Rehabilitation of the CP system of an ExxonMobil sour gas-gathering system

摘要

EXXONMOBIL's production district in South Oldenburg in Northern Germany, with its local office at the City of Schneiderkrug, accounts for approximately 35 percent of Germany's annual domestic natural gas production of 20bn cum. The district comprises about 35 gas reservoirs with about 200 operations sites, which are connected via more than 40 mixing, gathering, and transfer stations, and approximately 1000 km of pipeline. There is a total of 110 production wells, of which 67 produce H_2S-containing natural gas; of the typical annual production of 7.4bn cum from this production district, 80 percent contains H_2S, and 20 percent is free of hydrogen sulphide (also called "sweet"). Most of the reservoirs in South Oldenburg were discovered in the 1960s and 1970s, and during this period the system of gathering lines and production sites was continuously expanded. With this expansion, the cathodic protection (CP) system grew as well. In the late 1990s, within the continuous CP maintenance programme, the entire CP programme was reviewed for its overall effectiveness.