Reliable solution to minimising drilling downtime
26 February 2010
Bob Hunt gives an overview of the aggressive environments experienced while drilling in the oil and gas sector and the high reliability microelectronics that have been developed to cope with them.
The oil and gas industry’s need for electronics that can perform consistently and reliably in ever harsher environments and higher temperatures is growing steadily as the sector evolves. Yet, like any cost-conscious and conservative business, avoiding expensive technology investment mistakes is mission-critical, while still delivering operating efficiency and reducing system failure. Oil and gas companies can certainly benefit from other sectors, notably aerospace and automotive, where hybrid microelectronics have been used for years, operating in some of the toughest environments both on and beyond the planet.
Over the past decade, drilling for hydrocarbon fuels has become increasingly challenging and is being driven by the fact that the more readily accessible oil and gas reserves were tapped long ago. Consequently the industry is being forced to drill in harsher environments, along horizontal paths (rather than conventional vertical bore holes) at ever increasing depths. This means that the cost of exploring and extracting these reserves is growing at an exponential rate and the value and volume of oil and gas in these challenging locations is much harder to evaluate.
As such, the failure of a measurement tool in drilling a 20,000 feet deep well could readily incur two days delay, which for an offshore platform is in the region of a $1,000,000-$2,000,000 loss. Therefore, the accuracy of drilling and the characterisation and analysis of minerals and rock structures, as well as oil and gas sampling, must be performed with the highest precision. This ‘real time’ judgement on drill direction and depth is still undertaken by the consultant geophysicists with their vast experience, but the accuracy of their conclusions is only as good as the data provided by the down well measurement instrumentation.
Down hole instrumentation electronics
There are three key areas in oil and gas drilling that require reliable ‘down-hole’ instrumentation electronics, which are commonly known as ‘tools’:
1. Wireline logging tools – these are used for measurement and contain sensors (electro-magnetic, gamma, seismic, acoustic and vibration) that gather snapshot information about the quality and production capability of the well. These are usually electrically connected to the well head for power supply and signal communications
2. Measurement while drilling (MWD) and logging while drilling (LWD) tools – these are mounted directly behind the drill head and are based around sensors that detect drill orientation and direction and measure the mineral and organic material characteristics within the well. They are exposed to the high temperature of the environments and the shock and vibration associated with the drilling activity
3. Intelligent completions – these systems incorporate sensors that measure parameters such as oil and gas pressure to enable prediction and hence management of the quality and productivity of the well. They are installed in ‘producing’ wells and deliver information to the well head throughout the lifetime of the well which may extend to many years
The increasing importance placed on down well measurement tools means there is now a pressing need for robust electronics that have enhanced functionality to quickly and reliability monitor and process data such as temperature, pressure, resistivity, neutron porosity and gamma trace as well as providing drill directional guidance. Over recent years, the extent of research and the level of financial investment in the development and qualification of high temperature electronics has grown significantly as the requirement for complex electronic systems that operate with predictable lifetime under challenging mechanical shock and vibration increases.
Evolution of high reliability microelectronics
Traditionally, conventional PCBs with packaged components soldered onto them would be the technology of choice for these tools. Yet, although they are mature across all market sectors and globally available they have severe limitations in their ability for longevity in harsh environments. It remains true that for any mechanical activity such as oil drilling, the whole process is only as good as the weakest point. Conventional FR4 PCB is based on a glass fibre laminate with copper traces for circuit connectivity and this will not operate above 150ºC to 175ºC. Likewise conventional silicon semiconductor devices will often be limited to a maximum operating temperature of 175ºC. Therefore, fundamental technology changes are necessary to achieve reliable operation and acceptable lifetimes at temperatures of 200ºC and above.
Consequently, the oil and gas industry should be looking to high reliability electronic subsystems that are constructed with multi chip module (MCM) technology, or hybrid microelectronics as they are more commonly known. MCMs, and in particular MCM-Cs (where ‘C’ refers to ceramic as the support substrate) are hermetically sealed cavity packages incorporating un-encapsulated (bare) semiconductors (integrated circuits and transistors) which are wire bonded to printed precious metal, multi layer interconnect on ceramic substrates. This technology provides a high degree of protection for sensitive semiconductors and reduces the number of electrical connections required on the circuit, which in turn reduces the overall size and complexity of the electronics hardware in the system.
