On the mechanism of cyclic flooding for oil extraction

A two-dimensional model is considered for the displacement of oil by water from a stratum that is nonuniform over its thickness when a periodic elastic flow regime is employed.Translated from Izvestiya Akademii Nauk SSSR, Meknanika Zhidkosti i Gaza, No. 3, pp. 58–66, May–June, 1980.     

Hydrodynamic features of the exploitation of highly nonuniform source-type oil formations

The flow of a weakly compressible fluid in a highly nonuniform formation with block structure, classified as source-type, is considered. An analytic solution of the problem of fluid flow into a well in a bounded circular reservoir is obtained. On the basis of this solution the effect of the fluid offtake rate on the depletion of the reservoir is investigated. It is shown that in highly nonuniform media a number of unsteady effects, which cannot be described by the classical model with steady mass transfer, occur.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 113–120, September–October, 1993.     

Numerical solution of shallow water magnetohydrodynamic equations with non-flat bottom topography

The governing equations of shallow water magnetohydrodynamics describe the dynamics of a thin layer of nearly incompressible and electrically conducting fluids for which the evolution is nearly two-dimensional with magnetic equilibrium in the third direction. A high-resolution central-upwind scheme is applied to solve the model equations considering non-flat bottom topography. The suggested method is an upwind biased non-oscillatory finite volume scheme which doées not require a Riemann solver at each time step. To satisfy the divergence-free constraint, the projection method is used. Several case studies are carried out. For validation, a gas kinetic flux vector splitting scheme is also applied to the same model.     

Estimate of the residual volume of viscoplastic oil after flooding

The problem of calculating regions of residual viscoplastic oil with a critical pressure gradient is considered. This problem has hitherto been solved mainly for uniform strata (see, for example, [1–3]) but in the present paper, which follows the work of Entov, Pankov, and Pan'ko [4], the problem is considered not only for uniform strata but also for layered strata and vertically nonuniform strata. It is shown that for sufficiently thin strata allowing free flow between individual seams the formulation of the problem is the same for the piston model and the Buckley-Leverett model and reduces to a two-dimensional boundary value problem with a continuous nonlinear effective flow law for the water. An approximate numerical method of calculating regions of residual oil that is suitable for the three listed types of strata is described and illustrated by examples.     

Over-reflection and instabilities in shear flows of shallow water with bottom friction

In a two-dimensional shear flow of shallow water, the bottom friction relates uniquely the spanwise profile of the depth-averaged velocity to the bottom topography. If the basic flow varies weakly in the spanwise direction, the local analysis of stability at every spanwise position gives the region of the flow parameters for which the classic hydraulic instability due to the bottom friction cannot occur. In this region, the linear analyses of the waves scattering and instability due to the lateral shear can be performed effectively by means of the frictionless linearized equations if both the bottom slope and friction are equally small.The energy of the total perturbed flow can be split into three main parts that correspond to the basic flow, small amplitude wave motion and induced mean flow. The waves can be either amplified or damped near the critical layers, where their streamwise phase velocity equals the velocity of the basic flow. Two physical mechanisms of this amplification exist. The first one is similar to that suggested by Takehiro and Hayashi for a linear frictionless shallow water flow. The incident and transmitted waves carry energy of opposite signs, which results in an increase in the amplitude of the reflected wave compared to that of the incident one. This mechanism of over-reflection operates for any combination of the flow parameters. The other mechanism is similar to Landau damping in plasma flows; it is related to the energy exchange between the waves and fluid particles at the critical layers due to the velocity synchronism. It may lead to either additional amplification or damping of the waves for different flow conditions. In particular, its significance can be reduced by stronger bottom friction. If the basic flow has uniform potential vorticity, Landau damping is negligible, and over-reflection always occurs. If the feed-back is provided by another critical layer, the net over-reflection results in the formation of trapped modes.     

Simulation of micellar-polymer flooding of a layered oil reservoir of nonuniform thickness

The dynamics of oil displacement from a layered reservoir of nonuniform thickness consisting of two hydrodynamically connected layers of different absolute permeability is studied. Results of numerical calculations are given. The influence of the main determining factors on the oil displacement dynamics is studied. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 115–123, November–December, 2008.     

浅水舰船引起水底附近的扰动速度研究

基于浅水波浪理论,建立了亚临界和超临界航速条件下舰船运动引起水底附近扰动速度的理论计算模型。通过数值计算,揭示了扰动速度分量的变化规律和分布特点。建立了舰船扰动速度的测试系统,对船模运动引起的扰动速度进行了测量。横向扰动速度分量计算结果与实验结果基本吻合,纵向扰动速度分量计算结果与实验结果定性一致。理论与实验研究表明,...     

Comparative analysis of methods of areal flooding of stratified reservoirs of anomalous oil

When anomalous oils in productive reservoirs are displaced by water [1], residual undisplaced oil remains [2, 3]. For calculating the volume of the unrecovered oil, most studies have been of homogeneous reservoirs [4–8]. In the present paper, the residual volume is assessed using an inhomogeneous-stratified-model. The inhomogeneity of the strata is described by the random distributions of Weibull or Pearson (gamma-distribution), which are characteristic of oilfields possessing anomalous properties (see, for example, [9]). A parametric study is made of four known schemes of areal flooding: two-point (straight line), five-, seven-, and nine-point [10]. The obtained estimates of the volume of the residual oil can be used for rational selection of the parameters for exploiting anomalous oilfields.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 121–126, May–June, 1985.     

