Pumps – Successive stages
Reexamination Certificate
2001-02-06
2001-10-23
Wolfe, Willis R. (Department: 3747)
Pumps
Successive stages
C417S247000, C417S251000, C418S048000
Reexamination Certificate
active
06305911
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and to a system for delivering energy to several fluids and simultaneously for mixing them, one of the fluids being miscible in the other fluid or fluids.
2. Description of the Prior Art
The prior art describes various solutions for eliminating acid gases.
One solution consists in injecting the acid gases individually into a reservoir by using centrifugal or reciprocating compressors.
Another procedure consists in injecting the acid gases with another fluid, for example the formation water available in the reservoir. This solution notably has the advantage of eliminating simultaneously the acid gases and the formation water, considered as two pollutants.
Pan Canadian Limited's formation water and acid gas reinjection process, whose main stages are summed up hereafter and described in
FIG. 1
, is based on this principle.
The fluid coming from production wells is split into an oil phase which is recovered, an aqueous phase and a gas phase circulating respectively in lines
1
and
2
. The aqueous phase is stored in atmospheric tanks
3
, whereas the gas phase containing the acid gases is processed in an amine treating plant
4
in order to obtain a gas without acid components and a gas with a high acid component content at a pressure close to the atmospheric pressure. The gas fraction rich in acid gases is sent to a compressor
5
and the formation water is sent to a single-phase pump
6
. The gas and the formation water, which have separately reached a given pressure level, are then mixed together in a mixer
7
. Mixing is performed at a high pressure in order to facilitate dissolution of the gases in the water, the amount of dissolved acid gases increasing with the pressure level. This mixture occurring in the liquid form is then reinjected for example into an underground reservoir by means of a single-phase pump
8
suited to pump liquid single-phase fluids. Upstream from the high-pressure pump, the gas must be entirely dissolved in the liquid and the NPSHA (suction head available in relation to the vapor pressure of the gas) must also be higher than the NPSHR (suction head required at the pump inlet in relation to the vapour pressure).
In the case of high reinjection pressure applications and for production fluids with a high gas content, mixing of the water and of the gas is performed in successive separate pumping, compression and mixing stages.
This process requires equipment which has the drawback of being heavy and expensive, using both single-phase pumps and compressors, as well as many heat exchangers. Furthermore, as dissolution of the acid gases in the water is not instantaneous, it is necessary to use static or dynamic mixers in order to obtain perfect dissolution of the gas in the liquid upstream from the single-phase pumps, thus increasing even further the complexity of the materials, the cost and the overall dimensions of such a system.
SUMMARY OF THE INVENTION
The present invention proposes to overcome the drawbacks of the prior art by adopting a new approach allowing notably to minimize the number of equipments commonly used.
The invention is notably applicable to fluids which occur in an essentially gaseous form and which are miscible or soluble in an essentially liquid fluid.
The present invention notably allows, by means of a single machine, both compression of an acid gas and formation water from an oil reservoir, and mixing of them in an essentially liquid form, the acid gases being particularly soluble in formation water. The liquid mixture obtained can be sent to a storage zone or reinjected in a production well or an aquifer.
The invention is in particular applied to the processing of natural gas containing acid gases, carbon dioxide and/or hydrogen sulfide, which are generally at least partly separated from the natural gas. When present in small amounts, these separated acid gases can be discharged into the atmosphere, directly or after incineration. However, pollution control standards being increasingly stringent, these discharges into the atmosphere are less and less allowed, and it has become necessary to find other solutions compliant with these new standards with a minimum investment.
According to the invention, a two-phase compression device is used capable of delivering energy to several fluids, at least one of the fluids being soluble in at least one other fluid, and of mixing simultaneously the fluids, so as to obtain at the outlet a fluid in an essentially or completely liquid form.
The present invention is a two-phase compression device which delivers energy to several fluids such as an essentially liquid fluid and an essentially gaseous fluid, at least one of the fluids being miscible in at least one other fluid, and allowing mixing of one.
The invention comprises at least one two-phase compression element which mixes the essentially liquid and essentially gaseous fluids and provides each one of them a given energy value, the mixture coming from said two-phase compression element being in a liquid or essentially liquid form and at a given pressure level.
According to an embodiment, the two-phase compression device can comprise at least one inlet stage and/or at least one outlet stage, each of the stages comprising hydraulics which pump an essentially liquid fluid.
The compression device can have at least two sections, the first section providing a mixture Mi with a pressure level Pi and the second section providing from mixture Mi, a mixture Ms with a pressure level Ps, a discharge line for mixture Mi and a delivery line for fluid Mi in the second section, said two sections being separated by a sealing device and the hydraulics of the two sections being mounted “back to back” so as to minimize axial thrust stresses.
The two-phase compression device can comprise a device positioned between two compression stages and suited to mix at least the essentially liquid fluid and the essentially gaseous fluid, for example in cases where these two fluids are introduced at stages of different ranks.
The compression device can also comprise a fluid processing and/or mixing unit, said processing and/or mixing unit being connected to the compression device by fluid delivery and discharge lines, before and after processing.
In some instances, the processing unit comprises a refrigeration device included in the processing unit.
The processing unit can comprise a circuit for cooling at least part of the two-phase mixture withdrawn from the two-phase compression device and/or part of the liquid phase coming from the two-phase compression device.
The compression device comprises for example means for determining parameters linked with the fluid and/or the functioning thereof, data computing and processing means capable of changing the rotating speed of the two-phase compression device and/or of acting on the efficiency of the refrigeration means and/or on the flow rate of the fluid recycled at the level of the cooling circuit.
The object of the invention is also a process for delivering energy to several fluids, at least one of the fluids being miscible in at least one other fluid, and for simultaneously mixing fluids such as an essentially gaseous fluid and an essentially liquid fluid.
The essentially gaseous fluid and the essentially liquid fluid at least are sent to the same two-phase compression device which delivers energy to at least each one of the two fluids, and which mixes the two fluids together in order to obtain at the outlet an essentially liquid fluid at a given pressure.
According to the process, the pressure difference between the fluids to be mixed is for example determined prior to feeding them into the two-phase compression device, and
if the value of this difference is less than a set value, the two fluids are sent to the same two-phase compression stage of the compression device, and
if the value of this difference is greater than a set value, the fluid with the lower pressure is sent to a stage of the compression device of rank i and
Antonelli Terry Stout & Kraus LLP
Institut Francais du Pe'trole
Wolfe Willis R.
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