Goal The goal of this project is to accelerate the development of high performance, lightweight drill pipe to help extend drilling capabilities to greater depths onshore and into ultra-deep water offshore. In addition, this project will attempt to increase the capabilities for short-radius drilling.
Advanced Composite Products & Technology, Inc. (ACPT), Huntington Beach, CA 92649
Maurer Technology, Inc., Sugar Land, Texas 77478
Deep, extended reach and deep water drilling are limited to a certain extent by the weight of steel drill pipe. The lighter the pipe, the less torque and drag are created, and the greater the distance that can be drilled both vertically and horizontally. Also, the depth to which drilling can be carried out from offshore drilling vessels is limited by weight carrying capacity of those vessels.
Composite materials made of carbon fibers and epoxy resin could offer mechanical properties comparable to steel at less than half the weight. Pipe made from such composite materials could also offer superior flexibility for drilling the short radius well bores required to extend horizontal laterals at shallow depths. It could also facilitate high-speed data transfer via cables or fiber optic leads embedded within the body of the pipe during construction. As carbon composites are becoming less expensive to manufacture, the opportunity exists to develop a composite drill pipe with some or all of these features that is cost competitive with steel. Also, because the mechanical properties of composites are well established and are a function of the types of resins and fibers used and the amount and orientation of the fibers, sections of CDP can be optimized for specific applications.
CDP consists of a composite material tube with steel box and pin connections. The tube is manufactured by winding graphite fibers and an epoxy resin around a metal mandrel and the metal box and pin connections. This is then cured and the mandrel is removed. The cured pipe section is machine finished and the abrasion resistant coating is applied. Standard centralizers are added in the field. While the coating can be field repaired, more extensive wear, should it occur, must be repaired at the factory.
CDP could bring new life to thousands of idle wells drilled in the early 20th century. In many fields, unproduced oil-bearing formations lie 100 feet or less below existing well total depths (TDs) or remain by-passed behind casing because the reserves were not considered significant when the well was drilled. Using short-radius drilling to drill a horizontal lateral into these formations from existing wells could bring many of these older wells back into production without the environmental disturbance that drilling new wells from the surface would create.
In addition to its application to short-radius drilling, CDP shows promise for enabling the economic development of oil and gas resources in other challenging locations. Because CDP combines lighter weight (less than ½ the weight of steel) with the performance properties of steel pipe, it is considered one of the technologies needed for resource development in extended reach (ER), ultra deep (UD), and deep directional drilling (DDD) applications.
Onshore, it will allow the existing fleet of drill rigs to drill at much greater depths. CDP also has significant potential to enable technologies requiring high-speed communications (“smart” drilling technologies) through the drill pipe via the embedding of cables and/or fiber optic leads within the body of the drill pipe. The loads required to be transported and supported by drilling platforms can provide substantial cost savings for deep offshore drilling and deep water drilling activity.
To date, significant progress has been made on a number of tasks. The performers developed specifications for both nominal 6-inch and 2½ -inch composite drill pipe (CDP), selected materials for the composite, adhesives, and abrasion coatings based on laboratory testing, and designed and tested a composite tube/metal tool joint interfacial connection. After modifying existing composite fabrication facilities to allow pilot production of 30-foot sections of CDP, they began fabrication and testing of full-sized, 30-foot joints.
Initial work on this project concentrated on specifying the requirements for a “typical” drill pipe as a target for the CDP. Industry partners supplied mechanical requirements of 5 7/8 inch high strength steel drill pipe, which were adjusted through open forum industry discussions. The revised mechanical requirements were then converted to conform to the mechanical/weight characteristics possible with reasonable cost composite materials.
Laboratory testing included verification of mechanical, thermal and environmental properties of resins, fibers, and adhesives, and measurement of erosion and mechanical abrasion characteristics of interior and exterior coatings for CDP.
