Gas Lock Research Articles

Iatrogenic systemic air embolism treated with hyperbaric oxygen therapy

Air embolism is a rare and potentially severe complication of surgical and invasive procedures. Emboli large enough to produce symptoms require immediate treatment because of the risk of 'gas lock' in the right side of the heart and subsequent circulatory failure. If air is transmitted to the arterial circulation through a shunt, it may cause cerebral emboli with neurological symptoms. We present two cases with venous air emboli and concurrent cerebral arterial emboli. Both patients were successfully treated with hyperbaric oxygen therapy.

Dewatering Unconventional Gas Resources With Sucker-Rod-Pumping Equipment

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 104547, "New Methods and Equipment for Dewatering Unconventional Gas Resources Using Sucker-Rod- Pumping Equipment," by Mark W. Mahoney, SPE, and Randy DeWerff, SPE, Harbison-Fischer, prepared for the 2006 SPE Eastern Regional Meeting, Canton, Ohio, 11–13 October. Dewatering coalbed-methane and low-pressure gas wells is a challenge. Compared to electrical-submersible and progressing-cavity pumps, sucker-rod pumps are very forgiving, and wells can be pumped at very low pump-intake pressure without damaging the pumping equipment. New designs in sucker-rod-pumping equipment and rod-pumping systems for high gas/liquid ratios (GLRs), coal fines, and solids have changed the approach to dewatering unconventional gas resources. Introduction Understanding gas wells and how they affect the sucker-rod pump is needed to apply sucker-rod pumps under mild-, medium-, and high-GLR conditions. Gas lock, gas interference, compression, and decompression often are misunderstood and lead to use of the wrong equipment. Gas Separation Downhole gas separation in front of pump intake can solve gas problems with sucker-rod pumps. The term gas lock often is used to describe any gas problem in a sucker-rod pump. Surface-valve checks and dynamometer-card analysis cannot distinguish between various gas problems. True gas lock exists when the hydrostatic pressure above the traveling-valve ball is greater than the pressure in the pump chamber at the bottom of the downstroke. On the upstroke, the gas expands in the pump chamber but the pressure in the chamber remains greater than the pump-intake pressure; therefore, the standing valve does not open. With true gas lock, the valves stay closed and the same column of fluid is raised and lowered with each cycle, with no fluid being pumped. Compression and decompression must be avoided. A better description of gas lock is "the pump has pumped down to its pump-chamber decompression limit." The ideal-gas law gives the relationship between volume, pressure, and temperature. In simple terms, if the temperature is near constant, then pressure and volume are inversely proportional. On the upstroke, the pump chamber starts with an uncompressible volume according to the design constraints of the traveling and standing valves. As the plunger moves upward, the volume increases and the pressure decreases. When the pump-chamber pressure drops below the pump-intake pressure, the standing valve opens. Pumps contain a certain volume that does not contribute to the pumped volume. This nonpumping volume includes the standing-valve section with the valve ball, ball-guide portion, and the upper-fluid-port portion. Another nonpumping volume is the traveling valve, with its seat, seat retainer, and cage, that functions inside the pump barrel. Pumps are assembled such that the traveling valve does not touch the standing valve when the valve rod bushing is seated in the clutch of the valve rod guide. Space out, when the well is put on pump, can be too far off bot-tom, which increases the nonpumping volume.

Mitigation of surface contamination from resist outgassing in EUV lithography

Contamination of optics and mask is one of the possible show stoppers for Extreme Ultraviolet Lithography. One of the important sources of hydrocarbon contamination is the outgassing of photoresist coated wafers. Due to the vacuum conditions, these hydrocarbons can freely travel to coat the first optical component they encountcr. This leads to unacceptably short life times which should be increased with 5 orders of magnitude. A new gas lock system is presented to prevent this type of contamination and which eliminates the need for a window between the optics and the wafer. Experimental results are in agreement with numerical calculations and an analytical model. Based on agreement between the experiments and the models, it is predicted that in realistic EUV tools this method can give 5 orders of magnitude debris suppression at 15 mbar·1/s flow with 5% absorption of EUV.

Producing High GLR Stripper Wells With an Automatic Casing Swab

Abstract An automatic casing swab system has been developed and tested over a two-year period in high gas/liquid ratio (GLR) stripper wells in the Appalachian Basin. Wells in the Basin typically produce lesser amounts of liquids in their later productive lives. These amounts are usually too small for efficient operation of the rod pumps or tubing plunger systems that were originally installed. Normal practice has been to periodically remove the liquid with a wireline casing swab or to plug and abandon the well. The system described herein is capable of prolonging the economic producing lives of these wells. This system consists of a cylindrical swab tool configured to seal against the casing wall when moving upward, but capable of falling through wellbore fluids when released from a specially-designed wellhead. A "stop "in the casing prevents the swab from falling into the perforations and closes the liquid bypass valve. The cycling frequency of the swab is dependent on the strength of the individual well. The automatic swab system is usually less expensive to purchase, install, and operate than sucker rod pumps or tubing plungers. It can operate unattended for extended periods, can frequently increase gas output, and provide a smoother orifice meter chart for easier integration. In addition, the system is suitable for operations in remote locations. Field experimentation has shown the ideal candidate well for this system to have a GLR over 900 std m3/st m3, a bottomhole pressure between 1.4 and 6.9 MPa, low fines production, and modest paraffin output. Introduction The typical stripper oil and gas well is characterized by low total liquid output, low reservoir pressure, and a relatively high gas-liquid ratio (GLR). Wells of this type are plentiful throughout the world, but are predominantly located in the United States and Canada. Because of the relatively poor output from these wells, they are first to face abandonment at times of low product prices. Beam pump-sucker rod (pumpjack) and tubing plunger (rabbit) systems are ordinarily found in use on these stripper wells. They were typically installed when the well had greater reservoir pressure and liquid output. Once the well declines in pressure and output each of these systems becomes inefficient. The pumpjack may tend to pump-off the well even though it may operate only a few hours each month or gas lock and fluid-pound from the scarcity of liquid entering the wellbore. The tubing plunger will become less efficient because of slow plunger movement to the surface, liquid fallback, and the necessity of "blowing-down" the well to atmospheric pressure periodically in order to bring the plunger to the surface. A common practice is to convert these wells to "swab wells, "where all downhole equipment is removed and the wells are produced by periodically removing accumulated liquids by a wireline swabbing unit. Gas production continues for a certain period of time before the well "loads-up" and requires swabbing once again. Even though it may appear simple and inexpensive, this practice can be even more expensive than before when factoring in the cost of the swabbing unit and the frequent need for it.

A Precision Alpha-Proportional Counter

An instrument is described which will detect and record the alpha-disintegration rate of prepared radioactive samples even though soft beta-radiation up to 5×109 disintegrations per minute may also be present. The counting losses arising from the detector, electronic amplifier, scaler, and recorder total 0.8 percent with an alpha-counting rate of 105 counts per minute. The instrument employs a proportional counter through which 99 percent CH4 at one atmosphere slowly flows. The proportional counting region is approximately 300 volts in length, with 0.5 percent change in counting rate in an interval of 200 volts. Thin radioactive samples deposited on metal disks up to 2.5 cm in diameter are easily inserted into the counter volume by means of a special gas lock. The counter detects 0.50 of the disintegrations from a thin radioactive sample. The counter background can be maintained at about 14 counts per hour. A high vacuum, low geometry attachment provides reductions in geometry down to at least 10−5 of the sample counting rate. Some theory of gas-flow proportional counters is presented along with details of the instrument construction.