RAPID DEPLOYMENT SUBSEA CHEMICAL INJECTION SYSTEM

Abstract

A rapid deployment, subsea chemical injection skid assembly includes a non-buoyant skid lowered on a weight bearing line from a surface vessel. The skid carries a chemical injection pump, as well as at least one chemical tank in fluid communication with the chemical injection pump. The skid assembly may include a recirculation/mixing system to limit separation or solids drop out of chemicals arising from medium or long-term storage of chemicals in the chemical tank. The skid assembly may include a seawater filtration system to supply seawater for mixing with chemicals prior to injection. The skid assembly is operable by a separately tethered remotely operated vehicle.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of, and priority to, U.S. Application No. 62/738,575, filed Sep. 28, 2018, the entire disclosure of which is hereby incorporated herein by reference.

This application also claims the benefit of the filing date of, and priority to, International Application No. PCT/US2018/068156, filed Dec. 31, 2018, the entire disclosure of which is hereby incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates, in general, to hydrocarbon production, and more particularly, to subsea facilities utilized in the production of hydrocarbons. Most particular, the disclosure relates to a rapid deployment chemical injection skid system and method for injection of chemicals in subsea hydrocarbon production facilities.

BACKGROUND

Subsea systems for the production of hydrocarbons such as oil and gas require injection of various chemicals into their production facilities. The chemicals typically improve production capacity and/or inhibit against corrosion, wax, asphaltene, hydrates, scale or other issues.

Normally the chemical injection system is incorporated into the design of the production facility and is installed and operated as an integral part of the production facility. Chemicals are typically pumped from a surface facility such as a floating production vessel, offshore platform, or onshore plant, through an umbilical system, entering the subsea system at the wellhead, pipeline end termination (PLET) subsea manifold or other apertures.

Some production facilities require subsea chemical injection in addition to the installed facilities or injection of specialized chemicals, which cannot be injected from surface through a long umbilical. There are existing subsea chemical injection systems, designed for permanent installation, these typically have a high capital cost and a lead-time of many months.

In some cases there is a need for rapid deployment of chemical injection to a subsea facility for a relatively short duration; there may be uncertainty on the effectiveness of a chemical treatment; and/or short remaining field life of the subsea facility.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description:

FIG. 1A is a schematic view of rapid deployment chemical injection system deployed from a vessel to carry out chemical injection in subsea hydrocarbon production facilities on the seabed.

FIG. 1B is a schematic view of rapid deployment chemical injection system suspended from a vessel to carry out chemical injection in subsea hydrocarbon production facilities within a wellbore.

FIG. 2A is a schematic view of a rapid deployment chemical injection system with a line having a stab to be connected to a hot stab on the subsea hydrocarbon production facility by a remote operated vehicle to carry out chemical injection in subsea hydrocarbon production facilities on the seabed.

FIG. 2B is a schematic view of a rapid deployment chemical injection system with a line having a stab to be connected to a hot stab on the subsea hydrocarbon production facility by a remote operated vehicle to carry out chemical injection in subsea hydrocarbon production facilities within a wellbore.

FIG. 3 is a perspective view of the chemical injection skid of the rapid deployment chemical injection system of FIG. 1.

FIG. 4 is an elevation view of the chemical injection skid of the rapid deployment chemical injection system.

FIG. 5 is a plan view of the chemical injection skid of the rapid deployment chemical injection system.

FIG. 6 is an end elevation view of the chemical injection skid of the rapid deployment chemical injection system.

FIG. 7 illustrates a method for injecting chemicals into a subsea hydrocarbon production facility.

DETAILED DESCRIPTION

Disclosed herein are embodiments of a subsea chemical injection skid assembly that will permit the rapid deployment and injection of chemicals to hydrocarbon production facilities located subsea. Carried on the skid is a high accuracy chemical injection pump, as well as at least one chemical tank in fluid communication with the chemical injection pump. The skid is connected to the production facilities using a remotely operated vehicle (ROV) deployed from a vessel.

A control panel may be provided for manipulation by the ROV. The chemical injection pumps can be powered by the ROV for short-term trial or pilot schemes of a few hours or days in length. For longer-term applications, which may run many days or months, the pumps may be driven electrically via an umbilical (existing or installed system which provides power from the host facility) and/or by batteries, generators or by a variety of power sources.

In some embodiments, the skid may be lowered down and deployed close to a chemical injection point with or without intervention from an ROV. In either case, once deployed, the ROV is used to carry a hose from the skid and connect it to the injection point on the wellhead, PLET or manifold or other location. In another embodiment, the skid may include a manipulator arm to connect the skid to the injection point. In one or more embodiments, the pump is a high accuracy chemical metering pump which allows pumping of very viscous and long chain chemical types.

As used herein, references to tanks include any chemical storage vessel.

In one or more embodiments, the skid may include two or more tanks for two or more separate chemicals, with each chemical stored in a separate tank. Each of the chemicals may be selected for evaluation of the effectiveness with respect to a particular task involving the production system. Thus, for any particular operation, multiple chemicals can be tested in order to identify the most appropriate chemical for the operation. In some embodiments, with multiple tanks on board the skid, this can occur in a single trip without the need for multiple trips. However, in other embodiments, it will be appreciated that because the chemical injection system is rapidly deployed and retrievable, the system may be retrieved to the surface; the chemicals on-board switched out; and the system rapidly redeployed in order to permit such evaluation, a method not possible by the prior art systems. Thus, the most appropriate chemical for a particular task can be readily identified.

