SYSTEM AND METHOD FOR SUBSEA STRUCTURE OBSTRUCTION REMEDIATION USING AN EXOTHERMIC CHEMICAL REACTION
Systems and methods comprise structures and methods for using a plurality of chemicals which are mixed subsea, resulting in a heated fluid which can be delivered by various means to an area about a subsea structure such as a pipe or other structure which has been compromised by a plug such as a solid gas hydrate or paraffinic plug. Various embodiments allow for selective use of insulated chambers and baffled conduits and the like, or combinations thereof, to aid in the mixing of the various chemicals and achieving a desired temperature.
1 . A system for providing a hot fluid subsea, comprising:
a. a plurality of reservoirs adapted to contain a corresponding plurality of chemical reactants;
b. a reaction chamber;
c. a plurality of chemical reactant fluid conduits providing a plurality of fluid pathways between a corresponding ones of the plurality of reservoirs and the reaction chamber;
d. a remotely operated vehicle (ROV) comprising a second hot fluid delivery conduit and a fluid exit portal; and
e. a first hot fluid delivery conduit in fluid communication with the reaction chamber and the second hot fluid delivery conduit, the first hot fluid delivery conduit comprising an internal baffle adapted to blend the chemical reactants.
2 . The system for providing a hot fluid subsea of claim 1 , wherein the fluid exit portal comprises an ROV-manipulatable heating wand.
3 . The system of claim 1 , further comprising a temperature sensor operatively in communication with the reaction chamber.
4 . The system of claim 1 , further comprising a temperature sensor operatively in communication with an external delivery point in fluid communication with the fluid exit portal.
5 . The system of claim 1 , further comprising a flow restrictor in fluid communication with the plurality of chemical reactant fluid conduits and the reaction chamber, the flow restrictor adapted to adjust flow rates of the reactants delivered to the reaction chamber.
6 . The system of claim 1 , further comprising a low pressure pump in fluid communication with the first hot fluid conduit, the low pressure pump adapted to mix ambient seawater into hot fluid provided to the first hot fluid conduit.
7 . The system of claim 1 , further comprising a flow diverter in fluid communication with the first hot fluid conduit, the flow diverter adapted to selectively divert flow of heated fluid away from the fluid exit portal.
8 . The system of claim 1 , further comprising a controllable valve in fluid communication with the first hot fluid conduit, the controllable valve adapted to shut off flow of heated fluid from the reaction chamber.
9 . The system of claim 8 , wherein the controllable valve comprises a remotely controllable valve.
10 . A method of removing an obstruction from a structure subsea, comprising:
a. selectively combining a plurality of chemical reactants in a reaction chamber, the plurality of chemical reactants obtained from a corresponding plurality of chemical reactant reservoirs, to create a hot fluid by an exothermic chemical reaction between the plurality chemical reactants;
b. routing the hot fluid through a remotely operated vehicle (ROV) hot fluid delivery conduit directed at an external mass located proximate a subsea structure; and
c. heating an area around the external mass with the hot fluid.
11 . The method of claim 10 , wherein the external mass comprises a hydrate plug.
12 . The method of claim 10 , wherein:
a. the ROV hot fluid delivery conduit comprises a heating wand which further comprises a fluid exit portal; and
b. routing the hot fluid through the ROV hot fluid delivery conduit further comprises directing hot fluid from the fluid exit portal towards the external mass.
13 . The method of claim 10 , wherein the chemical reactants comprise ammonium chloride (NH 4 Cl) and sodium nitrite (NaNO 2 ); hydrochloric acid (HCl) and ammonium hydroxide (NH 4 OH); hydrochloric acid (HCl) and sodium hydroxide (NaOH); or hydrogen peroxide (H 2 O 2 ) and a solution containing metal ions.
14 . The method of claim 10 , wherein the reservoirs comprise fluid reservoirs located proximate the seabed.
15 . The method of claim 10 , wherein:
a. the reservoirs comprise fluid reservoirs located on a supporting vessel; and
b. the chemical reactants comprise fluids delivered to the reaction chamber via separate coiled tubing strings.
16 . The method of claim 10 , wherein the reaction chamber is disposed proximate the subsea structure.
17 . The method of claim 10 , wherein the subsea structure comprises production piping.
18 . The method of claim 10 , wherein the external mass comprises at least one of a hydrate or paraffin.
19 . The method of claim 10 , further comprising:
a. disposing a temperature sensor at a predetermined position; and
b. controlling the temperature of hot fluid using feedback from the temperature sensor.
20 . The method of claim 19 , wherein disposing the temperature sensor at a predetermined position comprises disposing the temperature sensor proximate the reaction chamber or the wand.
21 . The method of claim 19 , wherein controlling the temperature comprises initially optimizing an aqueous concentration of the stored reactants.
22 . The method of claim 19 , wherein controlling the temperature comprises adjusting a bulk flow rate of the reactants delivered to the reaction chamber.
23 . The method of claim 19 , wherein controlling the temperature comprises adjusting a ratio of the reactants delivered to the reaction chamber to achieve a desired temperature.
24 . The method of claim 19 , wherein controlling the temperature comprises mixing ambient seawater into the hot fluid using a low pressure pump in fluid communication with the hot fluid.
25 . The method of claim 20 , wherein controlling the temperature comprises diverting the flow of heated fluid away from the wand.
26 . The method of claim 20 , wherein controlling the temperature comprises shutting off flow of the heated fluid from the reaction chamber using a controllable valve.