Tests performed after exposure to drilling fluids at simulated downhole temperatures and pressures for 10 days showed that the graphite fiber/epoxy matrix experienced a reduction in high temperature shear strength after exposure to moisture. However, when 1/3-scale CDP was tested (rather than the very small samples initially used) the results showed that the current composite matrix can be used in downhole conditions up to 325° Fahrenheit. More extreme temperatures, such as would be required for ultra deep drilling, could be accommodated with higher-temperature-capable resin systems.
As composites are much more susceptible to wear and abrasion than steel, it was recognized at the beginning of this program that CDP would have to be protected from mechanical wear. A dual approach was developed and applied for protecting the exterior of CDP from abrasion; the use of both wear resistant coating and “off-the-shelf” centralizers. Screening of more than 20 potential coating systems for external abrasion protection resulted in at least one coating that compared favorably with 4130 steel in abrasion resistance.
CDP development and testing was divided into two tasks: subscale design and testing and full-scale design and testing. The small-scale effort was carried out on 1/3 size (diameter) pipe and the full-scale work was divided into full diameter 10-foot sections and full diameter at the full joint length of 31.5 feet.
A major difficulty in producing a commercially useful composite drill pipe is the interface between the composite tube (pipe) and the steel joints. Fifteen different combinations of composite/metal joint interface and composite wall configuration were evaluated before a successful composite/metal interface design was achieved.
During testing of the large-scale CDP it became apparent that there was an immediate need for slightly smaller CDP for short radius drilling operations. Specifications were established, designs were modified and a 2½-inch short radius composite drill pipe (SR-CDP) was fabricated and successfully tested in two field tests. The first test was when Grand Resources, Inc. of Tulsa used the pipe to re-enter an existing vertical well that had stopped producing in 1923. Just below 1,200 feet, using 2½-inch diameter SR-CDP, drillers successfully kicked off a new borehole that curved into a horizontal lateral that extended 1,000 feet. SR-CDP was also used by J.B. Drilling in Leflore County, OK to drill a 60-foot radius, 1,000-foot lateral through hard and abrasive sandstone from a new natural gas well drilled to a depth of 1,385 feet. The SR-CDP was used with air-hammer drilling tools to convincingly test its fatigue life and mechanical strength. Five, 30-foot joints of SR-CDP were run for a total of more than 160,000 cycles at an average RPM of 70, air pressure of 300 psi, and torque of 1,000 lb-ft. After a week of drilling, the pipe showed little to no signs of wear. The first commercial order for short radius (2½-inch) composite drill pipe was also logged (Integrated Directional Resources of Lafayette, LA ordered 300 feet).
In terms of production capability, current equipment has been modified to allow “pilot plant” production of 30-foot sections of CDP. Additional capacity will require the incorporation of automation equipment for continuous operation of the winding, curing, and machining functions.
The mechanical qualification testing (Compression, tension, pressure and torque) of the full 30-foot sections of the 6-inch CDP was successfully completed.
ACPT and Maurer Technology Inc. also completed a successful test of the communications aspect of the smart composite drill pipe. The test included a complete 30-foot joint of Composite Drill Pipe and two 10-foot joints in which data were communicated into and out of a complete section of smart drill pipe. In December 2008, the smart pipe was field tested by Grand Resources in a well in Oklahoma. The plan was to use 1,000 feet of 2½-inch composite drill pipe featuring the ring-ring, direct electrical connections at each tool joint to drill a directional well to assess the pipe’s performance and reliability under typical operating conditions. The direction electrical connection feature was to be exercised by using it to supply electrical power to a commercial third-party MWD/gamma sensor package and positive mud pulse telemetry unit. The test was both a success and a failure. It was a success in that communications were demonstrated downhole through 19 joints of pipe. It was a failure in that several joints has problems with the contact rings spinning, causing the bayonet used to make the connection between the joints of pipe to break off. The contact rings will need to be redesigned before the pipe can be offered commercially.
The project is complete. The Final Report is available below under "Additional Information".