In one or more embodiments, the chemical tank or tanks may be carried on the skid on a first lower level and the chemical injection pump, as well as manifolds, valving and other equipment may be carried on the skid on a second upper level, above the chemical tank o the first level.

The pump may be operated from a variety of power sources, including ROV hydraulic or electrical power for short duration tests/trials and projects; electrical or hydraulic power via existing subsea umbilical from the host facility; temporary downline from surface vessel or power buoy; batteries; generators, driven by sea current, product flow or other means; or a combination of the above (for instance battery power may be used to meet high motor startup current, with running current provided via an umbilical).

In one or more embodiments, the skid may include a recirculation system and/or mixing system to allow medium or long-term storage of chemical, avoiding separation or solids drop out. This is particularly necessary for chemicals such as highly viscous chemicals or chemicals formed of long chain molecules.

The skid may also include a seawater filtration to supply seawater for mixing with chemicals prior to injection.

In one or more embodiments, the skid may include manifolds to allow the connection of additional or external chemical tanks. A manifold may also be utilized to refill onboard tanks.

In one or more embodiments, the chemical injection system is disposed to operate using multiple power sources, such as a first power source for startup and a second power source for on-going operation. In other embodiments, the chemical injection system may scavenge power from existing subsea umbilical systems.

In one or more embodiments, the skid has mud mats which can be fitted on the base, to prevent sinking in soft soil condition. The mud mats may be removed for transportation and storage. The mud mats are particularly desirable in certain embodiments because of the significant additional weight added to the system by virtue of the fully charged chemical tanks.

In FIG. 1A, a host facility 16 is positioned above a subsea hydrocarbon production facility 10. A chemical injection system 20 is launched from the host facility 16 and lowered to a location on the sea floor 18 near a chemical injection point of the hydrocarbon production facility 10, such as a wellhead or subsea manifold. As used herein, hydrocarbon production facility 10 may generally refer to any subsea system used in the production of hydrocarbons, including any one or more of the wellbore, downhole equipment, wellhead, manifolds, pipelines, or risers. As used herein, host facility 16 may include a platform on the surface, a floating vessel, a floating production storage and offloading (FPSO) unit or an onshore system. Likewise, as used herein, manifold is used as a generic term to refer any wellhead trees, pipeline end manifolds (PLEMs), and pipeline end terminators (PLETs), to name a few, to carry out chemical injection. More specifically, chemical injection system 20 is lowered by cable 22 above and in the vicinity of an injection point 12 of the hydrocarbon production facility 10. In FIG. 1A, a hydrocarbon production facility 10 is a deep-water pipeline which lies on or near the sea floor 18 between manifolds, such as a PLEMS 14, either of which may be chemical injection point 12.

In one or more embodiments, chemical injection system 20 comprises a non-buoyant structure 21, the weight of which must be supported by cable 22. In some embodiments, non-buoyant structure 21 may include a metal frame that functions as a platform to support one or more chemical tanks, and a chemical injection pump. Additionally, the frame may support chemical metering equipment, valving and the like. The frame may support one or more electric or hydraulic motors that drive one or more chemical injection pumps. The cable 22 may be an umbilical cord that can provide, either alone or in combination with other power sources, electric current for electric motors(s) or hydraulic power to drive the chemical injection system 20. In some embodiments, cable 22 is a crane wire deployed from host facility 16 and which cable 22 may be disconnected from the non-buoyant structure 21 once it is positioned on the sea floor 18. In other embodiments, cable 22 is an integral component of non-buoyant structure 21, where integral cable 22 may be used for one or more of deployment, recovery, supply of electrical or hydraulic power, control, feedback and monitoring.

Because of the weight of the chemical tanks and the length of many chemical injection operations, it will be appreciated that it is undesirable to suspend chemical injection system 20 from cable 22 during such operations. Rather, chemical injection system 20 is positioned on sea floor 18 near the chemical injection point 12 of hydrocarbon production facility 10. However, in other more abbreviated chemical injection operations, chemical injection system 20 may be suspended above sea floor 18 in the vicinity of the chemical injection point 12 of hydrocarbon production facility 10.

FIG. 1B is similar to FIG. 1A, but in FIG. 1B production facility 10 is shown as a wellhead 11 positioned over a wellbore 13 with production equipment 15 deployed therein. Wellhead 11 may include blowout preventers 17 or other equipment. Production equipment 15 is not limited by the disclosure, but will be understood to be any equipment deployed in wellbore 13 to facilitate production of hydrocarbons from formation 19, including, without limitation, pumps, upper production equipment and/or lower production equipment. Similarly, host facility 16 is positioned above wellhead 11 and a chemical injection system 20 is launched from host facility 16 and lowered to a location on the sea floor 18 near wellhead 11, where chemical injection system 20 may be utilized to inject a chemical into wellbore 13 or wellhead 11 for a particular task. In the illustrated embodiment, wellhead 11 is a chemical injection point 12 for production facility 10.

