Development of a High Pressure, High Temperature Retrievable Production Packer

Abstract

The trend to expand production into high pressure/high temperature (HP/HT) fields in the North Sea and other producing areas has created a demand for new equipment that is designed to reliably function in the extreme environmental conditions that are inherent to these fields. This paper will describe a joint project in which a major North Sea operator and an engineering/manufacturing company developed a retrievable-type production packer for HP/HT service. Included in the discussion will be the critical design issues that were addressed, the unique methodology that was used to resolve these issues, and the resulting packer design. Also covered will be the results concluded from the prototype testing that confirmed the functionality of the design in accordance with the operator's specifications. Introduction The production packer is a critical item in any completion. Although the surface-controlled subsurface safety valve (SCSSV) may be relied upon as a downhole safety barrier to close off well flow should a catastrophic situation occur at the surface, the packer must remain firmly anchored in the casing and must maintain sealing capability between the production tubing and casing1 even after the SCSSV has closed. While there have been many recommended practices, procedures and standards generated to define how the SCSSV should be designed, tested and operated, no standards have been established for production packers. As a result of the recent economic pressures in the oilfield, operating companies have felt that consideration should be directed toward developments that offer increased production. Often, however, these developments are in deeper, more corrosive environments with greater differential pressures and higher temperatures than were encountered in traditional environments. As is usually the case when any scope of application is enlarged, newer equipment that can maintain integrity in a wider range of conditions must be sought. When considering the high pressure/high temperature environment, in certain instances such as in the case of the retrievable packer, equipment has not been available that could withstand the rigorous conditions of the HP/HT environment. The equipment typically considered to be classed as HP/HT must have a rated working pressure of greater than 10,000 psi and a rated working temperature that is greater than 350 F. Until now, all production packers for HP/HT applications have been of the permanent type because HP/HT retrievable designs simply did not exist. Permanent HP/HT packers have been used successfully without catastrophic failures for more than ten years in severe conditions. However, because a retrievable packer can be removed during a workover or prior to well clean-up operations without milling, many consider it to be a more desirable option. The following problem areas exist in milling when considering development in an HP/HT environment:–Wells are up to 18,000 feet deep, highly deviated, or horizontal with complex S-profiles, complicating retrieving operations.–Casing is corrosion resistant alloy (CRA), and as such, is considered an asset too valuable to expose to potential milling damage.–The production tubing and packer components will also be of CRA material; thus, milling is difficult.–Milling difficulties increase costs. In the development of HP/HT equipment for these extreme environmental applications, the completion equipment must be thoroughly tested to verify the design calculations. Because of the wide scope of varied conditions encountered, the related completion equipment is typically nonstandard, usually having been developed for a particular field or operator. P. 513