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) (Wellflo)

Advanced Gas Valve ModelingAdvanced Gas Valve Modeling

Diagnosis and Verification (Dynalift)Diagnosis and Verification (Dynalift)

ImplementationImplementation

Wellflo Simulator (EPS)Wellflo Simulator (EPS)

USES Nodal Analysis for

Designing

Modeling

Optimizing

Troubleshooting

Input Data Summary Fluid Properties

- 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

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 continuousgas 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 heartof 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