Again, in one or more embodiments, chemical injection system 20 comprises a non-buoyant structure 21 which may include a metal frame that supports one or more chemical tanks, and one or more chemical injection pumps. Additionally, the frame may support chemical metering equipment, valving and the like. The frame may support one or more electric or hydraulic motors that drive the one or more chemical injection pumps. The cable 22 may be an umbilical cord that can provide, either alone or in combination with other power sources, electric current for the electric motor(s) or hydraulic power to drive the chemical injection system 20.

Turning to FIG. 2A, chemical injection system 20 is lowered by a cable 22 above and in the vicinity of PLEM 14, which is illustrated as a chemical injection point 12. Chemical injection system 20 is designed specifically for injection of chemicals to enhance hydrocarbon production. Chemical injection system 20 includes a non-buoyant skid 23 having a frame 24. The frame 24 may support an electric, hydraulic or elecro-hydraulic motor 26 which powers chemical injection pump(s) 30 that pumps chemicals into chemical injection point 12. A chemical conduit or line 35 having a stab for connecting to chemical injection point 12 in PLEM 14 transfers chemicals to PLEM 14. Chemical injection system 20 may further include a remote operating vehicle (ROV) 40 used to stab line 35 into chemical injection point 12. The ROV 40 has its own umbilical cable 42 which is shown connected to a tether management system (TMS) 44. The ROV's gripper 46 is manipulated to open and shut valves on the chemical injection system 20 to perform the operational tasks of injecting chemicals as described herein. It will be appreciated skid 23 is lowered and deployed independently of ROV 40. Moreover, the collective components of skid 23 render skid non-buoyant so that the weight of skid 23 must be supported by cable 22. In some embodiments, frame 24 may be weighted or constructed of materials that render skid 23 non-buoyant, while in other embodiments, the equipment carried by frame 24 render skid 23 non-buoyant.

In some embodiments, an on-board power supply 27 is also carried by frame 24. On-board power supply 27 may be a generator or batteries or another local power source. In some embodiments, cable 22 is an electric umbilical. In some embodiments where motor 26 is electric, power is supplied to motor 26 either through cable 22 or from on-board power supply 27. In other embodiments, both cable 22 and power supply 27 may be used at different times to operate electric motor 26. For example, power supply 27 may be utilized to power electric motor 26 at start-up and power from cable 22 may be utilized to operate electric motor 26 once pump 30 is in operation. In yet other embodiments, power to electric motor 26 may be supplied by ROV 40, either directly from an on-board power source on ROV or from TMS 44 shown suspended from an umbilical cable 42. Finally, in yet other embodiments, electric motor 26 may be eliminated altogether and pressurized hydraulic fluid from ROV 40 may be utilized to operate pump 30.

Frame 24 also supports at least one chemical tank 28. In some embodiments, frame 24 may support two or more chemical tanks, such as tanks 28a and 28b shown in FIG. 2A. In one or more embodiments, tank 28 may be a bladder tank, having a liquid contained by a flexible membrane or bladder which can expand and contract to allow filling and removal of chemicals in a subsea environment.

In one or more embodiments, the chemical tank or tanks 28 may be carried on the skid 23 on a first lower level 32 and the chemical injection pump and other equipment, such as electric motor 26, as well as manifolds, valving and other equipment, may be carried on the skid 23 on a second upper level 34, above the chemical tanks 28 of the first level 32.

The chemical contained within a tank 28 carried on skid 23 may be a chemical selected for a particular chemical injection task or operation, such to improve production capacity, to treat or inhibit against corrosion; to treat or inhibit wax; to inhibit asphaltene; to inhibit hydrates; to treat or inhibit scale. In one or more embodiments, two different chemicals or formulations for any one such task may be deployed in separate tanks and skid 23 may be utilized to try the effectiveness of each of the two chemicals for the task in order to evaluate which of the two chemicals is more effective. Thereafter, the more effective chemical may be deployed in a more long-term chemical injection solution. In this regard, in certain chemical injection tasks, two types of chemicals may be required for the task, and hence the need for two or more tanks.

In other chemical injection tasks, it may be desirable to compare the effectiveness of two different chemicals or treatments to identify which chemical is best suited for a task. Thus, multiple tanks allow the testing of multiple chemicals without the need to deploy skid 23 multiple times, whether the chemicals are the same chemical with different formulations or different chemicals altogether.

In one or more embodiments, a chemical preparation system 36 is also carried by frame 24. In some embodiments, chemical preparation system 36 is a recirculating pump or mechanism that may be utilized to recirculate chemicals such as emulsions or where solids are suspended in a liquid, thereby ensuring that mixtures do not separate or that solids do not settle out. This system 36 will maintain the chemical in a well-mixed, cohesive state and reduce separation of the components due to differing specific gravities.

In some embodiments, chemical preparation system 36 is a mixing system or mechanism that may be utilized to mix chemicals from two or more tanks 28 together before injection into PLEM 14. Thus, a first chemical may be contained in chemical tank 28a and a second chemical may be contained in tank 28b and system 36 may be utilized to mix the first and second chemicals prior to injection.

