Improving the Economics of Produced Water Filtration in Oil and Gas

Product

SupaPleat XP Special

Client

Multi-national Oil & Gas Producer

Application

Produced Water Filtration

Location

West Asia and East Africa

Value Added

Improved on-stream lifetime

Sector

Oil & Gas

Background

Produced water (PW) is a fundamental by-product of the oil and gas extraction process. With ever increasing environmental concerns around disposal and the increasing scarcity of precious water resources, producers are focussing on minimising waste streams. One method is to re-use the PW for hydraulic fracturing, water flooding, and enhanced oil recovery.

PW is a complex fluid which varies in chemical and physical characteristics, depending on the geology of the rock formations and the lifetime of the well. Early in a well's life, the amount of produced water can be relatively low. At the end, however, the volume of PW can be tens of times greater than the volume of oil extracted.

Typically there are three stages of treatment to prepare the water before re-injection into rock formation and a fourth purification stage (when it's used in non oil & gas applications, such as irrigation).

Pre-treatment: Dehydration vessels, storage tanks, strainers
Main treatment: Skim tanks, gas flotation, hydrocyclones, centrifuges
Polishing treatment: Dual media filters, cartridge filters, membranes
Tertiary treatment: Gas or steam stripping, biological, activated carbon adsorption

In this case study, we explore how to improve the polishing filtration stage using cartridge filters based on depth filtration.

The problem

Produced water is a complex, ever-changing, aqueous-based fluid with varying contaminants such as:

In this case, the client reported premature blocking of their polishing stage filters. This was resulting in high consumable costs, in conjunction with the logistical issues of transporting and installing high numbers of cartridge filters to an offshore rig. The time required to change out a full set of filters can result in significant downtime for production, with associated impact on revenue.

Working in conjunction with the PWT system provider and the operator, we studied the operating conditions and problems occurring on site, along with laboratory analysis of returned spent filter cartridges.

Close up of a clogged filter in the original produced water treatment system and a close-up of our SupaPleat XP filter

Sludge contamination on the original filters installed in the Produced Water Treatment (PWT) system (left) and our SupaPleat XP construction (right).

The solution

We determined that premature fouling of the solids removal filters with an oil/solids ‘sludge’ was the primary fouling mechanism, rather than excess solids in the system. We subsequently developed and supplied a bespoke filter media construction based on our SupaPleat XP extended life depth technology. We tested and validated the solution in our laboratory to ensure the required solids removal cut-off and guarantee efficiency. Additionally, we optimised the structure of the depth media to simultaneously provide more resistance to surface blinding from the fouling mechanism.

We also recommended changing the upstream chemical injection to minimise the precipitation of waxy crudes and coagulation of oil that was interacting with the solids to form the primary fouling mechanism.

The results

Following the upstream process improvements and the adoption of our filter cartridges, the client saw a noticeable improvement in filter life – from under one week to an on-specification life of a month or more with associated cost, logistical, and environmental benefits.

This is a 30-fold decrease in the number of cartridges used compared to the worst case performance of the previous filters. Not only does this deliver huge cost savings, but it also has a major impact on the amount of used cartridges going to landfill.

Key takeaways

Selecting the cheapest filter may seem logical from an initial procurement perspective, but it can have major financial impact down the line.
If OPEX is a key driver, it's prudent to work with a supplier who understands the process and has the ability to design and manufacture bespoke filtration solutions.
The chemical and solids make up of produced water can vary between formations and the life-cycle of the well. Working with a filtration supplier who can provide solutions for these changing requirements is paramount.

Improving the economics of produced water filtration