Near-wellbore formation treatment by injection of suspensions of deformable gel particles is explored as a method of prevention of lost circulation of drilling fluids, handling of reservoir permeability heterogeneity, and controlling water production in mature waterflooded oil fields containing highly permeable and weak zones. Conditioning and plugging of such formations and the resulting permeability impairment occurring during injection of suspensions of deformable gel particles are investigated experimentally. The effect of concentration, flow rate, and gel-particle sizes of suspensions on the prevailing pore-plugging processes is inferred by flow tests conducted with 3,800-md 16-to 20-mesh sandpacks. Prevailing particle-entrapment and -permeabilityimpairment mechanisms are identified under various conditions by means of specially formulated diagnostic equations. Appropriate dimensionless groups are used to develop several empirical correlations of the experimental data, which can assist in choosing suitable gel-particle suspensions and proper application conditions required for effective near-wellbore-formation treatment. This reveals valuable insights and information about the functional trends of sandpack plugging by gel-particle suspensions, which can help in successful design and mitigation of formation-plugging treatments in the field.

Conditions leading to plugging in weak or highly permeable formations and the resulting permeability impairment occurring during flow of suspensions of deformable gel particles are investigated by core flow tests. Effect of concentration, flow rate, and particle diameter of gel particle suspensions on the relevant pore plugging processes is studied. Effective impairment and trapping mechanisms are identified under various conditions by means of the diagnostic equations. Appropriate dimensionless groups are used to develop empirical correlations of experimental data. This reveals valuable information about the functional trends of porous media plugging by gel particle suspensions which is essential for successful mitigation of formation plugging in the field.

Analysis and interpretation of experimental data of laboratory tests of porous formation treatment by gel particles conducted at different gel particles suspension and application conditions are presented based on the dimensional analysis method. The measured permeability reduction caused by gel particles suspension injection into sand packs is correlated successfully by using the dimensionless groups developed from the relevant variables of sand packs, gel particles suspensions, and application operation conditions. The dimensionless correlations are shown to assist in quantifying the effect of the particlediameter to pore-throat size ratio on permeability reduction, evaluating the treatment of highly permeable and weak near well-bore formations by gel particles, and extrapolating from laboratory to field conditions. The present dimensionless correlations can predict the evolving permeability reduction under the varying conditions of gel particles suspension injection processes. The proposed dimensionless correlations can assist in effective design and mitigation of treatment of highpermeability near-wellbore formations by gel particles for avoiding drilling-fluids lost circulation, remediating reservoir permeability heterogeneity, and reducing water production in waterflooded mature oil fields. Review of Experimental StudiesZhang and Bai (2011) examined the effect of brine concentration, fracture width, and injection rate of the preformed particle gel (PPG) injectivity and plugging efficiency. They used brine concentrations 0.05% for 0.903% PPG concentration, and 0.25% for 1.597% PPG concentration, 1% for 2.731% PPG concentration, and 10% for 2.961% PPG concentration. The flow rates used are 5, 10, 15, 20, 25, and 30 mL/min and the fracture widths are 0.55 mm, 1.0 mm, and 1.5 mm. They used visual fracture models for the experiments to observe the PPG propagation through fracture and water flow through packed gel in the fracture. The fracture model of 55 cm length and 10 cm height consist from two acrylic plates with inlet and outlet and there is a rubber O-ring between the plates. The brine was injected first into the fracture model and then the PPG was injected by using an Isco pump. By means of twelve experiments, they showed that the injection pressure increased by the brine concentration because the swollen PPG particles are more soft and deformable at the low concentration than at the high concentration. The experiments showed that the injection pressure increased by the flow rate but the increase was not as much as the flow rate, and the injection pressure decreased by the fracture width because the conductivity increased by the

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The plugging and permeability impairment processes involved in the treatment and conditioning of high permeability porous formations is investigated at various temperatures by flowing of a suspension of gel particles through unconsolidated proppant packs. The permeability reduction and resistance factor are inferred by measurements of the pressure differentials with time across the proppant pack. Temperature effect is observed to be an important factor in suspended gel treatment of high permeability near-wellbore zones because temperature affects the gel properties and placement rate processes significantly. The effective mechanisms of the consecutive plugging and unplugging processes occurring during the flow of gel particles suspension through the proppant pack are identified and the best-estimate values of their rate coefficients are determined. The laboratory measurements of the viscosity, differential pressure, permeability reduction, and resistance factor are correlated successfully as functions of temperature. Various empirical correlations of practical importance developed in this work can be used for effective design of the suspended gel particles treatment in weak and highly permeable near-wellbore formations. These correlations can predict the effect of temperature on conditioning of the high permeability and weak formations by injection of suspension of gel particles.