Water plays an important role in oil drilling operations, both during the extraction process and in supporting activities. Two key factors for the management of this element in upstream operations are the use of ‘injection water’ and the resulting output of ‘produced water’. In both scenarios, appropriate filtration is necessary to remove contaminants to ensure efficient operation of oil processing equipment and meet strict environmental standards for water disposal.
During drilling, pressure in the well drops as the oil is initially released and recovered. To maintain the pressure, water is injected into the well to displace the oil and push it to the surface. The water used can be taken from rivers, lakes, the sea, or even from a previously used source, so pollutants must be removed. A lack of adequate filtration can lead to ineffective operations, corrosion of equipment and failure to comply with environmental legislation.
Filtration of injection water for efficient operations
If the water is unfiltered, it can contain suspended solids, microorganisms, dissolved chemicals or other residues – all of which can severely impact oil reservoirs, processing equipment, and the quality of the produced oil. In the reservoir, particulates and bacteria can plug pore spaces, reducing permeability and fluidity of oil flow, and injectivity of the water itself. This can lead to lower oil recovery and premature water breakthrough, whereby the water reaches the production wells too early, thereby reducing the efficiency of the oil extraction. Chemical pollutants can also cause scale layers to form, further blocking oil flow paths and shortening the life of the reservoir.
For processing equipment, inadequately filtered water accelerates corrosion, causes rust and leads to the formation of sludge, which clogs filters and reduces lubrication efficiency. This results in increased wear, frequent equipment failures, and higher maintenance costs. Water contamination also promotes microbial growth, leading to biofouling and further corrosion.
In terms of oil quality, contaminants in injection water can cause oil-water emulsions, making separation more difficult and reducing oil purity. Metals and dissolved organic material may degrade the oil quality and increase downstream processing costs.
Effective operations in offshore drilling
Some older types of filtration, such as strainers, separators and disposable cartridge filters, are no longer regarded as providing an optimal service, as one of our customers found. A Ghana-based oil company had been using another filtration supplier’s equipment to remove sulphates from seawater used for injection in offshore drilling but needed to reduce its operational costs. With five drilling vessels in service, 20 elements per housing and an average filter life of three weeks, the company required a more effective and economic option.
We provided advanced high-flow filtration systems with an average service life of 52 days – nearly 2.5 times longer than their previous supplier. Our units’ laid-over pleat design increased the filtration surface, thereby enhancing operational efficiency and reducing the Silt Density Index (a measure of particulate contamination) to 1.15 compared to 2.21 with the previous solution. An index figure below 5 is required to prevent equipment fouling. As a result of installing our units, filter change-out frequency and disposal of waste decreased, thereby reducing operational costs.
The challenges of meeting oil-in-water standards
In oil drilling, produced water refers to the water that comes out of the well along with the oil. It is a byproduct of the extraction process and typically makes up the largest volume of waste. Depending on the level of filtration that has been used during the injection phase, produced water can contain salts, chemicals, heavy metals, microorganisms and radioactive materials. It must be filtered and treated to remove pollutants and minimise any potential toxicity, whether for reinjection into the oil reservoir, reuse in another sector (such as agriculture) or disposal via evaporation ponds.
The Middle East oil industry is subject to increasingly strict environmental regulations on produced water discharge. Operators must meet oil-in-water (OIW) limits typically ranging from 10 to 40 mg/L (10-40ppm), with some jurisdictions enforcing even lower thresholds.
Produced water volumes can reach 50,000 barrels per day (332 m³/hr), often at high temperatures (75 °C / 167 °F) and average pressures of 3.45 barg (50 psig). Under these conditions, conventional treatment systems - such as gravity separators, hydrocyclones, dissolved air flotation (DAF) units and biological treatment systems -often struggle to consistently meet compliance standards. These systems are typically limited by several factors such as: inefficiency in removing fine or emulsified oil droplets; sensitivity to flow rate, temperature, and pressure fluctuations; high maintenance requirements and operational complexity; and inadequate scalability for high-volume operations
Exceeding environmental targets and reducing costs
One Middle Eastern oil company was experiencing significant challenges due to the limitations of its existing filtration systems. Its produced water had a high OIW content, averaging 286 ppm, far above the 50 ppm discharge limit set via regional standards, and so the company needed to remedy the situation quickly.
After conducting lab tests, our engineers concluded that the best option would be to supply two high-flow filtration systems, each containing 18 polypropylene filter elements, and a liquid/liquid coalescer vessel containing 68 cartridges that could separate and remove liquid contaminants to less than 20 ppm.
The units were supplied as rental equipment and subsequent tests showed that they removed 98.8% of oil-in-water (OIW), averaging just 3.2 ppm - far below the regulatory target of 50 ppm. This system not only exceeded environmental discharge requirements and avoided fines for legislative breaches, but also reduced operational downtime due to the quick installation. Based on this project’s success, the client decided to deploy Pall’s filtration systems at two additional locations.
In the oil industry, operational efficiency is key to the quality of the product and economic viability – as with many other sectors. Yet, there are few other industries where compliance with sustainability legislation is also critical on an international scale. The provision of advanced filtration systems supports oil operators through the combination of proven technology and expert support, to help them achieve business objectives while also meeting - or even exceeding - environmental standards.