IPTC 14285     Exposure to Phosphate-Based Completion      Brine Under HPHT Laboratory Conditions             Causes Signi...
Alkali metal phosphate brines                         Potassium phosphate brine - K2HPO4/KH2PO4                           ...
Potassium phosphate brine used as completion    fluid by Pertamina, 2008-9 (SPE 139169)    • Used in 5 exploration wells  ...
HPHT laboratory core flooding test with    phosphate brine    The objective of the core flooding test was to find out if  ...
Potassium phosphate brine, 1.637 g/cm3, pH 9.32    - Analysis (by ICP and ion chromatography)                      Analyte...
Cesium formate brine, 2.20 g/cm3, pH 10.5    - Analysis (by ICP and ion chromatography)                           Analyte ...
HPHT core flooding test rig – Corex, Aberdeen7   2011 International Petroleum Technology Conference
HPHT laboratory core flooding test for determining    effect of phosphate brine on gas permeability    Key features of met...
HPHT core flood test with phosphate brine             Test conditions              - 175o C              - 5,800 psi pore ...
HPHT core flood test with potassium     phosphate brine            Core dimensions and properties            Core         ...
Appearance of core face under SEM – before     exposure to brine                                                          ...
Ionic composition of the reservoir water*                   NaCl content of 79,330 mg/l and TDS of 89,260 mg/l            ...
Output of DownHole Sat scale prediction –     phosphate brine mixing with formation water     Red = definite chance of sca...
HPHT core flood testing with potassium     phosphate brine     24-carat gold film wrapped around circumference of core to ...
HPHT humidifier for gas used in core flooding                                                           Dry nitrogen gas e...
HPHT core flood test results with potassium     phosphate brine – Brine injection phase     Pressure development across co...
HPHT core flood test results with potassium     phosphate brine        Drawdown pressure ramping, gas volume throughput   ...
HPHT core flood test results with potassium      phosphate brine – Drawdown flow profile             Gas flow rates and cu...
HPHT core flood test results with cesium      formate brine – Drawdown flow profile             Gas flow rates and cumulat...
Gas flow rate profile during drawdown-Comparison of     cores flooded with phosphate and formate brines20   2011 Internati...
HPHT core flood test results with potassium     phosphate and cesium formate brines            Exposing the core to phosph...
Appearance of core face under SEM – before andafter exposure to phosphate brine and gas drawdown                      Befo...
Appearance of internal surface of core under SEM–     after exposure to phosphate brine and gas drawdown                  ...
Changes in ion content of fluids during HPHT coreflood test with potassium phosphate brine• Calcium and magnesium depleted...
HPHT core flood testing with potassium      phosphate brine                                                Conclusions    ...
HPHT core flood testing with potassium     phosphate brine         Acknowledgement         I would like to acknowledge and...
Upcoming SlideShare
Loading in …5
×

Iptc 14285 Presentation

996 views

Published on

Presentation describes the effects of phosphate brine on the gas permeability of a sandstone core. The results show that phosphate brine reduced gas permeability by more than 90%

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
996
On SlideShare
0
From Embeds
0
Number of Embeds
39
Actions
Shares
0
Downloads
25
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Iptc 14285 Presentation

