Deformable Microgel for Enhanced Oil Recovery in High-Temperature and Ultrahigh-Salinity Reservoirs: How to Design the Particle Size of Microgel to Achieve Its Optimal Match with Pore Throat of Porous Media

Abstract

Summary Conformance control treatment in high-temperature and ultrahigh-salinity reservoirs for easing water/gas channeling through high-permeability zones has been a great challenge. In this work, we propose a deformable microgel that can be used at more than 373.15 K and ultrahigh-salinity conditions (total dissolved solids > 200 kg/m3, Ca2+ + Mg2+ > 10 kg/m3) and present a method for choosing the suitable particle size of the microgel to achieve an optimal match with the pore throat of the core. First, the particle size distribution of the microgel was analyzed to decide d50, d10, and d90 (diameter when cumulative frequency is 50, 10, and 90%, respectively). Coreflooding experiments were conducted under different permeability conditions from 20 to 900 md to investigate the migration and plugging patterns of the microgel by analyzing and fitting injection pressure curves together with the change in the morphology of the produced microgel analyzed by a microscope. The migration and plugging patterns were divided into three patterns: complete plugging; plugging—passing through in a deformation or broken state—deep migration; and inefficient plugging—smoothly passing through—stable flow. The second pattern can be further divided into three subpatterns as strong plugging, general plugging, and weak plugging. Finally, on the basis of five patterns, we build a quantitative matching relation between the particle size distribution of microgel and the pore-throat size of cores by defining three matching coefficients α = d10/d, β = d50/d, γ = d90/d (d is the average pore-throat diameter). The effectiveness of this quantitative matching relation was verified by evaluating the plugging ability (residual resistance factor) in a post-waterflooding process after the injection of 1.5 pore volume (PV) of microgel. For a strong permeability heterogeneity, the strong plugging is believed to be the expected pattern. The particles size and the pore-throat size should meet the following relationship: 1 < α < 2, 2 < β < 4, 4 < γ < 6. In this scenario, the deformable microgel particles could achieve both an effective plugging and a deep migration. The quantitative matching relation with multiple matching coefficients determined based on the particle size distribution might help to choose suitable particles more precisely in comparison to the method based on one matching coefficient (mostly, the ratio of the average diameter of particles to the average pore-throat diameter). In addition, the method itself to build a quantitative matching relation according to particle size distribution can be used for designing different particle-type conformance control agents for profile control and water shutoff treatment in field applications.

Temperature- and Salt-Tolerant 2-Acrylamide-2-methylpropanesulfonic Acid/AM@SiO2 Microgel Particles: Synthesis and Enhanced Oil Recovery Performance Evaluation

“…After the injection of 0.5 PV AMPS/AM microgel particles, the resistance factor was 58.05 and 41.04 under the permeability of 509.3 and 3011.2 mD, respectively, and final plugging ratios were 98.28 and 97.56%, respectively. The resistance factor decreases with permeability, which indicated that the resistance of the AMPS/AM microgel particles will decrease in the large pore with high permeability, but it still has a good plugging performance due to the larger seepage resistance caused by the full expansion of the AMPS/AM microgel particles in the small pore with low permeability. , When the permeability was 1039.4 and 3040.6 mD, the plugging ratios were 98.25 and 93.85%, respectively, after the injection of the 0.5 PV AMPS/AM microgel particles with a mass fraction of 0.2 wt %.…”

“…Microgel is one of the profile control agents that can achieve remarkable profile control and EOR performance. The granuliform gel particles can enter the deep part of reservoirs and form a gel swelling body. – In the high permeable area, the large gel expansion body could block the big pore, divert the water flow to the low permeable region, and extend the swept efficiency of water flooding. – The successful application of gel particles has significantly improved the development efficiency of high water-cut reservoirs. – However, there are still some problems faced by profile control treatments using microgel particles. For example, with the migration of microgel, the particles will gradually break up under the extrusion deformation and shear action of heterogeneous porous media, reducing the ability of gel particles to plug the big pore throat. – Therefore, how to improve the mechanical strength of microgel particles and enhance their crushing resistance, achieving both an effective plugging and a deep remigration, has become a challenge.…”

Review of Microgels for Enhanced Oil Recovery: Properties and Cases of Application

“…The authors of the article [ 59 ] studied the matching factor of PPG in coreflooding experiments. Matching factor is the ratio of the PPG’s average diameter to the average pore-throat diameter.…”

Water Control with Gels Based on Synthetic Polymers under Extreme Conditions in Oil Wells

“…After 90 days of exposure under such conditions, the particles did not show signs of degradation maintaining good dispersibility. Core flooding experiments showed a strong plugging effect with 93.13 % of residual resistance for rock cores with 54-100 D permeability [30,72]. AM-based polymeric microgels displayed good stability when exposed to brines of 215 000 ppm (200 000 ppm NaCl + 15 000 ppm CaCl 2 ).…”