RIASSUNTO
Abstract
Development of a new pressure measuring tool has yielded critical bottom hole pressure data in the fields on the North Slope of Alaska. The new tool permits gathering bottom hole pressure and temperature data that previously was uneconomical to obtain. This paper outlines the development of the new pressure measuring tool, its application and the results obtained from the new data. Also presented are the large cost savings that have been realized through the use of this tool.
Introduction
A new, inexpensive method of gathering pressure data at the bottom of a wellbore with a small sized electronic memory type pressure tool has been developed. The new tool is the size of a standard 1-1/2"" gas lift or circulating valve and can be set in a standard gas lift mandrel (Figs. 1, 2). Conventional wireline operations are used to run and retrieve the pressure tool. Placing the pressure tool in a ""side-pocket"" mandrel causes no flow restriction during stimulation or production operations. Additionally, the tool is not subjected to excessive direct contact with stimulation fluids. Either tubing or annulus/casing pressure can be measured with a simple change of a set screw. Designed to withstand the rough treatment and jarring associated with wireline operations, it has a 97% success rate to date. Although the oil fields on the North Slope of Alaska currently use the tool exclusively, the technology is feasible in any oil or gas field that is capable of using standard 1-1/2"" gas lift or circulation mandrels.
The tool was initially used in the Kuparuk River Field (Fig. 3) to measure bottom hole pressures during fracturing to improve friction pressure correlations for pumping proppant laden slurries. Fracturing plays a large role in the development of the Kuparuk River Field as over half of the field's reserves lie in a formation that requires hydraulic fracturing to obtain economic flow rates. A modified version of the tool with a special carrier has been run on coiled tubing to monitor pressure and temperature during cement squeezes. Additionally, the new bottom hole pressure data gathering capability allowed an evaluation of an improved perforating technique which reduced perforation and near wellbore excess friction in deviated wells. Finally, the tool has found many additional uses beyond Kuparuk fracturing. One application has been measuring bottom hole pressures during production or pressure transient tests in selective completions (Fig. 4). Measurement of friction pressure during acid stimulations as well as during fracturing at the Prudhoe Bay Field has also occurred.
Development of this technology has led to gathering data that would have otherwise been cost prohibitive to obtain. Improved friction correlations resulted from the bottom hole pressure data which was gathered and thus allowed placement of more proppant in the formation during future fracturing operations. Once the friction pressure during fracturing was better understood, the first attempts at performing ""tip screen-out"" treatments occurred.
This paper outlines the development and application of the new pressure tool.
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