Fracture Strength Analysis Of Pumping Well Tubing

Fracture Strength Analysis of Pumping Well TubingIn 2010, China's GDP has surpassed that of Japan because of continued high growth, and China has become the second largest economic entity in the world. In the same year, China also becomes the largest cars'producing and consuming country in the world. With the sustained progress of industrialization of society and rapid development of automotive industry, China's demand on energy (especially oil energy) is increasing dramatically. Facing the situation discussed above, on the one hand, China has invested much more money in overseas oil industry, on the other hand, China has put forward higher requirement on the domestic oil production, however, the majority of domestic oil fields have exploited for decades, and now have entered into the middle and later mining period, because of the increased water and mining depth of oil well, the oil tubes working environment continue to deteriorates, which results in frequent accidents of tubes'failure.From the point of view of failure type, tubes'failure can be roughly divided into three types, such as pipeline rupture, pipeline leaking and pipeline trip. From the location of failure, tubes failures often occur in two places that are tube and thread. Because the failure of tube rupture brings out the largest damage, at the same time, the failure of tube rupture has become the most prominent form in recent years, so around fracture failure of tube, the main contents of this paper are as follows:I. Theoretical investigation1. Through field investigation, research on the analysis of relevant literature and plastic amendment of the crack size in tube, and the most common elliptical crack in tube is studied in the field of linear elastic fracture;2. Based on the research that have been done by previous investigators, the working model of tube which is suitable for pumping in direct well is established, and stress analysis of tube is carried out based on the working model. â…¡.Analysis of fracture strength1. The calculation of stress intensity factor which is suitable for analysis of fracture strength is figured out based on theory of linear elastic fracture;2. Stress parameter method fracture criterion, the maximum tensile stress fracture criterion and engineering fracture criterion are used to establish method of analyzing static fracture strength, the formula of calculating maximum allowed defected size or maximum working stress is educed through the method talked above;3. Through the use of Paris law, the fatigue fracture strength of the tube is analyzed, and the formula of calculating residual fatigue life of the Defected tube is also set up;â…¢. Authentication1. The latest extended finite element method is employed to analyze the fracture strength tube as well as the traditional method, and the new method provides useful complement and checksum for the traditional method;2. Based on Criteria of ASTM standard test, test of strain fracture toughness of tube material plane is carried out to demonstrate the method that is established and used to analyze fracture strength of tube.â…£. Application1. Procurement of new pipelineStrain fracture toughness of tube material plane is required from the pipeline suppliers in the process of procurement, the comparison between the suppliers'data and the data obtained from this paper is made to determine eligibility of tube purchasing;2. Testimony of the scrapped tubeThe maximum allowable crack size of tube is determined under the condition of knowing the working stress, if the actual defect size in tube is greater than the value calculated in the paper, then the tube which contains defect size is convicted of retirement. 3. Prediction of fatigue lifeAccording to defect size provided from practical application, residual fatigue life of the defected tube is predicted.The general method of analyzing rupture strength of pipeline is established, and series formulas of analyzing rupture strength which is suitable for pumping system of direct well are also educed through the research talked above. And these formulas provide standard reference for the rational use of tube in pumping system of direct well; meanwhile, the method of analyzing fracture strength can also offer useful reference for analysis of fracture strength in the same engineering structures.