In either of the foregoing descriptions, chemical preparation system 36 may include a pump in fluid communication with a tank 28 and used to draw a chemical from the bottom of a tank 28, such as a bladder tank, and return the chemical to the top of the tank, or top of the bladder within tank 28, as the case may be. Thus, one or more of the tanks 28 may have a first port for the withdrawal of chemicals and a second port for injecting the chemicals back into tank 28. The first port may be located at or near the bottom of the tank 28 and the second port may be located at or near the top of the tank 28. In other embodiments, system 36 may include an Archimedes screw within a tube, driven by a slow speed motor, drawing chemical in at the base of the tube from the bottom of the tank or bladder, and discharging at the top of the tube and cascading onto the top of the chemical in the bladder.

It will be appreciated that pump 30 as described herein may be much smaller and lighter than high pressure hydrostatic testing pumps or a boost pump used for pigging. Rather, pump 30 is designed to pump and meter low volumes of viscous or long chain chemical formulations. Thus, in contrast to other types of pumps for other operations, pump 30 may be a high accuracy pump, such as a positive displacement metering type pumps or rotary gear pumps or linear piston/syringe type pumps, which, monitors pump/motor rotation in order to determine the volume of chemical pumped and flowrate. It will be appreciated that such smaller pumps are more readily driven hydraulically by ROV hydraulics for the short-term application and/or electrically as described above.

FIG. 2B is similar to FIG. 2A, but FIG. 2B illustrates chemical injection system 20 being lowered by a cable 22 above and in the vicinity of wellhead 11 positioned over a wellbore 13 with production equipment 15 deployed therein and used for the production of hydrocarbons from formation 19. Wellhead 11 may include blowout preventers 17 or other equipment. Skid 23 is shown as constructed of a frame 24, which may have a first lower level 32 and a second upper level 34. Frame 24 supports a chemical injection pump 30 and one or more tanks 28. Frame 24 may support an electric motor 26 which powers a hydraulic motor that provides high pressure hydraulic fluid for powering chemical injection pump 30 that pumps chemicals from the one or more tanks 28, such as tanks 28a, 28b, into wellhead 11 via line 35. ROV 40 is used to stab line 35 into wellhead 11 utilizing gripper 46. ROV 40 is suspended from TMS 44 which has its own umbilical cable 42 through which power may be supplied to ROV 40, and in some embodiments, to electric motor 26 of skid 23 as described above.

In some embodiments, on-board power supply 27 is also carried by frame 24.

In one or more embodiments, a recirculating or mixing system 36 is also carried by frame 24.

Turning to FIG. 3, chemical injection system 20 is shown suspended from cable 22. Specifically, chemical injection system 20 includes a skid 23 formed of a frame 24 having a first lower level 32 and a second upper level 34. A tank 28 is shown on lower level 32. Chemical injection system 20 also includes a control panel 41 into which an ROV (not shown) can stab for various operations.

In one or more embodiments, skid 23 may include a mud mat assembly 48 extending from frame 24. Mud mat assembly 48 may include one or more mud mats 50 extending outward from a lower portion of frame 24, such as lower level 32. In the illustrated embodiment, mud mats 50 extend around the perimeter of lower level 32 of skid 23 and are supported by a frame 52. Preferably, mud mats 50 are generally horizontal when skid 23 is suspended from cable 22. It will be appreciated that mud mats 50 are not limited to a particular structure, but may be any structure extends from skid 23 to provide stability to skid 23 to prevent sinking in soft soil condition. For example, mud mats 50 may be flat, or corrugated plates or screen. The mud mat assembly 48 may be detachable from frame 24 for transportation and storage. The mud mat assembly 48 is particularly desirable in certain embodiments because of the significant additional weight added to the chemical injection system 20 by virtue of the fully charged chemical tanks 28. In this regard, because skid 23 is lowered to the sea floor independently of the ROV, mud mat assembly 48 assists in ensuring that chemical injection systems 20 remains correctly oriented during operation.

FIG. 4 is an elevation view of chemical injection system 20 shown suspended from cable 22. In this particular embodiment, cable 22 is not utilized as an umbilical for power supply. In any event, frame 24 of skid 23 supports a chemical injection pump 30 and a first chemical tank 28a and a second chemical tank 28b. A recirculating or mixing system 36 is also carried by frame 24. Similarly, a control panel 41 is shown into which an ROV (not shown) may stab for an operation. For example, ROV may stab into control panel 41 to provide high pressure hydraulic fluid to operate (via a hydraulic motor) chemical injection pump 30 or to operate system 36. Chemical tanks 28a, 28b are supported on a first lower level 32, while chemical injection pump 30, recirculating or mixing system 36 and control panel 41 are supported on a second upper level 34 above tanks 28.

A mud mat assembly 48 extends from frame 24. Mud mat assembly 48 includes one or more mud mats 50 extending outward from first lower level 32. Mud mats 50 are supported by a mud mat frame 52 and are shown extending generally horizontally from skid 23.

