Simulation of gas-condensate well blowout under permafront conditions

The blowout problem for a gas-conjugate condensate well is considered in a new formulation. The effect of the fluid flow in the well shaft on the temperature of the surrounding rock and the reaction of the surrounding permanently frozen rock on the flow regime in the shaft during the thawing process are simulated and studied under ordinary operating and blowout conditions.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 101–108, May–June, 1994.     

Self-similar solution of a problem of freezing of finely dispersed soils with allowance for moisture migration in thawed and frozen zones

Heat transfer in freezing and thawing soils is accompanied by various processes among which phase transition of moisture and mass transfer should be distinguished in both the thawed and the frozen zones. Their consequence is the formation of ice schlieren and the swelling associated with this. In developing the methods of calculation of moisture migration it was assumed (see, for example, [1, 2]) that the mass transfer occurs only in the thawed part of the soil and is realized predominantly in the liquid phase through the diffusion-film mechanism. It was assumed that the phase conversion of water into ice occurs wholly on the phase interface (the Stefan formulation) and at the same time supplementary conditions for the moisture function are specified on it. Not all these assumptions are valid. In particular, the marked redistribution of moisture in the frozen zone is an important factor in the freezing of moist rocks [3, 4]. This last is also observed in the thawing of dispersed rocks and in frozen samples which are under the influence of a temperature gradient. These phenomena were modeled in [5, 7] on the basis of a single mathematical model which describes the conductive heat transfer, the moisture transfer in thawed and frozen zones, the phase transition of moisture in the temperature range, and the kinetic relaxation effects of moisture crystallization and ice melting. Analysis of the solutions obtained by means of a finite difference method showed that the proposed method of calculation gives results near the experiment. The present paper is devoted to a further study of the model indicated.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 113–120, March–April, 1986.     

Effect of the percolation heat transfer component on the temperature field and thawing dynamics of soils

The effect of the convective heat transfer component on the temperature field and thawing front dynamics of soils is investigated for high fluid percolation velocities in the thawed zone. The steady state interchange and approximate self-similarity methods are used to obtain upper and lower bounds of the solution of the Stefan problem with a convective heat transfer component in a porous medium. From the results of the calculations conclusions are drawn concerning the accuracy and limits of applicability of the solutions obtained.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 166–171, March–April, 1987.     

Saltwater Upconing and Decay Beneath a Well Pumping Above an Interface Zone

Saltwater, or brine, underlies freshwater in many aquifers, with a transition zone separating them. Pumping freshwater by a well located above the transition zone produces upconing of the latter, eventually salinizing the pumped water, forcing shut-off. Following the well’s shut-off, the upconed saltwater mound undergoes decay, tending to return to the pre-pumping regime. The FEAS code is used for the simulation of coupled density-dependent flow and salt transport involved in the upconing–decay process. In this code, the flow equation is solved by the Galerkin finite element method (FEM), while the advective–dispersive salt transport equation is solved in the Eulerian–Lagrangian framework. The code does not suffer from the instability constraint on the Peclet number. The code is used to investigate the transient upconing–decay process in an axially symmetric system and to discover how the process is affected by two major factors: the density difference factor (DDF) and the dispersivities. Simulation results show that under certain conditions, pumping essentially freshwater can be maintained for a certain time period, the length of which depends on the dispersivity values used. A recirculating flow cell may occur in the saltwater layer beneath the pumping well, widening the saltwater mound. The decay process is lengthy; it takes a long time for the upconed saltwater to migrate back to its original shape of a horizontal transition zone prior to pumping. However, the wider transition zone caused by hydrodynamic dispersion can never return to the initial one. This indicates that once a pumping well is abandoned because of high salinity, it can be reused for groundwater utilization only after a long time. It is also shown that the upconing–decay process is very sensitive to DDF, which, in our work, ranges from 0 (for an ideal tracer) to 0.2 (for brine). For a DDF of 0.025 (for seawater), local upconing occurs only for low iso-salinity surfaces, while those of high salt concentration remain stable after a short time. For an ideal tracer, all iso-salinity surfaces rise toward the pumping well, whereas for brine only iso-salinity surfaces of very low salinity upcone towards the pumping well. This may imply that the traditional finding that the sharp interface approximation is practically close to the 0.5 iso-salinity surface may not be true for a high DDF solution.     

Numerical Modeling of Unsteady Radiative–Convective Heat Transfer on a Flat–Plate Boundary Layer in a Selectively Emitting and Scattering Medium

A conjugation problem for radiative–convective heat transfer in a turbulent flow of a high–temperature gas—particle medium around a thermally thin plate is considered. The plate experiences intense heating from an outside source that emits radiation in a restricted spectral range. Unsteady temperature fields and heat–flux distributions along the plate are calculated. The results permit prediction of the effect of the type and concentration of particles on the dynamics of the thermal state of both the medium in the boundary layer and the plate itself under conditions of its outside heating by a high–temperature source of radiation.     

