Rapid Breakthrough Research Articles

Improved Interpretation of the Inaccessible Pore-Volume Phenomenon

Summary In laboratory corefloods, polymer solutions used in EOR, such as partially hydrolyzed polyacrylamides (PHPA), often break through at less than 1 PV injected compared to the breakthrough of pure water. The rapid breakthrough is erroneously used to determine the ratio of pores accessible to polymer to total PV (accessible PV). Through numerical simulation and steady-state analysis, we show that the rapid breakthrough of such polymer solutions is not a measure of accessible PV. The only thing that can be inferred from the polymer solution breakthrough time is that polymer solution travels faster than water. Breakthrough time depends on the injected polymer concentration and shear rate. Our results significantly affect interpretation of polymer flow in porous media. Laboratory-measured polymer bulk properties are not those that should be used in conventional reservoir simulation and pressure-transient test analysis of polymer solutions. We show two different forms of the same partial differential equation used to describe rapid polymer breakthrough. The finite-difference solutions lead to two different polymer concentrations for each gridblock—a flowing concentration and a bulk (volume-average) concentration. The polymer-concentration-dependent properties required for each formulation must be interpreted correctly.

Methyl Isocyanate Liquid and Vapor Permeation Through Selected Respirator Diaphragms and Chemical Protective Clothing

Initially, a study was undertaken to evaluate selected chemical protective clothing suitable for use by emergency response personnel confronted with methyl isocyanate (MIC). Twenty-two chemical protective clothing materials were tested against liquid methyl isocyanate. Chemical permeation, breakthrough times for these clothing materials demonstrate that only one of these garments can be considered as a candidate material against liquid MIC. In a subsequent study, three chemical protective clothing materials were evaluated against approximately 800 ppm MIC vapor. Chemical permeation breakthrough times demonstrate that these materials can be considered candidate materials. A final study tested self-contained breathing apparatus (SCBA) diaphragms. Four SCBA diaphragms were tested and all experienced rapid breakthrough when exposed to liquid MIC. Next, three SCBA diaphragms were exposed to approximately 800 ppm MIC vapor. The data demonstrate that the SCBA should be worn inside a total encapsulating suit.

Methyl Isocyanate Liquid and Vapor Permeation Through Selected Respirator Diaphragms and Chemical Protective Clothing

Initially, a study was undertaken to evaluate selected chemical protective clothing suitable for use by emergency response personnel confronted with methyl isocyanate (MIC). Twenty-two chemical protective clothing materials were tested against liquid methyl isocyanate. Chemical permeation breakthrough times for these clothing materials demonstrate that only one of these garments can be considered as a candidate material against liquid MIC. In a subsequent study, three chemical protective clothing materials were evaluated against approximately 800 ppm MIC vapor. Chemical permeation breakthrough times demonstrate that these materials can be considered candidate materials. A final study tested self-contained breathing apparatus (SCBA) diaphragms. Four SCBA diaphragms were tested and all experienced rapid breakthrough when exposed to liquid MIC. Next, three SCBA diaphragms were exposed to approximately 800 ppm MIC vapor. The data demonstrate that the SCBA should be worn inside a total encapsulating suit.

A Controlled Method Of Preparing Plan-View Silicon Samples For Transmission Electron Microscopy Studies

ABSTRACTTransmission electron microscopy (TEM) is an important technique for studies of extended defects and other microstructural features in semiconductor materials. An efficient, plan-view thinning technique is always desirable for these TEM studies. The problems associated with wet chemical thinning of silicon are often surface residues, pitting and rapid breakthrough. A controlled method for obtaining thin, plan-view TEM silicon samples by chemical thinning was developed and the method is described in this paper. Results indicate that the method minimizes the above cited problems and has several other advantages over previously reported thinning methods.

Steam Zone Growth in Cylindrical Channels

Abstract The rapid breakthrough of steam that sometimes occurs in steam injection projects has been treated as a case of steam flow through a channel of high permeability. With the assumption of a cylindrical cross-section and steam zone growth limited by heat losses normal to the channel wall and sensible heat requirements within the zone, it is possible to estimate the channel size from the time of steam breakthrough at a producer.

Assessing the Suitability of Soils With Macropores for Subsurface Liquid Waste Disposal

AbstractThe capacity of soils to accept and purify liquid waste can be manipulated by using different application regimes. The associated transient soil physical conditions, which govern purification processes, were measured experimentally in soil columns and in situ, and were predicted by simulation in three soils of which two had macropores.Measurements of pressure heads, outflow rates, and breakthrough curves were made following intermittent liquid applications of 2 cm d−1. Rapid breakthrough and short‐circuiting, which were observed in the soils with the macropores, could be reduced by adding a light crust.Predictions involved computer simulation of pressure heads during infiltration and redistribution, and of outflow rates in the columns. Good agreement was found between measured and calculated values, but only when the model for soils with macropores was modified to include a subprogram for macropore flow. Simulation required hydraulic conductivity (K) at and near saturation, which was obtained with a modified crust test procedure.Use of the simulation program allows the prediction of soil physical conditions for a range of application rates in terms of ponding times and drainage rates, which affect purification and clogging. Measurement of breakthrough curves yields travel times as a function of application rates. Optimal application rates can be estimated by considering these two types of data, as is illustrated with an example. This approach is preferred over the current procedure using a single hydraulic parameter.

Radial Motion of a Surface Between Fluids Within a Porous Medium

Abstract Economic use of solvent flooding for secondary recovery of oil requires thelimitation of miscible solvent. In turn, solvent requirements depend onspreading from dispersion; reservoir heterogeneity, viscous fingering, and thetendency for low-density solvent to rise above oil, or to override. This paper considers miscible displacement outward from a central well in alarge cylindrical system. Under appropriate conditions, initial viscous fingersmay become damped out as they are spread in several directions by gravity anddispersion. Mathematically, displacement behaviour is represented by theradially outward motion of a free surface, representing the "interface" betweenfluids, from injection well toward producing wells. The equivalent linearproblem has been reported by several authors, but extrapolation to thecylindrical case is not justified. An approximate equation of motion for the free surface is deduced. Solutionsof the nonlinear equation are obtained by finite difference methods. For thelimiting case of a small density difference, just enough to cause fluidsegregation, a simple analytical solution describes the motion of the endpoints of the surface. Comparison with numerical results shows that the simplesolution provides a useful measure of the anticipated overrideforessentially all practical conditions. Introduction The injection of a miscible solvent to displace oil from a reservoir is apotentially valuable secondary recovery method. Field application has shownvarying degrees of success, however. Economic use of the process places a limiton the quantity of miscible solvent that may be used. In turn, the solventrequirement depends on the spreading initiated by viscous fingering (1), dispersion (2), pattern effects which cause incomplete sweepout, reservoirheterogeneity which leads to rapid breakthrough in portions of the reservoir,an d on the tendency for the solvent to override the oil. The latter is causedby a combination of density and viscosity differences.