Subsea system and method for pressurization of a subsea oil reserve by injecting at least one of water and gas

Abstract

The present invention relates to the injection of water and gas, either simultaneously or alternately, into subsea wells in order to enhance production and the oil recovery level. Thus, the present invention provides a subsea system for pressurizing a subsea oil reservoir injecting at least one of water and gas, comprising (i) at least two subsea injection wells (4, 4′), each subsea injection well (4, 4′) being connected to a production unit (5) by means of a single subsea line (1, 2) which is connected to the respective subsea injection well (4, 4′) by a main injection mandrel (6, 6′), and (ii) at least one jumper (3), each jumper (3) hydraulically connecting two of the at least two adjacent subsea injection wells (4, 4′) through annular mandrels (7, 7′). The present invention further provides a subsea reservoir pressurization method associated with the above-described system.

Claims

1. A subsea system for pressurizing a subsea oil reservoir injecting at least one of water and gas, the system comprising: at least two subsea injection wells each of the subsea injection wells is interconnected to a production unit using a single submarine line that connects to each of the respective subsea injection wells through a main injection mandrel, and at least one jumper, wherein each jumper fluidly communicates directly between two of the at least two subsea injection wells through adjacent annular mandrels of the subsea injection wells.

2. A system according to claim 1, wherein the jumper further comprises a taking up and injecting seawater subsea system.

3. A system according to claim 2, wherein the taking up and injecting seawater subsea system comprises at least one valve, at least one choke, at least one flowmeter, a discharge pipe, a check valve, an injection pump, a suction valve, a filter and a suction pipe.

4. A system according to claim 2, wherein the taking up and injecting seawater subsea system is in fluid communication with the annular mandrels of the at least two adjacent subsea injection wells through the at least one jumper.

5. A system according to claim 2, wherein the taking up and injecting seawater subsea system further comprises at least one dual hydraulic tap.

6. A system according to claim 2, wherein the taking up and injecting seawater subsea system further comprises at least one auxiliary valve remotely operated by remotely operated vehicle (ROV).

7. A subsea method for pressurizing a subsea oil reservoir injecting at least one of water and gas, the method comprising: injecting at least one of water and gas a subsea injection well of an assembly comprising at least two subsea injection wells, each of the subsea injection wells is interconnected to a production unit using a single submarine line which connects to each of the respective subsea injection wells via a main injection mandrel, wherein a jumper hydraulically connects two of the at least two adjacent subsea injection wells directly through annular mandrels, wherein the injecting of at least one of water and gas in the subsea injection well is from the production unit or from a subsea system for capturing and injecting in fluid communication with the at least one subsea injection well.

8. A method according to claim 7, wherein the injecting of at least one of water and gas into at least one subsea injection well comprises continuous or alternate injection of at least one of water and gas through the different single submarine lines from the production unit.

9. A method according to claim 8, wherein the alternate injection of at least one of water and gas through the different single submarine lines from the production unit further comprises the injection of pads of an inert fluid in the interfaces between water and gas.

10. A method according to claim 7, wherein the injecting comprises injecting gas through the different single submarine lines from the production unit and injecting seawater from the subsea system for capturing and injecting in fluid communication with the at least one subsea injection well.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The detailed description set forth below refers to the accompanying figures and the respective reference numerals thereof representing embodiments of the present invention.

(2) FIG. 1 illustrates a schematic view of a system according to a first embodiment of the present invention, comprising a pair of injecting wells hydraulically connected by single short subsea line (jumper).

(3) FIG. 2 illustrates a schematic view of the system according to a second embodiment of present invention, further comprising water taking up and injecting subsea system.

(4) FIG. 3 illustrates a detailed schematic view of the water taking up and injecting subsea system of the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) Firstly, it is emphasized that the following description describes preferred embodiments of the invention. As will be apparent to one skilled in the art, however, the invention is not limited to such particular embodiments.

(6) In a first embodiment of present invention illustrated in the schematic view of FIG. 1, two subsea injection wells 4, 4′ are interconnected to a production unit 5 such as a FPSO (Floating Production Storage and Offloading) through their respective subsea injection lines 1, 2 connected to respective main injection mandrels 6, 6′ of each subsea injection wells 4, 4′. The wells 4 and 4′ are connected hydraulically through a short subsea line, such as a jumper 3, which connects by annular mandrels 7, 7′ of each of subsea injection wells 4, 4′.

(7) The jumper 3 facilitates the switching and exchange of fluid in subsea lines 1, 2, facilitating the displacement of pads of inert fluids, for example: diesel.

