3-D software reduces design time for offshore drilling system
Transocean Offshore of Houston, Texas, specializes in technically demanding segments of the offshore drilling business such as deepwater and harsh-environment drilling services. Transocean recently completed construction of one of three new, technologically advanced drilling ships designed for 10,000-ft deep water and a drilling depth of 35,000 ft. These ships, Discoverer Enterprise, Discoverer Spirit, and Discoverer Deep Seas, are dynamically positioned drillships. The ships feature a new and unique well-construction methodology developed by Transocean. It improves drilling efficiency by allowing both drilling and pipe assembly to take place simultaneously.
By using 3-D plant modeling software, Power Management Inc. completed the design and documentation of the world’s. deepest offshore drilling system in about 23,000 hours, an estimated 17,000 hours less than if the project had been done with 2-D CAD. By creating a 3-D model of the topside system, engineers were able to get feedback early from Transocean Offshore. This allowed them to incorporate the customer’s changes sooner and saved many hours of rework.
Topside design. The contract called for the design of all topside equipment, including substructure, drill floor, BOP module and all interconnects. On a previous project involving an oil and gas production system, engineers had used 2-D CAD to lay out all system components and generate drawings. However, they found it difficult to communicate their designs to the customer using 2-D drawings, e.g., a fake floor above the pipes that was difficult for the customer to visualize on the drawings. It was often necessary to revise the design to change features that the customer had not understood when initially looking at the drawings. Another drawback to working in 2-D was the difficulty of detecting interfering objects.
To overcome 2-D design limitations, engineers decided to do the Transocean project in 3-D. The software they used was AutoPLANT 97 from Rebis, Walnut Creek, California. This software runs as an addon to AutoCAD, which was attractive since many clients use this program. Customers can take AutoPLANT drawings and edit them with plain AutoCAD rather than having to use a specific plant-design program. In addition, the software sells for about one-third the cost of other workstation-based plant design systems, yet provides all the necessary functionality. Another attractive feature was the ability to buy only the needed modules, unlike other plant-design products, where it is necessary to buy the complete system.
To start the project, the topside of the Transocean drillship was divided into three separate sections. This way, each section could be drawn in parts and assembled on the ground while the ship’s hull was being built in Spain. The first step in assembling a 3-D model of the drilling system was creating digital models of all components. This was done using the software’s Equipment Module, which automates the modeling process by providing a library of parametrically defined components. With this library, a designer simply enters a few values representing the equipment specifications, and the software draws the model.
For example, the designers got equipment specifications either from manufacturer’s catalogs or from AutoCAD drawings supplied by the manufacturers. Then, to create an AutoPLANT model of a pump, they chose a pump from the software’s equipment library, typed in a few dimensions representing the manufacturer’s specifications such as height of the suction and discharge flanges, and the software automatically created the pump model with the flanges in the correct locations.
Single-model benefits. After placing equipment in the AutoPLANT model, the steel framing structures, pipe racks and supports were modeled using the software’s Multi-Steel Modeler. This module provides the functionality needed to place 3-D structural steel, including drawing setup and creation, 3-D grid placement, steel placement, database management, steel editing, display options, steel annotation and accessway (stairs, ladders, platforms, handrails) placement. Similar to the Equipment Module, the Multi-Steel Modeler has a library of standard shapes. When a designer wanted to run a beam, he simply chose the beam shape he wanted and indicated the desired location. The software drew the 3-D beam model automatically.
As this work was being done, piping designers were using the software’s Piping Module to route pipes in 3-D. They found working in 3-D to be much better than working in 2-D, because they could see the impact of their work immediately, rather than flipping through 2-D drawings and trying to follow the entire line.
At this time, electrical designers were using the software to route electrical trays. Because all the different design disciplines were contributing to the creation of the entire system’s 3-D model, interferences were avoided as the initial design work was going on. For example, when electrical designers routed trays, they could see the location of pipe racks and work around them. This was a big improvement over working in 2-D, where electrical designers worked from steel background drawings that typically were not up to date.
Another way that interferences were prevented was by using the Explorer/Interference Detection module. As designers navigated through the model, they could look at the layout from any angle to spot interferences that they might not have seen when they first created the design. The software recognized all one, two and 3-D AutoCAD entities for viewing and interference detection; these included lines, polylines, 2-D surfaces, meshes, 3-D faces, ACIS solids and blocks, as well as any custom 3-D objects created.
This module was also helpful for determining the suitability of certain design decisions, e.g., whether there was sufficient access to equipment or whether a valve was too high to reach. The walkthroughs were recorded and turned into movies as another design evaluation tool.
Faster documentation. The software generated drawings automatically from the’3-D model, which, facilitated the required project documentation. Time-savings were most evident during production of isometric drawings;, an automatic isometric-generation program, called ISOGEN, was used. Rather than needing four hours to produce an isometric drawing from scratch, ISOGEN created them in minutes directly from the 3-D model. Only about 30 minutes were needed to check each drawing and make minor changes. The Transocean project required 1,100 isometrics, so nearly 4,000 hours of drawing time were eliminated.
The company saw additional timesavings when producing the project’s bill of materials. The software keeps track of all materials used in the model, and when finished, the program prints out a list of all items. This was faster and more accurate than searching through drawings and counting materials. It also made it possible to give Transocean the information before producing any drawings.
Summary. In addition to saving time, creating a 3-D model resulted in a better overall design. With the enhanced visualization provided by the software, designers were able to do a better job of piping and placing equipment, particularly in confined areas. They could see the space they had to work in well enough to compress the equipment and pipes, fitting three pipes into an area where they might have only put two had they worked in 2-D. Although this did not decrease the overall size of the drilling system, it did help design better equipment access.
For Transocean Offshore, working on this project in 3-D had many positive results. It gave them a set of clash-free drawings that were available sooner than they would have been if only 2-D had been used. It gave them an accurate bill-of-materials report much quicker as well, which allowed the company to avoid construction delays due to untimely delivery of materials. Most important, it provided the time and tools needed to optimize drilling system design, allowing the drillship to perform reliably in demanding deepwater conditions.
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Ivan Curiel, President, Power Management Inc., New Orleans, Louisiana
COPYRIGHT 1999 Gulf Publishing Co.
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