Lisa Hernandez, NOV, USA, investigates a produced water handling solution designed to recover more lost oil.
Every year, more than 10 million bbls of oil are lost in produced water across the globe because inefficient water treatment processes lead operators to dispose of millions of barrels of water that still contain valuable oil. The WaterWolf™ Dynamic Oil Recovery (DOR) system recovers that lost oil from produced water in a single stage process without the use of chemicals or filters.
Developed by NOV Completion & Production Solutions, the WaterWolf DOR combines deoiling and desanding hydrocyclones with the non-shearing action of Moyno™ progressing cavity pumps. The system does not rely on upstream separator pressure and provides consistent performance regardless of variations in flowrate or pressure from the upstream water source. Produced water is partially recirculated within the system in a dynamic loop which maintains ideal process conditions for both hydrocyclones with optimum efficiency and 100% turndown.
Since solids are removed from the water separately from the oil, the discharged solids are practically oil free, eliminating the oil contaminated, chemical sludge that is produced by the gas flotation process. The recovered oil is also uncontaminated by chemicals or solids and can be returned directly to the separation process, bypassing a closed drains or slops handling system.
This technology is designed to increase oil recovery revenue, deliver maximum operational efficiencies, achieve environmental, health and safety benefits and significantly reduce the overall footprint for onsite water treatment and waste removal.
The vast majority of produced water comes from conventional wells that have been producing water for years. As wells in conventional reservoirs age, they tend to produce more water and less oil and gas. This leads to an economic challenge for operations to handle high water volumes, which ignited development of WaterWolf system.
The first design concepts for the system were developed in 2010. A team began building a pilot unit and detailed engineering work commenced quickly. By September 2012, the pilot skid was delivered to the first field test location in Ventura, California, and development continued onsite for almost a full year.
The WaterWolf is a new solution designed to treat and recover oil from produced water. While conventional pumps and valves shear oil into tiny, hard to separate droplets, Moyno progressing cavity pumps (PCPs) coalesce smaller oil droplets into fewer larger droplets. Just like sand will settle to the bottom of a pool quicker than fine silt, large oil droplets are easier to recover than tiny oil microdroplets. The WaterWolf DOR system replaces both centrifugal pumps and control valves with PCPs to control the hydrocyclone, significantly improving its efficiency.
WaterWolf inventor, Mark Wolf, at the control panel as he explains the dynamic loop operating modes.
Hydrocyclone technology has long been used in offshore oilfields to optimise produced water handling and extend the life of a well. The WaterWolf, built off the foundation of hydrocyclone technology, improves the process by operating without upstream pressure requirements and independent of flowrate variation. When conventional methods produce less shearing, then larger oil particles that remain are easier and faster to recover.
This technology is an advanced solution compared to traditional water treatment methods and offers proven financial, operational and environmental benefits. Industry groups that benefit include: mature fields with high water production, conventional producing wells, areas with high HSE and regulatory concerns, operators with high chemical costs, saltwater disposal operators and offshore production facilities.
With maximum hydrocarbon recovery, the WaterWolf process adds value by recovering more of the usable hydrocarbons in the produced water; as much as 30 bpd for every 10 000 bbls of water produced. As more valuable hydrocarbons recovered, there is less hazardous waste to treat, store, transport and dispose of later.
Expensive treatment chemicals or filters are reduced or eliminated. As an efficient process, water treatment and hydrocarbon recovery takes place in one integrated operation. The need for multiple skim tank configurations and gas floatation devices are also reduced or eliminated.
The total cost reduction using the system versus conventional methods can be as much as US$0.15/bbl of water. Reductions occur in treatment chemical costs, equipment costs and savings connected with sludge movement, well maintenance, storage, transportation and disposal.
The system is environmentally sound with its closed-loop contained approach, which eliminates air emissions. This provides cleaner and safer air for the environment, neighbouring communities and operations personnel.
Another benefit of the technology is its quick and easy installation and operation. Designed to be compact and light, the WaterWolf can be shipped by standard container and flatbed truck. Installations can easily be completed in one day with a work crew and crane truck. Higher capacity models can be delivered by non-permit loads to most locations. The technology offers significant cost savings by eliminating pumps, tanks, controls, vapour recovery, gas blanketing and air emissions permitting.
The WaterWolf DOR system uses the non-shearing action of Moyno PCPs to produce a new water treatment solution – eliminating the need for costly chemicals altogether.
One of the challenges in the industry is that a well’s produced water can become very expensive in relation to oil produced, causing operators to make a decision in shutting in the well. However, the WaterWolf is a more efficient solution to extend a well’s life when dealing with high water production challenges and ending in cleaner, safer and more profitable results.
Case study: Rocky Mountain operator challenge
Many oilfields will continue to produce for decades after they are first drilled until the costs of producing the oil exceeds the value that it brings in the market. The biggest factor that limits the economics for most wells is the cost of lifting and handling the water that is co-produced with the oil. NOV has worked with customers whose liquid production is over 98% water and less than 2% oil. One operator explained that he operates a water production field and just skims the oil from the water. Higher cost fields hit the economic limit at much lower concentrations leaving millions of bbls of uneconomic oil in the reservoir.
In today’s challenging oil price environment, operators are seeking solutions to recover more oil from their existing production stream. Another challenge for producers, as they work to operate safely and profitably while extending asset life, is handling the large volumes of water produced from an oil well throughout its existence.
In a developed case study, a Rocky Mountain operator was seeking a solution to optimise water treatment and handling for its mature oilfield of 2500 to 2800 bpd. Since the 1930s, the field has been a major player to US oil production. Yet with ageing fields in the industry, water production steadily increases through the years of its life. Today, the field produces more than 90 bbls of water for every barrel of oil produced. High concentrations of hydrogen sulfide and carbon dioxide gas in the water were a major driving force for this Wyoming operator to try a new approach. Treating the water with a conventional tank based system causes hazardous dissolved gases to be released to the atmosphere. The WaterWolf, which is a pressurised system, prevents the release of gases to the atmosphere.
Results in Rockies
In May 2014, the WaterWolf was delivered and installed for 18 weeks. The system delivered positive results in every major category of the pilot project: reducing air pollution, recovering more valuable oil, and reducing costs and risks of dealing with associated waste.
The system was able to recover an additional one to four barrels of oil from every 10 000 bbls of water produced. This equates to an additional 25 to 100 bpd. The installation also led to the elimination of H2S and CO2 emissions, along with associated flaring requirements. The project reduced total operating costs to less than US$0.01/bbl of water produced.
Current and future case studies
Another customer is running the WaterWolf at a newly drilled field in the Eagle Ford. The low oil price has driven this operator to focus on ways to reduce the cost of producing the wells and they are looking to the WaterWolf technology as an important part of privatising their water disposal operations to maximise oil recovery and minimise costs.
A third customer is testing this technology on a commercial salt water disposal well. Early results are showing that they will be able to significantly improve oil recovery and increase the profitability of their operations.
These are just a few of the many customers that are realising the payoff of this ground-breaking system.
This technology helps increase oil recovery revenue, delivers enhanced operational efficiencies with proven cost savings, achieves environmental, health and safety benefits, and significantly reduces the overall footprint for onsite water treatment and waste removal processes.
The value of increasing oil recovery and decreasing waste is undeniable. Compared with traditional water treatment methods, new systems such as the WaterWolf offer proven financial, operational and environmental benefits.
Adapted by David Bizley