Failure Analysis Of Elbow Piercing Leakage In Gas Gathering System And Research On Anti-Erosion Coating

With the extension of the development time of Jingbian gas field,corrosive media in natural gas and formation water,tubular column corrosion products,and incoming fluids can cause organic or inorganic blockage in gas wellbore and near-well zone,resulting in rapid decline of gas well production and even failure of normal production,which seriously affects the performance of single-well capacity.At present,Jingbian gas field is still facing the problems of unclear blockage composition,unclear blockage mechanism,and imperfect unblocking technology.To this end,this paper uses a variety of means to analyze the target gas wells with full water quality analysis,XRD testing of product layer composition,macro and micro morphological analysis,and other means to analyze the composition of the extracted fluid,scale samples,and returned material taken from the field,and systematically study and clarify the blockage mechanism and influencing factors in the gas wellbore and near-well zone.Subsequently,the software for predicting gas wellbore fouling in carbonate gas reservoirs was developed through a combination of indoor high-temperature and high-pressure experiments and software simulations.The main work and research results are as follows:（1）Test and analysis of several typical well scale samples or unblocked returns using the dissolved scale analysis method and XRD method showed that the scale samples are mixtures,mainly composed of organic matter,acid insoluble matter and various salt scales.Calcium carbonate is the main component,followed by barium sulfate,calcium oxide,magnesium carbonate,etc.Chemical scale analysis and XRD analysis were used to analyze the composition of the product layer in several gas wells.The results showed that there were three main types of scale samples collected directly from the unblocked and the pipe wall,the inorganic components in the scale samples of the first type of wellbore were mainly CaCO₃and CaO,which were easy to scale and unblock.The inorganic components in the second type of wellbore scale samples are mainly CaCO₃ and a small amount of Ba SO₄,and it is difficult to declog this type of wells.The inorganic components in the scale sample of the third type of wellbore are mainly Ba SO₄,and it is difficult to unblock this type of wells.The analysis of scanning electron microscopy and energy spectrum results of the field scale samples showed that the scale samples were scaled in three layers:upper,middle and lower,which resulted in the analysis of the scale sample stratification problem and scale sample composition.In addition,the analysis of the stratigraphic water and the test results of different stages of rejection fluid show that the water samples have Ca²⁺>Na⁺>Mg²⁺,and the content of Ca²⁺is very high,and the content of scale forming anions such as HCO₃^-is relatively high,so the water quality has a strong scaling ability.（2）A study of the single-factor influence law of gas well fouling volume was conducted indoors.Numerical simulation was used to calculate the blockage of water sample data obtained from typical wells in Jingbian gas field.Firstly,the single-factor numerical simulation showed that the fouling volume increased when the temperature increased and decreased when the pressure increased.Secondly,the analysis of the Jingbian gas field through-well data showed that most gas wells had more scaling in the range of 50-200m upward from the bottom of the tubing,and the scaling amount varied significantly.Based on the calculation and simulation of fouling prediction based on the comprehensive consideration of temperature and pressure,the obtained fouling volume variation pattern is much smaller than the actual fouling volume variation in the wellbore.Finally,five typical wells were selected for numerical simulation of ion concentration variation law,and it was found that the variation of fouling amount was consistent with the through-well data.Therefore,in this paper,the ion concentration variation law with well depth and scaling volume is applied to modify the calculation model to predict the scaling volume and scaling rate in Jingbian gas field.（3）The software requirement and feasibility are analyzed,and the scaling prediction software is developed by using the calculation model.In the overall design stage of the software system,Visual Studio 2013 is used for software development,and the program is written in C language.The software can achieve efficient human-computer interaction on the Windows platform.In addition,the software constructs a scaling prediction system based on business logic layer,presentation layer and data access layer,and uses entity-relation method to design the logical structure of database.Finally,the feasibility of the software is verified by analyzing typical well cases and testing the software.