Technology. Mechanism IEA EOR Workshop & Symposium Aberdeen, th October BP plc September 2010

Transcription

1 Application Understanding of Bright the LoSal Water Technology Mechanism 21 IEA EOR Workshop & Symposium Aberdeen, 182 th October 21

2 LoSal Mechanism Outline of Presentation The Benefit Outline the conditions that the LoSal EOR Mechanism must satisfy The evidence showed that modifying these conditions alters the LoSal recovery Explain the LoSal EOR Mechanism of oil release and relate this to brine chemistry Review the evidence that the process works at scale

3 osal EOR Evidence: econdary Core Flood Type Response Comparison of Res Con Oil Production Low Salinity Oil Plateau Extension ppm 125 ppm.5 25 ppm High Salinity Oil Plateau PV OIL Prod % SFW 2% SFW 5% SFW PV Inj When low and high salinity secondary corefloods are compared the low salinity produces significantly more dry oil before water breakthrough

4 LoSal Mechanism : Conditions to be satisfied Mechanism has to explain: The need for the presence of connate brine The need for polar compounds in the oil The need for the presence of active clay minerals Why the LoSal brine needs to have a divalent cation concentration < than that of the connate brine Why the LoSal brine needs to have a TDS below a certain value That LoSal EOR works in both acidic and basic conditions Why LoSal does not work in a purely monovalent ionic brine system

5 The first three needs Work by Tang and Morrow using berea core with crude oil and reservoir brine The presence of connate brine If connate brine was not present, secondary low salinity flooding gave no additional recovery Polar compounds in the oil If kerosene is used instead of crude oil, secondary low salinity flooding gave no additional recovery The presence of active clay minerals If the berea core was fired and acidised, secondary low salinity flooding gave no additional recovery Tang, G. and Morrow, N.R., "Influence of Brine Composition and Fine Particles on Crude Oil/Brine/Rock Interactions and Oil Recovery," Journal of Petroleum Science and Engineering, (Dec., 1999), Vol. 24, pp.99111

6 The presence of active clay minerals 3 Well Tests & 1 Core SWCTT 2 18 LoSal AdRec, AdRec, % Pore % Pore Volume Vol CORE SWCTT 1 SWCTT 3 Clay content

7 Effect of salinity & divalent ion concentration: SWCTT Results Increase in recovery only occurs if the LoSal TM brine has a concentration of Ca 2 and Mg 2 lower than the connate brine The salinity is below a threshold (ca. 7, ppm TDS) Divalent ratio = [2 ions in injection water]/[ 2 ions in connate water] 14 Total salinity Additional recovery % Additional recovery, % Divalent ratio Salinity, TDS Salinity, TDS

8 Effect of divalent cation presence % Recovery 1% 9% 8% 7% 6% 5% 4% 3% 2% 1% High salinity NaCl brine after total removal of all divalent ions and with NaCl brine Low Salinity Brine Injection Started No Additional Recovery Observed Increase in oil recovery only after removal of all divalent ions Base line recovery with the core containing Ca 2 and Mg 2 and high salinity brine % Pore Volume of Water Injected % of oil recovered with no Ca and Mg present on the mineral surface (high and low salinity) % of oil recovered with Ca and Mg present on the surface(high salinity only) Lager et al; Low Salinity Oil Recovery An Experimental Investigation," SCA26

9 Evidence for divalent ion interactions 25 7 Corefloods show adsorption of Ca and Mg on surface during a secondary LoSal flood Similar behaviour is seen at field scale Chloride concentration (ppm) Chloride Mg Magnesium concentration (ppm) Pore volume MPU LPad Data.5 Base Mg (mol//) /17/25 5/28/25 9/5/25 12/14/25 3/24/26 7/2/26 1/1/26 1/18/27 4/28/27 8/6/27 11/14/27

10 Effect of acidic & basic conditions Incremental LoSal recovery is not correlated to crude oil acid no. The best results obtained so far for LoSal was with an oil with an acid number of ca Increase in oil recovery % Acid Number

11 ph changes during low salinity flooding ph can rise or fall during a low salinity flood with no correlation to incremental recovery A LoSal effect was observed while the ph stay in the acidic region is a strong evidence that the mechanism involve is not due to alkaline ph ph ph pressure drop Pressure drop, psi Formation brine flooding Dilute brine flooding (HW): ph Values for Low Salinity Water Flood ph pressure drop Injected brine, PV Pressure drop, psi ph 5 1 ph Formation brine flooding Dilute brine flooding Pore Volumes Injected brine, PV

12 Elements of the proposed mechanisms Dominant mechanisms Cation bridging Expansion of Electrical Double Layer Ion Exchange/surfactant desorption Cation exchange is fast and dependent on clay concentration. Could account for ph changes seen in some corefloods Recognising that other mechanisms almost certainly can be present and may be important under some conditions and with some rocks

