Study On Pigging Slug Prevention Technology In Condensate Gas Subsea Pipeline

With the development and exploration of the offshore condensate gas field,thegas-liquid mixing transporting technology has been widely used. However，The accumulationof condensate liquid in pipeline can cause a series of harmful effects on pipelinetransportation. Pigging to the pipeline at regular intervals can effectively eliminate theseeffects. Whereas large amounts of liquid accumulate before pig in its movement, which willform a long slug in the end of pipe. The pigging liquid slug will cause overflow when it flowinto slug catcher. The stable production of oil and gas fields will be influenced as a result.This paper aims to study on pigging slug prevention method in condensate gas subsea pipelinefrom pigging equipment and pigging process.Bypass pigging model is established to calculate the maximum diameter of bypass holewhen research on bypass pig structure. In order to improve the dispersing effect of bypassnatural gas on liquid slug, the following structure is recommended: single bypass holeinstalled in the middle of the pig; convergent nozzle with the angle set at15°~35°;framework material made of titanium alloy.Simulation has been carried out to compare the movement of bypass pig andconventional pig. Result suggest that bypass pig tends to lower the pigging speed, lengthenthe pigging time, and be helpful for reducing pigging slug flowrate and terminal gasstarvation.The effect becomes stronger with the increase of bypass fraction.This paper explores new ways to eliminate the pigging slug from the production processadjustment and pigging process design used OLGA software. The study results suggest thatproduction transient adjustment can effectively reduce the slug flowrate. Circularity piggingmethod can directly use the compressed gas of platform.It can reduce the influence ofpigging slugs on platform facilities through adjustment of compressed gas flowrate. At thesame time, this paper compares the simulation results of OLGA on steady and regular piggingconditions with the field data, found it has high accuracy, Therefore, OLGA simulation resulthas important significance for fieldwork guidance.