FIELD EXPERIENCE OF DOWNHOLE EQUIPMENT OPERATION IN HYDROGEN SULFIDE-CONTAINING ENVIRONMENTS

Abstract

The article describes the results of operation of downhole equipment in hydrogen sulfide-containing media in relation to local and corrosion-mechanical failures. Useful life (without anti-corrosion protection) for most common manganese steel tubing before the appearance of through fracture was shown. The minimum concentrations of H2S and CO2 in the water phase for wellhead sample are shown when determining the degree of corrosivity of well media and types of corrosion depending on their concentration, in relation to carbon and low-alloy steels. The corrosion-mechanical destructions the downhole equipment were visualized according to GOST 53679. The necessity of taking into account the tendency of stainless steel grade 40Х13 (foreign analogue in the USA is AISI 420) of intersection splined couplings and shafts of an electric centrifugal pump unit made of steel grade 05Х16Н4Д2Б (foreign analogue is not defined) to hydrogen embrittlement as a result of exposure to acidic compositions (12–15 % HCl), used in technological operations, is shown. Practical solutions are proposed for tubing resistant to local and corrosion-mechanical failures (by steel grades and strength groups) based on the proposals of a domestic manufacturer. Two main factors are shown that reduce the service life of tubing and couplings to them to one year. Four polymorphic forms of iron sulfide (the main products of hydrogen sulfide (H2S-) and mixed (CO2 + H2S) corrosion), the conditions for their formation and the maximum rate of local corrosion, up to a through ulcer, under sulfide deposits, were identified. The statistics of tubing by steel grades and the percentage of their use in the fields operated by the Company are shown.