13 LoSal Mechanism : Oil Release Chemistry Multiple Component Ion Exchange (MIE) Multiplecomponent cations act as bridges between the negatively charged molecules in the oil and the negatively charged clay surface. OIL OIL OIL In an oilwet systems, multivalent cations at a clay surface (eg kaolinite) will bond to polar compounds present in the oil phase. When these cations transfer between the low salinity brine and the clay surface to satisfy the equilibrium condition, the link between the oil and the clay is broken and bound oil becomes movable C O O Ca 2 O Clay Cation bridging C O O Ca 2 O Clay Ligand bridging C O O H H O Mg 2 O Clay Water bridging Breaking the Divalent Bond

14 LoSal TM Mechanisms: Role of the double layer High Salinity Brine Clay Divalent Ion Diffuse Layer Polar molecule Low Salinity Brine Clay Access to the divalent ions is blocked by the tightly packed ions in a high salinity environment This is known as the double layer The double layer expands with reducing salinity reaching the point where the monovalent ions can access the relevant divalent ones

15 Impact of Salinity and Divalent Concentration on Water Thickness Similar trends in water layer thickness as for the sand like system. The variation in water size for monovalent cations appears broadly less than for divalent ions. Exchange of divalent ions for monovalent ions at low concentration can significantly enhance the thickness of the water layer at the mineral surface Thickness (A) M.1 M.1 M 7 5 LiCl NaCl KCl MgCl2 Ca Cl2 Na2SO4 MgSO4 Fitted water layer thickness summary for the Ludox AM ( Clay Like ) system. Lee et al; Low Salinity Oil Recovery Increasing Understanding of the Underlying

16 Other mechanisms Fines migration Possible if the ionic strength of the brine is equal or lower than the critical flocculation concentration (CFC) typically below what we have for LoSal No evidence in BP corefloods either from direct observation of the effluent or any increase in Al concentration Carbonate dissolution Kinetically limited and dependent on Ca concentration If it occurs, it is after majority of oil has been produced

17 Summary of Coreflood & SWCTT Data Coreflood All reservoir clastic systems studied at reservoir conditions with reservoir fluids show benefit. 2% to about 4%benefit (over high salinity recovery) SWCTT All the reservoirs show a positive response to LoSal. Variation of results for same reservoirs Consistent with reservoir condition corefloods 2 15% decrease in Sor

18 Endicott lowsalinity EOR pilot Low Salinity Waterflooding works at scale. Mixing did not affect the lowsalinity EOR process at scale. Viscous fingering of lowsalinity water into the oil bank was not evident. Lowsalinity EOR works as predicted: Right Time.lowsalinity breakthrough marks start of drop in watercut Right Size volume in agreement with corefloods and single well tracer tests Right Shape profile overlays the coreflood (scaled for clay content). fw fw Analytical hisal extrapolation red eye.e 5.E5 1.E6 1.5E Incremental Oil Recovery, fraction PV Scaled up Coreflood Based on water cut meter Based on separator tests Total Fluid Produced, stb PV of Low Salinity Water Injected

19 LoSal Mechanism : Conclusion The proposed mechanism can explain the evidence for the controls on improved recovery during a low salinity flood There is strong evidence that it works at scale Core SWCTT field trial

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21 Backup

22 osal Mechanism : DVLO Theory Mechanism Organic functional group involved According to the extended DLVO theory, 8 different possible mechanisms of organic matter adsorption onto clay minerals are possible depending upon the chemistry (functional groups) of the organic matter and the condition of the clay surfaces. Of these 8 mechanisms, 4 will be strongly affected by cation exchange occurring during the injection of LoSal water: cation exchange, ligand bonding (exchange), and cation and water bridging. Cation exchange Water bridging Cation bridging Ligand exchange Protonation Anion exchange amino, ring NH, Heterocyclic N (aromatic ring) Amino, Carboxylate, carbonyl, alcoholic OH Carboxylate, amines, carbonyl, alcoholic OH carboxylate amino, heterocyclic N, carbonyl, carboxylate carboxylate Hydrogen bonding Amino, carbonyl, carboxyl, phenolic OH Van der Waals interaction Uncharged organic units

23 The need for the presence of connate brine Berea Core Low Salinity Brine Reservoir Brine Tang, G. and Morrow, N.R., "Influence of Brine Composition and Fine Particles on Crude Oil/Brine/Rock Interactions and Oil Recovery," Journal of Petroleum Science and Engineering, (Dec., 1999), Vol. 24, pp.99111

24 The need for polar compounds in the oil Berea Core Low Salinity Brine Reservoir Brine Tang, G. and Morrow, N.R., "Influence of Brine Composition and Fine Particles on Crude Oil/Brine/Rock Interactions and Oil Recovery," Journal of Petroleum Science and Engineering, (Dec., 1999), Vol. 24, pp.99111

25 The need for the presence of active clay minerals Fired/Acidized Berea Core Low Salinity Brine Reservoir Brine Tang, G. and Morrow, N.R., "Influence of Brine Composition and Fine Particles on Crude Oil/Brine/Rock Interactions and Oil Recovery," Journal of Petroleum Science and Engineering, (Dec., 1999), Vol. 24, pp.99111