Papers by Keyword: Pipeline

Abstract: A large number of blockage appeared in gas wells and pipeline appeared, which causedplugging, corrosion and the increasing of wellbore pressure difference, and seriously affect thenormal production of gas well of problems. In this paper, the water quality of produced water fromthe severe cases of single wells or pipeline water were analyzed, also include the composition ofblockage and core with the chemical volumetric method (CVM) , X-Ray Diffraction (XRD) and x-rayfluorescence (XFS) method. Meanwhile, the core powder was leached in simulated acid worksolution, and then the leaching solution was analyzed with CVM. The experimental results show thatThe produced water has high salinity, high contents of Ca2+, Ba2+ and Sr2+, low pH value, which leadto corrosion and scaling. The main components of the blockage are acid insoluble strontium sulfate(barium) scale or corrosion product or mixture of corrosion and CaCO3 scaling product. Ca2+, Ba2+and Sr2+ were easy to scale in wellbore or pipeline when they encountered other produced water fromdifferent formation. The Ca2+, Mg2+, Ba2+, Sr2+ and Fe 2+/3+ mainly derived from the dissolution offormation debris in formation water and working fluid (especially acidic working fluid) to reservoirrock, so the salinity of the produced water increased, and the trend of scaling and corrosion alsoincreased with the gas field development.

Abstract: This paper presents corrosion failure analysis of an underground natural gas pipeline. The pipeline material grade is 20# steel. The pipeline transfers multiphase fluid (Crude oil and water) from an oil well to an oil gathering plant. A portion of the line failed due to pitting corrosion under unknown circumstances. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are employed to characterize the scales and/or corrosion products near the failed portion. Based on visual and microscopic analyses and reviewing the background information, the following pitting corrosion sequences were identified: When the water ratio was smaller than 50%, the oil slick could cover the surface of the 20# test samples. Some uncovered surface would be corroded. When the water ratio was more than 70%, the surface of 20# steel contacted with more water. The average corrosion rate increased, and the corrosion products also formed, which would behave as a good diffusion barrier to prevent the underlying steel from further dissolution. Meanwhile, because of the corrosion products, the penetration rate also increased, the trend of local corrosion became weak with the water ratio continued to increase. The pitting corrosion varied with the water ratio because of the protection conferred by the oil slick or the corrosion product layer. Under such conditions, pits emerged on the steel surface until one of them grew faster and failed the oil pipeline.

Abstract: Currently, a problem of destruction of field and interfiled pipelines is topical. One of effective ways to increase an operational reliability of pipes is to protect them with different coatings. To protect the inner surface of oil pipelines the polymer coatings are used which cover the full length except the end sections – zones of mounted welded joints. Oil companies are interested in development of a technology of metal coating applying to the end sections, which provides both reliability of protection system of inner surfaces of pipes, and workability and high speed of mounting of pipelines. This paper shows the analysis of protection methods of pipeline end sections. The tests of metallized coatings are held. We identified the significant shortcomings of metallized coatings. There is a held experiment on applying of corrosion resistant coating by surfacing. There are the calculated heating zones while the surfacing operation. We defined the minimum necessary length of section for applying the protection coating. A chemical analysis showed that the expected structure in a surfaced coating is an austenite with inclusions of ferrite and martensite. Metallographic research showed that the protection layer is fully melted with a base metal of a pipe and represents a homogeneous structure without pores and slag inclusions. Mechanical tests confirmed the compliance of pipe metal properties to the requirements of normative and technical standards.

Abstract: The stress-strain behaviour of two dents with different depth and shape during the fatigue pressure and burst pressure test is described. The internal inspection carried out on a high-pressure line DN 300 revealed the presence of two dents. Then, the part containing the dents was dug out, removed from operation and the pressure tests were carried out. The stress-strain behaviour was measured with help of nine strain gauges placed on the external pipe surface in the vicinity of dents. The fatigue pressure test simulated fluctuation of pressure, temperature and landslides during operation. During the fatigue pressure test, the profile changes of dents were observed; on the other hand, no fracture occurred. It followed the pressure burst test, the results of which enabled to determine the limit state, burst pressure and position of fracture.