FIG. 5 is a top view of chemical injection system 20. Frame 24 of skid 23 supports a chemical injection pump 30 and a chemical tank 28. A recirculating or mixing system 36 may also be carried by frame 24. Similarly, a control panel 41 is shown into which an ROV (not shown) may stab for an operation. For example, ROV may stab into control panel 41 to provide high pressure hydraulic fluid to operate (via a hydraulic motor) chemical injection pump 30 or to operate system 36. A mud mat assembly 48 extends from frame 24. Mud mat assembly 48 includes one or more mud mats 50 extending outward from first lower level 32. Mud mats 50 are supported by a mud mat frame 52 and are shown extending generally horizontally from skid 23.

FIG. 6 illustrates another embodiment of chemical injection system 20. In this embodiment, chemical injection system 20 is shown suspended from cable 22. In this particular embodiment, cable 22 is not utilized as an umbilical for power supply. In any event, frame 24 of skid 23 supports a chemical injection pump 30 and a first chemical tank 28a and a second chemical tank 28b. A control panel 41 is shown into which an ROV (not shown) may stab for an operation. Chemical tanks 28a, 28b are supported on a first lower level 32, while chemical injection pump 30 and control panel 41 are supported on a second upper level 34 above tanks 28.

A mud mat assembly 48 extends from frame 24. Mud mat assembly 48 includes one or more mud mats 50 extending outward from first lower level 32. Mud mats 50 are supported by a mud mat frame 52 and are shown extending generally horizontally from skid 23.

In this embodiment, chemical injection system 20 includes a seawater filtration system 56, which may include seawater filters, seawater flow control and a seawater pump. It will be appreciated that in certain chemical injection operations, the chemicals may require to be diluted with seawater prior to injection. In some embodiments, such a system may further include a boost pump and/or high pressure pump to provide the dilution water where such pumps may already be on board skid 23 for other purposes.

In operation, a method 100 for injecting chemicals into a subsea hydrocarbon production facility is illustrated in FIG. 7. In a first step 102, a skid carrying a chemical injection pump and chemical tank is lowered to a subsea location adjacent a hydrocarbon production facility. In some embodiments, at least two chemical tanks are carried by the skid and lowered as part of the skid. The skid is non-buoyant and as such, the weight of the skid is supported by a cable deployed from a platform or vessel. In one or more embodiments where the chemical injection operations are to continue for a more extended period of time, such as days or months, the subsea location is on the sea floor adjacent the hydrocarbon production facility. Once in position on the sea floor, the cable may be released, or alternatively, tension on the cable may be released in those instances where the cable also functions to provide electrical power and/or hydraulic fluid to the skid. In other embodiments, where the chemical injection operation is of only a short duration, such as hours, the skid may continue to be supported by the cable by suspending the skid above the sea floor adjacent the hydrocarbon production facility.

In a second step 104, an ROV is utilized to attach a chemical injection line in fluid communication with the chemical injection pump to an injection point of the hydrocarbon production facility. The ROV is tethered on an umbilical cable separate from the weight bearing cable utilized to lower the skid. In any event, the ROV attaches the chemical injection line to a chemical injection point, such as a manifold or wellhead of hydrocarbon production facility.

In step 106, a first power source may be utilized to initiate start-up of the pump and thereafter, a second different power source may be utilized to continue operation of the pump during pumping, it being appreciated that a pump may draw more power during start up, but require less power during on-going operation. The first power source is selected from the group consisting of an on-board power source carried by the skid, an electrical cable extending from a surface vessel and power supplied by the ROV; and the second power source is selected from the group consisting of an on-board power source carried by the skid, an electrical cable extending from a surface vessel and power supplied by the ROV.

In any event, at step 108, once the chemical injection line has been attached to the chemical injection point and the pump has been powered up, the chemical injection pump is operated to inject the chemical from the chemical tank into the subsea hydrocarbon production facility. In this regard, the chemical may be introduced into a manifold, a wellhead, or directly into a wellbore.

In step 110, the chemical is utilized to conduct a particular chemical treatment operation. Thus, the pump may be operated to treat production equipment within a wellbore. In other embodiments, the pump may be operated to improve production capacity of the hydrocarbon production facility. In other embodiments, the pump may be operated to treat or inhibit corrosion in the hydrocarbon production facility. In other embodiments, the pump may be operated to inject the chemical from the chemical tank into a subsea manifold or pipeline system. In other embodiments, the pump may be operated to treat or inhibit wax within the hydrocarbon production facility. In other embodiments, the pump may be operated to inhibit asphaltene within the hydrocarbon production facility. In other embodiments, the pump may be operated to inhibit hydrates within the hydrocarbon production facility. In other embodiments, the pump may be operated to treat or inhibit scale within the hydrocarbon production facility.

