A gamma-ray tomography system to determine wax deposition distribution in oil pipelines

Abstract

Monitoring wax deposition in pipelines is of particular importance for oil extraction companies. In this work, a new gamma-ray tomography system based on using a rod CsI(Na) scintillator and 137Cs gamma source was developed to view the cross section of oil pipelines. The system can estimate the interaction position of gamma-rays by measuring light attenuation in the rod scintillator using two photomultiplier tubes coupled to its ends. Therefore, despite the simple structure of the employed detector, it can act as a position-sensitive instrument. In order to test the proposed tomography system, a selection of desired polyethylene round-bar pieces (as different wax thicknesses) was prepared to be placed in iron pipes, and their projections at different angles were acquired to construct cross-sectional images as well. The results showed that the designed system had the ability to scan the interior of the pipes and determine wax thickness with an error between 2.4% and 11.4%.

Prompt gamma-ray methods for industrial process evaluation: A simulation study

“…Gamma-ray sources like cobalt-60 ( 60 Co) and cesium-137 ( 137 Cs) are placed on one side of the process equipment and a radiation detector on the opposite side to measure the transmitted radiation, which is then correlated to the densities of the process materials. Gamma scanning and tomography have been used for the inspection of distillation columns [10,11], and used for the detection of pipelines anomalies [12][13][14].…”

Wax Deposition Characterization under Flowing Conditions Using an Oscillatory Flow Setup

“…For most wax deposition experiments, thickness and wax content of the formed deposit are two major parameters in characterizing wax deposition . Deposit thickness is commonly obtained from indirect measurement, either using pressure drop data across the test section or collected deposit weight after pigging the pipe. ,, Some new measurement methods have been proposed to get more precise data of wax deposit thickness, such as the laser-based technique. , This method is conducted by scanning the inner pipe wall with a coaxial laser beam, to get the axial thickness distribution of the wax deposit. However, improvements are required to solve the challenging issues with the method, such as interference of mechanic vibration, laser light absorption by specific oil components, and its relatively high cost .…”

“…15,26,27 Some new measurement methods have been proposed to get more precise data of wax deposit thickness, such as the laser-based technique. 28,29 This method is conducted by scanning the inner pipe wall with a coaxial laser beam, to get the axial thickness distribution of the wax deposit. However, improvements are required to solve the challenging issues with the method, such as interference of mechanic vibration, laser light absorption by specific oil components, and its relatively high cost.…”

Wax and Wax–Hydrate Deposition Characteristics in Single-, Two-, and Three-Phase Pipelines: A Review

“…Because oil–gas exploitation is performed from offshore to the deep sea gradually, the oil–gas products are transported under lower-temperature conditions by pipeline, and the solubility of wax in oil products will decrease with decreases in the oil temperature. Therefore, with the decrease of temperature and pressure along the pipeline, when the temperature is decreased below the wax precipitation temperature (WAT), the dissolved wax molecules will continuously precipitate out and gradually deposit on the pipe wall, reducing the effective circulation area and increasing the resistance loss along the pipelines. , At the same time, it will also cause serious deterioration of crude oil rheology, affect the process of oil-gas transportation pipelines badly, and even lead to complete blockage of pipelines, ultimately causing huge production and economic losses …”

“…Therefore, with the decrease of temperature and pressure along the pipeline, when the temperature is decreased below the wax precipitation temperature (WAT), the dissolved wax molecules will continuously precipitate out and gradually deposit on the pipe wall, reducing the effective circulation area and increasing the resistance loss along the pipelines. 1,2 At the same time, it will also cause serious deterioration of crude oil rheology, affect the process of oil-gas transportation pipelines badly, and even lead to complete blockage of pipelines, ultimately causing huge production and economic losses. 3 In the actual production process, most of the crude oil contains high wax content, which is very susceptible to the wax deposition during long-distance transportation.…”