THE OIL & GAS INDUSTRY
January 2011
Filtration in the Oil & Gas Industry is as you might expect an area that encompasses many different types of filtration processes very often used in series as part of a staged process each contributing to the end purity required.
This month I will cover some of the processes in which our Bollfilters are used and give an overview of the process.
SEAWATER
One of the principal application for seawater is for injection water, seawater is pumped into the well to boost pressure and aid production and to increase the amount of oil that can be recovered.
As seawater can be corrosive to the well casing and/or elements in the seawater can react with elements in the oil and cause scaling in the reservoir it is necessary to treat the seawater or chemically dose the well. A common form of treatment is a Sulphate Removal Package which involves a number of stages.
Coarse Filters, such as the Boll 6.18, are the first stage normally filtering to 80 micron on the seawater intake to the Injection Water Package removing coarse particles, seaweed/algal blooms to prevent fouling of the plant. The treatment process after the coarse seawater filters involves many different stages from multimedia filters; large vessels containing a "bed" of media - commonly pumice, sand, anthracite or garnet that trap particle between the grains of media.
Multimedia filters are not "block" filters so need cartridge filters downstream to catch any particles, usually throwaway cartridges with 10 micron woven material.
All this pre-treatment is needed before the process of removing the harmful elements can take place. This is done using either Reverse osmosis or Nano-filtration both of which essentially use a semi permeable membrane through which water can pass but the elements suspended in it can't.
CASE STUDY: Lundin
Boll BFD-P Duplex Filters have been installed on the Ikdam FPSO vessel producing the Oudna field in the Gulf of Hammamet offshore Tunisia operated by Lundin Tunisia B, part of Lundin petroleum.
Lundin Petroleum is an independent Swedish oil and gas exploration and production company with an active exploration programme and production assets throughout the world. It currently produces over 30,000 barrels of oil equivalent (boepd) per day and has proven and probable reserves of over 180 million barrels of oil equivalent (mmboe).
Discovered in 1978, production at the Oudna field started in 2006 using the Ikdam FPSO vessel. Due to the very low gas content of the Oudna crude oil, water injection is required to maintain reservoir pressure and to provide reservoir energy.
The high pressure injection pumps for jet pump power fluid necessary to extract the crude oil were experiencing damage from contaminants in the crude oil that is re-injected to boost production. Bollfilter BFD-P Oil Duplex filters with carbon steel pressure vessels were installed to remove the particulates. Designed for the most demanding applications and certified to ASME V111 Div. 1/NACE MR 01-75, BFD-P Filters provide 100% duty and standby, with a high filtration area and solids handling and low differential pressure.
Installation of the Bollfilters solved the problem of damage to the high pressure injection pumps preventing associated production downtime.
PRODUCED WATER
As part of the production of oil and gas, water is produced from the well. Produced water can be naturally occurring formation water or injected water and can hold sand, mud, gas and hydrocarbons which all have to be removed.
For this application, the coarse filters mentioned above are often used at a later stage in the process which itself also requires several stages. Sand and the heavier parts of mud are typically removed by hydrocyclones which use gravitational force to spin out the heavier particles. Gas is settled out of the water and sent to the flare or recycled. Hydrocarbons are extracted from the water by a number of different proprietary products in the form of a multi-media filter bed where the media is used to draw the hydrocarbon from the water or de-oiling hydrocyclones using centrifugal force to separate the liquids of different specific gravity.
It is after these final processes that the coarse filters are used to ensure removal of any remaining harmful solids before the water is reused being fed back into the injection water SRP package.
The 6.18 is also used for diverse applications such a service water, fire main water and utilities water. The 6.18 is specified because of its robust design, precision engineering and reliable operation. The internal working parts are kept to a minimum and only the optimum grade of materials used to ensure efficient and effective operation in the most arduous conditions.
FUEL OIL
Offshore oil & gas installations use a vast amount of power to explore, drill, produce, treat & transport the product to the shore. All this power usually has to be generated on the installations so large diesel engines and turbines are needed. These require fuel, fuel oil which needs to be filtered to protect the injectors and pumps from damage. The Bollfilters type 6.60 & 6.72 are frequently used for this.
LUBRICATING OIL
The generating machinery also requires lubrication for the rotating parts. To ensure smooth operation with minimal wear between the rotating parts the lubricating oil must be filtered to precise levels of fineness. For this the Bollfilters type 6.61, 6.46, 6.64 & BFD are trusted due to their proven track record.
ETHYLENE GLYCOL
Ethylene Glycol is used to dehydrate hydrocarbon gases in dehydration towers where ethylene glycol flows down the tower and meets a rising mixture of water vapour and gas. The water vapour mixes with the glycol and dry gas exits from the top of the tower. The glycol/water mix needs to be filtered and separated before being reused.
GAS
Dry gas seals are used in the offshore industry on many applications involving rotating machinery, typically centrifugal compressors for shaft sealing. The dry gas seal is used in the harsh offshore environment due to its reliability and stability. Compressor discharge gas, reduced to a pressure slightly higher than the process gas, must be filtered to remove particles and traces of liquid.
Our Boll BFD-C duplex filter is used for this important function to ensure complete barrier filtration and coalescing of the seal gas.
As installed on Lundin FPSO, the Boll BFD-P Oil Duplex Filter is available with vessels manufactured from carbon or stainless steel, Duplex or super Duplex.
John Dow can be contacted at:
Bollfilter UK Ltd
Unit 9, Station Road
Tolleshunt D'arcy
Essex CM9 8TY
Tel: 01621 862180
Fax: 01621 869257
E-mail:
john@bollfilter.co.uk
web:
www.bollfilter.co.uk
To view previous issues of John Dow's Filtration Column click on the links below:
