seawater injection system Solutions

---

Upstream offshore Oil ang Gas facilities use treated seawater for a broad range of purposes, i.e. for production of potable water, cooling water as well as Enhanced Oil Recovery (EOR). The abundance of seawater in an offshore environment makes it any easy source of water supply for the facility. 

When seawater is being used for EOR, it is injected into the oil reservoir to enhance or maintain crude oil production. This is generally termed Seawater Injection. Depending on the geochemistry of the reservoirs, the seawater must be treated to specific reservoir requirements. Therefore, the seawater process treatment will vary from one facility to the next.  These variations could range from just reduction of Total Suspended Solids (TSS) to reduction of Totals Dissolved Solids (TDS) or reduction of Sulfate Ions. And as is often the case, the capacity of treated seawater required for Injection also varies from location to location. 

The reduction of TSS only processes are primarily conventional systems mostly prevalent in Asia Pacific. Reservoirs offshore Norway, Brazil, West Africa and in the Gulf of Mexico (GoM) require some form of TDS reduction, mostly targeting Sulfate ions. These processes are regarded as Sulfate Reduction Systems and would require the use of Nanofiltration (Sulfate Reduction) membranes to be part of the process. The removal or reduction of Sulfate Ions is performed in order to prevent reservoir scaling and formation of Hydrogen Sulfide (H2S). The reservoir scaling can adversely impact the production of oil whereas H2S will result in severe corrosion of process equipment or pose a health hazard to personnel. 

4M Process Solutions has a team of experienced engineers who are well versed in Seawater Injection Systems from design of conventional systems to more advanced membranes systems. The team has experience encompassing design, startups, commissioning, operation and health maintenance of systems that have been installed in West Africa, Gulf of Mexico, and offshore Brazil.  Our experience includes designs for fixed as well as floating platforms (TLPs, Spars and FPSOs).

4M Process Solutions is not restricted to any particular vendor or supplier.  We will recommend the best solution for your Seawater treatment project. Therefore, our designs are project specific - providing the best solution for each project.   

4M Process experiences extend to every conceivable application whether it is onshore, offshore, or for an FPSO. The company’s wide experience addresses all possible feed waters including seawater, river water, aquifer water and produced water for re-injection.  The following products and services can be offered on a ‘standalone’ basis or as part of a complete system integration. 

In the treatment process train for seawater Injection, the seawater Lift pumps are followed by automatic backflushing strainer to prevent macro fouling of the downstream equipment by capturing and removing fine suspended particles. The system self-cleans automatically without interrupting flow. Several technologies are offered in the industry ranging from basket type to candle or wedge wire type screens. 

Media Filters are generally located downstream of the Coarse Filters in conventional seawater Injection systems. Due to their established reliability when designed and operated properly, they are still being used in today's designs even where advanced membranes are used downstream.  

Media filtration processes take place inside a pressure vessel with treated seawater from coarse strainer entering at the top of the vessel and flowing down through a single or multilayer media bed. By varying the media layers, and the type of media used, 98 percent removal of particles larger than two microns can be achieved.

Media filters are generally supplied as N+1 running in parallel so that one unit can be pulled out to undergo backwashing while the online (N) vessels continue to meet design capacity. This provides uninterrupted flow of filtered water.  

Cartridge Filters technology provides absolute protection of the downstream equipment, especially if Media Filters or Coarse Filters are located upstream. 4M Process has experience in designing Cartridge Filter Packages. Cartridge Filters are often regarded as "guard" filters when used in a seawater treatment process train.

Cartridge filters retain solids on a fixed filtration media that has a restricted pore size. As the solids collect on the cartridge media the resistance to flow (pressure drop) increases until it reaches a point where the cartridges need to be either replaced or backwashed, depending on the design of the system.  In a similar fashion as media filters, the cartridge vessels are generally supplied as N+1 running in parallel so that one unit can be pulled out to undergo cartridge filters replacement or backwashing while the online (N) vessels continue to meet design capacity. This provides uninterrupted flow of filtered water.  

4M Process offers Ultrafiltration (UF) systems design and supply of packaged or module integrated systems. These units may be followed by a Sulfate Reduction or Low Salinity membrane system if the process dictates. The UF pore sizes range from 0.01 to 0.1 micron.  The UF designs can operate in Cross flow or dead-end filtration mode. The UF systems are used primarily to remove suspended solids, bacteria and to reduce turbidity.  In more advanced system they are used in lieu of multi-media filters. Typical membranes used for Ultrafiltration are hollow fiber type either of the Polyether Sulfone (PES) or the PVDF kind. 

In Offshore applications, the Ultrafiltration processes take place inside a pressure vessel with treated seawater from coarse strainer as the feed water. And these applications, generally use the dead-end filtration mode.

4M Process in not tied up to any specific membrane supplier and therefore can specify membrane technology based on customer requirements and projects specifications.

4M Process is able to offer membrane separation solutions incorporating sulfate reduction or Low Salinity technologies. These processes are specified on reservoirs with a high scaling tendency. 

Sulfate reduction and Low Salinity technologies can help solve the scaling and souring problems at source allowing increased productivity and lower operating costs in many areas including:  vertical production wells, gravel packed wells, dilution water in HP/HT environments, horizontal wells with sub-sea backs, floating production systems and reservoir souring control. 

Again, it also important to note here that 4M Process in not tied up to any specific membrane supplier and therefore can specify membrane technology based on customer requirements and projects specifications.

4M Process team of engineers has a vast experience of design and supply of vacuum and gas stripping deaerators.  Vacuum deaeration is the most common deaeration technology in the oilfield, preventing corrosion of downstream equipment and inhibiting aerobic bacterial growth. 

4M Process vacuum strip packed bed deaerator tower designs are performed to ensure a balance between tower and vacuum pump sizes.  The corrosion resistant tower internals maximize mass transfer and give effective distribution and redistribution of the liquid phase. 4M Process vacuum tower solutions also extend to the use on FPSOs where motion is an important factor in the design of towers and internals. 

The gas stripping deaerators also employ packed bed technology. A stream of inert gas flows counter current to the water. The oxygen free gas creates a driving force for mass transfer to deaerate the seawater. 

In addition, 4M Process can work with the customer to implement membrane deaeration technology in a project.

4M Process offers a range of chemical injection packages to suit customer specifications.  A typical package could consist of sodium hypochlorite, ferric sulfate and polyelectrolyte storage and dosing systems to increase filtration efficiency. Other chemicals might include antifoams where the water has a tendency to foam, oxygen scavenger to remove residual dissolved oxygen, scale inhibitors, corrosion inhibitors and biocides to protect subsurface facilities downstream of the deaerator.  Other chemical injections packages may be designed in accordance with Ultrafiltration and Sulfate Reductions process requirements. 

4M Process is fully committed to the successful installation and operation of the water injection system; and most importantly we stand behind our designs. 4M Process Solutions has unequalled experience in long term operational issues and problem solving on water injection equipment. 

4M Process has a dedicated team of commissioning and service engineers, fully experienced in all aspects of equipment operation and maintenance. The commissioning team is backed up by process engineers experienced in site operation, monitoring, analysis and troubleshooting.  4M Process runs training programs, both classrooms based and hands-on for new or existing installations.