Displacement mechanisms of enhanced heavy oil recovery by alkaline flooding in a micromodel

Enhanced oil recovery (EOR) by alkaline flooding for conventional oils has been extensively studied. For heavy oils, investigations are very limited due to the unfavorable mobility ratio between the water and oil phases. In this study, the displacement mechanisms of alkaline flooding for heavy oil EOR are investigated by conducting flood tests in a micromodel. Two different displacement mechanisms are observed for enhancing heavy oil recovery. One is in situ water-in-oil (W/O) emulsion formation and partial wettability alteration. The W/O emulsion formed during the injection of alkaline solution plugs high permeability water channels, and pore walls are altered to become partially oil-wetted, leading to an improvement in sweep efficiency and high tertiary oil recovery. The other mechanism is the formation of an oil-in-water (O/W) emulsion. Heavy oil is dispersed into the water phase by injecting an alkaline solution containing a very dilute surfactant. The oil is then entrained in the water phase and flows out of the model with the water phase.     

An analysis of the viability of polymer flooding as an enhanced oil recovery technology

The concept of improving oil recovery through polymer flooding is analysed. It is shown that while the injection of a polymer solution improves reservoir conformance, this beneficial effect ceases as soon as one attempts to push the polymer solution with water. Once water injection begins, the water quickly passes through the polymer creating a path along which all future injected water flows. Thus, the volume of the polymer slug is important to the process and an efficient recovery would require that the vast majority of the reservoir be flooded by polymer. It is also shown that the concept of grading a polymer slug to match the mobilities of the fluids at the leading and trailing edges of a polymer slug does not work in a petroleum reservoir. While this process can supply some additional stability to the slug, it is shown that for the purposes of enhanced oil recovery this additional stability is not great enough to be of any practical use. It is found that in this case the instability has simply been hidden in the interior of the slug and causes the same sort of instability to occur as was the case for the uniform slug.     

Higher order Boussinesq-type equations for water waves on uneven bottom

Higher order Boussinesq-type equations for wave propagation over variable bathymetry were derived. The time dependent free surface boundary conditions were used to compute the change of the free surface in time domain. The free surface velocities and the bottom velocities were connected by the exact solution of the Laplace equation. Taking the velocities on half relative water depth as the fundamental unknowns, terms relating to the gradient of the water depth were retained in the inverse series expansion of the exact solution, with which the problem was closed. With enhancements of the finite order Taylor expansion for the velocity field, the application range of the present model was extended to the slope bottom which is not so mild. For linear properties, some validation computations of linear shoaling and Booij' s tests were carried out. The problems of wave-current interactions were also studied numerically to test the performance of the enhanced Boussinesq equations associated with the effect of currents. All these computational results confirm perfectly to the theoretical solution as well as other numerical solutions of the full potential problem available.     

Convective heat transfer for cold tube bundles with ice formations in a stream of water at steady state

Experiments were conducted on cold-tube banks subjected to a cross-flow of water. The tubes were internally cooled below the freezing temperature and became enveloped in ice. The resulting ice shapes, which formed on the outside surfaces of the tubes, were allowed to stabilize, and their impact on the total steady-state rate of energy exchange between the tubes and the flowing water was investigated.

Both in-line and staggered tube-bank geometries were considered, with tests conducted in the low to moderate Reynolds number range (Re_d = 100−2,000) and for cooling-temperature ratio variations of 0.5 < Θ < 8. The ice formations were directly observed and photographed, and the total heat transfer rate for the tube bank was inferred from a simple energy balance on the system.

The ice shapes that formed around the tubes were described by one of three distinct categories: ice formutions with no linkage occurring between any adjacent tubes; ice formations with partial linkage of some adjacent tubes; and, for the staggered tube bank, a complete linkage of a majority of the tubes.

The experiments showed that the ice formations dramatically affected the convective heat transfer rate of the tube banks (when compared to nonicing tube banks at the same Re_d) and that the change in heat transfer rate is dependent on the tube-bank geometry. In the no-link category, the ice formations were found to either increase or decrease the tube-bank heat transfer rate depending on the amount of ice-build accumulation, the staggered configuration showing a greater overall rise with Θ than the in-line geometry. Ice linkage between adjacent tubes was found to be detrimental to the heat transfer rate of the staggered bank; however, the same phenomenon on the in-line tube bank did not seriously impede its heat transfer rate. Correlations expressing the heat transfer behavior of both in-line and staggered tube banks with ice formations at steady state have been developed.     

Oil low to a lateral well in the presence of bottom water

Exact solutions are obtained for a number of two-dimensional problems of steady-state fluid flow to a lateral hole in a reservoir with a quiescent bottom fluid of higher density or with a fluid of lower density at the reservoir top __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 5, pp. 114–126, September–October, 2008.     

Optimal deployment of spin-stabilized tethered formations with continuous thrusters

Nonlinear Dynamics - This paper addresses issues relevant to thruster-aided deployment of spin-stabilized tethered formations in a circular orbit. The dynamics of the tethered formation are first...