Pressure Pulse Injection Research Articles

Innovative use of a pressure‐pulse injection tool to increase transmissivity in a collection trench

AbstractPressure‐pulse injection tools are widely used in the oil and gas extraction industry to increase well production yields; however, they have been sparingly used in the environmental industry. These injection tools work by applying a pressure pulse to the subsurface that can open subsurface pore throats in unconsolidated material, increasing yields or increasing a radius of influence from a substrate injection. Collection trenches at an industrial site were installed to increase recovery of No. 2 fuel oil in the subsurface and maintain hydraulic control of the contaminant plume. However, after operating for seven years, significant reduction in recovery was observed. Diminished recovery was attributed to biofouling, iron fouling, and/or excessive scaling. A pilot test was conducted in 2009 to determine if a pressure‐pulse injection tool could be used to inject an antifouling agent and rehabilitate two of the site collection trenches. The pilot test was successful in increasing the transmissivity of both trenches, with an order‐of‐magnitude increase in groundwater recovery at Collection Trench 1 and a 50 percent increase in recovery at Collection Trench 2. The trench rehabilitation using the pressure‐pulse injection tool was conducted at two other site collection trenches in 2010 with similar success and is now proposed as part of regular maintenance of the trenches on an as‐needed basis. © 2011 Wiley Periodicals, Inc.

Single potential electrophoresis microchip with reduced bias using pressure pulse injection

We propose two variants of a new injection technique for use in electrophoresis microchips, called "front gate pressure injection" and "back gate pressure injection", that both enable a controlled and reproducible sample introduction with reduced bias compared to electrokinetic gated injection. A continuous flow of a test solution of fluorescein/rhodamine B in 20 mM Tris/boric acid buffer (pH 8.6) sample test solution is electrokinetically driven near to the entrance of the separation channel, using a single voltage (3 kV) that is constant in time. A sample plug is injected in the separation channel by a pressure pulse of the order of 0.1 s. The latter is generated using the mechanical deflection of a PDMS membrane that is loosely placed on a dedicated chip reservoir. The analysis of the peak area ratio of the separated compounds demonstrates a nearly constant sample composition when using pressure-based injection. A small remaining injection bias for the shortest membrane deflection times can be attributed to a dilution effect of the charged compound due to the presence of an electrical field transverse to the sample flow boundary in the channel junction.

Pressure injection in continuous sample flow electrophoresis microchips

Pressure pulse injection is proposed as an alternative technique to electrokinetic injection for use in continuous sample flow electrophoresis microchips. During chip operation, sample and buffer solutions are electrokinetically driven near to the entrance of the separation channel in a continuous way. A short sample plug is then injected in the separation channel by a pressure pulse of a few hundred of milliseconds, by mechanically deflecting a soft polymer membrane placed on a dedicated chip reservoir. Our pressure pulse injection technique does not depend on the charge of the analytes and, hence, is characterized by a strongly reduced bias compared to a classical gated flow injection sequence.

Field Demonstration of DNAPL Dehalogenation Using Emulsified Zero-Valent Iron

This paper describes the results of the first field-scale demonstration conducted to evaluate the performance of nanoscale emulsified zero-valent iron (EZVI) injected into the saturated zone to enhance in situ dehalogenation of dense, nonaqueous phase liquids (DNAPLs) containing trichloroethene (TCE). EZVI is an innovative and emerging remediation technology. EZVI is a surfactant-stabilized, biodegradable emulsion that forms emulsion droplets consisting of an oil-liquid membrane surrounding zero-valent iron (ZVI) particles in water. EZVI was injected over a five day period into eight wells in a demonstration test area within a larger DNAPL source area at NASA's Launch Complex 34 (LC34) using a pressure pulse injection method. Soil and groundwater samples were collected before and after treatment and analyzed for volatile organic compounds (VOCs) to evaluate the changes in VOC mass, concentration and mass flux. Significant reductions in TCE soil concentrations (>80%) were observed at four of the six soil sampling locations within 90 days of EZVI injection. Somewhat lower reductions were observed at the other two soil sampling locations where visual observations suggest that most of the EZVI migrated up above the target treatment depth. Significant reductions in TCE groundwater concentrations (57 to 100%) were observed at all depths targeted with EZVI. Groundwater samples from the treatment area also showed significant increases in the concentrations of cis-1,2-dichloroethene (cDCE), vinyl chloride (VC) and ethene. The decrease in concentrations of TCE in soil and groundwater samples following treatment with EZVI is believed to be due to abiotic degradation associated with the ZVI as well as biodegradation enhanced by the presence of the oil and surfactant in the EZVI emulsion.

Pressure pulse injection: a powerful alternative to electrokinetic sample loading in electrophoresis microchips.

We present a new and simple capillary electrophoresis microsystem in which the sample is injected hydrodynamically using a pressure pulse. This technique maintains the sample composition, in contrast to a classical electrokinetic injection, in which the magnitude of the electric field in the sample reservoir in combination with variations in electrophoretic mobility can lead to a biased injection. The sample is loaded using a well controlled and variable pressure pulse (0.1-1.0 s) generated by the mechanical actuation of a flexible membrane placed on the chip sample reservoir. A fluorescein/calcein-containing borate-Tris-hydroxymethylaminoethane (TRIS) sample solution is taken as a model system for CE analysis. The separation results using pressure pulse injection clearly demonstrate the advantages of our technique. In addition to the reduced bias due to the absence of an electrode in the sample well, this method allows injection of variable plug volumes by simply changing the pulse length. Moreover, a very high speed, repeatability, and sensitivity of the separation is obtained.

Optimized pressure-pulse splitless injection and electron-capture, negative ionization detection for the congener specific determination of compounds of technical toxaphene

The goal of the study is the optimization of the congener specific determination of compounds of technical toxaphene (CTTs). For this reason GC/ECNI-MS and CTT standard mixtures are applied. The splitless injection is improved by pressure-pulse injection which yields significantly higher abundance of the CTTs than by the conventional constant flow injection technique. The abundance of low volatile CTTs like B9-1025 (Parlar #62) is increased by factor 3 or more. The pressure-pulse injection can easily be integrated in standard (constant flow splitless injection) methods without influencing the retention times and reproducibility. The GC oven program and the flow are optimized for the separation of CTTs on a non-polar CP-Sil 2 column. Problems caused by oxygen in the ion source are discussed.

Determination of hydraulic normal stiffness of fractures in hard rock from well testing

This technical note aims at determining the joint normal stiffness of fracture planes by two kinds of hydraulic field tests and coupled hydromechanical numerical modelling. The initial hydraulic aperture of the fracture is determined from a pressure pulse injection test. Thereafter, a step pressure test (hydraulic jacking) is conducted from which the normal stiffness of the fracture plane is back-calculated by numerical modelling. The test procedure is applied to six sub-horizontal joints located in crystalline rock at depths of between 80 and 417 m.