Replacement and Cleaning of Deserted Inshore Oil and Gas Pipelines

摘要

Because of many engineering projects of the sea-beach industrial district of ZGBX offshore oil and gas field under construction, the routes of two oil and gas pipelines which pass through the district must be deserted and alternated. Considering that their recovery would inevitably obstruct the construction of the industrial district and also be expensive, it is reasonable for the deserted pipelines to stay in the original location. However, there was a large amount of oil and gas remained in the deserted pipelines, which would bring great hidden danger to the large scale construction of the industrial district. Thus the deserted pipelines had to be replaced and cleaned. Then according to the practical situation of the deserted pipelines, a treatment method for them to be replaced with pig and seawater prior to being washed with chemical agents was proposed. Based on the characteristics of the remained crude oil, the safe replacement time was determined. Focus on the cleaning quality, operability and costs, environmental requirements, the technological and economic feasibility of the cleaning methods for seawater, a single chemical agent and three kinds of chemical agents with a pig train were compared and analyzed, and then an optimal cleaning plan for the deserted pipelines was determined. Based on the evaluation of the oil dissolving capability and amount used, the corrosion and environmental pollution for chemical agents, an economical and effective cleaning agent was screened. Then a replacement and cleaning plan for the deserted pipelines was proposed and its realization was very successful. The results show that the safety shutdown time for the deserted oil-gas combined pipeline and crude oil pipeline are 89.8h and 54.9h respectively, and their replacement operation should be finished within 24h; the cleaning method of the single chemical agent is better than the others, and emulsified cleaning effect of the agent AQ-12 is the best; the replacement and cleaning operation was completed by using the designed plan successfully.