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Surfactant Enhanced Water Flooding

 

        

 

Alkaline Surfactant Polymer and Surfactant Polymer Floods

 

      The oil production from a water flood is limited by geology (heterogeneity) and trapping.  Surfactants, polymers and foams can be used to both reduce trapping and improve sweep efficiency.  At current oil prices this can revitalize a field and generate substantial profit.

       Background - As reservoir engineers know, water is an effective fluid for maintaining reservoir pressure and driving oil towards a producer.  Thus, it is the dominant secondary recovery technique.  However, when the water saturation increases, oil is trapped as capillary forces cause the water to collect at pore throats.  Thus, the water blocks movement of oil. Production declines as more oil becomes trapped.  Surfactants are useful because they reduce capillary forces and free the trapped oil.
 

Figure 1 Interfacial Tension and Capillary Number

 

     Figure 1 illustrates how a surfactant combined with an alkaline chemical such as sodium hydroxide or sodium carbonate reduces interfacial tension and raises the ratio of viscous to capillary forces known as the capillary number.   Oil is trapped when the capillary number is low, at about 10-7.  Oil is released when the capillary number rises to at least 10-3.

     ASP (Alkaline Surfactant Polymer) - The interfacial tension is lowered when a surface-active chemical (surfactant or soap) concentrates at the interface between the oil and water because the chemical has an oil loving part (hydrophobe) and a part that is water soluble (hydrophile).  Adding Alkaline chemicals converts acids in the oil to soaps.  These reduce the interfacial tension and capillary forces.  Then 0.05% to 0.5% of a commercial Surfactant is added to optimize the formula. Often this works well without alkali.  Reservoir sweep is improved by adding a Polymer to the water to increase its viscosity.   The chemicals cost between $2 and $5 per barrel of oil recovered.

 

Figure 2 Oil Production in 1.25-Acre Sho-Vel-Tum ASP Pilot at Duncan, OK

 

  

     Production - Figure 2 shows the production response from a 1.25-acre, 5-spot pilot in a 29-foot sand having 12 layers with permeabilities of 25 to 3,250 md and an average oil saturation of 30%.   The field has been in production since 1910 and under water flood for 45 years with production less than 1 barrel per day of 26 API (41 cp) oil per well.

     Figure 2 shows that production of 41-cp oil from this small shallow pattern doubled in 40 days and increased to 25 bpd in about 1 year.  Fifteen percent of the original oil in place was recovered in less than three years, that is 50% of the viscous residual oil.

A  section (32 hectare) of a 10-meter (33 ft) thick field with 25% residual oil contains almost 1,000,000 barrels of recoverable oil.  If surfactant/polymer and a polymer chase were injected for one and two years respectively (0.3 PV and 0.6 PV) into a  section with 2.5 acre spacing, production could reach 1,000 barrels per day in two years and be completed in five years.  Alternatively, the production could be sustained at 250 bbl per day for a decade if the injection were staged 40 acres at a time.

     These results suggest 50% to 70% of the remaining oil in a field could be recovered in a surfactant enhanced water flood project.  Thus, 4,000,000 barrels of oil could be recovered from each 33-foot (10-meter) thick square mile of a reservoir.

     Surfactant flooding is ideal for shallow fields with small well spacing owned by independents because the technology enhances an existing water flooding and is not difficult to implement. There are reported to be 12 ASP projects underway in the United States and more are operating overseas.  The technology was developed and demonstrated in the 1980s by major oil companies who now own few fields in the United States where the technology can be applied.  Surfactant technology has improved dramatically since then enhancing the economics substantially.

     Economics of ASP - Consider 40 acre, 160 acre and one-section projects (16, 64 and 256 hectares respectively).   These are projects that a small, medium sized or large independent could consider.  Table 1 summarizes cost and profit for 10 meters of net pay.

 

Table 1 Potential Economics of Surfactant Water Flooding Projects

 
 

Acres 

40 

160 

640

Income

$3.74MM

$14.98 MM

$59.9MM

Royality

$0.47MM

$1.87MM

$7.5MM

Chemicals

$0.72MM

$2.88MM

$11.5MM

Operations

$0.80MM

$3.19MM

$12.7MM

Facilities

$0.08MM

$0.25MM

$0.45MM

Engineering

$0.15MM

$0.25MM

$0.45MM

Testing

$0.06MM

$0.12MM

$0.50MM

Overhead

$0.37MM

$2.00MM

$7.0MM

Gross Profit

$1.09MM

$4.48MM

$19.4MM

% Profit

29.1%

29.9%

32.4%

     The table compares the three projects at an oil price of $25/bbl.  It is assumed that equipment is being reused in subsequent projects.  Economies of scale reduce the relative cost of engineering and facilities, so that the larger project could be more profitable.  However, larger projects require more management.  Thus, higher overhead will equalize profits on the projects.

     Projects like this should remain profitable when oil prices are in the $18-$20 range.  The 1984 National Petroleum Council report showed that surfactants could recover approximately 10 billion barrels of oil in the United States. For more information and for help to consider IOR methods for your reservoirs please contact MK Tech Solutions.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

To Discuss Possibilities Please Contact Us At

MK Tech Solutions, Inc. - Houston, Tx - Phone: 281 - 564 - 8851, ASKMKTS@MKTechSolutions.com