Gas hydrate crystallisation: from laboratory to pilot plant tests A. Sinquin Institut Français du Pétrole
HYDRATES Water salted or not Production lines + Hydrocarbon phase(s) 2 High pressure and /or low temperature gas liquid 2 Hydrate formation region P (bar) 1 1 CH4 Plug formation -1-1 1 2 2 T ( C) Natural gas Dissociation curve Nucleation workshop. June 17-19th 23, St Etienne, France 2
Industrial context A major problem for the deep offshore production Platform 2 m X X X wellhead Pipeline Riser Sea bed Gaz Condensat Plug formation Hydrates Nucleation workshop. June 17-19th 23, St Etienne, France 3
Experimental approach Systems Kinetic inhibitor formulations in water Anti agglomerant additive in condensate Scale up From laboratory to pilot plant From simplified systems to real systems Experimental apparatus Semi batch reactor Laboratory loop Pilot loop Nucleation workshop. June 17-19th 23, St Etienne, France 4
Semi batch reactor Command PID CH 4 N 2 FR P Réf. N 2 DP T P RP PR Pressure regulator P Pressure sensor T Temperature probe FR Flow rate regulator DP Differential Pressure gauge COOLING FLUID Nucleation workshop. June 17-19th 23, St Etienne, France
Semi batch reactor Volume: 2 L Constant pressure Decreasing temperature Working pressure: 7 bar Stirring rate: 6 or 8 rpm Nucleating agent: sand 2% wt Temperature ( C) 2 2 Exothermicity due to the hydrate formation Cum. Gas cons. (moles) 1.2 1 Semi batch reactor limitation: - cooling system Data: - Induction time - Temperature of hydrate formation - Initial rate of gas consumption at the hydrate formation - Cumulated gas consumption 1 1 Induction time Temperature ( C) m.cons. (moles) Initiale rate of gas cons. 2 4 6 8 1 12 Time (sec) Nucleation workshop. June 17-19th 23, St Etienne, France 6.8.6.4.2
Laboratory loop G PR Gas circulation Liquid circulation Sapphire Cell P T T G A S DP PUMP Fl COOLING FLUID PR Pressure regulator G Gas flow meter P Pressure sensor T Temperature probe Fl Mass flow meter (liquid) DP Differential Pressure gauge Nucleation workshop. June 17-19th 23, St Etienne, France 7
Laboratory loop Int. diameter: 7 mm Length: 1 m Liquid saturated by gas Maximum pressure 1 bar Decreasing temperature Working pressure: 7 bar Liquid flow rate 11 Kg/h Laboratory loop limitations: - viscosity of the fluid - water cut: 1 to 1% vol. Data measured for KHI: - induction time - temperature of hydrate formation - Plugging time - water to hydrate conversion Data measured for anti-agglomerant: - induction time - temperature of hydrate formation - water to hydrate conversion - flow rate and pressure drop evolution vs time - shut-in/restart in presence of hydrates Nucleation workshop. June 17-19th 23, St Etienne, France 8
Pilot Loop P Cooling Loop COLD PLANTS Separator tank FT Window DP FT DP WAX DEPOSITION SECTION Window P Liquid Moineau Pump FT P Window P D P LOW POINT SECTION Gas FT Toward Cold Plant Compressor Compressor Vapor HEAT EXCHANGERS Gas Reserve Water Nucleation workshop. June 17-19th 23, St Etienne, France 9
Pilot Loop Diameter: 2 ( cm) Length: 14 m gas velocity 1 to 6 m/s Liquid velocity.2 to 3 m/s FT FT g P T DP Vortex flow meter (gas phase) Mass flow meter (liquid phase) Gamma ray densitometers (multiphase flow line) Pressure sensor Temperature probe Differential Pressure gauge Nucleation workshop. June 17-19th 23, St Etienne, France 1
Results KHI Semi batch reactor Température ( C) Cons.cum (l) KHI Additives Temp. Form. ( C) Induction time (min.) -@Tmin- 2 1.2 Pure water 7.1 126 -- 2 1 KHI 1 2. 168 -- 1.8 KHI 2 2. 39 -- KHI 3 1. 24-33- 1.6.4.2 1 1 2 2 3 3 4 Temps (mn) Nucleation workshop. June 17-19th 23, St Etienne, France 11
Results KHI Laboratory flow loop Water +.3%wt KHI 3 Gas: CH4, Flow rate: 11 kg/h, 7 bar Additive Temp. Form. ( C) Induction time (min) 2 2 Température ( C) Cons.cum (l) DBt (kg/h) Dp (mbar) Dp/DBt * 1 1 8 Blank (water) 9.8 (8.7-1.7) 29 1 1 6 4 KHI 3 2.2 (2.-2.3) 11 2 2 4 6 8 1 12 14 16 Temps (mn) Temp. Form.: 2.3 C Induction time: 11 min. Gas consumption: 37.3 L plugging time: 98 min. Nucleation workshop. June 17-19th 23, St Etienne, France 12
