Search

A model of Wyoming's carbon dioxide pipeline network has been developed and used to analyze its capacity. The inlet to this pipeline is at Exxon Mobil's Shute Creek gas processing plant, and supercritical gas is then sent to Rangeley (Colorado), Rock Springs, Monell, Baroil and Salt Creek (all in Wyoming) fields. Along the way, the supercritical gas is cooled to a liquid. Here it is shown that the pipeline could easily accommodate a rate increase from the current 250 MMSCFD to 325 MMSCFD, utilizing the gas that is currently being vented from the Shute Creek intermediate separator, while maintaining the current inlet temperature and pressure. If new CO2 supplies became available it would be possible to increase the carbon dioxide throughput from 250 MMSCFD to 600 MMSCFD while extending the pipeline to other oilfields such as Beaver Creek and Hartzog Draw. In certain circumstances, this high rate may produce output pressures below the required miscibility pressures and also produce phase changes in the pipeline. However, this could be easily remedied by adding relatively modest horsepower pumps at intermediate pipeline locations. [ABSTRACT FROM AUTHOR]

This paper aims to theoretically investigate and characterize the failure mechanism of hydrated bentonite plugs, when used as a sealing material in wellbores. Using the proposed theoretical models, it was determined that when hydrated bentonite plugs failed due to friction at the walls, created by internal swelling pressure or through internal shear failure, the resulting failure pressure was linear with the plug height (H), coefficient of friction or internal shear strength, and inversely proportional to plug diameter (D). On the other hand, if the friction at the walls was created by plug weight then the failure pressure was a function of H 2 /D. However, in this case, the frictional strength increased parabolically with height, and, at reasonable plug heights, the frictional strength became greater than shear strength, and resulted in failure due to internal shear failure, which also made the failure pressure a function of H/D. This suggests that plug strength is usually a linear function of H/D. Moreover, the coefficient of friction and internal shear strength are dependent on final moisture content of the hydrated plug, the salinity of the hydration water, pressure, temperature and hydration time. The strength of a bentonite plug is inversely proportional the total volume by which it expands during hydration and takes in excess of 185 days to achieve this state. Plug strength decreased in saline water, although even at elevated concentrations sufficient strength remained to produce and adequate seal.From very limited data, shown here, Queensland bentonite, from the 5D zone of Amcol's Gurulmundi mine, appeared to have similar plugging strength as Wyoming bentonite. • Developed novel models to predict the failure pressure of bentonite plugs. • Provided insights into the failure mechanisms of bentonite plugs. • Bentonite plug strength is a linear function of plug height to diameter ratio. • Friction coefficient is dependent on final moisture content of the hydrated plug. • Bentonite plug strength increases with hydration time and decreases in saline water. [ABSTRACT FROM AUTHOR]