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[[In-situ combustion]] requires standard field equipment for oil production, but with particular attention to air compression, ignition, well design, completion, and production practices.  
[[In-situ_combustion|In-situ combustion]] requires standard field equipment for oil production, but with particular attention to air compression, ignition, well design, completion, and production practices.


== Compressors ==
== Compressors ==
Air-compression systems are critical to the success of any in-situ combustion field project. Past failures often can be traced to poor compressor design, faulty maintenance, or operating mistakes. See [[Compressors]] for a detailed discussion of compressors and sizing considerations. Other discussions are available in Sarathi.<ref name="r1" />


The factors to be considered when selecting compressors include peak air requirements, injection pressure, capital cost, power requirements, operation and maintenance costs, and other relevant technical and economic parameters specific to the field considered. Compressor terminology varies among manufacturers. It is best to obtain a complete description including compressor, driver, interstage cooling system, and all ancillary equipment, including control and safety systems from each vendor being consulted.  
Air-compression systems are critical to the success of any in-situ combustion field project. Past failures often can be traced to poor compressor design, faulty maintenance, or operating mistakes. See [[Compressors|Compressors]] for a detailed discussion of compressors and sizing considerations. Other discussions are available in Sarathi.<ref name="r1">Sarathi, P. 1999. In-Situ Combustion Handbook Principles And Practices. Report DOE/PC/91008-0374, OSTI ID 3175 (January).</ref>


Air compression causes high temperatures because of the large heat capacity (''c''<sub>''p''</sub>/''c''<sub>''v''</sub> ratio). Compressor design must consider these high temperatures to ensure continuous, sustained operations free from the corrosive effects of air and the explosion hazards of some lubricating fluids. Mineral oils are not recommended. Synthetic lubricants withstand the higher temperatures and offer lower volatility and flammability than conventional lubricants.  
The factors to be considered when selecting compressors include peak air requirements, injection pressure, capital cost, power requirements, operation and maintenance costs, and other relevant technical and economic parameters specific to the field considered. Compressor terminology varies among manufacturers. It is best to obtain a complete description including compressor, driver, interstage cooling system, and all ancillary equipment, including control and safety systems from each vendor being consulted.
 
Air compression causes high temperatures because of the large heat capacity (''c''<sub>''p''</sub>/''c''<sub>''v''</sub> ratio). Compressor design must consider these high temperatures to ensure continuous, sustained operations free from the corrosive effects of air and the explosion hazards of some lubricating fluids. Mineral oils are not recommended. Synthetic lubricants withstand the higher temperatures and offer lower volatility and flammability than conventional lubricants.


== Ignition ==
== Ignition ==
Ignition and maintenance of high combustion temperatures, especially in heavy oil projects, are the most critical factors of an in-situ combustion project. Shallcross<ref name="r2" /> presented a complete review of ignition methods. The following is a summary of this study.


Ignition can occur spontaneously if the oil is reactive, the reservoir temperature is high enough, and the reservoir is reasonably thick. Various models have been proposed to determine the time for spontaneous ignition.<ref name="r3" /><ref name="r4" />  
Ignition and maintenance of high combustion temperatures, especially in heavy oil projects, are the most critical factors of an in-situ combustion project. Shallcross<ref name="r2">Shallcross, D.C. 1989. Devices and Methods for In-Situ Combustion Ignition. Report No. DOE/BC/14126-12 (DE 89000766). Washington, DC: US Dept. of Energy.</ref> presented a complete review of ignition methods. The following is a summary of this study.