In the past, with conventional silicon integrated circuits, transistor and diodes would have a maximum operating temperature typically between 140 and 175°C, with their lifetime significantly reducing as the temperature increased. However there is now a new and rapidly expanding range of high operating temperature semiconductor devices and passive components (such as resistors, capacitors, inductors) that are designed and fabricated for reliable operation in excess of 200°C. Therefore, by coupling this new generation of components with MCM-C technology the need for conventional plastic packaging components can be eliminated and the number of interconnections between components can be dramatically reduced. This means that an unprecedented and predictable level of reliability can be achieved for the oil and gas industry without venturing into new and unproven technology solutions.
In the future, reliability of systems and processes will continue to be one of the major drivers of technology investment in the industry. Some C-MAC customers are already asking for MCM-C based electronics that currently work at 225oC to see if they can be retro-fitted to 150oC tools to achieve extended life and wider usage from them. So ultimately it becomes a balance between price, performance and reliability. The market certainly seems to be moving towards hybrid multichip modules as the technology of choice due to its compact physical size, inherent reliability and high mechanical strength and is gradually realising that the overall lifetime costs can be significantly lower.
Learning lessons from other industries
A key learning that can be borrowed from the automotive and aerospace sector is in obsolescence management – with high reliability, business critical applications, an electronic system may need to last up to 20 years. Because of the rigours of the aerospace industry, some manufacturers, including C-MAC, have been supplying MCM-C technology and providing technical and obsolescence support that is un-heard of in other market sectors. Another major lesson is ensuring proper traceability of electronic components. Many high reliability electronic products are identified with a serial number, and companies who have their heritage in the aerospace sector can trace every single component right back to the individual manufacturer and analyse the manufacturing process that was used to produce it. This instils great customer confidence by providing stringent quality assurance and in the worse case offers damage limitation in the event of a failed component in a system.
Furthermore, with hybrid microtechnology passive components can be embedded within the printed layers, enabling increased circuit packing density, simplified assembly and the realisation of precise component values through techniques such as laser trimming – a procedure that is invaluable in analogue circuits where ‘off-the-shelf’ resistor values are inadequate. Ultimately, as aerospace and automotive companies will attest, reliability and the physical space savings from changing a circuit board to a microcircuit are invaluable. Reducing the size of a module increases the applications that it can be used in, and since width is an issue for down well drilling, microcircuits that can fit more processing power in the same space are very appealing.
The future of the industry
The oil and gas sector has historically been very conservative – similar to the aerospace and automotive industries a few decades ago, and understandable considering how high the cost of failure is. However, hybrid multichip microelectronics have the right performance, physical size, reliability and mechanical strength requirements that cannot be rivalled by competing technology and this is becoming recognised and will enable the oil and gas industry to continue to drill for reserves in increasingly challenging environments. Although there have been movements in the industry to actively qualify and adopt this technology for its new generation systems, there still lacks the volume manufacturing capability and application experience to produce complete solutions and the cross fertilisation of technology from established industries such as aerospace and automotive will ensure operational failure does not continue to cost the oil and gas industry millions in lost revenue just because its electronics could not stand the heat.
DC-DC convertor
C-MAC MicroTechnology recently announced that it is supplying its high reliability microelectronics products and technologies to the oil and gas sector and C-MAC’s DC-DC converter for down-well drilling is now commercially available. The converter provides a range of step down, regulated supply voltages and fulfils the high aspect ratio footprint requirements for narrow tube, deep drilling requirements. The product is constructed using C-MAC’s proprietary technologies, as a multi chip module which, along with constructional techniques and materials that have been extensively evaluated and qualified within a series of test circuits in C-MAC’s on-site UKAS accredited Test House, ensures the product is fully operational and reliable up to 225°C.
The electrical functionality of the converter has been extensively simulated to verify conformance to the electrical specification over the whole range of electrical input voltages and output load conditions over the full operating temperature range required by the unit. In addition environmental testing has subjected the product to the full range of climatic and dynamic conditions likely to be experienced during its storage, transportation and operation. This includes:-
• Mechanical shock
• Mechanical vibration
• Thermal shock
• Temperature cycle
Key oil and gas statistics:
• High temperature well monitoring at 200°C for data acquisition (primary requirement), with memory, telemetry systems, batteries and DC/DC converters required to last for several years
• An MWD (Measurement While Drilling) tool typically operates from 30°C to 175°C (90% of operations) and with occasional transitions up to 225°C (99% of operations).
• Planned natural gas wells at depths of greater than 30,000ft will see temperatures top 250°C
• Cost of lost time drilling is c. $500,000-$1,000,000per day
• Temperatures up to at 175°C today, but an increasing number of wells requiring 225°C and above
• Pressure and vibrations are considerable
• Reducing flat time is a major industry objective
• Considerable research is being done into high temperature down-hole electronics
Bob Hunt is Head of Strategic Technology, C-MAC MicroTechnology
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