Fall 2001 ASME/API Gas Lift Workshop Aberdeen

1. NUMERICAL MODEL FOR THE PREDICTION OF FLUID PRODUCTION AND GAS CONSUMPTION OF GAS CHAMBER PUMPS Fall 2001 ASME/API Gas Lift Workshop Aberdeen

2. Outline • Introduction • Numerical Model • Field Test Facility • Field Test Results • Conclusions

3. Valve 2. open open Valve 1. closed Introduction

4. Valve 2. open Valve 2. open open Valve 1. closed open Valve 1. closed Introduction

5. Introduction

6. Introduction

7. Introduction

8. Introduction • Advantages • Can Handle: gassy & viscous fluids • High Temperatures (stimulation by cyclic steam injection) • Can be run and pulled with wire line equipment • No fallback losses • Completions can be very simple

9. Introduction • Disadvantages • Higher cost in surface controller equipment than in Gas Lift • For complex designs parts are subject to wear and replacement • A High-Pressure gas source is required

10. MAXIMUM LEVEL 80% OF STATIC RESERVOIR PRESSURE 2)Calc. minimum and maximum liquid level MINIMUM LEVEL 3)Calc. column increments 1 2 3 4 ….N 4)For each column calculates the liquid prod. and gas consumption separately Numerical Model General Calculation Algorithm 1)Input data: reservoir, completion,fluid properties, separation & injection pressure

11. Numerical Model Calculation procedure for each column (1,2,3,….n) Model Stages • Column accumulation • Gas Injection • Fluids displacement by gas expansion without injection • Gas Venting • Fluids into the well (Pgas<Pres<Pcas) • No Reservoir inflow (Pres<Pgas<Pcas) • No Reservoir inflow & (Pres<Pcas<Pgas) • Fluid displacement • Gas depressurization No Reservoir inflow (Pres<Pcas<Pgas)

12. no yes Numerical Model Calculation procedure for each column (1,2,3,….n) Liquid Column Accumulation

13. Numerical Model Calculation procedure for each column (1,2,3,….n) All other Stages • System divided in the following control volumes • Gas injection tubing • Liquid chamber+subsurface valve • annulus space • flow line

14. For each C.V. :Continuity, Momentum, Eq. of state, Gas flow through chokes, liquid flow through chokes Conditions at t2: L, Pwf, Pinj, time, gas injected, liquid velocity... Stage check Finishstage Numerical Model Calculation procedure for each column (1,2,3,….n) All other Stages Initial conditions: L, Pwf, Pinj, time, gas injected=0, liquid velocity

15. Test Facility Valve 2. open open Valve 1. closed 2500 ft 3 1/2” tubing R-28 23 API Pressure and temp. sensors

16. Test Program Average liquid column length = 520 ft Gas injection and venting stages

17. Test Results

18. Test Results

19. Test Results

20. Test Results

21. Test Results • Very inefficient completion used for the tests • Very small liquid columns simulating a low producer well • Tests with c-t gave less than 50% of these GLRs

22. Test Results

23. Conclusions • A numerical model was developed for gas chamber pumps • A field scale test program was carried out on gas pumps. • Even though the completion used for the tests was highly inefficient, the injection GLR measured for each test were within the economical limit. • The model predicts the test results within a 10% global accuracy for the operating conditions found during the tests.