  1. 1. IPTC 14285 Exposure to Phosphate-Based Completion Brine Under HPHT Laboratory Conditions Causes Significant Gas Permeability Reduction in Sandstone Cores John Downs Cabot Specialty Fluids2011 International Petroleum Technology Conference
  2. 2. Alkali metal phosphate brines Potassium phosphate brine - K2HPO4/KH2PO4 Max density = 1.77 g/cm3 K Phosphate KH2PO4 K2HPO4 pH Density (g/100 g H2O) (%) (%) (g/cm3) 25.19 100 0 4.01 1.15 34.84 75.13 24.87 5.58 1.20 48.12 58.56 41.44 6.19 1.28 73.52 43.18 56.82 6.92 1.40 124.31 28.93 71.07 8.06 1.58 201.89 15.63 84.37 9.51 1.77 173.32 3.24 96.79 10.39 1.72 165.72 0 165.72 10.98 1.72 Also cesium phosphate brine - Cs2HPO4/CsH2PO4 Max density = 2.80 g/cm32 2011 International Petroleum Technology Conference
  3. 3. Potassium phosphate brine used as completion fluid by Pertamina, 2008-9 (SPE 139169) • Used in 5 exploration wells • Fluid density up to 1.67 g/cm3 • HPHT wells up to 335oF, up to 20,000 ppm H2S and 35% CO2 • NPT due to elastomer failures, DST tool failures, tubing connection failures, incompatibility with brines and cements • Formed a film on downhole metal surfaces • No mention of testing for formation damage3 2011 International Petroleum Technology Conference
  4. 4. HPHT laboratory core flooding test with phosphate brine The objective of the core flooding test was to find out if potassium phosphate brine is compatible with sandstone gas reservoirs under HPHT conditions • To determine the effect of potassium phosphate brine invasion on the gas permeability of sandstone under HPHT conditions • To determine the cause/mechanism of any change in the gas permeability of sandstone after exposure to the phosphate brine Use cesium formate brine (a standard HPHT well completion fluid) as a control substance, for comparison4 2011 International Petroleum Technology Conference
  5. 5. Potassium phosphate brine, 1.637 g/cm3, pH 9.32 - Analysis (by ICP and ion chromatography) Analyte in solution Concentration (mg/l) K 248,742 PO4 481,196 Na 131 Cl 96 NO3 45 SO4 45 Ba, Ca, Sr, Mg <1 Pb < 23 Al, Cd, Cu, Hg, Mn, Mo, Ni, Zn <5 Fe < 0.5 Cr 6.1 B 8.15 2011 International Petroleum Technology Conference
  6. 6. Cesium formate brine, 2.20 g/cm3, pH 10.5 - Analysis (by ICP and ion chromatography) Analyte in solution Concentration (mg/l) Cs 1,261,000 K 17,850 Rb 7,621 Na 7,836 Li 1,516 Cl 938 S 201 NO3, SO4, PO4 <5 Ca 14.3 Ba, Sr, Mg <2 Zn 3.4 Al, Cd, Cu, Hg, Mn, Mo, Ni, Cr, Pb <1 Fe 0.08 P 35 B 11.56 2011 International Petroleum Technology Conference
  7. 7. HPHT core flooding test rig – Corex, Aberdeen7 2011 International Petroleum Technology Conference
  8. 8. HPHT laboratory core flooding test for determining effect of phosphate brine on gas permeability Key features of methodology • Clean core, saturate with reservoir water, then centrifuge to irreducible • Measure permeability to gas (30 mD) under HPHT conditions • Forward flow of 10 PV test brine, followed by 48 hour soak period • Realistic drawdown build-up, simulating production start-up • Flow large volume of gas under drawdown to achieve clean-up • Measure permeabilityunder HPHT conditions with humidified gas • Do SEM on core samples to identify source of any damage8 2011 International Petroleum Technology Conference
  9. 9. HPHT core flood test with phosphate brine Test conditions - 175o C - 5,800 psi pore pressure - Clashach sandstone core flooded with North Sea reservoir water and then centrifuged to irreducible saturation Programme - Measure initial permeability to gas at Swi under HPHT conditions - 10 PV flush with test brine at 1 ml/minute - Soak for 48 hours at balance under HPHT conditions - Drawdown ramped up in stages to 100 psi (5,700 psi in wellbore) using 2,000 PV of humidified gas - Measure return permeability to gas under HPHT conditions - Examine core (dry/cryo SEM) for any signs of damage9 2011 International Petroleum Technology Conference
