Customer Solutions

Cold Cuts In Deep Water Using LabVIEW and NI Data Acquisition

Author(s):

Mark Trotman, ICON Technologies Pty Ltd

Industry:

Water/Wastewater

Product:

Data Acquisition, LabVIEW, LabVIEW Datalogging and Supervisory Control, PXI/CompactPCI

The Challenge:

Combining conventional SCADA with high-speed data acquisition and in-line signal processing in a single application interface to control a highpressure underwater cold cutting system.

The Solution:

Using NI LabVIEW with the LabVIEW Datalogging and Supervisory Control Module to monitor and control a highpressure underwater cold cutting system.

Introduction
As community sensitivity to protecting marine environments increases, oil and gas companies feel pressure to return undersea production fields to their "preproduction" state once the company abandons the field. The traditional method of severing undersea wellheads involves the use of explosives - a potentially dangerous and obviously environmentally unfriendly technology.

Oil and gas companies find it difficult to apply conventional hot cutting techniques because the wellhead overhang severely limits external access to the well lining. Cold cutting techniques that use high-pressure abrasive fluids can operate in confined spaces, and in principle, could sever the wellhead from inside the well lining. However, conventional cold cutting systems typically operate at pressures of less than 690 bar (10,000 psi), and therefore, companies cannot employ this technique for deep-water work. Jetcut Offshore Technology, a Western Australian company, developed a new high-pressure Subsea Cold Cutting system (SCC) that can develop fluid pressures in excess of 2,000 bar and can perform underwater cutting and demolition work down to depths of 500 m. ICON Technologies developed the monitoring and control system for the SCC using LabVIEW and other tools from the NI Developer Suite Professional Control Edition.

Overview of the SCC Operation
The complete SCC combines:

• A diesel-driven, ultra-high pressure pump
• Two 10,000 L water storage tanks, with reverse osmosis desalinator
• A storage and handling system for the abrasive slurry
• A control room/workshop with generator and air compressor
• A launching frame, tool carrier, and a suite of tools for inserting and manipulating the slurry stream within the well lining
  

A three-man crew operates the SCC, which is readily transportable on a typical small (60 to 70 m) workboat. In operation, the tool tip of the SCC inserts into the well lining below the seabed level, and feeds from the surface with high-pressure abrasive slurry. All manipulation of the tool and monitoring of the cut takes place remotely from the surface vessel. The operators can optimize the SCC tool tip and slurry pressure for the depth and profile of each cut. Operating at higher pressures than an optimum cut requires greatly increases the cost, complexity, and bulk of the supporting equipment. Well liners are typically a sandwich of concentric steel and concrete layers, with steel crossbars between the layers. The concrete may contain undocumented and heterogeneously distributed "rubble," including significant amounts of metal scrap. To monitor and optimize the progress of the cut through this heterogeneous mix of materials, the operators place accelerometers on the tool jig to record variations in the acoustic signature as the cut proceeds.

Not a Traditional Control Problem
Conventional SCADA software does not easily handle the mix of conventional real-time control and waveform acquisition and processing that this application requires. Jetcut Offshore Technology needed the monitoring and control system to provide real-time control of all the diesel engine and high-pressure pump hardware, while simultaneously acquiring and processing acoustic signatures at sample rates up to 44 kSamples/s. In addition, they needed to archive all critical operating data, including the acoustic waveforms, for off-line analysis and auditing. Finally, for a number of reasons beyond our control, we had very little time available for developing the system - around three weeks from concept to offshore deployment.
A conventional PLC - an Allen-Bradley SLC505 comfortably handles the critical real-time control of the diesel engine and high-pressure pump hardware. We acquired acoustic signatures using a National Instruments PCI-6025E multifunction I/O card.

We developed the control and monitoring system for the SCC using LabVIEW and the LabVIEW DSC Module. The LabVIEW DSC engine directly handled all communication with the SLC505 via the standard Allen-Bradley SLC500 Series device driver. The system, continuously monitored around 120 operating parameters with more than 30 core parameters, logged to a database for archival storage.
We acquired acoustic data at sample rates up to 44 kSamples/s and streamed directly to the local disk for archival storage along with all other core parameters. We retransmitted the raw acoustic data via TCP/IP to a supplementary network PC for backup archiving and frequency processing. The processed signals provided a "near real-time" view of the progress of the cut.

Results
In its first commercial trial, Woodside Energy Ltd successfully used the SCC to remove wellheads in 80 m of seawater. Woodside concluded that Jetcut’s new technology is a success, and the company wants to use it in future severance programs. LabVIEW and the LabVIEWDSC Module were important factors in the successful and timely deployment of the SCC. Together they offer an application development environment that is unique in its ability to seamlessly blend a conventional configurable SCADA environment with the power and flexibility of a full-function programming language.They are a natural fit with any application that pushes the bounds of conventional SCADA in terms of I/O complexity or bandwidth, programming power, and network or inter-application connectivity.

For more information, contact:

 Mark Trotman

ICON Technologies

1st Flr, Alberman House, 20 Teddington Rd.

East Vic. Park, WA, 6100

Australia

Tel: +618 9470 4275

E-Mail: mt@icon-tech.com.au

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