Abstract: In the pipeline construction, the girth welds tend to be the weakness because of defects and microstructural heterogeneities. The importance of suitable assessment of various defects in the weld is not only to prevent the cracks from unstable growth to cause catastrophic accident but also can effectively reduce the weld repair to reduce construction cost. Although many welding defects assessment methods and codes have been applied in this field, there are many differences among them. In this paper, the application of weld defect assessment methods was extensively studied. The key points of ECA applications, such as the pipeline axial stress and toughness, have been introduced. Furthermore, some suggestions were given on the application of girth weld ECA assessment.

Abstract: As the natural gas pipeline system in China is extremely complex and busy, people are coming to realize that existing system safety evaluation methods, which are premised on single pipelines or small-scale pipeline networks, are in fact not technical and rational enough for assessing the safety of a large-scale pipeline network. Therefore, ideas for ensuring the reliability of a large-scale natural gas pipeline network have recently been proposed. To calculate system reliability, the primary task is assessing the reliability of individual system components, such as pipelines and gas stations. This paper advances a reliability calculation model based on the Monte Carlo simulation for pipelines with corrosion def ects determined through in-line inspection. An example of the calculation method is provided; in this example, the reliability of a particular PetroChina natural gas pipeline project is ascertained in order to offer some experiences and references for pipeline reliability assessors.

Abstract: Dents in an oil and gas pipeline can be detected by In-line-Inspection (ILI), and structure integrity analysis of the pipe with theses reported dents is important for the safe operation. Strain analysis of the dented pipe is a way of fine assessment and ASME B31.8 has established the strain assessment code and its acceptable range. However, the method of strain assessment is rarely used due to the difficulty of strain calculation for a buried pipe. In this study, features of ILI data are investigated to elaborate the necessary of filtering analysis for strain analysis of the dent with ILI data. Then typical filtering methods are used to smooth the ILI data, and strain analysis are carried out with the smoothed data to study the practicability of strain assessment. Profile and strain of a dent in D813 pipe were obtained by Finite Element Method (FEM). Then different filtering methods were used to smooth the simulated ILI data of the dent which were selected from FEM profile. Strain of the dent were also calculated by smoothed data with the latest ASME B31.8 code, and compared with it from FEM at last to prove the feasibility and validity of the filtering methods with ASME B31.8 code.

Abstract: Corrosion on the water pipelines can potentially cause substantial human and economic losses. This paper concentrates on corrosion observation on the underground pipeline material as a part of our continuous study regarding this work. The samples which is mild steel taken from actually used pipeline at the site. Mild steels have been investigated intensively as a promising pipe material for underground pipeline due to their advantages such as high availability, low cost, environmental friendliness and high resistance to corrosion. However, their practical application exposes them to the attack of corrosion related to the soil condition. In this study, microscopic observations were performed on the surface of pipeline material using scanning electron microscope (SEM) and energy-dispersive x-ray (EDX) technique in order to study the morphology and basic composition of the corrosion, respectively. Based on the observation and visual analyses, it was determined that the surface of the mild steel was affected by continuous exposure to moist soil, which leads to pitting type of corrosion.

Abstract: The oil industry has sought to minimize the environmental impact from mining activities and oil transportation. Oil transportation by pipelines is subject to failures and leaks which cause financial losses and environmental damage, often irreparable. Currently, the study of leaks in pipelines has attracted the attention of many researchers. The aim of this study is to evaluate the influence of the curved curvature radius connection in pipeline leakage. We used a mathematical model of multiphase flow to describe the two-phase flow, based on the particle model. Oil is the continuous phase while water a dispersed phase. To model this effect we used the turbulence model SST. All simulations were carried out using the Ansys CFX ® commercial code. Results of the total pressure and pressure drop are presented and discussed. The results confirm the influence of the bending radius of curved connection on the behavior of the total pressure and the total pressure drop in two-phase flow in pipelines with and without leakage.

Abstract: In this paper, the failure analysis was conducted on a non-occupation refined-oil pipeline, in which corrosion perforation occurs when the pipeline was filled with 1.2 MPa air for more than 1 year, and the material of the corrosion pipeline was L245. To find out the reason of the corrosion, some tests such as XRD analysis for corrosion products, corrosion pits analysis, inclusions and microstructure inspection, as well as corrosion simulation trial were conducted. The experimental results showed that the failure was caused by electro-chemical corrosion because of the dissolved oxygen, while the existence of 1.2 MPa inner air and non-metallic inclusions accelerated the corrosion.