Gareth Innes
TWMA
Strict environmental regulations are in place for managing the disposal of drilling waste, with operators required to transfer, store, and process drill cuttings in a responsible manner. TWMA has developed a new technology which facilitates the processing of drill cuttings at source which not only optimizes drilling operations, but simultaneously delivers cost efficiencies, enhances safety, and significantly reduces environmental impact.
Conventionally, ship-to-shore services have been utilized for transferring drilling waste offshore. This involves the drilling waste being transferred from the shakers, where the drill cuttings have been separated from the mud, to skips and then onto a vessel where it will be taken to an onshore treatment facility. The transportation of contaminated drilling waste is expensive, comes with inherent safety implications, and can result in significant delays to drilling operations. This is particularly the case when transporting large volumes over a large distance over land and sea in often difficult climatic conditions.
TWMA says that at-source processing overcomes the challenge of transporting large volumes of drilling wastes.
At-source processing overcomes the challenge of transporting large volumes of drilling wastes. Additionally, TWMA’s proprietary technology enables the hydrocarbons trapped in the drill cuttings to be recovered and recycled. TWMA’s TCC RotoMill and EfficientC systems provide efficient and safe solutions and provide a complete at-source drilling waste management service.
With strict regulations in force, managing drilling waste responsibly is an important part of drilling operations. With the ability to customize and integrate its technology to suit clients’ operations, TWMA has recently been working with an international operator engaged in a continuous five-year drilling campaign in the North Sea.
TWMA was tasked with delivering a complete drill cuttings management service on a rig which already featured the client’s own drill cuttings and storage system. In this scenario TWMA’s engineering team proposed to build a solution which could be integrated with the existing design. Following a rig survey, TWMA proposed a combination of technologies: TCC RotoMill and EfficientC, would be combined with a bespoke Air Transfer System.
TWMA designed and manufactured the lightest and most compact electrically powered TCC RotoMill which was engineered specifically to fit the available footprint for this campaign. The TCC RotoMill treats offshore drilling waste by using a process of thermal desorption to separate non-aqueous based drilling fluid (NAF), drill cuttings and associated materials into their three constituent parts; oil, water and solids. Recovered water and solids can be disposed of safely on location, while recovered base oil, which retains its original properties, can be directly reintroduced back into the drilling mud system, representing significant cost savings for operators. Furthermore, the water and solids recovered from the process surpass the stringent regulations set by the OSPAR convention and can be dispersed overboard with no risk to the environment.
The system eliminates drilling waste and removes the need to transport drill cuttings and associated drilling wastes to landfill sites globally, thereby significantly reducing logistical costs and the likelihood of environmental or safety incidents. Additionally, research carried out confirmed that the carbon footprint of offshore processing is more than 50% less compared to conventional skip and ship operations.
The wellsite storage and transfer of drill cuttings and associated materials plays a vital part in offshore waste-handling. TWMA’s EfficientC is a fully certified collection and distribution system, and a safe and efficient method for transferring drill cuttings at the rig site.
The Air Transfer System was designed following a series of onshore trials that verified it could safely and effectively remove and transfer drill cuttings from the rigs existing preload tanks. In addition to removing drill cuttings from the preload tanks, the Air Transfer System would also be used as a back-up system, to allow drill cuttings to be collected at-source and transferred directly to the TCC RotoMill if required.
Following this, vertical transfer was introduced in conjunction with horizontal transfer, and drill cuttings were collected from a 10 m deep storage container and seamlessly transferred along a horizontal stretch of 100 m. The vertical transfer simulated the safe and efficient transfer of drill cuttings from the maximum depths of the preload tanks on the rig.
Before project kick off, TWMA organized a risk review meeting where it was agreed that as a contingency measure, a skip station and further air transfer methods would be installed on deck to support the 17½-in. section of the well where large volumes of drill cuttings were expected.
TWMA’s solution significantly enhanced its clients’ operations and is delivering a safe and efficient drill cuttings management service. Some 1,154 mt of drill cuttings have been successfully transferred via the Air Transfer System from the preload tanks and successfully processed offshore with the TWMA TCC RotoMill (950Kw) at an average throughput rate of 5.14 mt/hour. Currently the best recorded throughput is 6.51 mt/hour.
The benefits of processing at-source are further illustrated when analysing the recovered components. Significant cost efficiencies have been realised as 185.66 m3 of high quality base oil has been recovered so far and reused in the drilling process. To date, this is equivalent to more than £600,000 ($788,000). The process also reduces overall well costs through reuse activities, removing the need for a costly logistics network, and in turn reducing risk by minimizing handling (manual and mechanical) of drilling wastes.
Recovered solids which were cleaned and treated were discharged over-board with an average TPH of 0.059% which is significantly below the North Sea allowable discharge limit of <1%. 101.39 M3 of clean recovered water has also been discharged overboard with an average of 1.26 ppm which again is well below the North Sea allowable discharge limit of <30ppm.
This successful project for an international operator has seen TWMA install its EfficientC system to store and transport drill cuttings from the rig shakers through TWMA’s Air Transfer System to the existing preload tanks, then air transfer to the TWMA TCC RotoMill for processing. TWMA was also responsible for monitoring the flow of drill cuttings from the shaker house via the transfer system and providing the client with discharge sampling data on recovered materials to demonstrate quality and discharge regulations were being met.
Working in partnership with its clients, TWMA is able to support operators by providing a complete drilling waste management service which can be integrated into existing designs and tailored to suit their needs. Treating materials at-source delivers substantial benefits to operators as it completely eliminates the need to transport hazardous drilling waste material off-site and back to shore for treatment and disposal. This significantly reduces logistics costs and the likelihood of environmental or safety incidents.
