Kichenko S.,OJSC TNK BP |
Petrunin M.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry |
Marshakov A.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
European Corrosion Congress 2010 - EUROCORR 2010 | Year: 2010
The significance of corrosion protection in oil industry has always been very high. The reason is that corrosion often results in pipeline failure leading to oil spill and environmental damage. Wide application of inhibitor protection in TNK-BP in the recent years allowed to suppress internal corrosion to a great degree. At the same time, the problem of external corrosion of TNK-BP field pipelines remains acute. The situation is worsened by complexity of corrosion protection and absence of reliable methods to assess the corrosion of pipelines beyond design life. Traditional methods of inspection in the pits enable to evaluate selectively thickness of pipe wall and calculate the probabilistic remaining service life but they do not reflect real corrosion condition of pipeline especially in case of local corrosion which is the main cause of accidents. During this study over than 20 different field pipelines were inspected. The factors of intensive (3-5 mm/year) local corrosion of steel were identified and comprehensive ground instrument-aided corrosion inspection scheme was proposed. This scheme allows to identify sections of pipelines which are subject to pitting corrosion most of all. Inspection scheme consists of three stages: 1) analysis of design and service documentation for identification of pipeline sections for instrumental inspection; 2) instrumental "surface" inspection for localization of potentially dangerous sections which includes measurement of coating resistance, detection of coating holidays, analysis of chemical composition of soil (pH, chloride-, nitrate-, sulphide-, calcium and magnesium ions), express measurement of steel corrosion rate, identification of corrosion macro-couples; 3) corrosion monitoring at selected sections using corrosion indicators. Based on the results of measurement of general and local corrosion rates, pipeline sections with high corrosion risk are defined and recommendations on application of urgent anti-corrosion measures are provided. A low-cost but efficient method of local sacrificial anode protection was proposed based on the results of this work. This method ensures higher integrity of field pipelines by applying selective protection only to sections with corrosion risk. Proposed instrumental inspection methodology and local sacrificial anode protection method were successfully tested in 2006-2008 in TNK-BP and were applied to 57 pipelines of Orenburgneft allowing to reduce number of failure in these pipeline in several times.