Impact of choke valves on the IOR polymer flooding Lessons learned from large scale tests

Transcription

1 Impact of choke valves on the IOR polymer flooding Lessons learned from large scale tests Arne Stavland and Siv Marie Åsen, IRIS; Amare Mebratu, Halliburton; and Flavien Gathier, SNF Presented at the IEA- EOR th Annual Workshop & Symposium, Rueil- Malmaison, September 2016

2 Acknowledgement The authors acknowledge the Research Council of Norway and the industry partners; ConocoPhillips Skandinavia AS, BP Norge AS, Det Norske Oljeselskap AS, Eni Norge AS, Maersk Oil Norway AS, DONG Energy A/S, Denmark, Statoil Petroleum AS, ENGIE E&P NORGE AS, Lundin Norway AS, Halliburton AS, Schlumberger Norge AS, Wintershall Norge AS of The NaYonal IOR Centre of Norway for support.

3 Outline ObjecYve IntroducYon DegradaYon tests Lessons learned

4 Objec?ve Polymer flooding is a promissing IOR method IOR potenyal is reduced by polymer degradayon Will choke valves be compayble with polymer flooding?

5 Polymers Brine Experimental Polymer 5000 ppm NaCl at field- scale 5000 ppm NaCl and SSW at lab- scale Fixed chokes, length of 0.01 to 400 m ID = to 1.75 mm lab- scale ID = 7.94 to 35.1 mm field- scale Standard choke- valves Mw, MDa Tests HPAM, Lab- to field- scale HPAM, Lab- scale ATBS, Lab- scale ATBS, AN125 8 Lab- to field- scale

6 Introduc?on EOR polymers are at lab scale degraded when flooded through capillary tubes DegradaYon mechanism understood by applied shear rate Laminar Hagen- Poiseuille flow Normalized Viscoisity ID = mm ID =.254 mm ID =.127 mm ID = 1.01 mm ID =.760 mm ID =.508 mm E E E E+06 4QR - 3 /π τ w =η γ = ΔP/l R/2 =η 4Q/π R 3 =η 4<v>/R On general form: τ w = f/8 ρ <v> 2 where f=64/re and Re=2<v>R ρ/η

7 Degrada?on is not controlled by pressure, but by applied shear rate 1000 ppm 3630 in 5000 ppm NaCl flooded through mm capillary tubes with length varying from 13.7 to 1500 mm

8 Upscaled ID=0.1 mm, Q = cm 3 /min to ID= 50 mm, Q = m 3 /min

9 Assump?ons Non- Newtonian polymer lowers f basis for drag reducyon, DR= f N f P / f N Re=2<v>R ρ /η Shear thinning polymer; viscosity decreases by increasing shear rate Here η = 2.5 cp Increasing polymer concentrayon supresses Re, lowering τ w /η and less degradayon

10 Upscaled ID=0.1 mm, q = cm 3 /min ID= 100 mm, Q = m 3 /min τ w = f/8 ρ <v> 2 where f=a/ Re 1/4, for Re > 3000 In turbulent regime γ = γ (v,r,ρ,η)

11 Large scale yard test Test matrix Flow rate liter/min 2 different polymers (HMW HPAM 3630 and LMW ATBS AN125) 3 concentrayons (1000, 2000 and ppm) DifferenYal pressure up to 50 bar 5 different choke concepts Fixed brine salinity (0.5% NaCl) IdenYfy feasible choking methods at acceptable degradayon

12 Choke concepts Standard adjustable choke valve (Choke1) Matek choke valve (Choke 2) SNF Linear pressure reducer, LPR, (Choke 3) Fixed choke valve - ID of 20/64 (Choke 4) and 24/64 (Choke 5) Standard adjustable chokes in series

13 Data collec?on

14 Standard adjustable choke (1) The higher the concentrayon the lower the polymer degradayon Note, LMW ATBS only marginally more stable than HMW HPAM

15 Matek Adjustable choke (2) AN AN Choke ppm Degradation before to after choke, % Differential pressure, bar

16 SNF LPR Choke (3) Degradation before to after choke, % AN Differential pressure, bar

17 Summary single chokes Degradation before to after choke, % AN AN AN AN AN Choke ppm Choke ppm Choke ppm ppm Differential pressure, bar Note, fixed chokes, l=0.1 m, behaves similar to standard flexible choke valves Increase choke length or choked concentrayon improves stability

18 Mul?ple chokes

19 Effect of salinity ATBS ATBS (AN125) polymer revealed improved shear stability by increasing polymer- and salt- concentrayon, Effect of salinity can be explained by salt sensiyve [η] Laminar flow through ID = mm and turbulent flow through ID = 1.75 mm

20 Effect of salinity HPAM As for ATBS, improved polymer shear stability by increasing the polymer concentrayon In contrast to ATBS, HPAM (3630) is salt sensiyve; poorer shear stability by increasing salt- concentrayon

21 LMW HPAM 3330 At same polymer concentrayon (1000 ppm) 3630 and 3330 degradayon is similar in low salinity brine At same polymer concentrayon (1000 ppm) 3630 is more degraded than 3330 in SSW At same viscosity, 400 ppm 3630 is more degraded than 1000 ppm 3330, both in low salinity brine and SSW This supports the existence of a criycal overlap concentrayon, which above prevents degradayon

22 On how to minimize polymer degrada?on Increased brine salinity Increased polymer concentrayon

23 Conclusions Choke valves induce differenyal pressure which potenyally degrade polymers, but degradayon is not controlled by differenyal pressure Polymer degradayon at field scale matched experiments at laboratory scale by using applied shear rate as scaling parameter Choke valves are no show stopper for polymer injecyon High concentrated polymer soluyons are less degraded Low pressure gradient choke systems, such as SNF LPR choke or serially mounted standard chokes reduce degradayon However, polymer systems need to be carefully evaluated for degradayon before field implementayon as success depends on it!