Moderate Optimal Salinity with High Sol Ratio. Solubilisation Parameter, ml/ml. Typical band Optimal Salinity, %NaCl

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1 Application of Internal Olefin Sulfonates and Other Surfactants to EOR. Part 2: The Design and Execution of an ASP Field Test. Marten Buijse, Ruth Prelicz, Julian Barnes, Shell, Claudio Cosmo, Salym Petroleum Development

2 West Salym field Western Siberia > 1 bln stb oil in place > 1, stb/day Waterflood Recovery efficiency < 5% selected candidate for ASP Reservoir properties depth = 22 m., zonal thickness = 5-15 m. "dirty" sandstone with clays, permeability = md reservoir temperature = 83ºC crude API density = 3.4, crude viscosity = 2 cp TAN = low (no soaps!)

3 ASP design Surfactant selection General surfactant requirements ultra-low low IFT at low surfactant concentration optimal salinity must match salinity field brine (2-3% NaCl) low rock adsorption anionic surfactants stable at reservoir temperature (83ºC) sulfonates (R-SO 3- ) low emulsion viscosity, no liquid crystals good water solubility cheap Selected: Internal Olefin Sulfonates (IOS) Solubilisation Parameter, ml/ml Moderate Optimal Salinity with High Sol Ratio Typical band IOS IOS 2-24 Low SO3 IOS 2-24 High SO3 IOS Low SO3 IOS High SO3 IOS also see Part 1 paper: SPE Optimal Salinity, %NaCl

4 ASP design Surfactant selection benefits of long surfactant tail Ultra-low low IFT (high solubilization) requires large surfactant oil interaction energy. Preference for surfactants with long/bulky alkyl tails (such as IOS C24-28) 28) oil brine Tail E Tail-Oil Head E Head-Brine E Tail-Oil WR = E Head-Brine Ultra-low IFT: WR = 1 E Tail-Oil and E Head-Brine must be large. E tail-oil (and solubilization) decreases with increasing oil MW. High MW oils benefit from long-tailed surfactants.

5 Surfactant selection and crude oil properties Salym crude oil: average MW is relatively high. Solubilization generally decreases with increasing MW of oil. Heavy components (asphaltenes, naphtenic acids) are often surface active and move to the oil-brine interface. High MW surfactants for improved crude oil compatibility. surface active crude components at interface from Narve Aske, Thesis, 22 SARA analysis Saturates 28.6% Aromatics 53.9% Resins 12.2% Asphaltenes 5.3% C2+ fraction 56.6%

6 Surfactant selection Phase behavior tests oil brine.5% IOS C24-28: long tail, main active surfactant.2% IOS C15-18: 18: increases optimal salinity and improves solubilization 1% SBA: improves solubilization salinity % KCl: %

7 ASP design Laboratory tests Phase behavior tests, to optimize surfactant formulation.5% IOS % IOS % SBA optimum salinity: 1.3% KCl (+ 1% Na 2 CO 3 ) Surfactant solubility tests not ideal, but acceptable at reservoir conditions Polymer selection: temperature stability, viscosity, rheology, filtration and core flow tests 15 ppm Flopaam 323s 3 cp at reservoir conditions Alkali (minimize surfactant adsorption) 1% Na 2 CO 3 Core flow tests for oil displacement efficiency and surfactant adsorption

8 ASP design Core flow tests l or Surfactant % Oil 1% 9% 8% 7% 6% 5% 4% 3% 2% 1% % Oil cut start of emulsion Surfactant Cumulative oil Pore Volumes Produced 36 md Berea, 2" diameter, 12" length recovered 95% of oil remaining after waterflood gravity effects (horizontal core)

9 ASP Single well tracer test How does it work? Injection: Ester (4m 3 ) + Push water (16 m 3 ). Ester partially partitions in oil. Ester Ethanol Shut-in: 3 days. Ester partially hydrolyses to ethanol. Ethanol in water phase. Back production: Ethanol travels faster than ester. Figure 5 EtOH (Product) and EtAc (Cover) Tracers Hypothetical 1-Layer Test Result Result: Ethanol and ester return as separate peaks. Peak distance is used to calculate S or. Concentration EtOH (ppm) EtOH Example Data EtAc Example Data Concentration EtAc (ppm) Produced Volume (barrels)

10 ASP Single well tracer test pump schedule Stage Volume (m3) Rate (m3/day) Comments Waterflood injectivity decline due to skin? Tracer injection penetration depth: 3 m (1 ft) Shut-in 3.5 days Tracer hydrolysis EtAc EtOH Tracer prod. 18 m3 12 KCl preflush Spacer; Remove Ca/Mg. ASP PV, based on tracer vol. Polymer/brine displace ASP Tracer injection Shut-in 4 days Tracer hydrolysis EtAc EtOH Tracer prod

11 ASP Single well tracer test Pressure and rate 3 27 BHTP m3/day or bar Injection rate Start injection ASP. Brine in wellbore. ASP at perfs Finished ASP injection. Start post buffer 12: 16: 2: : 4: 8: 12: Time - hrs

12 ASP Single well tracer test Results Complex (non-ideal) tracer response Can be explained assuming multiple layers + crossflow Concentration EtOH (ppm) EtOH Layer 1 accepted 22% of the tracercarrying fluid. NPA tracer Layer 3 accepted 6% of the tracer-carrying fluid. Best-Fit 3-Layer Model: S or =.23 Layer 2 accepted 18% of the tracer-carrying fluid Produced Volume (m 3 ) Concentration NPA (ppm) Remaining oil saturation reduced from 23% to 2%

13 ASP Single well tracer test. Complex tracer response. Non-ideal tracer response traced back to multiple layers + crossflow. Shut-in. Tracer hydrolysis EtAc EtOH Backproduction. EtOH travels faster than EtAc. Tracer response Conc. EtOH (ppm) no crossflow shut-in, tracer hydrolysis backproduction tracer injection push single peak EtOH and EtAc EtOH Example Data Produced Volume (m 3 ) EtAc Example Data Conc. EtAc (ppm) Concentration EtOH (ppm) low k high k medium k EtAc EtOH with crossflow shut-in, hydrolysis + crossflow backproduction EtOH complex tracer response Layer 1 accepted 22% of the tracercarrying fluid. NPA tracer Layer 3 accepted 6% of the tracer-carrying fluid. Best-Fit 3-Layer Model: Sor =.23 Layer 2 accepted 18% of the tracer-carrying fluid Produced Volume (m 3 ) Concentration NPA (ppm)

14 Conclusions West Salym crude oil has a significant fraction of high MW components that are (partly) surface active and interact with the surfactant at the oil-brine interface. Theoretical considerations suggest the use of surfactants with a long alkyl tail, to maximize interaction energy with oil. In phase behavior tests, high solubilization was observed with a high MW (long tailed) IOS surfactant (IOS C24-28). 28). In core flow tests, the ASP formulation based on IOS recovered 9+% of the oil remaining after waterflooding. A successful ASP test was performed in the field, in which the S or in the near wellbore was reduced by more than 9%

Experiment Studies on N 2 - viscosity Depressant with Steam Stimulation for Shallow Thin Superheavy Oil Reservoirs. Prof.

2 nd World Congress on Petroleum and Refinery Experiment Studies on N 2 - viscosity Depressant with Steam Stimulation for Shallow Thin Superheavy Oil Reservoirs Prof. Renyuan SUN China University of Petroleum