Logging Operations in Sour Gas Wells

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract The presence of hydrogen sulfide gas in a well has, in the past, imposed severe limitations on wireline logging services. Operations were sometimes attempted in wells containing low concentrations of H2S (less than two percent by volume), but these attempts often led to trouble. With continued discoveries of wells having appreciable concentrations of hydrogen sulfide, it became evident that new operating techniques must be developed to overcome the associated problems. These problems fall into three main areas: danger to personnel, failure of the logging cable, and failure of the pressure-control equipment. People must be educated in the safety procedures for working around hydrogen sulfide. procedures for working around hydrogen sulfide. The operation of monitoring and safety equipment must be understood. Standard logging cables, whose armor is made of high-carbon steel, can fail after quite brief exposure, even to low concentrations of hydrogen sulfide. However, it has been found that, in these concentrations, the standard cable can often be used if proper precautions are taken. For wells having hydrogen-sulfide concentrations greater than two percent, it has been necessary to develop a new cable-material technology. A hydrogen-sulfide-resistant monocable design has been developed, and such cables are available upon request. Standard blowout preventers and lubricators for use with logging cables are also subject to early failure in a hydrogen sulfide environment. In low concentrations of the gas and low pressures, standard blowout preventers and pressures, standard blowout preventers and lubricators can be used if proper precautionary steps are taken. However, for high H2S concentrations, it was again necessary to develop new technology for the fabrication of H2S-resistant blowout-preventer and lubricator systems. Logging and other wireline operations can now be performed safely, even in wells having heavy concentrations of hydrogen sulfide. Careful planning on the part of the lease operator and logging company are needed for safe and systematic operations.