When spontaneous ignition does not occur or is not desired (i.e., in heavy oil reservoirs, where it is important to maintain high combustion temperatures), the most appropriate ignition method depends on the reservoir and the equipment available on site.  
Ignition can occur spontaneously if the oil is reactive, the reservoir temperature is high enough, and the reservoir is reasonably thick. Various models have been proposed to determine the time for spontaneous ignition.<ref name="r3">Burger, J.G. 1976. Spontaneous Ignition in Oil Reservoirs. SPE Journal 16 (2): 73-81. SPE-5455-PA. http://dx.doi.org/10.2118/5455-PA</ref><ref name="r4">Tadema, H.J. and Weidjeima, J. Spontaneous ignition of oils. Oil & Gas J. 68 (50).</ref>


Downhole gas-fired burners allow good control of the temperature of injected gases and may be operated at a greater depth than other methods. The disadvantages include the need to run multiple tubing strings in the injection wells. Some particulates such as soot may be carried into the formation if the gas does not burn cleanly.  
When spontaneous ignition does not occur or is not desired (i.e., in heavy oil reservoirs, where it is important to maintain high combustion temperatures), the most appropriate ignition method depends on the reservoir and the equipment available on site.


Catalytic heaters run at lower temperatures but are sometimes prohibitively expensive. Electrical heaters can be lowered with a single cable, can provide excellent temperature control, and can be reused repeatedly. There is, however, a depth limitation because of electrical power losses in the cable.  
Downhole gas-fired burners allow good control of the temperature of injected gases and may be operated at a greater depth than other methods. The disadvantages include the need to run multiple tubing strings in the injection wells. Some particulates such as soot may be carried into the formation if the gas does not burn cleanly.


Chemically enhanced ignition does not have a depth limitation but may require handling and storage of dangerous materials. Fuel packs are not recommended because of poor temperature control and nonuniform ignition across the entire reservoir thickness. Well damage from elevated temperatures and plugging by particulate matter may occur.  
Catalytic heaters run at lower temperatures but are sometimes prohibitively expensive. Electrical heaters can be lowered with a single cable, can provide excellent temperature control, and can be reused repeatedly. There is, however, a depth limitation because of electrical power losses in the cable.


Steam may be used to locally increase reservoir temperature and facilitate auto ignition. It suffers from depth limitation because of wellbore heat losses, but when the conditions are right, it can be a very simple and effective method for ignition.  
Chemically enhanced ignition does not have a depth limitation but may require handling and storage of dangerous materials. Fuel packs are not recommended because of poor temperature control and nonuniform ignition across the entire reservoir thickness. Well damage from elevated temperatures and plugging by particulate matter may occur.
 
Steam may be used to locally increase reservoir temperature and facilitate auto ignition. It suffers from depth limitation because of wellbore heat losses, but when the conditions are right, it can be a very simple and effective method for ignition.


== Well design and completions ==
== Well design and completions ==
Wells used in in-situ combustion must be designed to account for several factors amplified by the combustion, namely high temperature, corrosive environment, and sand and clay control. Safe operations should be the primary concern.


Typical well designs for injection and production are shown in '''Figs. 1 and 2'''. Completion type and design depends on the reservoir being considered. Laboratory testing for [[sand control]] and completions can help to determine the best completion technique for a given field. Care must be taken to [[Cementing operations|cement]] the wells properly. There are [[Cement composition and classification|cement formulations]] that are stable at high temperatures.<ref name="r5" /> Openhole completions may be used in conjunction with slotted liners, screens, gravel packs, or various other sand and clay control methods. To maximize productivity, producing wells should be completed toward the bottom of the zone of interest to take advantage of gravity drainage and avoid hot gases as long as possible. [[Glossary:Rat hole|Rat holes]] have been used successfully in certain heavy oil combustion projects to increase the effect of gravity drainage.<ref name="r6" />  
Wells used in in-situ combustion must be designed to account for several factors amplified by the combustion, namely high temperature, corrosive environment, and sand and clay control. Safe operations should be the primary concern.
 