(8) Additionally, the jumper 3 enables the passage of tools and fluids through the subsea lines and subsea injection wells 4, 4′, such as scraper, also known as pig. To facilitate understanding, further illustrates are the commonly existing valves in the assembly comprised of production base and wet Christmas tree installed in subsea wellheads, where:

(9) M1—injection master valve;

(10) M2—annular valve;

(11) W1—main wing valve;

(12) W2—annular wing valve;

(13) S1—main swab valve;

(14) S2—annular swab valve;

(15) XO—cross over valve;

(16) PXO—cross over pig valve;

(17) DHSV—downhole safe valve.

(18) Optionally, according to a second embodiment illustrated in the schematic view of FIG. 2, water is collected, filtered and injected directly from the seabed in each of the subsea injection wells 4, 4′ through a taking up and injecting seawater subsea system 8.

(19) Preferably, the taking up and injecting seawater subsea system 8 is in fluid communication with the annular mandrels 7, 7′ of adjacent subsea injection wells 4,4′ through at least one jumper 3. More preferably, the taking up and injecting seawater subsea system 8 is positioned along jumper 3, as shown in FIG. 2.

(20) Preferably, the taking up and injecting seawater subsea system 8 comprises valve 10, chokes 11, 11′, flow meters 12, 12′, discharge pipe 13, check valve 14, injection pump 15, suction valve 16, filter 17 and suction pipe 18.

(21) Optionally, at least one dual hydraulic tap 20, hot stab type, is used for the depressurizing operation and hydrate mitigation. Further optionally, auxiliary valves 19, 19′ remotely operated by ROV (Remotely Operated Vehicle) are provided. Through the dual hydraulic tap 20 it is possible to draw fluid from one side of valve 10 and return to the other side, promoting depressurization on the desired side.

(22) The present invention further provides a subsea method for pressurizing a subsea oil reservoir by injection of at least one of water and gas, comprising the step of injecting at least one of water and gas in at least one subsea injection well 4, 4′ of an assembly comprised of at least two subsea injection wells 4, 4′, each subsea injection well 4, 4′ being interconnected to a production unit 5 through a single subsea line 1, 2 that connects to the respective subsea injection well 4, 4′ via a main injection mandrel 6, 6′.

(23) The method of present invention also relies on a jumper 3, connecting physically and hydraulically two of the at least two adjacent subsea injection wells 4, 4′ through annular mandrels 7, 7′, facilitating the operations of displacement and exchange of fluids in subsea lines 1 and 2, with or without pig passage.

(24) Additionally, the step of injecting at least one of water and gas in at least one subsea injection well 4, 4′ is carried out from the production unit 5 or from subsea taking up and injecting system 8 in hydraulic communication with the at least one subsea injection well 4, 4′.

(25) Optionally, the injecting step comprises injecting continuously or alternately at least one of water and gas through the different single subsea lines 1, 2 only from the production unit 5.

(26) Optionally, the alternate injection of at least one of water and gas through the different single subsea lines 1, 2 from the production unit 5 further comprises injecting inert fluid pads in the interfaces between water and gas. Preferably, the inert fluid is diesel oil.

(27) Alternatively, the step of injecting comprises the injecting gas through different single subsea lines 1, 2 from the production unit 5 and injecting seawater from the subsea taking up and injecting system 8 in fluid communication with the at least one subsea injection well 4, 4′.

(28) Therefore, it is pointed out that a number of technical advantages are obtained by the present invention, since the same:

(29) (i) provides a subsea gas and water injection system designed to improve the recovery factor in petroleum production projects in deep water;

(30) (ii) provides a subsea injection system that can inject one single fluid or more than one fluid alternately;

(31) (iii) provides a subsea injection system and respective method that allows making alternate injection of gas or water, with displacement of fluid through the switching of the position of blocking valves located in the production unit and the wet Christmas trees of the injection wells;

(32) (iv) simultaneously provides a method of injection and assurance of flow more robust facilitating depressurization of lines for the prevention or even remediation of hydrates;

(33) (v) does not show technological obstacles with regard to the equipment used, since the system according to the present invention comprises integration of components and proven technologies; and

(34) (vi) provides a subsea injection system of water and gas alternately with a minimum number of connections and risers and without the need of manifold, significantly reducing the cost and complexity of construction, installation and maintenance.

(35) A number of variations falling in the scope of protection of present application are allowed. Thus, it is emphasized that present invention is not limited to the particular embodiments/configurations described above.