Failure Mechanism Analysis Of Heavy Oil Thermal Production Well Casing And Research On Relevant Countermeasures

Casing damage is common in the process of oil and gas exploitation,especially in thermal production wells,which brings huge economic losses.Based on the statistics of casing damage in oil field and the existing investigation of casing damage mechanism,based on the characteristics of high temperature and serious sand production in the thermal production horizontal wells,this paper studies the casing damage mechanism and puts forward the corresponding countermeasures by using the method of combining experimental research and numerical calculation.The strain-based design method is used to evaluate the thermal stress resistance of perforating casing in thermal production Wells.The results show that the perforation parameters with more perforations and smaller perforation diameter can enhance the axial safety of the perforating casing.Multiple steam huff and puff processes have cumulative effect on thermal deformation of casing.The higher the perforation density and the higher the number of perforations on the perforating row,the greater the risk of casing collapse.The results of this study provide a reference for the optimization of casing perforation parameters from the perspectives of casing axial safety and external extrusion strength.A two-dimensional casing-cement-formation model was established by using finite element software to analyze the safety of casings in the formation of sand-producing cavities and the influence of relevant factors.The results show that the formation of sand-producing cavity can easily lead to plastic deformation of casing,and the casing safety is worse with larger sand-producing hole and lower elastic modulus formation.The safety of the casing can be effectively improved by the application of high temperature resistant and high strength steel casing and high elastic modulus cement.Using the finite element buckling analysis method,a three-dimensional casing model of the sand production section was established,the mechanism of the action of the sand on the casing axial instability was given,the influence law of the sand production degree on the casing instability failure was compared,and the influence law of perforation parameters on the casing axial stability was analyzed.The results show that the casing of thermal production well is prone to buckling in the sand-producing section,and the higher the degree of sand-producing,the higher the risk of buckling instability.The critical buckling load of casing decreases significantly with the increase of perforation diameter and perforation density,and is less affected by the perforation phase.The results provide a theoretical basis for casing string design in horizontal thermal production well.