Nonisothermal displacement of high-paraffin oils by water with allowance for solid-phase precipitation

A mathematical model of the nonisothermal displacement of oil by water with allowance for solid-phase precipitation is proposed. Self-similar solutions of the problem of nonisothermal displacement of oil from a homogeneous, thermally insulated formation are obtained. The inverse problems of determining the relative phase permeabilities and the temperature dependence of the paraffin saturation concentration from laboratory displacement data are solved. Exact solutions of the non-self-similar problems of the displacement of high-paraffin oil by a slug of hot water and of the thermal delay problem are obtained. The nonisothermal displacement of high-paraffin oils by water with allowance for heat transfer to the surrounding strata is subjected to qualitative analysis.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 126–137, May–June, 1989.The authors are grateful to A. K. Kurbanov and Yu. V. Kapyrin for useful discussions and their interest in the work.     

Two-dimensional flow in porous strata with conductivity modeling by a harmonic function of the coordinates

Boundary-value problems of two-dimensional flows in porous media are investigated in finite form for a broad class of strata with harmonic conductivity. The conformal covariance of the conjugation problem formulated is demonstrated. This makes it possible to reduce it to a canonical problem whose solutions are represented by quadratures. The solutions obtained are applied to new problems associated with the operation of a well in soil strata under complex geological conditions.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 102–112, May–June, 1995.     

Multi–Front Phase Transitions During Nonisothermal Filtration of Live Paraffin–Base Crude

By numerical modeling of nonisothermal filtration of multicomponent oil with allowance for the Joule—Thomson effect, adiabatic effect, and heat of phase transitions that occur during oil degassing and paraffin crystallization, the formation of profiles of phase–saturation, concentrations of oil components, and temperature in oil beds is studied. It is shown that consideration of many components results in occurrence of phase–transition fronts during degassing of oil components and paraffin crystallization. In turn, paraffin crystallization gives rise to temperature oscillations. Depending on the initial paraffin concentration and on the ratio of phase–transition heats for oil degassing and paraffin crystallization in an oil bed, either decaying or steady–state temperature oscillations are observed.     

A computerized technique for measuringin-situ concentrations during miscible displacements in porous media

A technique for measurement of thein-situ concentration in an unconsolidated porous medium has been developed. The method involves measurement of electrical conductivityin-situ, under dynamic conditions, for flow involving brine of differing concentrations, at selected locations along the porous medium and relating it to the brine strength. Data acquisition and analysis is carried out using a Hewlett — Packard micro-computer and its interface. A user-friendly software was designed and developed for the system. The measurement technique was evaluated by studying the effect of brine concentration, brine flow rate, and by conducting miscible displacements experiment. The experimentally measured dispersion coefficients for the porous medium agreed closely with the value predicted by the correlation available in the literature.     

Flow around and heat and mass transfer of a sphere with blowing at medium reynolds numbers

The Navier-Stokes and heat- and mass-transfer equations are solved numerically for a sphere with uniform blowing over the surface in the Reynolds number range up to 20. A method of refining the boundary conditions far from the sphere is proposed in both problems. A difference scheme from other authors is used to solve the hydrodynamic problem, and an explicit difference scheme with a second order of approximation is used for the heat problem. It is shown that blowing diminishes the aerodynamic drag of the sphere and the temperature or concentration gradient at its surface, i.e., the heat- and mass-transfer intensity.Translated from Zhurnal Priladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 148–156, July–August, 1975.     

Slip boundary conditions on a catalytic surface in a multicomponent gas flow

The boundary conditions for the velocity slip and temperature and concentration jumps on the surface of a body in a rarefied multicomponent gas flow are obtained. The mathematical treatment is given in detail because of the need to examine critically some previous results which disagree with each other in spite of the fact that the initial premises and the methods of solution were the same. The results of this study, which are given in a convenient form, represent the boundary conditions for both the simplified and the complete Navier-Stokes equations in problems of hypersonic rarefied gas flow past bodies with a catalytically active surface.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 159–168, January–February, 1996.     

Heat mass transfer in a turbulent layer above permeable membranes

The temperature and concentration fields in a boundary layer above perforated membranes are presented, and their relationship with the velocity fields given in [1] is established. Measurements of the thermal state of membranes are made with various geometric and thermophysical properties and various coolant drafts. Empirical formulas are also presented for thermal flux and temperature of the permeable walls.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 22–31, July–August, 1973.     

A lattice Boltzmann model for adsorption breakthrough

A lattice Boltzmann model is developed to simulate the one-dimensional (1D) unsteady state concentration profiles, including breakthrough curves, in a fixed tubular bed of non-porous adsorbent particles. The lattice model solves the 1D time dependent convection–diffusion–reaction equation for an ideal binary gaseous mixture, with solute concentrations at parts per million levels. The model developed in this study is also able to explain the experimental adsortption/desorption data of organic vapours (toluene) on silica gel under varying conditions of temperature, concentrations and flowrates. Additionally, the programming code written for simulating the adsorption breakthrough is modified with minimum changes to successfully simulate a few flow problems, such as Poiseuille flow, Couette flow, and axial dispersion in a tube. The present study provides an alternative numerical approach to solving such types of mass transfer related problems.     