Typical well designs for injection and production are shown in '''Figs. 1 and 2'''. Completion type and design depends on the reservoir being considered. Laboratory testing for [[Sand_control|sand control]] and completions can help to determine the best completion technique for a given field. Care must be taken to [[Cementing_operations|cement]] the wells properly. There are [[Cement_composition_and_classification|cement formulations]] that are stable at high temperatures.<ref name="r5">Smith, D.K. 1976. Cementing, Vol. 4. Richardson, Texas: Monograph Series, SPE.</ref> Openhole completions may be used in conjunction with slotted liners, screens, gravel packs, or various other sand and clay control methods. To maximize productivity, producing wells should be completed toward the bottom of the zone of interest to take advantage of gravity drainage and avoid hot gases as long as possible. [[Glossary:Rat_hole|Rat holes]] have been used successfully in certain heavy oil combustion projects to increase the effect of gravity drainage.<ref name="r6">Ramey, H.J.J., Stamp, V.W., Pebdani, F.N. et al. 1992. Case History of South Belridge, California, In-Situ Combustion Oil Recovery. Presented at the SPE/DOE Enhanced Oil Recovery Symposium, Tulsa, Oklahoma, 22–24 April. SPE-24200-MS. http://dx.doi.org/10.2118/24200-MS</ref>


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== Injection and production practices ==
== Injection and production practices ==
Safe air injection requires that the surface injection equipment and the injection well are free of hydrocarbons. All lubricants used in compression and downhole operations should be synthetic or nonhydrocarbon types. All of the following must be clean and hydrocarbon free:
Safe air injection requires that the surface injection equipment and the injection well are free of hydrocarbons. All lubricants used in compression and downhole operations should be synthetic or nonhydrocarbon types. All of the following must be clean and hydrocarbon free:
*Equipment
*Equipment
*Tools
*Tools
Line 43: Line 48:
*Injection strings
*Injection strings


Personnel at all levels should be aware of the importance of preventing hydrocarbons in the injection wells. As a safety measure to protect injection wells if the compressor is shut down, a system to prevent backflow of oil from the formation must be present at every injection well.  
Personnel at all levels should be aware of the importance of preventing hydrocarbons in the injection wells. As a safety measure to protect injection wells if the compressor is shut down, a system to prevent backflow of oil from the formation must be present at every injection well.


Downhole temperatures in producing wells increase as displaced oil, hot water, and steam fronts reach the well. Producers are preserved by downhole cooling and proper material selection. '''Fig. 3''' provides an estimate of the water requirements to maintain bottomhole temperature no higher than 250°F as a function of oil and water production rate and formation flowing temperature. Significant additional oil recovery can be obtained from hot wells with downhole cooling, especially if the well is completed in the lower section of the producing zone to maximize gravity segregation in the reservoir. In many cases, after the combustion front has moved through the well, it is possible to convert the former producer to a new air injector, thus realizing significant cost reductions over the life of the project.  
Downhole temperatures in producing wells increase as displaced oil, hot water, and steam fronts reach the well. Producers are preserved by downhole cooling and proper material selection. '''Fig. 3''' provides an estimate of the water requirements to maintain bottomhole temperature no higher than 250°F as a function of oil and water production rate and formation flowing temperature. Significant additional oil recovery can be obtained from hot wells with downhole cooling, especially if the well is completed in the lower section of the producing zone to maximize gravity segregation in the reservoir. In many cases, after the combustion front has moved through the well, it is possible to convert the former producer to a new air injector, thus realizing significant cost reductions over the life of the project.


<gallery widths="300px" heights="200px">
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Line 51: Line 56:
</gallery>
</gallery>


Monitoring is crucial for proper combustion operations. In addition to testing individual producers for oil and water rates, injected fluids must be measured. Also, produced gases must be measured and analyzed to determine the efficiency of the combustion operation. Downhole temperature measurements are essential to calculate the size and location of the burned zone. Flowline temperatures can indicate thermal stimulation or downhole problems.  
Monitoring is crucial for proper combustion operations. In addition to testing individual producers for oil and water rates, injected fluids must be measured. Also, produced gases must be measured and analyzed to determine the efficiency of the combustion operation. Downhole temperature measurements are essential to calculate the size and location of the burned zone. Flowline temperatures can indicate thermal stimulation or downhole problems.


