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Honeywell Introduces Enabling Technology for High Temperature Intelligent Completions |
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 Problem
As exploration companies drill deeper wells, bottom hole temperatures are rising. In addition, intelligent completions are desired to increase the useful life and production capacity of multilateral wells. These factors are now driving the need for reliable high temperature electronics. Multilateral wells need to monitor the pressure, temperature, and multiphase flow in each lateral to optimize the production of the reservoir. This push requires permanently installed gauges and data acquisition systems which can last for up to 10 years in harsh high temperature environments. These temperatures and lifetimes are far beyond the capabilities of conventional silicon integrated circuits, however recent developments at Honeywell's Solid State Electronics Center have identified a solution to this problem.
Solution
Honeywell's new line of reliable high temperature integrated circuits is based on Silicon On Insulator(SOI) technology. The SOI circuits allow total isolation of individual transistors which can significantly reduce the effects of high temperature induced leakage currents. This coupled with specific high temperature design techniques and high temperature packaging results in reliable high temperature data acquisition systems. These systems can operate within manufacturing specification to temperatures in excess of 225 degrees Centigrade with expected lifetimes of greater than 5 years. Honeywell's HTMOST high temperature electronics product line with production integrated circuits is targeted to meet these needs.
SOI technology was originally developed to meet Aerospace needs for instrumentation, data acquisition and distributed control. The temperature and reliability requirements for the Aerospace applications supported the development of reliable integrated circuits to operate for long periods of time at high temperatures. The HTMOST production circuits are fully tested over an extended temperature range of -55 degrees Centigrade to 225 degrees Centigrade. All the parts receive a 250 degree Centigrade burn-in for up to 240 hours to eliminate infant mortality.
A number of aspects factor into the increased reliability of these systems. A grounds-up design approach which utilizes high temperature SOI components is only the starting point. To maximize the reliability we need to minimize the number of individually packaged components on a typical data acquisition board, and also minimize the interconnections within a board. Data have shown these areas to be the most unreliable. To meet the smaller overall physical size requirements and reduce the number of actual components, an Application Specific Integrated Circuit (ASIC) can be utilized. A HT2160 SOI gate array can be customized for the specific application with only back end metal processing. This level of ASIC can integrate a 16-bit processor, serial bus protocol, memory, and random glue logic onto a single integrated circuit. This level of circuit integration can eliminate as many as 4 or 5 separate components if assembled with traditional standard products, and not only reduce the physical size, but significantly increase the reliability of the overall system by reducing the parts count and the board level interconnects.
The second aspect of size reduction and reliability improvement is the packaging. The HT2160 gate array can be coupled with standard SOI analog components such as operational amplifiers, multiplexers, and an analog to digital converter into a single Multi-Chip Module( MCM). This technique has been widely used and proven successful in Aerospace applications. The utilization of such a packaging system within a down hole application provides significant reliability and size advantages over conventional board level integration. When the HT2160 gate array is assembled with analog components into a MCM package the resulting data acquisition system can be completely housed in one MCM package with pin counts ranging from 48 to 64 or more pins. To meet the need of down hole applications, the overall dimensions of these packages can be tailored to meet footprints as small as .6 by 3.5 inches with a height of less than .5 inches.
The addition of SOI power regulation circuitry can be coupled at the board level with the data acquisition MCM to complete the system. The power regulation can be handled with a small reliable linear regulator or a switching type regulator. Either style of regulator has advantages depending upon the parameters of the system being optimized. The linear regulator is not as efficient as the switching regulator with respect to power utilization, but the reduced parts count needed in capacitors and inductors keeps the design complexity down. The reduced complexity translates directly into higher reliability since fewer components are needed to implement the system.
Another significant feature of SOI integrated circuits is the lower power requirements of the digital circuits. The lower power needs can lead to smaller regulators and reduced power wire size which can provide significant operational and reliability advantages over traditional integrated circuits. The SOI circuits utilize total oxide isolation of transistors which significantly reduces the CMOS transistor junction capacitance. The reduction in junction capacitance being switched directly reduces the current draw in the circuit. For a typical SOI digital circuit a 30% reduction in current requirements can be expected compared to traditional integrated circuits of comparable complexity and performance.
The SOI technology, coupled with high temperature design techniques, are being used in the Aerospace market today. There are currently several major projects ongoing which are in various stages of development, testing, and demonstration. The reliability testing of components has been ongoing for several years. Data collection of reliability at the component level has indicated the ability to operate within specification for 5 years or more at 225 degrees Centigrade. These results have included thermal cycling, package mechanical testing as well as accelerated temperature and voltage testing. A total of 176,500 device hours of life testing have been completed at temperatures ranging from 250 degrees Centigrade to 300 degrees Centigrade. The life test data is used to project the failure rate and lifetime of the SOI components presented. In addition the use of individual HTMOST components in down hole logging tools have proven reliable up to 300 degrees Centigrade.
The adaptation of these SOI components with high temperature design techniques can provide dramatic improvements in the reliability and lifetime of intelligent completions. The data acquisition portion of these systems has been demonstrated with currently available SOI integrated circuits. With the addition of MCM packaging approaches and customized digital ASIC gate arrays the data acquisition system can be customized for specific intelligent completions. These systems have demonstrated significant improvements in reliability and lifetime over traditional silicon systems at high temperatures. Lifetimes in excess of 10 years with bottom hole temperatures of 200 degrees Centigrade are now possible. |
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