This is the story about how we came up with a low cost high speed oil detector. The Dual Sensor Gas Analyzer by
Geospect.
Early Mud Logging Gas Analysis
Mud logger's are the folks that do the work of trying to find oil and gas bearing zones while a well is being drilled. Mud logging has been around since 1939 and first consisted of a basic gas sniffer. Over the years the a few more technologies have been added to mudlogging. One of those technologies, the gas chromatograph, was added sometimes during the 1950's. The chromatograph complimented the basic gas sniffer or gas detector as it is commonly referred to. The chromatograph allowed the mudlogger to not only know that he was getting gas while drilling through potentially productive zones, but it also allowed him to break the gas down into its component gases. The longer it took the sample of gas to come out of the chromatograph column, the heavier the gas was deemed to be. Methane came out first because it had fewer hydrogen and carbon atoms. Methane was considered a light gas. Then if heavier gases were present they came out next in order from lightest to heaviest. Ethane came out immediately after methane, then propane, iso-butane, and normal butane respectively. That basically meant that the mudlogger could determine by reading his instruments whether the gas he saw contained oil or if it primarily contained natural gas. If heavies, which was any gas heavier than methane was present then the mudlogger quickly began looking for other signs of oil such as fluorescence or oil visible on the mud pits. As one could imagine the gas chromatograph was, and still is, a critical tool for determining if an oil bearing formation is being drilled through.
The Problem With The Mudlogging Chromatograph
As critical as the gas chromatograph is for gas analysis on a mudlogging unit, it isn't perfect. One of the main problems with a chromatograph is that it is too slow for modern drilling. Drilling technology has increased dramatically in the last few years. Wells are now being drilled faster and more efficiently than ever before. A typical mudlogging chromatograph takes five minute to analyze a sample of gas before it can take another sample. The possibility exists that entire oil bearing zones can be missed because the chromatograph was too slow to keep up with fast drilling.There are faster chromatographs, but with faster speeds, relability typically suffers and cost increases significantly.
A Little Background On The Basic Mudlogging Gas Detector (It's Important)
The basic gas detector that was used in 1939 incorporated a hotwire sensor, also known as a catalytic combustion sensor, in conjunction with a Wheatstone Bridge circuit. A coiled platinum wire was heated until it glowed. Gas from the well was pumped over the platinum wire. The more gas that came into contact with the wire the hotter it got. Since the platinum wire changed its electrical resistance in direct proportion to its temperature the mud logger was able to output his results to a chart recorder, thus plotting a curve of the gas present.
The detectors response to all of the various hydrocarbons was fairly linear in relation to on another. The hotwire detector is still being used in today's mudlogging units and is widely accepted as a good method of detecting gas.
Enter Infrared Gas Detectors
Recent breakthroughs in infrared gas detection sensors has made the infrared detector a popular choice for the modern mud logging unit.
Modern infrared sensors are extremely stable and sensitive to even minute traces of gas. They are capable of detecting from 0% to 100% gas in air without additional calibration. They are an excellent choice for total gas detection on drilling rigs. The infrared detector, however, is not without its issues. One drawback of the infrared detector is that it is not particularly linear across the spectrum of hydrocarbon gases that it detects. For example, if the infrared detector is calibrated so that 100 units is equal to 1% methane in air it will read three times that many units when exposed to 1% propane in air. While it is still acceptable because we are only measuring relative quantities of gas, it is sometimes difficult to explain to our oil company bosses how we can read 300% gas in air during high gas situations.
The Dual Sensor Gas Analyzer ( The low cost, high speed oil detector)
Here at
Geospect Instruments, we have been building both hotwire and infrared mud logging gas detectors for many years. For years we were bombarded with requests for a faster more reliable chromatograph and also questions about higher than normal gas readings while drilling through heavies with an infrared detector. We finally realized that the answer to both issues was sitting right under our noses the whole time. We discovered that by placing a hotwire sensor and an infrared sensor in the same gas detector that we could detect heavy hydorcarbons in real time without even needing a chromatograph.
Basically, we invented a low cost, high speed oil detector. We call our invention the
Dual Sensor Gas Analyzer. We are very excited about our new mudlogging gadget and hope you will be too.
Sophisticated mudlogging software by geospect