Combustion projects generate waste water, flue gases, and pollutants from compression and oil-handling equipment. Local pollution disposal regulations must be consulted before designing any in-situ combustion operation.  
Combustion projects generate waste water, flue gases, and pollutants from compression and oil-handling equipment. Local pollution disposal regulations must be consulted before designing any in-situ combustion operation.


In general, environmental problems are similar to those posed by steam injection. The produced water may contain H<sub>2</sub>S and/or CO<sub>2</sub>, which may require special handling and anticorrosion equipment. Flue gases may contain hydrocarbons, H<sub>2</sub>S, CO<sub>2</sub>, CO, and other trace amounts of sulfur gases. '''Table 1'''<ref name="r1" /> summarizes the various pollution-control systems suitable for combustion projects and their recommended applications. Sarathi<ref name="r1" /> also provides detailed descriptions of the various types of systems and their uses. Other problems that can be encountered are sand production, corrosion, emulsions, well failures, and compressor failures.
In general, environmental problems are similar to those posed by steam injection. The produced water may contain H<sub>2</sub>S and/or CO<sub>2</sub>, which may require special handling and anticorrosion equipment. Flue gases may contain hydrocarbons, H<sub>2</sub>S, CO<sub>2</sub>, CO, and other trace amounts of sulfur gases. '''Table 1'''<ref name="r1">Sarathi, P. 1999. In-Situ Combustion Handbook Principles And Practices. Report DOE/PC/91008-0374, OSTI ID 3175 (January).</ref> summarizes the various pollution-control systems suitable for combustion projects and their recommended applications. Sarathi<ref name="r1">Sarathi, P. 1999. In-Situ Combustion Handbook Principles And Practices. Report DOE/PC/91008-0374, OSTI ID 3175 (January).</ref> also provides detailed descriptions of the various types of systems and their uses. Other problems that can be encountered are sand production, corrosion, emulsions, well failures, and compressor failures.


<gallery widths=300px heights=200px>
<gallery widths="300px" heights="200px">
File:Vol5 Page 1392 Image 0001.png|'''Table 1'''
File:Vol5 Page 1392 Image 0001.png|'''Table 1'''
</gallery>
</gallery>


==References==
== References ==
<references>
 
<ref name="r1">Sarathi, P. 1999. In-Situ Combustion Handbook Principles And Practices. Report DOE/PC/91008-0374, OSTI ID 3175 (January).</ref>
<references />
<ref name="r2">Shallcross, D.C. 1989. Devices and Methods for In-Situ Combustion Ignition. Report No. DOE/BC/14126-12 (DE 89000766). Washington, DC: US Dept. of Energy. </ref>
 
<ref name="r3">Burger, J.G. 1976. Spontaneous Ignition in Oil Reservoirs. ''SPE Journal'' '''16''' (2): 73-81. SPE-5455-PA. http://dx.doi.org/10.2118/5455-PA </ref>
== Noteworthy papers in OnePetro ==
<ref name="r4">Tadema, H.J. and Weidjeima, J. Spontaneous ignition of oils. ''Oil & Gas J''.  '''68''' (50). </ref>
<ref name="r5">Smith, D.K. 1976. ''Cementing'', Vol. 4. Richardson, Texas: Monograph Series, SPE. </ref>
<ref name="r6">Ramey, H.J.J., Stamp, V.W., Pebdani, F.N. et al. 1992. Case History of South Belridge, California, In-Situ Combustion Oil Recovery. Presented at the SPE/DOE Enhanced Oil Recovery Symposium, Tulsa, Oklahoma, 22–24 April. SPE-24200-MS. http://dx.doi.org/10.2118/24200-MS </ref>
</references>


==Noteworthy papers in OnePetro==
Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read
Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read


