ENERGIE program technology
April 2000 Vol. 221 No. 4 Feature Article TECHNOLOGY FROM EUROPE ENERGIE program technology Jonathan Shackleton, Ythan PS, Aberdeen The European Commission has launched a new progr
TECHNOLOGY FROM EUROPEENERGIE program technologyJonathan Shackleton, Ythan PS, Aberdeen The European Commission has launched a new program, called ENERGIE, which aims to improve the efficiency with which hydrocarbons reserves are identified and exploited. Reducing both production costs and environmental impact of the industry are major elements of the program. By 2010, ENERGIE aims to have increased the exploration-drilling success rate to 40% from its current 20%, while at the same time reducing exploration and development costs by about 30%. Deepwater technology is also a major theme of the new program. ENERGIE, which replaces THERMIE, will continue to sponsor innovative projects. Seven of these are presented here. WELLCOM – A Cost-Effective Production Booster Production from many oil and gas fields is restricted due to low reservoir pressure. Reservoir fragmentation and production from different zones or satellite fields often results in wells having different production pressures. When these wells’ outputs are manifolded together, the high-pressure (HP) wells are choked down to reduce back pressure on the low-pressure (LP) wells. This is a waste of energy, and it is this energy which is put to good use by the WELLCOM system to boost production from the LP wells. The system uses jet-pump technology to transfer energy from HP to LP wells. In oil- and some gas-production applications, a mixture of oil, water and gas is produced. Handling such multiphase mixtures by jet pump requires a special design to achieve optimum efficiency. The system comprises three components: 1) an in-line compact separator, 2) the specially designed jet pump and 3) the commingling spool. The in-line separator separates gas from the HP mixture; the liquid phase is then fed to the jet pump as the motive flow. The LP mixture is taken into the suction side of the jet pump, while gas from the HP in-line separator is combined with flow from the jet-pump discharge using the commingling spool, Fig. 1.
The system offers two main benefits. First, it allows LP wells to operate at a lower production pressure and, therefore, at a higher production rate, enabling higher total recovery. Second, it boosts LP production system pressure to enable or improve pipeline transportation of products. Apart from the economic benefit, the system’s simplicity makes it highly reliable. It has minimal maintenance and virtually no operating costs (it uses no fuel – primary or secondary – and has no emissions). The system was patented by CALTEC and underwent three stages of development during 1994 – 1997, culminating in successful field trials in Italy’s Agip Trecate field. The demonstration work received support from a number of companies, including Agip Spa, Amerada Hess Ltd., Marathon Oil UK Ltd., Mobil (North Sea) Ltd., Sarawak Shell Berhad, Wood Group Engineering (J.P. Kenny) and Score Europe Ltd. CoPilot – Improving Drilling Economics Vibrations in the bottomhole assembly can affect penetration rates. This, in turn, has negative implications for drilling-operation economics. In addition, this adds risk that the drillstring and drilling equipment could suffer catastrophic failure. Baker Hughes INTEQ and Elf Exploration & Production are developing an innovative instrument for real-time measurement of downhole drilling parameters. The new CoPilot system has a downhole sub and surface control unit. A closed information loop between the downhole drilling process and the surface-based drilling supervisor is established. By using a clear and simple display screen, drilling personnel will be made aware, in real time, of any unfavorable downhole conditions with respect to dynamics and forces. Since effective drilling parameters will be fully under control, the system can adjust the drilling regime as required for the highest penetration rate and long-term durability of BHA members. Basically, it can optimize the whole process. As a result, drilling costs and environmental impact, in terms of drilling time, can be substantially reduced. The system (Fig. 2) uses high-frequency, dynamic data from various downhole sensors, including: weight on bit, torque- and bending-moment strain gauges, magnetometers, axial and lateral accelerometers, and internal and annular pressure sensors.
Algorithms embedded in the downhole-tool sensors compare actual output to pre-determined benchmark values and communicate to the surface, via mud pulse, any variances as a measure of drilling conditions. Additionally, full wave sequences of dynamic data are stored in the tool’s downhole memory. After tripping out of the hole, these will be retrieved on surface via a high-speed, readout unit. Four pilot-series tools of 6-3/4-in. dia. have been produced. They all passed initial field verification and are now commissioned for field operation. MacDRILL – A New Concept In Hydraulic Drilling Motors This is a radically new concept in hydraulic downhole drilling motor technology. Developed by Rotech Holdings Ltd. of Aberdeen, it is distinguished from conventional axial turbine and Moineau PDMs by its short length, "all-metal" stainless steel construction and patented rigid-vane technology in its power section, Fig. 3. The unique combination of these features and perfectly concentric, vibration-free rotation of the rotor enable the motor to:
The MacDrill motor is a substitute for turbodrills and Moineau PDMs in restoring / improving well productivity and maximizing reservoir potential of the world’s high-temperature and geologically complex crude oil, gas and geothermal energy reserves. An exclusive worldwide license to exploit this motor technology was granted to Weatherford in November 1999. Innovative Production Systems For Heavy Oil Development of marginal, heavy-oil fields by means of traditional technologies (generally using a diluent to reduce oil viscosity and density) can be uneconomical due to heavy crude’s low value and the high cost of diluent (usually diesel). A project undertaken by Eni-Agip aimed to demonstrate the technical and economic feasibility of oil-in-water production for exploiting heavy-oil fields. The production system was designed for offshore fields, but some of the technologies, such as multiphase pumping, can also be fitted to onshore satellite fields. The system is based on:
This fluidization technology has been successfully developed from lab to industrial pilot. Long-distance, heavy-oil-in-water transportation has also been achieved. However, further R&D effort is required before it can be applied industrially. Artificial lifting by jet pump has already been undertaken in a production test where a multiphase heavy-oil pump was used to boost an onshore satellite field in Sicily, Fig. 4. The main characteristics of the pump are shown in Table 1.
