High-Viscosity Polymer Injection for Enhanced Oil Recovery in West Texas

Case Study 2: High-Viscosity Polymer Injection for Enhanced Oil Recovery in West Texas

Scenario

An EOR (Enhanced Oil Recovery) operation near Midland, TX, injects a partially hydrolyzed polyacrylamide (HPAM) solution (3,200 cP at shear rate 10 s⁻¹) into a high-pressure injection well. The polymer solution must be metered at 18.3 m³/h under a fixed pressure drop of 4.2 bar across the control valve — dictated by upstream booster pump discharge and downhole packer pressure. Ambient desert temperatures (up to 45°C) reduce viscosity slightly but require material compatibility verification. Corrosion risk from trace H₂S mandates duplex stainless steel construction.

Given Data

• Flow Rate: 18.3 m³/h
• Pressure Drop: 4.2 bar
• Fluid Density: 1012 kg/m³ (dilute HPAM solution)
• Specific Gravity: 1.012
• Viscosity: 3200 cP

Calculation

Using the Control Valve Sizing Calculator:

• Inputs: flow_rate=18.3, pressure_drop=4.2, fluid_density=1012, specific_gravity=1.012, viscosity=3200
• Initial Cv calculation (non-viscous assumption):
  $$ C_v = \frac{18.3}{\sqrt{4.2 / 1.012}} \approx \frac{18.3}{2.04} \approx 8.97 $$
• However, the calculator detects viscosity > 1000 cP and activates laminar/turbulent transition correction per ISO 5167 Annex D. It computes Reynolds number:
  $$ Re = \frac{3160 \cdot Q \cdot SG}{\nu \cdot d} \quad \text{(using estimated d = 1.5")} \Rightarrow Re \approx 210 \ll 2300 $$ Confirming laminar flow regime.
• The tool applies viscous Cv correction:
  $$ C_{v,\text{visc}} = C_v \cdot \left( \frac{Re}{1000} \right)^{0.33} \approx 8.97 \cdot (0.21)^{0.33} \approx 8.97 \cdot 0.59 \approx 5.3 $$
• Based on corrected Cv = 5.3 and laminar-flow valve curves, the tool recommends a 1.5-inch valve — verified against manufacturer data for eccentric plug valves optimized for high-viscosity service (e.g., Cv = 5.8 at 100% opening for 1.5" class 300 duplex trim).

Result and Decision

A 1.5-inch class 300 duplex stainless steel (UNS S32205) eccentric rotary plug valve with low-shear profile was procured and commissioned. Field testing confirmed stable modulation from 10–100% stroke with <±2% flow deviation and zero plugging over 6 months of continuous operation.

Lesson

For fluids with viscosity > 500 cP, always enable and validate the calculator’s viscous flow correction — neglecting Reynolds-number-based derating leads to severe undersizing, erratic control, and premature valve failure due to excessive shear-induced polymer degradation.