Simulation Study On Sand Production Law Of Reservoir Instability And Crushing In Deepwater L Gas Field

With the continuous development of global industrialization and urbanization,the problem of energy shortage is becoming more and more serious.In recent years,the exploration and development of deepwater oil and gas has become an effective way to alleviate the problem.The compaction degree of deepwater reservoirs is low,most of which are edge and bottom water gas reservoirs,and sand production is easy in the production process.Deep water L gas field is characterized by complex geological structure,high production allocation and high temperature and high pressure in the lower section of the gas well,which leads to complex sand production in the process of production and development.In addition,with the development of edge and bottom water,sand production is more severe.Therefore,the research on the mechanism of reservoir instability and the law of fracturing and sand production in deepwater L gas field is helpful to ensure the safe and efficient development of L gas field,and also has reference significance for the prevention and control of sand production.In order to solve the problem of sand production in deepwater L gas field,based on logging data,triaxial test and thin section identification of rock pore casting,this paper calculated and analyzed the mineral composition,microstructure,rock mechanical properties and the magnitude and direction of in-situ stress of the reservoir.And through the analysis of gas reservoir L instability mechanism,considering the high temperature and high pressure plastic yielding of the reservoir rock destruction,for excluding joint rock,optimization rule of D-P,for joint structural plane of rock mass,such as selection of weak plane failure criterion,undisturbed formation and wall rock stress distribution,reservoir rock crushing sand mechanics model is established,and the iterative calculation of the program reservoir critical production pressure difference,so as to judge the sand risk of reservoir emergence.According to the lithologic physical characteristics,pore structure and joint occurrence of reservoir rock,the parallel bonding model was selected to represent the rock particle contact model,and the smooth joint model to represent the joint contact model.The physical model of pore-throat structure of sandstone with joint was constructed and the meso-parameter calibration was carried out.Based on the micro-element stress state of rock,the simulation control flow is designed,and then the dynamic process of rock fracture is simulated,the process of crack generation and propagation and the characteristics of rock bond failure are analyzed,and the corresponding algorithm is developed to statistically analyze the distribution of rock fragmentation and sand production,and the discrete element simulation method of rock fragmentation and sand production is formed.Based on the established mechanical model of rock breakage and sand production,the risk of rock breakage and sand production in L gas field under the condition of reservoir pressure depletion and water breakthrough is analyzed.According to the stress distribution of reservoir rock and the discrete element simulation method of rock sand production,the law of rock sand production with and without joints is simulated.The results show that the median initial grain size of sand produced by fractured rock in well L-1 in the second year of development is about437.4-664.2 μm,considering pressure depletion and water emergence of reservoir.In the fourth year of development,the median initial particle size of sand produced by rock fragmentation is about 337.1-544.7 μm.The simulation results can provide some reference for sand control in L gas field.