  10. 10. HPHT core flood test with potassium phosphate brine Core dimensions and properties Core Coring Length Volume Pore Porosity Grain Gas sample Depth (cm) (cc) volume (%) density permeability (m) (cc) (g/cc) (mD) #1 n/a 4.78 23.802 2.07 8.7 2.62 27.6 #2 n/a 3.97 19.919 1.98 10.0 2.63 34.0 Core from Clashach sandstone, quarried near Edinburgh, Scotland10 2011 International Petroleum Technology Conference
  11. 11. Appearance of core face under SEM – before exposure to brine High magnification Low magnification Fine/medium grained sand (D50=190µ), with grain-coating and pore-filling illite clay, chlorite, quartz and calcite. Pore throat D50=6 µ (<1 -11 µ range)11 2011 International Petroleum Technology Conference
  12. 12. Ionic composition of the reservoir water* NaCl content of 79,330 mg/l and TDS of 89,260 mg/l Ion concentration (mg/l) Na K Ca Mg Ba Fe Cl HCO3 31,190 300 2,300 350 1,000 10 53,500 610 Principal scaling ions : Ca, Mg and Ba *Simulation of reservoir water from Franklin field (HPHT gas) in UK North Sea12 2011 International Petroleum Technology Conference
  13. 13. Output of DownHole Sat scale prediction – phosphate brine mixing with formation water Red = definite chance of scale formation (calcium and iron products) Phosphate brine in mix (% v/v) Scale 0 16.67 33.33 50 66.67 83.33 100 Calcite CaCO3 0.538 0.0638 0.0223 0.00907 0.00335 < 0.001 0 Aragonite CaCO3 0.401 0.0476 0.0166 0.00676 0.0025 < 0.001 0 Witherite BaCO3 0.0409 0.0484 0.0206 0.00848 0.00285 < 0.001 0 Strontiante SrCO3 0 0 0 0 0 0 0 Magnesite MgCO3 1.16 0.00457 0.00103 < 0.001 < 0.001 < 0.001 0 Anhydrite CaSO4 0 0 0 0 0 0 0 Gypsum CaSO4*2H2O 0 0 0 0 0 0 0 Barite BaSO4 0 0 0 0 0 0 0 Celestite SrSO4 0 0 0 0 0 0 0 Tricalcium phosphate 0 223472 111060 58608 26373 6628 0 Hydroxylapatite 0 2.80E+01 7.30E+09 2.20E+09 5.30E+08 4.90E+07 0 Fluorite CaF2 0 0 0 0 0 0 0 Silica SiO2 0 0 0 0 0 0 0 Brucite Mg(OH)2 2.12 0.00404 0.00139 < 0.001 < 0.001 < 0.001 0 Magnesium silicate 0 0 0 0 0 0 0 Ferric hydroxide Fe(OH)3 254 45.69 24.51 14.92 8.8 4.26 0 Siderite FeCO3 9.07 3.47 1.25 0.508 0.184 0.0409 0 Strengite FePO4*2H2O 0 3.20E+07 2.80E+07 2.10E+07 1.40E+07 6418781 0 Halite NaCl 0.00591 0.0109 0.0171 0.0243 0.0316 0.0334 0 Thenardite Na2SO4 0 0 0 0 0 0 0 Iron sulfide FeS 0 0 0 0 0 0 013 2011 International Petroleum Technology Conference
  14. 14. HPHT core flood testing with potassium phosphate brine 24-carat gold film wrapped around circumference of core to create a barrier to gas diffusion/leakage under hydrothermal conditions Encased with layers of PTFE tape, heat-shrink tubing and an outer Kalrez sleeve before mounting in core holder14 2011 International Petroleum Technology Conference
  15. 15. HPHT humidifier for gas used in core flooding Dry nitrogen gas enters base of humidifier, passes through column filled with high surface area spheres saturated with water, and exits from top. 22.50" Pressure vessel mounted vertically in oven at test temperature/pressure. Materials all in Hastelloy C-276 2.75"15 2011 International Petroleum Technology Conference
  16. 16. HPHT core flood test results with potassium phosphate brine – Brine injection phase Pressure development across core during injection of 10 PV of phosphate brine @ 1ml/min (frontal advance rate of 80 cm/hour) 160.00 140.00 Differential pressure (psi) 120.00 100.00 80.00 60.00 40.00 20.00 0.00 0 2 4 6 8 10 Cumulative brine throughput (pore volumes) Differential pressure did not stabilise16 2011 International Petroleum Technology Conference
  17. 17. HPHT core flood test results with potassium phosphate brine Drawdown pressure ramping, gas volume throughput and stabilised flow rate Drawdown pressure Cumulative gas Cumulative gas Stabilised flow rate (psi) throughput throughput (ml/min) (ml) (PV) 10 150 75.6 0.41 25 500 252 4.24 50 900 454 13.4 75 1700 857 26.0 100 4000 2017 39.717 2011 International Petroleum Technology Conference
