Study On Erosion And Residual Strength Of Sand-carrying String In Gas Well

Unconsolidated sandstone oil and gas reservoirs have become an important source of exploitation in my country,and their exploitation potential is huge.The large-reach horizontal well fracturing technology is mainly used to increase oil and gas production.However,prop pant reflux and formation sand productions are important issues that endanger the health and safety of oil and gas wells.The sand particles will cause erosion damage to the inner wall of the pipe string during the upward and backward process of the drag force of the airflow,resulting in the thinning of the casing wall thickness,the weakening of the anti-collapse ability,and the reduction of the service life.Studying the law of wellbore erosion is significant for reducing production costs and formulating efficient development plans.Based on previous erosion studies,this paper establishes a particle migration velocity calculation formula considering factors such as gas production,particle diameter,casing inner diameter,particle shape,etc.,by analyzing the movement of gas-solid two-phase flow,and brings it into Into the casing erosion calculation model,it can reflect the relationship between the casing erosion rate and the above factors.By calculating the erosion rate of N80 steel casing with an outer diameter of 177.8mm under different working conditions,the analysis results show that the erosion rate of the casing is positively correlated with gas production and particle mass flow,and is related to the inner diameter of the casing,particle size,and particle size.There is a negative correlation between the radius of the buildup section and the degree of the particle-like ball.On this basis,the various factors affecting the erosion rate were quantitatively characterized,and the relationship between each factor and the erosion rate was evaluated by the gray correlation method,and the weight of each influencing factor on the erosion rate was obtained.The results showed that the particle quality Flow rate and gas production have a greater impact on the casing erosion rate,while other factors have less impact.The order is in order of casing inner diameter,bevel radius,particle size,and particle shape.Finally,the remaining strength changes of the casing after 5 years of cumulative erosion under the action of various factors are analyzed,and the remaining service life prediction model of the casing that varies with the average annual erosion rate is established,and the use of the casing under different gas production conditions is calculated.It provides reference for safety evaluation of pipe string on site.