==External links==
== External links ==
 
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro


==See also==
== See also ==
[[Laboratory studies of in-situ combustion]]
 
[[Laboratory_studies_of_in-situ_combustion|Laboratory studies of in-situ combustion]]
 
[[In-situ_combustion|In-situ combustion]]


[[In-situ combustion]]
[[Predicting_behavior_of_in-situ_combustion|Predicting behavior of in-situ combustion]]


[[Predicting behavior of in-situ combustion]]
[[Predicting_performance_of_in-situ_combustion|Predicting performance of in-situ combustion]]


[[Predicting performance of in-situ combustion]]
[[PEH:In-Situ_Combustion]]


[[PEH:In-Situ Combustion]]
[[Category:5.4.6 Thermal methods]]

Revision as of 11:56, 9 June 2015

In-situ combustion requires standard field equipment for oil production, but with particular attention to air compression, ignition, well design, completion, and production practices.

Compressors

Air-compression systems are critical to the success of any in-situ combustion field project. Past failures often can be traced to poor compressor design, faulty maintenance, or operating mistakes. See Compressors for a detailed discussion of compressors and sizing considerations. Other discussions are available in Sarathi.[1]

The factors to be considered when selecting compressors include peak air requirements, injection pressure, capital cost, power requirements, operation and maintenance costs, and other relevant technical and economic parameters specific to the field considered. Compressor terminology varies among manufacturers. It is best to obtain a complete description including compressor, driver, interstage cooling system, and all ancillary equipment, including control and safety systems from each vendor being consulted.

Air compression causes high temperatures because of the large heat capacity (cp/cv ratio). Compressor design must consider these high temperatures to ensure continuous, sustained operations free from the corrosive effects of air and the explosion hazards of some lubricating fluids. Mineral oils are not recommended. Synthetic lubricants withstand the higher temperatures and offer lower volatility and flammability than conventional lubricants.

Ignition

Ignition and maintenance of high combustion temperatures, especially in heavy oil projects, are the most critical factors of an in-situ combustion project. Shallcross[2] presented a complete review of ignition methods. The following is a summary of this study.

Ignition can occur spontaneously if the oil is reactive, the reservoir temperature is high enough, and the reservoir is reasonably thick. Various models have been proposed to determine the time for spontaneous ignition.[3][4]

When spontaneous ignition does not occur or is not desired (i.e., in heavy oil reservoirs, where it is important to maintain high combustion temperatures), the most appropriate ignition method depends on the reservoir and the equipment available on site.

Downhole gas-fired burners allow good control of the temperature of injected gases and may be operated at a greater depth than other methods. The disadvantages include the need to run multiple tubing strings in the injection wells. Some particulates such as soot may be carried into the formation if the gas does not burn cleanly.

Catalytic heaters run at lower temperatures but are sometimes prohibitively expensive. Electrical heaters can be lowered with a single cable, can provide excellent temperature control, and can be reused repeatedly. There is, however, a depth limitation because of electrical power losses in the cable.

Chemically enhanced ignition does not have a depth limitation but may require handling and storage of dangerous materials. Fuel packs are not recommended because of poor temperature control and nonuniform ignition across the entire reservoir thickness. Well damage from elevated temperatures and plugging by particulate matter may occur.

Steam may be used to locally increase reservoir temperature and facilitate auto ignition. It suffers from depth limitation because of wellbore heat losses, but when the conditions are right, it can be a very simple and effective method for ignition.

Well design and completions

Wells used in in-situ combustion must be designed to account for several factors amplified by the combustion, namely high temperature, corrosive environment, and sand and clay control. Safe operations should be the primary concern.