In step 112, the pump may be operated to compare the effectiveness of a treatment operation of each of a first chemical and a second chemical carried by the skid. Thus, a first chemical form a first chemical tank may be injected into the hydrocarbon production facility and the effect of the first chemical on the hydrocarbon production facility may be evaluated. Thereafter, a second chemical from a second chemical tank may be injected into the hydrocarbon production facility and the effect of the second chemical on the hydrocarbon production facility may be evaluated, after which, the chemical with the most desirable effects can continue to be utilized without the need to retrieve the skid or deploy additional equipment. In this regard, based on the evaluation and effectiveness of the two chemicals, one chemical may be selected for long term treatment of the hydrocarbon production facility, whereas another chemical may be selected for short term treatment of the hydrocarbon production facility, and thus, the pump may be operated accordingly first to inject one chemical for a short term treatment and the other chemical for a long term treatment. As used herein, short term and long term are relative and are simply utilized to distinguish a shorter period of time from a longer period of time. In some embodiments, a third chemical tank having a third chemical is lowered with the first and second chemical tanks; and the ROV is utilized to operate the chemical injection skid in order to inject the third chemical into the hydrocarbon production facility, after which, similar to above, the effect of the third chemical on the hydrocarbon production facility may be evaluated and the most desirable chemical for a desired effect may be selected, again, without the need for retrieving the skid or deploying additional equipment, all of which can be costly and time consuming. In one or more embodiments, at least one of the chemicals is highly viscous chemical. In one or more embodiments, at least one of the chemicals is a long chain compound. In embodiments where two or more chemical are evaluated, the two or more chemicals may be the same chemical with different formulations.

In step 114, a chemical preparation mechanism may be lowered with the skid and operated for a particular function. In one or more embodiments, a chemical preparation mechanism carried by the skid may be operated to recirculate chemicals contained within a chemical tank so as reduce the likelihood of settling of the constituent components of the chemicals. In some embodiments, this recirculation may continue to occur even during chemical injection operations, while in other embodiments, it will be appreciated that the step of recirculating chemicals contained within a chemical tank may be carried out before the step of injecting the chemical into the hydrocarbon production facility. Operating a chemical preparation mechanism to mix a first chemical carried in a first tank on the skid and second chemical carried in a second tank on the skid together prior to the step of injecting.

In one or more embodiments of step 114, a chemical preparation mechanism carried by the skid may be operated to mix two or more chemicals prior to injection of the mixture into the hydrocarbon production facility. Thus, a first chemical taken from a first tank on the skid may be mixed with a second chemical taken from a second tank on the skid.

It will be appreciated that a subsea chemical injection system such as the embodiments described above can be quickly mobilized, deployed on the seabed and operated, giving cost effective and timely chemical injection for a short to medium term: typically from a few days to several months. The system may be a temporary installation at significantly less cost than permanent systems. This is particularly useful where there is uncertainty on the effectiveness of chemical treatment and/or short remaining field life, thus permitting a trial system for a short duration with a low investment. The trial allows further allows for an informed decision regarding the most efficient longer term chemical injection scheme without the foregoing costs. Moreover, because the system is deployed more rapidly than existing subsea chemical injection systems, it allows for benefits to be more quickly realized. Benefits can include increased production, avoidance of flow restriction/blockages, reduction in corrosion etc. This can also generate early additional revenue or reduce cost.

Thus, a system for treating subsea hydrocarbon production facilities has been described. The system includes a non-buoyant skid suspended from a first cable configured to support the weight of the skid, the skid including a chemical injection pump and a chemical tank mounted thereon; and a remotely operated vehicle independent of the skid and attached to a second umbilical, wherein the remotely operated vehicle is configured to couple the pump to the subsea hydrocarbon production facilities. Likewise, in another embodiment, the system includes a skid suspended from a first cable configured to support the weight of the skid, the skid including a chemical injection pump, a first chemical tank and a second chemical tank, all mounted on the skid; and a remotely operated vehicle independent of the skid and attached to a second umbilical, wherein the remotely operated vehicle is configured to couple the pump to the subsea hydrocarbon production facilities. Similarly, a chemical injection skid for deployment to a subsea hydrocarbon production facility has been described. The skid includes a skid frame; a chemical tank mounted on the skid frame; and a chemical injection pump mounted on the skid frame and in fluid communication with the chemical tank, wherein said chemical injection pump is adapted to inject a lower volume of viscous chemical into a subsea hydrocarbon production facility.

Any one of the foregoing embodiments may include any one or more of the following elements, alone or in combination with other elements:

• • At least two chemical tanks mounted on the skid frame.
  • At least two chemical tanks mounted on the skid.
  • The skid frame, chemical tank and chemical injection pump comprise a non-buoyant structure.
  • The skid is non-buoyant.
  • A first level on which the chemical tank is mounted and a second level above the chemical tank to which the chemical injection pump is mounted.
  • The skid comprises a first level on which the chemical tank is mounted and a second level above the chemical tank to which the chemical injection pump is mounted.
  • An electric motor carried by the skid frame and disposed to drive the pump.
  • An electric motor carried by the skid and disposed to drive the pump.
  • A first cable supporting the skid frame and a second cable supporting the ROV.
  • A first cable supporting the skid and a second cable supporting the ROV.
  • The first cable is non-conducting and the second cable is a tether.
  • The first cable comprises a conducting electrical cable and the second cable is a tether.
  • A power supply carried by the skid frame and disposed to power an electric motor carried by the skid.
  • The skid comprises an on-board power supply carried by the skid and disposed to power an electric motor carried by the skid.
  • The first cable is an electrical umbilical cable.
  • The on-board power supply is a generator.
  • The on-board power supply is a battery.
  • The chemical tank is a bladder tank.
  • A recirculating or mixing system 36 carried by the skid and in fluid communication with the tank.
  • A recirculating or mixing system mounted on the skid frame, wherein the recirculating system is in fluid communication with the tank.
  • A recirculating or mixing system mounted on the skid, wherein the recirculating system is in fluid communication with the tank.
  • The recirculating system is in fluid communication with two or more tanks.
  • The recirculating system comprises an Archimedes screw within a tube.
  • The skid further comprises a manipulator arm.
  • The chemical injection pump comprises a low volume metering pump.
  • A mud mat assembly extending from the skid frame.
  • A mud mat assembly extending from the skid.
  • A control panel operable mounted on the skid frame and operable by an ROV.
  • A control panel operable mounted on the skid and operable by an ROV.
  • A seawater filtration system mounted on the skid frame.
  • A seawater filtration system mounted on the skid.
  • The mud mat assembly comprises one or more mud mats extending outward from a lower portion of skid.
  • The mud mats extend around the periphery of the skid.
  • The mud mat assembly comprises one or more mud mats extending outward from a lower portion of skid frame.
  • The mud mats extend around the periphery of the skid frame.
  • A first power source and a second power source different from the first power source.

