Recent trends in gas and condensate production have been toward the development of areas with increasingly higher temperatures and pressures. Temperatures in the range of 300-400°F and pressures of up to 10,000 psig are encountered. It is fully anticipated that new developments will exceed these levels. Indeed, in some locations, operations are currently being carried out under substantially more severe conditions. When these temperature and pressure conditions are combined with production of very high concentrations of acid gases and large volumes of condensate, the result has been catastrophic failure of the equipment in many systems. This failure has been due to severe metal loss, embrittlement, and deposition of corrosion products. Failures have been found even in systems where production of water is practically nil. In systems of this type, sections of tubing have been examined which exhibit heavy internal coatings of corrosion products with extensive metal loss beneath. These deposits contain iron sulfide, magnitite (Fe3O4), and heavy organic materials. This combination forms a thick, partially protective coating which induces localized attack. It is interesting to note that a large number of the failures investigated have occurred in the lower section of the tubing string. This characteristic is contrary to the classic corrosion of gas condensate wells. Historically, the greatest problem in these systems have been found nearer the surface where moisture is condensed due to the cooling produced by pressure drop. Because of the location of the major corrosion problem and the frequent presence of high levels of hydrogen sulfide, field evaluation of the corrosivity of these systems has proven extremely difficult. Down hole corrosion coupons have been used as a field testing technique in some cases. Of course, this procedure is both costly and difficult to accomplish. With all of these problems it has become increasingly apparent that improved laboratory testing methods are required in order that optimum treating programs may be devised for these, as well as future systems.