Typical well designs for injection and production are shown in Figs. 1 and 2. Completion type and design depends on the reservoir being considered. Laboratory testing for sand control and completions can help to determine the best completion technique for a given field. Care must be taken to cement the wells properly. There are cement formulations that are stable at high temperatures.[5] Openhole completions may be used in conjunction with slotted liners, screens, gravel packs, or various other sand and clay control methods. To maximize productivity, producing wells should be completed toward the bottom of the zone of interest to take advantage of gravity drainage and avoid hot gases as long as possible. Rat holes have been used successfully in certain heavy oil combustion projects to increase the effect of gravity drainage.[6]

Injection and production practices

Safe air injection requires that the surface injection equipment and the injection well are free of hydrocarbons. All lubricants used in compression and downhole operations should be synthetic or nonhydrocarbon types. All of the following must be clean and hydrocarbon free:

  • Equipment
  • Tools
  • Lines
  • Tubing
  • Work strings
  • Injection strings

Personnel at all levels should be aware of the importance of preventing hydrocarbons in the injection wells. As a safety measure to protect injection wells if the compressor is shut down, a system to prevent backflow of oil from the formation must be present at every injection well.

Downhole temperatures in producing wells increase as displaced oil, hot water, and steam fronts reach the well. Producers are preserved by downhole cooling and proper material selection. Fig. 3 provides an estimate of the water requirements to maintain bottomhole temperature no higher than 250°F as a function of oil and water production rate and formation flowing temperature. Significant additional oil recovery can be obtained from hot wells with downhole cooling, especially if the well is completed in the lower section of the producing zone to maximize gravity segregation in the reservoir. In many cases, after the combustion front has moved through the well, it is possible to convert the former producer to a new air injector, thus realizing significant cost reductions over the life of the project.

Monitoring is crucial for proper combustion operations. In addition to testing individual producers for oil and water rates, injected fluids must be measured. Also, produced gases must be measured and analyzed to determine the efficiency of the combustion operation. Downhole temperature measurements are essential to calculate the size and location of the burned zone. Flowline temperatures can indicate thermal stimulation or downhole problems.

Combustion projects generate waste water, flue gases, and pollutants from compression and oil-handling equipment. Local pollution disposal regulations must be consulted before designing any in-situ combustion operation.

In general, environmental problems are similar to those posed by steam injection. The produced water may contain H2S and/or CO2, which may require special handling and anticorrosion equipment. Flue gases may contain hydrocarbons, H2S, CO2, CO, and other trace amounts of sulfur gases. Table 1[1] summarizes the various pollution-control systems suitable for combustion projects and their recommended applications. Sarathi[1] also provides detailed descriptions of the various types of systems and their uses. Other problems that can be encountered are sand production, corrosion, emulsions, well failures, and compressor failures.

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Sarathi, P. 1999. In-Situ Combustion Handbook Principles And Practices. Report DOE/PC/91008-0374, OSTI ID 3175 (January).
  2. Shallcross, D.C. 1989. Devices and Methods for In-Situ Combustion Ignition. Report No. DOE/BC/14126-12 (DE 89000766). Washington, DC: US Dept. of Energy.
  3. Burger, J.G. 1976. Spontaneous Ignition in Oil Reservoirs. SPE Journal 16 (2): 73-81. SPE-5455-PA. http://dx.doi.org/10.2118/5455-PA
  4. Tadema, H.J. and Weidjeima, J. Spontaneous ignition of oils. Oil & Gas J. 68 (50).
  5. Smith, D.K. 1976. Cementing, Vol. 4. Richardson, Texas: Monograph Series, SPE.
  6. Ramey, H.J.J., Stamp, V.W., Pebdani, F.N. et al. 1992. Case History of South Belridge, California, In-Situ Combustion Oil Recovery. Presented at the SPE/DOE Enhanced Oil Recovery Symposium, Tulsa, Oklahoma, 22–24 April. SPE-24200-MS. http://dx.doi.org/10.2118/24200-MS

Noteworthy papers in OnePetro

Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read

External links

Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro

See also

Laboratory studies of in-situ combustion

In-situ combustion

Predicting behavior of in-situ combustion

Predicting performance of in-situ combustion

PEH:In-Situ_Combustion