The first power source is selected from the group consisting of an on-board power source carried by the skid, an electrical cable extending from a surface vessel and power supplied by the ROV; and the second power source is selected from the group consisting of an on-board power source carried by the skid, an electrical cable extending from a surface vessel and power supplied by the ROV.

The chemical injection line is attached by the ROV to a subsea manifold or pipeline system. Thus, a method for injecting chemicals into a subsea hydrocarbon production facility has been described. The method includes lowering a skid carrying a chemical injection pump and chemical tank to a subsea position adjacent a hydrocarbon production facility; utilizing an ROV to attach a chemical injection line in fluid communication with the chemical injection pump to an injection point of the hydrocarbon production facility; once the chemical injection line has been attached, utilizing the ROV to operate the chemical injection skid in order to inject a chemical from the tank into the hydrocarbon production facility. In other embodiments, the method includes lowering a skid carrying a chemical injection pump, a first chemical tank having a first chemical and a second chemical injection tank having a second chemical different from the first chemical to a subsea position adjacent a hydrocarbon production facility; utilizing an ROV to attach a chemical injection line in fluid communication with the chemical injection pump to an injection point of the hydrocarbon production facility; once the chemical injection line has been attached, utilizing the ROV to operate the chemical injection skid in order to inject the first chemical into the hydrocarbon production facility and thereafter evaluating the effect of the first chemical on the hydrocarbon production facility; and utilizing the ROV to operate the chemical injection skid in order to inject the second chemical into the hydrocarbon production facility and thereafter evaluating the effect of the second chemical on the hydrocarbon production facility.

Any one of the foregoing embodiments may include any one or more of the following, alone or in combination with other limitations:

• • A third chemical tank having a third chemical is lowered with the first and second chemical tanks; and utilizing the ROV to operate the chemical injection skid in order to inject the third chemical into the hydrocarbon production facility and thereafter valuating the effect of the third chemical on the hydrocarbon production facility.
  • The skid is lowered on a first cable and the ROV is tethered to a separate cable.
  • At least two chemical tanks are lowered by the skid, with a different chemical disposed in each tank.
  • The chemical injection line is attached by the ROV to a manifold.
  • The chemical injection line is attached by the ROV to a wellhead.
  • Operating the chemical injection pump to inject the chemical from the chemical tank into a manifold.
  • Operating the chemical injection pump to inject the chemical from the chemical tank into a wellhead.
  • Operating the chemical injection pump to inject the chemical from the chemical tank into a wellbore.
  • Operating the chemical injection pump to treat production equipment within a wellbore.
  • Operating the chemical injection pump to compare the effectiveness of each of a first chemical and a second chemical carried by the skid.
  • Operating the chemical injection pump to improve production capacity of the hydrocarbon production facility.
  • Operating the chemical injection pump to treat or inhibit corrosion in the hydrocarbon production facility.
  • Operating the chemical injection pump to inject the chemical from the chemical tank into a subsea manifold or pipeline system.
  • Operating the chemical injection pump to treat or inhibit wax within the hydrocarbon production facility.
  • Operating the chemical injection pump to inhibit asphaltene within the hydrocarbon production facility.
  • Operating the chemical injection pump to inhibit hydrates within the hydrocarbon production facility.
  • Operating the chemical injection pump to treat or inhibit scale within the hydrocarbon production facility.
  • Utilizing a first power source to initiate start-up of the pump and a second different power source to continue operation of the pump during pumping.
  • Evaluating the effect of the first chemical on the hydrocarbon production facility; and utilizing the ROV to operate the chemical injection skid in order to inject the second chemical into the hydrocarbon production facility and thereafter evaluating the effect of the second chemical on the hydrocarbon production facility.
  • The first power source is selected from the group consisting of an on-board power source carried by the skid, an electrical cable extending from a surface vessel and power supplied by the ROV; and the second power source is selected from the group consisting of an on-board power source carried by the skid, an electrical cable extending from a surface vessel and power supplied by the ROV.
  • Operating the chemical injection pump to pump a first chemical carried in a first tank on the skid into the hydrocarbon production facility and evaluating the effect of the first chemical on the hydrocarbon production facility and thereafter; operating the chemical injection pump to pump a second chemical carried in a second tank on the skid into the hydrocarbon production facility and evaluating the effect of the second chemical on the hydrocarbon production facility; and based on the effectiveness of the two chemicals, selecting one chemical for long term treatment of the hydrocarbon production facility.
  • Operating a chemical preparation mechanism carried by the skid to recirculate chemicals contained within the chemical tank.
  • Continuing recirculation during chemical injection operations.
  • Prior to the step of injecting, recirculating chemicals contained within a chemical tank.
  • Operating a chemical preparation mechanism to mix a first chemical carried in a first tank on the skid and second chemical carried in a second tank on the skid together prior to the step of injecting.
  • The step of injecting comprises injecting a mixture of a first chemical taken from a first tank on the skid and a second chemical taken from a second tank on the skid.
  • The chemicals are highly viscous chemicals.
  • The chemicals are long chain compounds.
  • The two chemicals are the same chemical with different formulations.

