Wellbore Multi-scale Four-dimensional Geomechanical Simulation Of Gas Storage Trap

With the continuous growth of China ’s energy demand and the increasingly severe international energy situation,under the determination of the " carbon peaking and carbon neutrality" target,natural gas,as a clean,efficient and highly schedulable low-carbon energy,plays a key role in the task of carbon peak in 2030 and carbon neutralization in 2060.China’s natural gas consumption will usher in a demand peak in winter,and the demand will decrease in summer.The imbalance between supply and demand is very serious.As an important facility for energy strategic reserve and seasonal peak shaving,underground gas storage plays an important role in energy facilities.Therefore,it is of great significance to ensure the safe operation of gas storage in the life cycle.The safe operation of gas storage should not only ensure the integrity of cap rock,reservoir and fault,but also put forward an important test for the integrity of injection-production wellbore.A large number of engineering problems in the field mainly focus on casing damage.In order to prevent casing damage and reduce economic losses,this paper uses numerical simulation methods to analyze the casing damage mechanism from the perspective of near wellbore geomechanics to ensure the safe and efficient operation of gas storage.Firstly,combined with the actual situation of the near wellbore structure,the mechanical properties of the casing-cement sheath-formation combination are mastered from two aspects of theoretical formula and experimental data.Secondly,the casing damage mechanism is analyzed from the perspective of analytical solution,and the cross-scale coupling simulation from reservoir scale to wellbore scale is realized by numerical simulation.Finally,based on the integration of geological engineering,the integrated numerical simulation method of volcanic gas storage from geological modeling,gas reservoir numerical simulation,four-dimensional geomechanics to near-wellbore geomechanics simulation is realized,and the possible damage parts of casing are predicted from the perspective of engineering practice.The results show that the rock failure mode of S volcanic gas storage is mainly conjugate shear failure.Under high confining pressure,the rock has certain bearing capacity after peak failure.The interlayer load between casing-cement sheath and cement sheath-formation increases with the increase of elastic modulus of cement sheath.In soft formation,the use of cement sheath with larger stiffness can reduce the external load of casing and have better protection for casing.In the formation with large stiffness,if the elastic modulus of cement sheath is increased,the effect of casing load reduction is small;the vertical principal stress distribution range of S volcanic gas storage is between 60 MPa and 80 MPa,concentrated around 68 MPa,and the maximum horizontal principal stress distribution range is between 50 MPa and 80 MPa,concentrated around 64 MPa.The minimum horizontal principal stress ranges from 45 MPa to 70 MPa,concentrated at about56 MPa.The Von mises stress of Well-2 is larger at about 2900 m,and the casing is prone to yield failure at this position.The casing does not produce equivalent plastic strain,but there is equivalent plastic strain in the surrounding rock of the wellbore,so the surrounding rock of the wellbore is prone to cracks,which will cause the risk of leakage..