Results KHI Température ( C) 2 2 1 1 EAU PURE Hydrate formation 1 8 6 4 2 Conv. (%) Experimental conditions: pressure: 7 barg hydrodynamic conditions: stratified flow Gas flow rate 21 m 3 /h; liquid flow rate = m 3 /h Fluids tested water + domestic gas* + KHI.2.4.6.8 1 t (hr) * gas composition varies from one test to another Subcooling ( C) -2-4 -6-8 -1-12 KHI 3 KHI 1 KHI 2-14 -16-1 1 2 3 4 6 Concentration (ppm) Nucleation workshop. June 17-19th 23, St Etienne, France 13
KHI conclusions Pure water KHI 4, 4 3, 3 2, subcooling 16 14 12 1 8 + +33 + KHI 1 KHI 2 KHI3 2 1, 1, 6 4 2 reactor lab. loop pilot loop reactor lab. loop pilot loop 1- No direct link between subcooling obtained in the reactor and the two loops even if a nucleating agent is used in the reactor 2-Tests performed in the lab loop and the pilot loop are very similar despite the change of flow regime and gas composition 1-KHI additive classification is possible and consistent in the experimental set up as long as the induction and subcooling are taking account in the reactor. 2- Performances of KHI 3 in the lab loop and the pilot loop are directly comparable. Nucleation workshop. June 17-19th 23, St Etienne, France 14
Results AA Dispersant or AA additive W/O Emulsion Dispersion Semi batch reactor Temperature 3 / 7 3 / 7 (+dispersant) Cumulated gas consumption 3 / 7 3 / 7 (+dispersant) 2 2. System Temp. Form. ( C) Induction time (min.) Blank 6.1 119 AA.1 14 Temperature ( C) 1 1 2 1. 1. Cumulated gas consumption (moles) - 1 1 2 2 3 Time (min) AA additive in water + condensate (3/7 %) Nucleation workshop. June 17-19th 23, St Etienne, France 1
Results AA Laboratory loop Condensate/water (9/1); AA 1.%wgt Gas: CH4, Flow rate: 11 kg/h, 7 bar System Blank Temp. Form. ( C) Induction time (min.) 9.1 (1.7-8.7) 2 2 1 1 Température ( C) Cons.cum (l) DBt (kg/h) Dp (mbar) Dp/DBt * 1 4 3 2 AA 8.4 (8.-8.1) 3 1 1 1 2 2 3 Temps (mn) Temp. Form.: 8.4 C Induction time: 3 min. water to hydrate conversion: 62% 24 hours Circulation => OK Shut in: 3 hours Restart => OK Nucleation workshop. June 17-19th 23, St Etienne, France 16
Results AA Water/Condensate (3/7) +.8% AA Pilot loop 2 2 1 1 T ( C) Conv (%) Hydrates formation T 11. C 1 1 2 t (hr) 1 8 6 4 2-2 2 2 1 1 T ( C) Conv (%) Hydrates formation T 11.9 C 1 1 2 t (hr) 1 8 6 4 2-2 Liquid flow 1.3 m/s 2 2 1 1 T ( C) Conv (%) Hydrates formation T 11. C 1 1 2 t (hr) Slug flow vl = 1 m/s vg = 1 m/s 1 8 6 4 2-2 Stratified flow vl =.3 m/s vg = 2. m/s Nucleation workshop. June 17-19th 23, St Etienne, France 17
Condensate + water 7 6 4 3 2 1 reactor lab. loop pilot loop Blank AA AA slug AA strat AA conclusions 1- Hydrate formation is obtained at higher subcooling in the reactor even if a nucleating agent is used 2-As long as a stable emulsion is made -> the subcooling is increased (size of the reactor = size of the droplet) -> this emulsion effect decrease with the apparatus size and is negligible in the pilot loop 3- With a condensate/water/aa, no flow regime effect is seen 7 1- In the reactor hydrate formation is easier to achieve without hydrocarbon phase 2-In the pilot loop no difference between water and water + condensate is seen. 6 4 3 2 1 H2O H2O/cond reactor lab. loop pilot loop Nucleation workshop. June 17-19th 23, St Etienne, France 18
Conclusions In all apparatus and with all systems, a residual subcooling is measured. The nucleation effect decreases from the reactor to the pilot plant. For the systems presented, constant nucleation effect in the pilot plant. Classification of different KHIs possible in all experimental set-ups. Evaluation of maximum subcooling only in the loops. Difficulties to evaluate the time of maximum protection at a given subcooling, even in the pilot loop. Better reproducibility of the formation temperature with AA additive, especially in the reactor. Nucleation workshop. June 17-19th 23, St Etienne, France 19