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51317--9718-SSC Resistance of a Double Quench and Tempered T-95 Casing in Extremely Sour and High Pressure Environment

In extremely sour reservoirs, H2S and CO2 concentrations have been observed to reach upwards of 45% and 20%, respectively. In addition, bottomhole conditions can experience extremely high pressure in excess of 10,000 psi.

Product Number: 51317--9718-SG
ISBN: 9718 2017 CP
Author: Weiji Huang
Publication Date: 2017
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In the recent development of upstream oil and gas fields we have extremely sour reservoir which contain high concentration of acid gases. The H2S and CO2 concentration can go up to 45% and 20% respectively. In addition the bottomhole pressure is over 10000 psi. To design the wells for safe operation the high SSC resistance of low alloy steel casing is demanded. In this study a double quench and tempered T-95 casing was selected. The casing has average KISSC valued 33 ksi in1/2 tested in NACE Solution A.The test matrix of this study was carefully designed to evaluate the penalties of temperature pH and pressure on KISSC of the T-95 casing. Also the formation of hydrate under high pressure tests was avoided by employing the solubility model developed in-house to select right conditions.The test results showed that the temperature penalty on KISSC was substantial in extreme sour environment. The pH effect is also significant. It is interesting to find that the KISSC is in a logarithm relationship with dissolved H2S concentration. In other words the KISSC initially drops very fast with increase of dissolved H2S but then does not change too much regardless very high concentration of dissolved H2S.

 Key words: KISSC, Hydrate, H2S solubility model, Dissolved H2S concentration.

In the recent development of upstream oil and gas fields we have extremely sour reservoir which contain high concentration of acid gases. The H2S and CO2 concentration can go up to 45% and 20% respectively. In addition the bottomhole pressure is over 10000 psi. To design the wells for safe operation the high SSC resistance of low alloy steel casing is demanded. In this study a double quench and tempered T-95 casing was selected. The casing has average KISSC valued 33 ksi in1/2 tested in NACE Solution A.The test matrix of this study was carefully designed to evaluate the penalties of temperature pH and pressure on KISSC of the T-95 casing. Also the formation of hydrate under high pressure tests was avoided by employing the solubility model developed in-house to select right conditions.The test results showed that the temperature penalty on KISSC was substantial in extreme sour environment. The pH effect is also significant. It is interesting to find that the KISSC is in a logarithm relationship with dissolved H2S concentration. In other words the KISSC initially drops very fast with increase of dissolved H2S but then does not change too much regardless very high concentration of dissolved H2S.

 Key words: KISSC, Hydrate, H2S solubility model, Dissolved H2S concentration.

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