1. A method for determining characteristic sizes of at least one fluid-filled crack in a medium, the method comprising the steps of:
registering oscillations of the at least one fluid-filled crack;
selecting lowest resonance frequencies from the registered oscillations;
determining frequencies v(n) (n is integer) of standing interface waves propagating along surfaces of the at least one fluid-filled crack as corresponding to the selected resonance frequencies; and
calculating the characteristic sizes of the at least one fluid-filled crack based on the determined frequencies v(n) of the standing interface waves and taking properties of the medium and the fluid into account.
2. The method of claim 1, further comprising the step of exciting the at least one fluid-filled crack oscillations prior to registering thereof, wherein the steps of the method are performed in real time.
3. The method of claim 1, wherein the medium is a subterranean formation, a crack mouth is adjacent to an injection well, and a crack width w is determined separately from other characteristic sizes thereof, and wherein:
the step of registering is based on registering fluid pressure oscillations in the injection well; and
the step of calculating comprises calculating an interface wave group velocity V(v(n),w) which further depends on properties of the formation and the fluid; and calculating a characteristic size L along the standing interface wave propagation in accordance with the following formula
L
n
=
V
\u2061
(
v
(
n
)
,
w
)
2
\u2062
v
(
n
)
.
4. The method of claim 3, further comprising the step of exciting oscillations of the at least one fluid-filled crack prior to registering thereof, wherein said oscillations of the at least one fluid-filled crack are excited by a sudden fluid pressure change in the injection well, said sudden fluid pressure change in the injection well being provided by a rapid cessation of pumping.
5. The method of claim 3, wherein the interface wave group velocity V(v(n),w) is determined either assuming, that the fluid is a non-viscous fluid, or assuming that the fluid is a viscous Newtonian fluid.
6. The method of claim 3, wherein the lowest resonance frequency v of oscillations of the at least one fluid-filled crack is determined and the maximum distance L between the crack edges is estimated as a characteristic size thereof in accordance with the following formula
L
=
V
\u2061
(
v
,
w
)
2
\u2062
v
.
7. The method of claim 3, wherein the formation and fluid properties, on which the interface wave group velocity depends, are refined based on the determined standing interface wave frequencies, the formation properties including porosity and permeability and the fluid properties including viscosity, the at least one fluid-filled crack being either a natural crack or an artificially-made crack, and, wherein the subterranean formation is a shelf subterranean formation.
8. The method of claim 3, wherein the crack width is either determined a priori by measurements, said measurements being implemented by at least one tilt-meter, or determined based on matching a known volume of the pumped fluid with a model estimation of the crack volume.
9. The method of claim 3, wherein oscillations of the at least one fluid-filled crack are registered by at least one transducer clamped in the vicinity of the at least one fluid-filled crack, said at least one transducer being clamped inside the injection well, or by registering oscillations of either natural or artificially-made objects, the oscillations being induced by oscillations of the at least one fluid-filled crack, or by registering at least one natural phenomenon, induced by oscillations of the at least one fluid-filled crack, said at least one natural phenomenon including gravitational, electromagnetic, seismo-electric, optical, thermodynamic, and electro-kinetic phenomena.
10. The method of claim 1, wherein the medium is a fluid-submerged part of a construction element, the at least one fluid-filled crack intersects a surface of the construction element fluid-submerged part, and a crack width is measured directly, and wherein:
the step of registering comprises clamping a transducer at the intersection of the at least one fluid-filled crack with a surface of the construction element fluid-submerged part, and registering oscillations by said transducer,
the step of calculating comprises calculating an interface wave group velocity V(v(n),w) which further depends on properties of the construction element and the fluid and calculating a characteristic size L along the standing interface wave propagation in accordance with the following formula
L
n
=
V
\u2061
(
v
(
n
)
,
w
)
2
\u2062
v
(
n
)
.
11. The method of claim 10, further comprising the step of exciting the at least one fluid-filled crack oscillations prior to registering thereof, wherein said at least one fluid-filled crack oscillations are excited by a sudden deformation of a crack edge.
12. The method of claim 10, wherein the construction element is one of the following: a bridge pier, a marine platform pier, or a building foundation, and wherein the at least one fluid-filled crack is either a natural crack or an artificially-made crack.
13. A system for determining characteristic sizes of at least one fluid-filled crack in a subterranean formation in accordance with the method of claim 3, the system comprising:
registration means for registering fluid pressure oscillations in an injection well;
data processing means for determining frequencies of standing interface waves propagating along surfaces of the at least one fluid-filled crack, calculating an interface wave group velocity, and calculating a characteristic size of the at least one fluid-filled crack along the standing interface wave propagation; means for generating a signal comprising results of the calculations.