ESMER – Multiphase Metering System Multiphase meters can achieve large cost savings for operators. However, despite the promise of improved productivity, multiphase meters may not be widely accepted if their price remains at the present level of $200,000. The reason for the high price is that existing meters rely on complex sensors, often with a radioactive source and/or complex flow-conditioning devices. A new, multiphase flowmeter, developed by Petroleum Software Ltd., combines a good understanding of fluid mechanics with signal processing and software. ESMER (Expert System for Multiphase Metering) is based on the application of digital-signal processing and artificial-intelligence techniques to the physics of multiphase flow. For calibration, the system characterizes and classifies the properties of turbulence in terms of the flowrates for each phase. For measurement, the process is inverted, i.e., the system predicts individual phase flowrates from observing characteristics of random turbulence. The system only requires a simple, mechanical spool with a very small pressure drop to be equipped with standard pressure and impedance sensors. The signals are digitally processed by means of an ordinary PC. A prototype was already undergoing field trials on Shell’s Auk platform when the project was expanded to include participation by Elf and BP, with the objective of expanding the scope of field testing. Three more systems were commissioned and are now being put through lab testing. Field trials are due to commence shortly at a number of onshore and offshore locations. In the meantime, the Auk prototype has been verified against separator measurements and accepted as a working tool by production-control operators. To expand the scope of use of the system at Auk, the meter was installed downstream of the production manifold to monitor the flowrate across a number of wells. Petroleum Software Ltd. will commercialize two models of the system. The T3 model is intended for multiphase metering applications, while the T2 model will be for gas / liquid metering applications. The mechanical design has been streamlined and modularized, in collaboration with Milltronics of the Netherlands, to enable configuration of the system as a T3 or a T2, depending on the requirements. T3 will sell for around $60,000 and T2 for around $40,000. Titanium Risers For Deep Water Increasing use is being made of floating production systems, and these depend on use of dynamic risers for production from subsea wells. This dynamic behavior, coupled with the need to handle high pressure, places heavy demands on the riser and its terminations. As field developments move into ever-deeper waters – combined with high pressure, high temperature and highly corrosive well fluids – there is concern that current flexible-pipe technology will be a limiting factor. Stolt Comex Seaway undertook a project to demonstrate the value of titanium alloy pipe as a practical alternative; its high strength, low weight, low elastic modulus and exceptional corrosion resistance make it attractive for dynamic riser applications. Example field-development projects were identified, and these were used to evaluate riser design and installation concepts for various configurations, ranging from simple catenary risers to more complex configurations such as the "steep wave." This included environmental conditions applicable to different geographic locations, several types of "floating" production systems (FPSO, semisubmersible, SPAR and TLP) and water depths to 1,500 m (4,900 ft). Titanium alloys were assessed in relation to the intended application, with the objective of selecting candidate material for the main test program. Ti-6Al-4V, the most readily-available, commercial titanium alloy, was fully validated for the application. Results demonstrated that excellent quality and properties could be achieved for pipe and welding processes such as gas tungsten arc and radial friction (RFW). The project concentrated on two, main installation methods: tow out and vertical laying. Both installation options rely on cost-effective fabrication and joining methods. Extensive testing was performed to demonstrate suitability of the selected processes for titanium, as well as development of equipment and procedures. Finally, a full-scale offshore trial was performed with 6-in.-dia. titanium pipe that was entered into the pipe handling and deployment system of the Seaway Falcon. The trials confirmed that controlled deployment could be achieved using equipment and procedures similar to those used for conventional pipelaying. For future commercial application, this means of installation, combined with the RFW joining process, should provide a cost-effective, high-quality solution. Deepwater Application For Flexible Risers Economic operation in deep waters and at high pressures requires development of new technologies. In the Flexriser project, the aim is to demonstrate that flexible risers can be used for deepwater oil fields. In addition, the nonproprietary prediction models PREFLEX, AFLEX and BFLEX will be verified and established as practical tools to calculate riser capacity and lifetime for future installations. Fatigue performance will also be established based on a number of small-scale tests on individual wires, steel and composite materials. The project will focus on design verification and service-life testing of large-diameter, high-pressure production and export risers for deep water. Three manufacturers will supply samples of risers at the limit of their technical capabilities, Table 2.
Analytical support will be used to document pipe-structure behavior up to, and including, failure. This data will be used to verify service conditions applicable for each riser and identify improvements that might allow further expansion of test parameters. The analytical work will also study the application envelope which can be reliably based on knowledge gained from each test. Each test will comprise a minimum of four samples, and the work will be split into four phases: 1) design and analysis of the proposed pipe structure; 2) static pressure and collapse tests on two short samples; 3) dynamic testing on high-pressure / deepwater flexible risers, including stiffener or bellmouth; and 4) dissection, post-test analysis and reporting. The project will benefit the oil industry in a number of
ways. First, oil companies will be able to develop fields that were previously uneconomic,
and they will be better placed to win contracts for similar fields. Second, manufacturers
will have an extended product range to offer oil companies. Third, consultants will extend
their abilities to calculate and advise on flexible-riser use for stable production without
hazards to installation, people or the marine environment. Participating oil companies
include Statoil (project coordinator), Shell International, Norsk Hydro and Esso Norge.
 The authorJonathan Shackleton is a freelance writer working in Aberdeen. Contact details for these projects can be obtained at: jonathan@ythanps.fsbusiness.co.uk |
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