Remote Reading Bottom-Hole Pressure Gauges- An Evaluation of Installation Techniques And Practical Applications

Abstract

Abstract Since 1959, 50 field installations of remote reading bottom-hole pressure gauges have been made on the Cedar Creek anticline in Eastern Montana. The installations were made in wells 9,000 ft deep with bottom-hole temperatures as high as 200F, and included both taut wire and bourdon tube bottom-hole pressure transducers. The initial installations had short periods of operational life because of cable and instrument failures. Continued investigation of installation techniques and types of cable have resulted in operational periods in excess of one year with an expected life of two years or more. Eleven types of cables were tested with various types of insulation and protective sheaths, various outside diameters, and solid and stranded conductors. Several methods of splicing were evaluated for mechanical strength and insulating qualities; a new cable clamp had to be designed; dawn-hole and surface conductor pack-offs were revised; and surface handling techniques had to be developed. Several case histories of practical applications are cited, which include bottom-hale pressure build-up surveys, water flood observation well surveillance and performances of producing wells. The installation cost figures included demonstrate that, although the use of remote bottom-hole pressure gauges cannot be justified in every producing well of this depth, installation in most key observation wells can be justified, depending upon the volume and importance of the data required. Practical installations of remote reading bottom-hole pressure gauges can now be made and have resulted in another valuable tool available to the petroleum engineer. Introduction Accurate and current down-hole pressure data are desirable to produce oil and gas wells at their optimum rate and by the most economical means. A permanently installed bottom-hole pressure gauge is an instrument which can provide such data for production personnel and engineers. The installation of remote reading bottom-hole pressure gauges in every producing well would be ideal from the standpoint of determining producing and static pressures and for detecting subtle equipment malfunctions. However, limited life expectancy and the existence of other indirect methods for determining bottom-hole pressure data have previously limited these installations to specialized cases. The development of the German-produced bottom-hole pressure transmitting system and its widespread use in the Schoonebeek and other fields in Europe prompted the investigation of practical applications in various Shell areas in the United States in 1958. Initial installations in the Pacific Coast, Texas and Rocky Mountain areas resulted in varying degrees of success. Fairly successful installations were made in relatively shallow wells, but the results were disappointing in wells ranging in depth from 6,000 to 9,000 ft. Short operational life and consequent expense were experienced in these wells. In view of the potential application of a direct reading and permanently installed pressure gauge, the development of practical installation techniques was classified as a General Development and Evaluation Project by Shell Oil and a sum of money was granted to the Rocky Mountain area for investigation and development of installation procedures and equipment evaluation. From these investigations, installation techniques have been refined and operating expenses have been reduced, permitting greater utilization and justification for these instruments. The remote reading bottom-hole pressure gauge has become an operational and a practical tool for wells producing highly aromatic hydrocarbons at depths to 9,000 ft, temperatures to 220F (104C) and pressures to 3,500 psi. Presently installed instruments have operated for an average duration of one year or more, and two year runs have been quite common. Installations in wells having less severe conditions should operate for significantly longer periods. This paper presents the experience obtained to date with these gauges and includes recommended installation and operating practices and materials. Theory of Operation of Existing Instruments To date two operational gauges are available for measuring bottomhole pressures on a remote reading basis. They are the German-produced taut wire gauge and the United States- produced bourdon tube-type gauge. The taut wire gauge was developed in 1948 and tested in German oil fields during 1950. JPT P. 1303^