14. The system of claim 13, further comprising means for pumping a fluid into the injection well to excite oscillations of the at least one fluid-filled crack, wherein the registering means are clamped in a vicinity of the crack mouth, the signaling means transmits the generated signal either to a local display device or to a remote display device, and the data processing means and the signaling means are integrated into a single device.
15. A method for determining properties of a fluid filling a layer in a subterranean formation, of the subterranean formation and of the layer, the method comprising the steps of:
registering interface waves propagating along surfaces of the fluid-filled layer;
determining frequencies and velocities of the registered interface waves; and
calculating the properties of the fluid, the subterranean formation and the fluid-filled layer based on the determined frequencies and velocities of the interface waves.
16. The method of claim 15, further comprising the step of exciting the interface waves propagating along the fluid-filled layer surfaces prior to registering thereof.
17. The method of claim 15 or 16, wherein the subterranean formation is a shelf subterranean formation, and wherein the fluid-filled layer property is a width thereof, the fluid properties are viscosity and density, and the subterranean formation properties are porosity and permeability, and wherein the step of calculating comprises
matching the determined velocities with the velocities calculated based on model equations which contain terms corresponding to the interface wave frequencies and the required properties enter, and
determining the required properties based on said model equations using the determined interface wave frequencies.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A battery pack comprising:
a cell module comprising a plurality of battery cells; and
a coil unit installed on one side of the cell module and having coils stacked therein, the coils being connected to the respective battery cells.
2. The battery pack according to claim 1, wherein the coil has one side connected to a first electrode of a cell and the other side connected to a battery management system (BMS).
3. The battery pack according to claim 2, wherein the first electrode comprises an anode.
4. A battery apparatus comprising:
a cell module comprising a plurality of battery cells;
a coil unit installed on one side of the cell module and having coils stacked therein, the coils being connected to the respective battery cells; and
a BMS configured to select a transmitting cell and one or more receiving cells based on states of charge (SOC) of the respective cells, and form an induced current between a coil connected to the transmitting cell and coils connected to the one or more receiving cells.
5. The battery apparatus according to claim 4, wherein the BMS comprises:
a cell management unit configured to manage IDs of the respective cells;
a voltage sensor configured to measure the SOC of each of the battery cells;
a cell selection unit configured to select a transmitting cell and one or more receiving cells based on the measurement result of the voltage sensor, when cell balancing is required; and
a path control unit connected between each battery cell and a coil connected to the battery cell, and configured to form a current path such that the coil connected to the transmitting cell and the coils connected to the one or more receiving cells cause magnetic induction therebetween.
6. The battery apparatus according to claim 5, wherein the cell selection unit selects a cell having the highest SOC as the transmitting cell.
7. The battery apparatus according to claim 5, wherein the cell selection unit selects the receiving cells by a designated number of receiving cells from a cell having the lowest SOC.
8. The battery apparatus according to claim 5, wherein the path control unit comprises:
a first switch connected to a first electrode of a battery cell;
a DC-to-AC converter connected to the first switch;
a third switch connected to the DC-to-AC converter and turned on or off in connection with the first switch;
a second switch connected to the first electrode of the battery cell in parallel to the first switch;
an AC-to-DC converter connected to the second switch; and
a fourth switch connected to the AC-to-DC converter, turned on or off in connection with the second switch, and having one end connected to one end of the third switch.
9. The battery apparatus according to claim 8, wherein a coil connected to the battery cell has one side connected to a second electrode of the battery cell and the other side connected to a common connection terminal of the third and fourth switches.
10. A cell balancing method of a battery apparatus which includes a cell module including a plurality of battery cells, a coil unit installed on one side of the cell module and having coils stacked therein, the coils being connected to the respective battery cells, and a BMS connected to one side of the coil, the cell balancing method comprising the steps of:
measuring, by the BMS, SOC of the respective cells included in the cell module;
determining, by the BMS, a transmitting cell and one or more receiving cells based on the SOC measurement results; and
forming, by the BMS, a current path such that a coil connected to the transmitting cell and coils connected to the one or more receiving cells cause magnetic induction.
11. The cell balancing method according to claim 10, wherein the step of determining the transmitting cell and the one or more receiving cells comprises the step of selecting a cell having the highest SOC.
12. The cell balancing method according to claim 10, wherein the step of determining the transmitting cell and the one or more receiving cells comprises the step of selecting the battery cells by a designated number of cells from a cell having the lowest SOC.