods for chemical and mineralogical analysis (X-ray tomography, SEM, XRD, TGA-TDA...) and mechanical testing. The main preliminary results show a reactive front (characterized by carbonation) progressing from the fluid-sample interface towards the sample centre. The carbonation front moves faster during Test 2 (at higher temperature) than during Test 1 (at lower temperature). SEM images of Test 2 also show a thin layer of dissolved carbonate at the sample's surface. The carbonated cement areas exhibit increased density and greater compressive strength. The results of coupled chemo-mechanical tests with injection of CO2-enriched water in samples under deviatoric stress show that the CO2 flow rate in the cement rapidly decreases, finally resulting in carbonation clogging of the cement sample. These results seem consistent with reported field observations.
CO2-induced changes in oilwell cements under downhole conditions: First experimental results
CO2-bedingte Veränderungen im Erdölbohrlochzement unter Tiefbohrbedingungen: erste Versuchsergebnisse
Garnier, Andre (author) / Laudet, Jean-Benoit (author) / Neuyille, Nadine (author) / Guen, Yvi le (author) / Fourmaintraux, Dominique (author) / Rafai, Noureddine (author) / Burlion, Nicolas (author) / Schao, Jian-Fu (author)
2010
16 Seiten, 15 Bilder, 1 Tabelle, 16 Quellen
Conference paper
English
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