  18. 18. HPHT core flood test results with potassium phosphate brine – Drawdown flow profile Gas flow rates and cumulative throughput during the drawdown sequence 45 40 35 30 25 Gas flow rate (ml/min) 20 15 10 DRAWDOWN PRESSURE UP TO 100psi 5 DRAWDOWN PRESSURE AT 100psi 0 0 500 1000 1500 2000 2500 Cumulative gas throughput ( pore volumes) 2,017 PV (4,000 cm3) of gas pulled through core in 566 minutes (118 mins at 50-100 psi drawdown)18 2011 International Petroleum Technology Conference
  19. 19. HPHT core flood test results with cesium formate brine – Drawdown flow profile Gas flow rates and cumulative throughput during the drawdown sequence 400 350 300 Gas flow rate ( ml/min) 250 200 150 100 50 DRAWDOWN PRESSURE UP TO 100psi DRAWDOWN AT 100psi 0 0 500 1000 1500 2000 2500 Cumulative gas throughput ( pore volumes) 1,931 PV (4,000 cm3) of gas pulled through core in 23 minutes (11 minutes at 50-100 psi drawdown)19 2011 International Petroleum Technology Conference
  20. 20. Gas flow rate profile during drawdown-Comparison of cores flooded with phosphate and formate brines20 2011 International Petroleum Technology Conference
  21. 21. HPHT core flood test results with potassium phosphate and cesium formate brines Exposing the core to phosphate brine reduced its permeability to gas by > 90% Completion brine Test Initial Final Change in system Temperature Permeability permeability permeability (oC) (mD) (mD) (%) Phosphate 175 10.2 0.86 -91.6 Formate 175 23.0 24.8 +7.821 2011 International Petroleum Technology Conference
  22. 22. Appearance of core face under SEM – before andafter exposure to phosphate brine and gas drawdown Before test After test Sand grains and pore throats covered in blanket of phosphate scale after test EDS analysis of the scale shows potassium, phosphorus, sodium and chloride22 2011 International Petroleum Technology Conference
  23. 23. Appearance of internal surface of core under SEM– after exposure to phosphate brine and gas drawdown Retained phosphate scale coating onto area of illite clay23 2011 International Petroleum Technology Conference
  24. 24. Changes in ion content of fluids during HPHT coreflood test with potassium phosphate brine• Calcium and magnesium depleted, both in wellbore fluid and filtrate. PO4 levels reduced . Suggests precipitation and/or scaling onto surfaces• Sodium and chloride also depleted (> x 40 diluted) in filtrate• pH of filtrate dropped from 9.7 to 8.75 after passage through core• Phosphate brine picked up 9-35 mg/l each of Cr, Fe, Ni and Mo during test Analyte Concentration in fluid (mg/l) Formation Phosphate Wellbore fluid Filtrate fluid water brine post-test post-test PO4 3.8 481,196 449,911 438,250 Na 31,265 131.7 < 195 <195 Cl 51,341 96.3 57.9 72.6 Ca 2,050 <1.0 <2.7 < 2.4 Mg 337 0.3 2.2 0.92011 International Petroleum Technology Conference
  25. 25. HPHT core flood testing with potassium phosphate brine Conclusions • Flooding a sandstone core with potassium phosphate brine under HPHT conditions reduced its gas permeability by > 90% after clean up by 2,000 PV drawdown. • SEM/EDS analysis of core samples indicates that the main cause of formation damage was phosphate scale formation blocking pore throats - Scale deposits concentrated on surfaces coated with illite clay - Reduced levels of Ca,Mg, PO4, Na and Cl in fluids post-test • Flooding a similar core with cesium formate brine under same HPHT conditions resulted in a slight improvement in permeability • Precipitation of phosphates onto mineral surfaces is a well-known phenomenon, and is the desired result of scale inhibitor squeezes25 2011 International Petroleum Technology Conference
  26. 26. HPHT core flood testing with potassium phosphate brine Acknowledgement I would like to acknowledge and thank Ian Patey, Murdo Munro and the laboratory staff of Corex in Aberdeen who planned, managed and executed the experimental programme described in this paper26 2011 International Petroleum Technology Conference

×