While various embodiments have been illustrated in detail, the disclosure is not limited to the embodiments shown. Modifications and adaptations of the above embodiments may occur to those skilled in the art. Such modifications and adaptations are in the spirit and scope of the disclosure.

Claims

1. A system for treating subsea hydrocarbon production facilities comprising:

a non-buoyant skid suspended from a first cable configured to support the weight of the skid, the skid including a chemical injection pump and a chemical tank mounted thereon; and

a remotely operated vehicle independent of the skid and attached to an umbilical cable, wherein the remotely operated vehicle is configured to couple the pump to the subsea hydrocarbon production facilities.

2. The system of claim 1, further comprising at least two chemical tanks mounted on the skid.

3. The system of claim 1, wherein the skid comprises an on-board power supply carried by the skid and disposed to power an electric motor carried by the skid.

4. The system of claim 1, wherein the chemical tank is a bladder tank.

5. The system of claim 1 further comprising a recirculating system mounted on the skid, wherein the recirculating system is in fluid communication with the chemical tank.

6. The system of claim 5, wherein the recirculating system is in fluid communication with two or more tanks.

7. The system of claim 5, wherein the recirculating system comprises an Archimedes screw within a tube.

8. The system of claim 1, further comprising a control panel operable mounted on the skid and operable by an ROV.

9. The system of claim 1, further comprising a seawater filtration system mounted on the skid.

10. The system of claim 1, further comprising one or more mud mats extending outward from a lower portion of skid.

11. A chemical injection skid for deployment to a subsea hydrocarbon production facility, the chemical injection skid comprising:

a skid frame:

a chemical tank mounted on the skid frame;

a chemical injection pump mounted on the skid frame and in fluid communication with the chemical tank, wherein said chemical injection pump is adapted to inject a lower volume of viscous chemical into a subsea hydrocarbon production facility.

12. The skid of claim 11, further comprising at least two chemical tanks mounted on the skid frame.

13. The skid of claim 12, further comprising a chemical mixing system mounted on the skid frame, wherein the chemical mixing system is in fluid communication with the chemical tank.

14. The skid of claim 13, further comprising a seawater filtration system mounted on the skid frame.

15. A method for injecting chemicals into a subsea hydrocarbon production facility, the method comprising:

lowering a skid carrying a chemical injection pump and chemical tank to a subsea position adjacent a hydrocarbon production facility;

utilizing an ROV to attach a chemical injection line in fluid communication with the chemical injection pump to an injection point of the hydrocarbon production facility; and

once the chemical injection line has been attached, utilizing the ROV to operate the skid in order to inject a first chemical from the tank into the hydrocarbon production facility.

16. The method of claim 15, further comprising evaluating an effect of the first chemical on the hydrocarbon production facility; and

utilizing the ROV to operate the chemical injection skid in order to inject a second chemical into the hydrocarbon production facility and thereafter evaluating an effect of the second chemical on the hydrocarbon production facility.

17. The method of claim 15, further comprising utilizing a first power source to initiate start-up of the chemical injection pump and a second power source, different from the first power source, to continue operation of the chemical injection pump during pumping.

18. The method of claim 17 where the first power source is selected from the group consisting of an on-board power source carried by the skid, an electrical cable extending from a surface vessel and power supplied by the ROV; and the second power source is selected from the group consisting of an on-board power source carried by the skid, an electrical cable extending from a surface vessel, power supplied by the ROV, power supplied by a subsea production system.

19. The method of claim 15, further comprising operating the chemical injection pump to pump a first chemical carried in a first tank on the skid into the hydrocarbon production facility and evaluating the effect of the first chemical on the hydrocarbon production facility and thereafter; operating the chemical injection pump to pump a second chemical carried in a second tank on the skid into the hydrocarbon production facility and evaluating the effect of the second chemical on the hydrocarbon production facility; and based on the evaluated effect of the first and second chemicals on the hydrocarbon production facility, selecting one of the first and second chemicals for long term treatment of the hydrocarbon production facility.

20. The method of claim 15, further comprising operating a chemical preparation mechanism carried by the skid to recirculate chemicals contained within the chemical tank in order to maintain the chemicals in a well-mixed, cohesive state and reduce separation of components due to differing specific gravities.