Economics of treating emulsions

The objective of operating oil producing properties is consistently to deliver the maximum volume of highest API gravity oil to the pipeline at the lowest possible cost. Emulsions should be prevented wherever feasible and, when unpreventable, should be treated at the lowest cost.

Implementation

Implementing the following nine directives can minimize the occurrence and treatment cost of emulsions:

Eliminate production of water

Eliminate production of water with oil where possible and practical.

Minimize the investment in emulsion treating equipment

By studying the treating problem and selecting appropriate treating methods, equipment, and procedures. The emulsion treating system should be as small as possible, yet capable of adequately handling treating requirements on the lease. A treating system may be oversized initially to allow for:

• future development
• lease expansion
• increased water production

Such future needs may be anticipated when purchasing treating equipment; however, a needlessly oversized system incurs unnecessary expense and accomplishes nothing more than a properly sized system does.

Minimize oil loss

Where feasible, minimize the amount of oil that is lost with discharged water, and salvage oil from interfacial sludge and tank bottoms. Oil might be discharged with the water as it flows from:

• Free Water Knock Outs (FWKOs)
• emulsion treaters
• gun barrels
• other treating vessels

The fraction of oil is low, and the oil usually is dispersed in small droplets. Sometimes this oil is pumped with the water to disposal wells or delivered to operators of water disposal companies without recovery or without being credited to the lease. Such oil loss can be minimized by maintaining proper operating variables with adequately sized and maintained vessels and controls and by properly designed water-treating systems.

Minimize chemical treating costs

Minimize chemical treating costs by using:

• the most appropriate chemical demulsifier compound(s)
• the optimum quantity of chemical
• the proper location and method of injection of chemical
• the proper means of intimately mixing chemical with emulsion
• the proper use of heat
• the low shear valves and low shear pumps to minimize emulsification

Treatment chemicals are not recoverable and are an ongoing expense. Some crude oil can be adequately treated by use of chemical injection with coalescence and/or settling without heat; however, some emulsions require an increased temperature during the coalescing and settling period. A proper balance of chemical and heat helps to provide the most economical and efficient treating system. The chemicals must be intimately mixed with emulsion so that a minimum amount of chemical will provide maximum benefit. Chemicals can be wasted by being injected into the oil in large slugs, rather than being intimately mixed with the emulsions.

Use compatible chemical fluids

Ensure that chemicals added to the produced fluids are compatible. Some corrosion inhibitors can cause emulsions or affect the action of oil-treating chemicals. Chemicals used in produced-water-treating systems might be recycled to the oil-treating system with the skimmed oil and cause emulsion-treating problems there.

Conserve oil

Conserve gravity and volume of oil by:

• using the optimum treating temperature
• cooling the oil before discharging it to storage
• discharging vent gases from treating vessels through cooler oil in stock tanks
• maintaining slight gas pressure on treating-system and storage tanks
• using vapor-recovery equipment on vessels and tanks

Resolve crude-oil emulsions at the lowest effective temperature. Excessive heat drives condensable vapors from the oil, and they are discharged with the gas. Loss of these light ends lowers the American Petroleum Institute (API) gravity of the oil and simultaneously reduces the oil volume. A further disadvantage of overheating is the increased maintenance on treating systems that is caused by:

• hot spots
• salt deposition
• scaling
• increased corrosion rate, especially of the fire tubes

Use equipment fully

Use all treating equipment to the best advantage. The emulsion-treating equipment can be used to maximum efficiency with constant and careful:

• observation
• testing
• supervision
• record keeping

Transferring equipment and making alterations or additions to the treating system can enable more effective use of existing equipment.

Preventive maintenance

Practice preventive maintenance to minimize irretrievable loss of oil production because of downtime for equipment repairs. The more complex the treating system, the greater the possibility of mechanical failure. Oversized and overly complex systems have a greater failure frequency than do more-appropriately designed, simpler, and more-compact systems.

Exchange information

Exchange information on treating methods and results among company personnel and with:

• other operators
• engineering firms
• vendors
• chemical-treating companies

Sharing such experience among personnel who are responsible for handling treating problems will lead to lower treating costs.

Cost records

Cost records are important in oil emulsion-treating operations. Achieving optimum operation of emulsion-treating equipment at minimum cost requires keeping proper records of the following:

• operating temperatures
• pressures
• fuel and/or power consumption
• chemical usage
• performance
• etc.

Such records should be kept on a daily, weekly, or monthly basis, and should be reviewed regularly and made available for supervisory personnel.

Cost records are important for determining whether an existing system should be modified or should be replaced. Which of these is justified will depend on the efficiency of the system, which is determined using accurate and reliable cost and performance records. Cost records on existing methods or systems assist in determining the type and size of treating systems for new leases.

Treatment costs

Treatment cost records should make it possible to determine:

• current operating costs
• probable installation costs for new systems
• probable future operating costs of similar systems

Each operator determines what is to be charged to emulsion-treating costs. Table 3.6 outlines items that may be considered part of the database for a cost-accounting system. Some of these items will not apply to all treating systems, and some operators will elect to group some of the categories. A comprehensive general listing is given for those who wish to consider all items of cost. Special systems and conditions might require additional cost items.

Complete and accurate treatment cost records must consider all factors listed in Table 3.6.

Equipment costs

Equipment investment costs must include the initial cost of all equipment used, including the costs of transporting it to the location and erecting and installing it, and of readying the system for operation. It also includes such items as:

• pipe and pipe fittings
• valves
• grade work
• foundations
• fencing

Labor costs

The labor costs should include:

• supervisory personnel
• cost of company and contract labor
• other labor required to obtain, install, and put into operation the treating system

Operating costs

Operating costs should be kept separately from maintenance costs and should include such items as:

• supervisory labor
• operating labor
• chemicals
• fuel
• miscellaneous supplies

Maintenance costs

Maintenance costs should include the cost of maintaining and repairing all treating equipment, e.g.:

• cleaning
• repairing
• painting

Overall system performance

The overall system performance section of the record should include an accurate record of the volume of oil treated and the volume of water separated, treated, and handled. This part of the record also should include reference to troubles experienced with the system, as well as a commentary on day-to-day performance of the unit or system.

References

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Noteworthy papers in OnePetro

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External links

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See also

PEH:Emulsion Treating

Emulsion treating subsystems

Emulsion treating methods

Operational considerations of emulsion treating

Desalting