Physical inspection and mathematical-model simulation are used to identify blockages in gas pipelines. Generally, the physical method can result in accurately detecting location and size of a blockage at the expense of production shutdown and high costs. The mathematical simulation detects a blockage through numerical modeling, which could give a quick evaluation at a much lower cost but with higher uncertainties. This paper presents a multirate-test method to detect locations and sizes of blockages in gas pipelines.
The consumption of natural gas is next to that of oil and coal according to Energy Information Administration statistics. New gas pipelines are constructed and existing pipelines are expanded to transport more natural gas to plants or end users. A blockage, which is a common problem in gas-pipeline operations, is a result of chemical or physical deposition caused by changes in composition, pressure, or temperature. The reliable and timely detection of blockages along pipelines is one of the critical topics in flow assurance.
The detection of pipeline blockage falls into two categories: physical inspections and mathematical models. Conventionally, physical-inspection methods include acoustic reflectometry, gamma ray transmission scanning, radio-isotope-tracer injection, tomography measurements, radiographic detection, and pipeline-diameter measurements. Physical inspections usually are accurate but come with the expense of production shutdown, high costs, and long downtimes, which may be infeasible with long pipelines or complex pipeline networks. Mathematical models use data such as flow rate, pressure, temperature, and pressure-wave reflection to locate a blockage. The models use mass conservation, momentum conservation, energy-balance equations, pressure-pulse decay, and phase shift to estimate blockage size and location. Mathematical models have the advantage of quick evaluation at lower costs and can monitor the pipeline continuously without interrupting pipeline operations. Usually, mathematical models require flow parameters, which are not always available; therefore, operators are more confident with physical inspection than mathematical modeling....
A New Method To Detect Blockage in Gas Pipelines
01 April 2016