Research On Permeability Damage Mechanism And Law Of Gravel Layer In Sandcontrol Wells Under Complex Conditions

The sandstone reservoirs in China’s oil reservoirs account for a large proportion,and are generally faced with the severe challenges of oil sand production.For the problem of sand production in the oil layer,gravel packing and sand control have become the main sand control technology for loose sandstone oil reservoirs at home and abroad.Gravel packing sand control wells will have better sand control effect and yield at the initial stage of production,but with the increase of production time,gravel The sand control layer was blocked due to formation sand intrusion,colloidal asphaltene adsorption,polymer micelle precipitation and other factors,and the permeability decreased,which directly led to a significant drop in oil well productivity.Therefore,qualitative analysis and quantitative study of the blockage mechanism and regularity of gravel sand retaining media under various complex well conditions are very important.Based on the above problems,this paper analyzes the blocking mechanism of gravel layer retaining media under common well conditions in several conventional onshore oilfields,including conventional water drive wells,heavy oil wells,injection wells and thermal recovery wells.The on-site production conditions were simulated,and a series of experiments on gravel layer-suppressing media under complex conditions were conducted to quantitatively study the law of permeability damage in gravel layers under different complex well conditions.The results show that under the compaction effect,the increase of applied pressure will lead to a significant decrease in the permeability of the gravel accumulation,and the permeability of the gravel layer under 40 MPa compaction is about 5% to 11% of the initial permeability.Under the effect of sand intrusion and blockage,along with the increase of gravel sand-median value ratio(GSR),crude oil viscosity,formation shale content,and average displacement flow,the formation sand is more likely to intrude into the gravel layer causing blockage and the final permeability of the gravel layer.The ratio is significantly lower;after the gravel layer heavy oil adsorption plugging experiment,the permeability of the gravel layer rapidly decreases after the displacement test,the blockage permeability ratio is approximately 0.25,and the final blockage permeability ratio changes with the displacement time of the heavy oil and the displacement temperature.Not great.The physical and chemical composite blockage of heavy oil and sand control wells is related to the wettability and adsorption properties of the surface of sand-retaining medium.The surface of the quartz sand filling layer is strong and hydrophilic,and its surface is the polymer and its derivatives,and the asphalt surface of the heavy oil.The adsorption capacity is higher;the adsorption capacity of HPAM on the surface of quartz sand increases gradually with time,and eventually the adsorption capacity tends to be stable with time.The experimental results of multiple rounds of steam-saturated gravel layer damage rule show that due to the adsorptive plugging of crude oil and the influence of remaining oil,the water permeability after reverse flooding is only about 15% of the initial water permeability,and the first high temperature After plugging with hot steam,the plugging action of the gravel layer is very obvious.The permeability of the water increases to about 93% of the initial water permeability.After the second high-temperature hot steam is removed,the water in the gravel layer penetrates.The rate is restored to about 85% of the initial water-side permeability,which basically shows that the high-temperature hot steam has a good deblocking effect on the gravel layer saturated with heavy oil,but as the steam deblocking pass increases,the solution The blocking effect gradually decreases.At the same time,a quantitative prediction model for the degree of permeability damage of gravel layers based on experimental conditions is obtained in this paper.Based on the experimental results,a dynamic production prediction model for gravel packing sand control wells is established,so that oil field workers can reasonably design well productivity and effective sand control period.Provides some theoretical basis for production forecasting of oil well production time.