Measuring and testing – Sampler – sample handling – etc. – With heating or cooling
Reexamination Certificate
2001-06-05
2003-12-23
Noland, Thomas P. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
With heating or cooling
Reexamination Certificate
active
06666099
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a system for the collection and extraction of gases entrained in a fluid, and more particularly, hydrocarbon gases in the return flow drilling mud material of an oil or gas exploration well.
BACKGROUND OF THE INVENTION
There is a demand for apparatus to collect gases emitted from and extract gases entrained in fluid and slurry materials. For example, gases entrained in the return flow material discharged from an oil or gas exploration well. This return flow material is generally in the form of a mud stream and is usually referred to as drilling mud. Collection, extraction and analysis of drilling mud gases can be used to indicate the hydrocarbon content in the well return flow material which, in turn, provides the basis for an assessment of the formation and any indications that the well drilling has hit a producing zone. In an oil and gas well, generally the primary hydrocarbon gas of interest is methane gas. Thus, information relating to the methane gas content of the well return flow material is the information that is usually of most interest. Although, under certain drilling conditions, there is also interest in information relating to some of the other hydrocarbons that may be present in the well return flow material.
The gases obtained from the return flow material discharged from the oil or gas exploration well are sampled for analysis. A gas collection, extraction device provided for this purpose is generally referred to as a gas trap. The gas trap apparatus is typically positioned in a “Shaker Box” or “Possum Belly” of a “Shaker Tank” into which the well return material is directed when it exits the well bore. Generally, the gas trap provides the collected, extracted gases to a sample tube extending from the gas trap to the sample analysis equipment. The sample tube typically has a small diameter and the collected gas sample is transported in the sample tube to sample analysis equipment on a continuous basis.
The current state of the art drilling mud gas sample collection, extraction systems have several problems that cause such systems to require high maintenance costs and attention. Current gas trap apparatus provides a canister with an electric motor mounted on top, which drives a centrifugal impeller housed centrally within the canister. The canister has a plate on the bottom with a small hole in the centre that acts as an inlet for the drilling mud. Another hole is provided in the side of the canister that forms an outlet for the drilling mud to be expelled from. This arrangement is designed both to pump mud through the gas trap sample canister and to agitate the mud contained within the sample canister sufficiently to permit entrained gases to be released. The gases are released from the return drilling fluid well mud stream as gas bubbles and are evacuated from the sample canister via a sample outlet, which couples to a sample tube.
Current gas traps are quite heavy, usually weighing 70 lbs. or more making the devices relatively heavy and, consequently, onerous to install, operate and maintain. Generally, the gas traps are attached to the shaker box and disposed inside of the shaker box, positioned at a particular depth in the drilling mud flowing through the shaker box. Typically, the apparatus for attaching the gas trap to the shaker box includes a bracket that permits up and down adjustment of the gas trap to allow the gas trap to be positioned at the correct depth in the drilling fluid. Positioning the gas trap at the prescribed or optimum depth in the drilling fluid is very important with the current design of gas traps. Any variation from the optimum depth causes the gas trap to change the amount of drilling mud it will pass in a given period of time as well as causing it to liberate more or less entrained gases from the drilling mud in that same given period of time. Furthermore, if the level of the drilling mud rises too high, drilling mud will be drawn into and through the sample tube by the sample pump toward the sample analyzer causing contamination of the equipment. Depending on the amount of drilling mud drawn into the sample tube, the sample handling, conditioning and analysis systems can all become contaminated with the drilling mud. At a minimum, drawing drilling mud into the sample tube will cause contamination that will require maintenance intervention and may necessitate replacement of the sample tube. In operation, most shaker boxes will experience a change in drilling mud level as the mass flow quantity of drilling mud changes or as the density and viscosity of the drilling mud changes. Drilling mud level changes in the shaker box can also occur as a result of the rig crew making adjustments to the shaker box itself.
Current oil and gas well drilling gas traps require operational maintenance and attention to operate in harsh winter environments. For example, the collected gas sample is typically delivered to analysis equipment that often is distances of hundreds of feet from the gas trap. A sample tube effects delivery of the sample, which is subject to freezing in the winter. Consequently, the sample is dehumidified to avoid freeze-up in the sample tube. Dehumidification apparatus typically includes a glycol dryer that the sample is bubbled through. The moisture removed from the sample causes the vessel holding the glycol to become full, requiring replacement of the glycol to rejuvenate the apparatus. Another, dryer apparatus generally found is a solid desiccant, for example calcium chloride, to further dry the sample. The solid desiccant will require replacement, often several times per day, to maintain operation of the dehumidifier systems. An example of such type of systems is described in U.S. Pat. No. 4,565,086 to Orr.
U.S. Pat. No. 5,199,509 to Wright for a controlled gas trap system provides a gas trap forming a sample chamber having an inlet and outlet both submersed in the fluid to be sampled. Disposed within the gas trap is a rotating agitator and a vent to admit substantially gas-free air into the housing and a means to draw off the gas evolved from the mud. To provide for varying mud levels, the apparatus of Wright relies on the rotation of agitator to maintain a constant mud level within the sample chamber.
U.S. Pat. No. 5,648,603 to Hansen describes a method and apparatus for stabilizing a quantitative measurement gas trap used in a drilling operation. The method involves providing a known quantity of standard gas for injection to the trap in which the gas stream is evolved, for example Ethylene, Isobutylene and Nitrous Oxide.
It is desirable to have a drilling mud gas sample collection, extraction system that is operable over a range of drilling mud levels within the sampled flow stream, for example, in a shaker box.
It is desirable to have a drilling mud gas sample collection, extraction system that operates consistently over a wide range of ambient temperatures, including freezing winter temperatures.
It is desirable to have a drilling mud gas sample collection, extraction system that operates consistently over a wide range of drilling mud viscosity.
It is desirable to have a drilling mud gas sample collection, extraction system that operates with little or no frequent operator maintenance or intervention.
SUMMARY OF THE INVENTION
The invention provides a gas trap assembly to recover sample gases from fluids having pneumatic motor driven agitator blade rotatably disposed within a gas sample collection canister. To enable operation of the pneumatic motor in winter conditions, the pneumatic motor compressed air supply has an air dryer to dry the air supply to a dew point below minus 40 degrees Celsius. The compressed air treatment system is housed in a heated environment to prevent the water extracted from the air from freezing up.
For operation in winter environments, a heater heats the motor compressed air supply. The heated compressed air is delivered to the gas trap to power the gas trap pneumatic motor. Before going to the motor at the gas trap, the heated compressed ai
Blake Cassels & Graydon LLP
Leier Terry L.
Noland Thomas P.
Pason Systems Corp.
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