NUMERICAL SIMULATION ANALYSIS OF WELLBORE COLLAPSE AND DEVELOPMENT ENVIRONMENT DAMAGE CONSIDERING THE STRESS SENSITIVITY OF LOOSE SANDSTONE

摘要

Engineering geological disasters such as borehole instability during the development of loose sandstone oil and gas reservoirs will damage the development environment of underground reservoirs.The current analysis of the mechanism of borehole collapse and instability of loose sandstone oil and gas reservoirs is still incomplete.For this reason,a fluid-solid coupling finite element model for studying the risk of wellbore collapse was constructed based on the stress sensitivity model of the physical parameters of the loose sandstone reservoir,and the influence of the difference in inclination angle and in-situ stress on wellbore stability was carried out.The results of the study found that the borehole expansion rate when considering the stress sensitivity of the loose sandstone reservoir is 3.24 times that of the borehole expansion rate when the stress sensitivity is not considered.In addition,with the increase of the inclination angle,the borehole expansion rate will gradually decrease,and the damage to the development environment of the reservoir around the well by drilling operations will correspondingly weaken.Under the same drilling conditions,the expansion rate of vertical wells is 4.44 times that of horizontal wells.In addition,during the drilling of loose sandstone oil and gas reservoirs,the borehole yield collapse will increase nonlinearly as the in-situ stress difference increases.The borehole expansion rate is 282.54% when the in-situ stress difference coefficient is equal to 1.23,but when the in-situ stress difference coefficient becomes 1.50,the borehole expansion rate rapidly increases to 423.73%.The research results can provide technical support for drilling and completion operations of loose sandstone oil and gas reservoirs and provide design basis for avoiding the protection of the underground development environment of loose sandstone oil and gas reservoirs.