Introduction Conceptual gas lift design Variables Pressure GLGIR Water cut Results Conclusion

Transcription

1 Lateef Akanji

2 Introduction Conceptual gas lift design Variables Pressure GLGIR Water cut Results Conclusion 2 2

3 Long string High PI High BHFP Excessive water production Short string Low PI Low BHFP Excessive water production Artificial lift is critical in maximising oil production within the limits of the facility where the rates are constrained by pressure excessive water production available lift gas 3

4 Key variables examined include: gas lift gas injection rate (GLGIR) water cut tubing sizes erosional velocity pressure versus rate 4

5 85ft 7256ft 7160ft 7199ft 7307ft 7506ft 8083ft 8328ft 9857ft 5

6 Table 1 SS LS Casing (10-3/4) MD (ft.) 9953 End of tubing, MD (2-3/8 in.) (ft.) Packer depth, MD (ft.) & 7506 Perforation MD (ft.) Maximum depth for a gas lift mandrel MD (ft.) Reservoir temperature ( o F)

7 Table 2: Fluid properties Variable LS SS o API gravity g w P b (psia) Water cut (%) R p (Scf/STB) R s (Scf/STB) Table 3: Reservoir data Variable LS SS Static pressure ( o F) Temperature ( o F) Liquid, PI (J) (STB/D-psi)

8 FWHT ( o F) FWHP (psig) Sep. press. (psig) Table 4: Production data Variable LS SS Flow line length (ft.) Flow line size ID (in.) Table 5: Well test data Variable LS SS q total (bbl/d) q o (bbl/d) Q w (bbl/d) q p,t q g/ q g,t (%) GLR (scf/bbl) FBHP (psia) FWHT ( o F)

9 Table 6: Gas lift system Variable LS SS P kickoff (psig) P inj (psig) Min valve inj. P (psi) Unloading grad. (psi/ft.) Unloading WHP (psig) g,inj q inj (MMScf/D) q max,inj (MMScf/D) T surf,inj ( o F)

10 IPR equation (Vogel, 1968) q q' P wf P R 0.8 P wf P R 2 q J P res P wf 10

11 11 h g v D M fq c m m m L m h P L g L L m H H 1 Tubing correlation, (Hagedorn and Brown, 1965)

12 V 8 f w c V max f is friction factor ρ is stream density (kg/m 3 ) V is stream velocity (m/s) Ʈ w is shear stress (N/M 2 ) 12

13 l = (1-f ) + o w w f w l = +( - ) f o w o w fw is water cut 13

14 Oil Viscosity (cp) GOR (scf/stb) Fig. 1: PVT plots showing the variation of μ o and R s 14

15 Oil rate STB/D Tubing sizes 2.38" 2.88" 3.5" Gaslift gas injection rate (MMScf/D) Fig. 2: Typical oil rate versus GLGIR for varying tubing sizes of 2-3/8, 2-7/8, 3-1/2 15

16 Oil rate STB/D WC = 0% WC = 10% WC = 50% WC = 80% Gaslift gas injection rate (MMScf/D) Fig. 3: Typical oil rate versus GLGIR at different water-cuts and 2-3/8 tubing. The optimal value is indicated by the arrow. 16

17 Heavier gas requires Lower surface pressure Higher injection rate per barrel of fluid lifted Higher compression horsepower Table 7: Summary of the sensitivity on well A2 performance GLGIR (MMScf/day) Water-cut (%) Tubing size ID (inches) SS LS SS LS SS LS /8 2 3/ / ½ 3 ½

18 Table 8: Sensitivity on well A2 performance SS Water cut (%) Liquid rate (STB/day) Oil rate (STB/day) Pressure (psig) Table 9: Sensitivity on well A2 performance LS Water cut (%) Liquid rate (STB/day) Oil rate (STB/day) Pressure (psig)

19 Pressure (psig) Fig. 4: IPR/VLP plots for SS at 10% WC Fig. 5: IPR/VLP plots for SS at 50% WC Liquid rate (STB/D) Liquid rate (STB/D) 19

20 Pressure (psig) Fig. 6: IPR/VLP plots for LS at 10% WC for tubing sizes of 2-3/8, 2-7/8, 3-1/2 ; the green marks indicate erosional velocity limits Fig. 7: IPR/VLP plots for LS at 50% WC tubing sizes of 2-3/8, 2-7/8, 3-1/2 ; the green marks indicate erosional velocity limits Liquid rate (STB/D) Liquid rate (STB/D) 20

21 Pressure (psig) Pressure (psig) Fig. 8: Performance plots comparison; current and optimal, for the SS Fig. 9: Performance plots comparison; current and optimal, for the LS VLP curve (Optimal) 2500 IPR curve (optimal) 5000 VLP curve (current) 2000 IPR curve (current) IPR curve (Optimal) VLP curve (Optimal) IPR curve (current) VLP curve (current) Oil rate (STB/D) Oil rate (STB/D) 21

22 An accurate dual completion gas-lift simulation model was designed to determine the optimum gas lift gas injection (GLIR ) rate the optimal production rates In the short string production increase of 53% was achieved with an optimum GLGIR of MMScf/Day at the current 50% water-cut production can be further increased by up to a factor of 4 if the water cut can be curtailed In the long string production was increased by 39% with an optimal GLGIR of 1 MMScf/Day at the current 50% water-cut curtailing the water production will further increase the production by up to a factor of 3 22

23 Incorporate the effects of well instabilities associated with casing heading density wave oscillation dynamic mixing (reservoir fluid/ injected gas) Smart gas lift design automatic gas lift mandrel positioning variable intelligent port size 23

24 A. Hagedorn and K. Brown, Experimental Study of Pressure Gradients Occurring During Continuous Two-Phase Flow in Small Diameter Vertical Conduits. Journal of Petroleum Technology Volume 17, Number 4, pages , (1965). J. V. Vogel, Inflow performance relationships for solution gas drive wells. Journal of Petroleum Technology. Volume 20, Number 1 pages (1968). Petroleum Experts Prosper Manual. (2010). Single Well Systems Analysis, Version

25 PTRG PETEX 25

26 THANK YOU 26