By Jayant Sadare Gas-Lift Optimization and Diagnosis by using Wellflo and Dynalift Simulators By Jayant Sadare & Dr. Faleh T. Al-Saadoon Texas A&M University-Kingsville ASME/API/ISO GAS-LIFT WORKSHOP-2004

Objectives Optimization (Wellflo) Advanced Gas Valve Modeling Diagnosis and Verification (Dynalift) Implementation

Wellflo Simulator (EPS) USES Nodal Analysis for Designing Modeling Optimizing Troubleshooting

Input Data Summary Fluid Properties Well-bore Data - Oil Gravity = 35 deg. API - Water Gravity = 1.03 - Gas Gravity = 0.70 - Produced Gas-Oil Ratio = 50.00 scf/STB - Percent Water (%) = 45 Well-bore Data - Production Casing: 7.000 inch OD × 6.094-inch ID set @ 7100 ft (TVD) - Tubing : 2.875- inch OD × 2.441-inch ID set @6950 ft (TVD) - Well Injection Angle (with vertical) = 0

Contd….. Reservoir Data Gas-Lift Data Reservoir shut-in pressure = 2400 psig @ 7000 ft Reservoir Temperature = 206 deg F Productivity Index (Straight line) = 2.00 STB/day/psi Gas-Lift Data Casing Head Pressure = 1450 psig Operating valve Differential Pressure = 150.00 psi Well-head pressure = 102.5 psig Minimum Valve Spacing = 350 ft Injection Gas Rate = 1.000 MMscf/day

Why Artificial lift??

Continuous Gas Lift design - Point of Injection Specify: - Casing head pressure - GLR or Qgi - Pressure drop across valve Calculates maximum depth of injection and well performance for gas lift Sensitivity to CHP, Qgi, GLR

Inflow / Outflow Performance Curve

Performance Analysis Curve

Pressure and Temperature Vs Depth Analysis

Gas Lift Design - valve spacing for continuous gas lift installations Specify - Casing head pressure - GLR or Qgi - Pressure drop across valve - Kill fluid gradient - Maximum depth - Target operating rate - Design Margins Calculates - depth of unloading and operating valves (IPO/PPO) - Corresponding tubing/casing pressures & temperatures

Gas-Lift Valve Spacing

Advanced Gas Valve Modeling (AGVM) True performance of commercial gas lift valves True operating point of system Sensitivity to valve type, port size, valve settings and gas injection parameters Gas-charged and orifice valve performance

True Valve Performance Curve

Valve Performance Curve For Orifice Valve

Curve Showing Closed Unloading Valve No. 1

Dynalift Simulator (EPS) Dynamic (Unsteady-State) simulation tool for Verification Troubleshooting Learning

Dynamic Gas-Lift Simulation This Dynamic simulator uses all the equations used by a steady-state simulator except it adds the dynamic variable (Time). Uses real correlations to simulate the behavior of gas-lift valves under bottom-hole dynamic conditions. By controlling the injection conditions, the production parameters are observed to define if the design will work with the selected gas-lift valves. More realistic performance can be generated Simulates the system by considering the casing head pressure, gas-injection rate and wellhead pressure at the same time.

Contd…… This Dynamic simulator is an excellent tool for identifying operational problems with gas-lift installations. Also best tool to understand the causes for unstable production conditions which not understood with a steady state simulator It is the best tool for gas lift valves to verify its performance from the unloading operation through all the production life.

Working Screen for Dynamic Simulator

Valve Data Screen

Comparison of Dynamic & Steady-state Performance Curve

Conclusion Combination of Wellflo and Dynalift is one of the best tool for students to understand gas-lift simulation. Advanced Gas Valve Modeling (AGVM) is the heart of steady-state simulation. Do we really need Dynamic Simulation? - Accurately model the well unloading for better design and diagnosis - Minimize unloading time - Accurate valve performance curves - Improve operational procedures

Thank you