Experimental And Numerical Study On Sanding Characteristics In Reservoir

Sand production is a common phenomenon during the extrusion of hydrocarbons,the problems like production reduction,suspension,and equipment wear caused by which pose a threat to the normal production.This paper aims at investigating the sanding characteristics of sandstones with weak to moderate strength through experimental and numerical simulations.The main contents are as follows.A novel sandstone preparation scheme is proposed to make up the defects in the existing methods.The deformation and failure characteristics of the cores cured by different epoxy curing systems are analyzed and the mechanism affecting the mechanical properties is investigated.The results show that the mechanical behavior of the synthetic rocks based on the cycloaliphatic epoxy resin 2021 P and the methylhexahydrophthalic anhydride with 3%～5% of the catalyst compares well with that of the natural sandstones.The sanding characteristics of sandstones with weak to moderate strength are studied in terms of hole failure modes,sanding forms and the particle size distribution(PSD)of the produced sand through laboratory sand production experiments.The results show that the degree of the hole failure localization increases with the increase of the core strength,which leads to the spiral-shaped breakout from uniform failure,and the core with smaller particle size produces a more obvious spiral-shaped breakout.For the sanding form,higher content of large sand aggregates(>1180um)in the produced sand is found in cores with higher strength and larger particle size,but this content can be reduced due to the secondary crushing when the core encounters a severe collapse.The produced sand shows a higher median size and lower content of small particles compared with that of the original sand,and such differences expand with the increase of the consolidation strength.A low computational cost modeling method based on a varied particle sizing scheme is proposed for sand production simulation by the particle flow code(PFC).The model stress distribution and contact network analysis show that the rationality of the model stress depends on the consistence of the macro mechanical properties among the model,which can be realized by scaling up the particles in the region away from the hole or adjusting the mesoscopic model parameters in the case of non-scaling up.The reliability of the modeling and the computational cost-efficiency are verified through the comparison of the model stress distribution and the number of particles and contacts before and after the application of the varied particle sizing scheme.The hole failure mechanism,characteristics of the produced sand and the sand production law of the cores with different mechanical properties are investigated through a 3D sand production numerical model.The results show that the different post-peak deformation properties of rock lead to the differences in the redistribution of stress around the hole,and the hole failure mode changes from the overall failure to the V-shaped breakout with the increase of the rock brittleness.Tensile spalling contributes to the hole failure of the rock with high brittleness,forming a slightly convex V-shaped breakout,while shear failure contributes to that of the brittle-ductile rock,forming a slightly concave V-shaped breakout.The overall failure around the hole,in the form of spiral-shaped breakout,develops in the ductile cores with low brittleness,which is dominated by shear failure.The core with low strength and high ductility usually shows a uniform failure around the hole.The slot-like breakout is frequently observed in cores with high porosity and high brittleness,which attributes to compressive failure,or to the process that the core first undergoes tensile spalling to form a convex notch,and then develops into compression failure.The core with low strength and high ductility mainly produces loose grains,containing some big sand aggregates,while the brittle-ductile or ductile ones can additionally produce some rock pieces.The produced sand of the brittle cores is almost in the form of loose grains.With the same strength,a more brittle core needs a lower critical drawdown pressure for sand production.The sand production prediction is more accurate when the post-peak deformation characteristics of rock are considered.This paper further reveals the characteristics and mechanism of sand production,which provides important experimental and theoretical basis for sand production prediction and sand control strategy.