Introduction

Crude oil at the wellhead typically consists of water, dissolved salts, gas and sediments in varying quantities. Howe-Baker’s unique experience in the design and supply of process equipment separates the wellstream into its component phases and then to treat each phase.

Howe-Baker’s technology and expertise has been successfully applied from the supply of specialist internals for single vessels, up to and including the design, supply and project management of oil gathering centres onshore and processed topside packages for floating offshore production systems.

Produced crude oil at the wellhead consists of a wellstream containing oil, water, dissolved salts, gas and sediment in varying quantities. Howe-Baker’s unique experience is in the design and supply of process equipment to separate the wellstream into its component phases and then to treat each phase.

Howe-Baker’s technology and expertise has been successfully applied to all sectors of the oil industry, from the supply of specialist internals for single vessels, up to and including the design, supply and project management of oil gathering centres onshore and processed topside packages for floating offshore production systems.

The Oil Treatment Process

The initial step in the oil treatment process is performed by a series of two or three phase separators. Here the pressure is gradually reduced and associated gas and free water, together with the solids are separated and drawn off from the wellstream. This removes the bulk of the water and gas from the oil phase of the wellstream before it passes to the next stage of the process.

The gas stream from the separator can be further treated using Howe-Baker’s range of heaters and filter separators to condition the gas to become a fuel source for turbine use.

The waterstream from the separators can also be further treated by Howe-Baker’s equipment to allow it to be used for water reinjection or to be disposed of.

The next stage of the oil treatment process is to remove the dissolved salts from the oil phase. This is achieved by using electrostatic dehydrator and/or desalter units to produce a stabilised crude oil to meet the end user’s specification.

Two and Three Phase Separators

Howe-Baker International Ltd has many years of experience in designing and supplying single or multi-stage separators for use in oil production schemes.

In order to optimise the initial separation stage and to minimise chemical usage, Howe-Baker in conjunction with independent laboratory studies has refined the design of its separator internals, resulting in an extremely efficient and compact separator design suitable for both onshore and offshore applications.

Having a compact separator design is of particular importance in offshore applications where space is at a premium.

Howe-Baker separators have been used successfully in many applications both onshore and offshore.

Electrostatic Dehydrators and Desalter

In order to remove the maximum amount of free water and therefore dissolved salts from a crude oil stream in the fastest possible time, the crude oil is fed into the dehydrators/desalters using Howe-Baker’s specially designed distribution headers. These are positioned beneath a grid assembly mounted in a pressure vessel where the crude oil stream is subjected to a high voltage electrostatic field in which the water droplets are encouraged to coalesce and separate from the oil. Howe-Baker’s desalter design, spaces and positions the electrical grids to ensure optimum power consumption and maximise the residence time of the crude oil between the grids, thus allowing more time for the water droplets to fall to the bottom of the vessel.

The water which contains the various impurities removed from the crude is continuously discharged into the effluent system for further treatment. Clean, dry crude oil flows from the top of the vessel for export or storage.

The efficiency of an electrostatic desalting system is linked to the intensity of the electrostatic field within the desalter vessel. Typically, a field of 20,000 volts is required. A special feature of all Howe-Baker desalters is the PTB certified power units. These are a special purpose design and are 100% reactive and therefore cannot be overloaded.

This ensures that they remain on line under all conditions thus maintaining the unit’s efficiency.

In refinery operations where the export quality crude may contain up to 100 pounds of salt per thousand barrels of crude, a two-stage desalting operation may be needed to reduce the salt content down to as little as lppm to reduce downstream corrosion and catalyst poisoning. In a two-stage desalting system, wash water can be added to dilute the formation water salinity and the salt content of the dehydrated crude. Howe-Baker’s single stage systems are capable of removing approximately 97% of the inlet salt, whilst two stage systems would be expected to better 99% removal.

Desalters Designs

Howe-Baker has a range of electrostatic desalters and dehydrators designed over many years of practical experience to optimise both process and commercial considerations.  For dry crude flow rates up to 50,000 bopd, the traditional single transformer desalting system with its proven balanced load is often the best choice.

For higher flows, Howe-Baker’s successful AC3™ system is usually selected. This is a unit consisting of three parallel horizontal electrode grids within the vessel; cross connected and supplied by its own power unit. To ensure continuous grid operation throughout the vessel, in the unlikely event of bushing or power unit failure, the spacing and connection of the grids has been optimised in our “deepfield” design to give the highest voltage gradient for the given power units.

The AC3™ design is typically used on throughputs in excess of 50,000 bopd, as it gives a high performance for a given electrode grid area, resulting in a smaller more cost effective pressure vessel for a given oil throughput.

DC Treaters

Our technology can also be used for refining white products, for example Howe Baker’s DC treater has been used on many Shell Merox units for acid neutralisation and the subsequent removal of the aqueous steam to ppm levels. The technology is also applied as part of our modular jet fuel treating units and for NGL dehydration together with specialised applications for removing polar solvents from more exotic process streams. The white products tend to contain low levels of aqueous phase when compared with unrefined crude oils, therefore the application of a DC electric field is most appropriate.

Here a DC system polarises the remaining aqueous phase in a field of typically 40,000 VOLTS to coalesce the water into larger droplets which then fall through the oil to the bottom of the vessel. These units, due to their varied size, can be either vertical or horizontal and are easily skid mounted to form complete process packages.

Associated Equipment

As well as being able to provide equipment to treat the oil phase of a wellstream, Howe-Baker can also design and supply equipment to treat both the gas and water phases.

Howe-Baker has a range of filters and coalescers that can be used to remove liquids and solids from a gas stream, allowing a clean gas stream to be used as fuel for gas turbines in an oil production operation.

Howe-Baker can offer a complete oil treatment system from separators, indirect fired heater, chemical injection packages and crude oil desalters. Howe-Baker heaters are particularly designed to suit stringent environmental regulations and efficient fuel consumption.

Upgrades and Retrofits

All Howe-Baker technologies can also be supplied to upgrade existing vessels. The advantage to the debottlenecking of an existing process vessel, to increase capacity and improve performance is evident considering that the vessels can be returned to service in days rather than the months required to install additional new units.

Howe-Baker has designed and supplied numerous packages which have doubled the capacity of existing separators, whilst at the same time raising separation efficiencies from 30% to 70% and halving operational chemical costs. This is of great benefit to the client where existing vessels can continue in service at an increased capacity.

Similarly, by replacing the internals in an existing desalter with the highly efficient AC3™ specialist internals, allows Howe-Baker to, in some cases, double the throughput that can be handled by an existing desalter.

In Summary

Howe-Baker, with its range of oil treatment, gas treatment and water treatment equipment, are in a unique position to being capable of offering a full oil production train to its customers for use either onshore or offshore.

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