High-frequency electrode discharge at reduced pressure

Results are presented for measured and calculated electron temperature and concentration, electric-field intensity, and electron collision frequency in a high frequency (hf) electrode discharge at pressures below atmospheric.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 13–17, July–August, 1973.     

Convection in mixtures with nonuniform heat release proportional to the density of an active component

A study is made of the stability of a horizontal layer of a two-component mixture with concentration gradient of the active (heat releasing) component directed upward. The nature of the instability depends strongly on the direction of the gradient. In the investigated case, the stability may be either monotonic or oscillatory in nature. The problem is also distinguished by the existence of two independent neutral curves associated with the thermal and concentration instability mechanisms. The regions in which monotonic and oscillatory convection occur are found by stepwise integration. Graphs of the amplitudes of the critical perturbations of the velocity, temperature, and concentration are given.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 21–27, November–December, 1980.We thank E. M. Zhukhovitskii for discussing the results.     

Boundary value problems for a model Boltzmann equation with frequency proportional to the molecule velocity

Exact solutions of a model Boltzmann equation with a collision frequency that depends on the molecule velocity and with a BGK (Bhatnagar-Gross-Krook) collision operator are constructed for the problems of weak evaporation and temperature jump in a rarefied vapor above a plane surface. The numerical calculations and a comparison with previous results are given.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 140–153, May–June, 1996.     

Comparison of numerical solutions of the Navier—Stokes equations and a kinetic model in the one-dimensional case

On the basis of the Navier—Stokes equations, numerical solutions are found to the problems of reflection of a plane shock wave from a wall and the convergence of a spherical wave on the symmetry center. Comparison with the well-known solutions of these problems in the framework of the kinetic S model reveals good agreement in the plane case and discrepancies in the spherically symmetric case, these being manifested especially in the temperature profiles.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 150–153, September–October, 1980.We thank O. S. Ryzhov for interest in the work.     

Measurement of translational temperature in low-density jets

A technique and method for measuring the velocity-distribution function of the atoms in rarefied gas flows are described. Some results obtained with flows of binary gas mixtures behind a sonic nozzle are presented. The temperature of the light component (helium) is determined from the half width of the distribution function. Incomplete restoration of the helium temperature occurs in the Mach disk. This effect is examined in relation to concentration. A qualitative explanation is proposed for the effect in question.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 30–34, January–February, 1973.     

Modification of a mouldboard plough surface using arrays of polyethylene protuberances

Surface design modifications have recently exhibited a means of reducing soil-tool adhesion. The tribological characteristics of soil-burrowing animals were employed on tillage machinery to study the effect on adhesion. Considering the characteristics of dung beetles, ultra high molecular weight polyethylene (UHMW-PE) protuberances were mounted as embossed arrays on a mouldboard plough. To investigate a suitable geometry of such protuberances, five shapes were studied (flat, semi-spherical, semi-oblate, semi short-prolate and semi long-prolate) using a combination of base diameters and protrusion heights. The dimensionless height to diameter ratio (HDR) was used to characterize the geometry. Experiments were conducted to evaluate the resultant influence of various geometrical shapes and sizes of the protuberances (base diameter: 20–50 mm; protrusion height: 0–50 mm) on lowering the ploughing resistance of the mouldboard plough in Bangkok clay soil. A comparison was made between the modified and the conventional plough in dry (21.8% (d.b.)), sticky (37.2% (d.b.)), wet (49.1% (d.b.)) and flooded (64.3% (d.b.)) Bangkok clay soil at 1, 3 and 5 km/h forward speeds. Percent reduction in ploughing resistance of bionic mouldboard plough in these soil conditions with HDR = 0 was 1–6% in dry soil, 16–22% in sticky soil, 14–20% in wet soil and 8–12% in flooded soil. With HDR = 0.25 the ploughing resistance was reduced by 2–7% in dry soil, 18–36% in sticky soil, 17–33% in wet soil and 15–28% in flooded soil. Similarly with HDR = 0.5, it reduced by 10–16% in sticky soil, 6–17% in wet soil and 12–26% in flooded soil. Whereas, HDR > 0.5 increased the ploughing resistance by 7–29%.     

Seepage from shallow channels and irrigation furrows

Two cases of two-dimensional steady seepage from broad channels and irrigation furrows through a layer of homogeneous isotropic soil into a highly permeable pressurized aquifer in the presence of soil capillarity are examined in the hydrodynamic formulation. A uniform method of solution in which the solution of the problem of seepage from an irrigation furrow can be obtained from the solution for a broad channel is given. The special and limiting cases studied in [1–3] and elsewhere are noted. Computer calculations are used to analyze the dependence of the rate of seepage from channels and irrigation furrows and the capillary spread on the profile and width of the channel or irrigation furrow, the thickness of the layer, the head and the capillarity of the soil.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 96–102, January–February, 1989.The authors are grateful to N. N. Verigin for valuable comments.