Abstract:
A method of treating a fluid stream underwater comprising integrally attaching a skid to a fluid stream treating vessel so that the fluid stream treating vessel can be disposed on an underwater floor in a position such that an opening in said vessel is at a highest point on said vessel when disposed on the underwater floor; remotely directing a fluid stream treating vessel to an underwater floor location sufficiently close to said fluid stream so that the fluid stream can be remotely attached in fluid communication with said fluid stream treating vessel; remotely connecting said underwater fluid stream to said fluid stream treating vessel for treatment of said fluid stream; treating said fluid stream by contact with a treatment media disposed within said treatment vessel, maintained at equilibrium water pressure at the depth of treatment; and flowing the treated fluid stream out of said treating vessel.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to methods and apparatus for remotely processing fluid streams, particularly at great depths on a river, lake, or ocean floor, for example, process streams created during the recovery of oil, water and/or natural gas from sub sea locations. 
     BACKGROUND 
     The increasing cost of oil and natural gas and this country&#39;s dependence on supplies of oil from foreign sources has resulted in it becoming more cost effective and more politically desirable to explore for oil and gas in areas that were not previously cost effective—particularly in ocean floor areas under thousands of feet of sea water. Such deep sea exploration and recovery of oil and gas and the future potential to explore for fresh water in undersea areas has increased the need for specialized equipment capable of remotely performing sub sea tasks using remotely operated vessels (ROVs) capable of performing tasks at sea floor locations that are thousands of feet under the sea at the extreme pressures encountered at such depths. 
     Remotely operated underwater vehicles (ROVs) are the common accepted name for tethered underwater robots in the offshore industry. ROVs are unmanned, maneuverable and operated by a person aboard a boat/ship or platform. They are linked by a tether (sometimes referred to as an umbilical cable), a group of cables that carry electrical power, video and data signals back and forth between the operator and the vehicle. High power applications will often use hydraulics in addition to electrical cabling. Most ROVs are equipped with at least a video camera and lights. Additional equipment and tools are commonly added to expand the vehicle&#39;s capabilities. These may include sonars, magnetometers, a still camera, a manipulator or cutting arm, water samplers. And instruments that measure water clarity, light penetration and temperature. 
     Conventional ROVs are constructed with a large floatation pack on top of a steel or alloy chassis, to provide the necessary buoyancy. Syntactic foam is often used for the flotation. A tool sled may be fitted at the bottom of the system and can accommodate a variety of sensors. By placing the light components on the top and the heavy components on the bottom, the overall system has a large separation between the center of buoyancy and the center of gravity, this provides stability and the stiffness to do work underwater. 
     Electrical cables may be run inside oil-filled tubing to protect them from corrosion in seawater. Thrusters are usually located in all three axes to provide full control. Cameras, lights and manipulators are on the front of the ROV or occasionally in the rear for assistance in maneuvering. An example of an ROV use underwater is disclosed in U.S. Pat. No. 5,927,901 (&#39;901) where the ROV is used in a pipeline pigging operation. As described in the &#39;901 patent, ROVs have been used sub-sea for extremely simple operations, such as opening of valves in pipelines to allow flow of a liquid or gas through a pipeline. The process and apparatus described herein provides for a fluid stream treating process to be carried out underwater, where such prior art treating processes were only used on land or on an above-sea platform. 
     One of the problems encountered in a deep sea oil and/or natural gas recovery operation is the cost of erecting a platform for processing the oil and/or gas recovered from the ocean floor. Construction of such platforms is extremely difficult and expensive, particularly when at a location far from shore. Another difficulty with off shore oil and/or gas exploration is that EPA regulations are very strict in allowing essentially no hydrocarbons or other contaminants to be released into the ocean water. These EPA regulations make it very difficult to recover hydrocarbons, e.g., oil and/or gas, from the ocean floor since the recovered hydrocarbons, at extreme ocean depths, contain water that quickly corrodes piping used to convey the recovered hydrocarbons up to a platform or shore processing location. In addition, any device deployed at great ocean depths is subjected to extreme pressures and cannot have any trapped gas inside, e.g., air, since at the pressure encountered under thousands of feet of ocean water, the vessel would implode. Further, the installed piping initially is treated with a variety of inorganic and organic chemicals, such as corrosion inhibitors, scale inhibitors, and preservation fluids to prevent bacteria from growing and scale and rust from forming during the recovery operation. These chemicals cannot be discharged to the ocean due to EPA regulations. It would be extremely desirable to treat fluid streams underwater at a floor of a river, lake or ocean, particularly at thousands of feet under sea water, on an ocean floor, to treat, e.g., separate and remove undesirable contaminants and treating chemicals from recovered oil, gas, and/or water process streams. 
     The apparatus, hereinafter sometimes called “NEMOH™,” and methods described herein are directed to a fluid stream treatment method that can be remotely operated to treat a fluid stream with a reaction or separation media underwater, particularly on the ocean floor, preferably at a depth of at least 500 feet (at a treatment vessel pressure of at least 237 psi), e.g., 1,000 to 10,000 feet at treatment vessel pressures of 455 psi to 4,480 psi, preferably 2,000 to 6,000 feet at treat vessel pressures of 910 psi to 2,696 psi, e.g., filter out contaminants such as water or a chemical additive, such as a corrosion inhibitor, scale inhibitor and/or a preservation fluid from a recovered hydrocarbon or water stream under water, particularly at a depth of thousands of feet under water. 
     SUMMARY 
     NEMOH™ is a pressure equalized underwater fluid stream treatment media-containing vessel. It is a vessel designed to host a treatment material (media) for processing a fluid stream underwater. It is designed to be a temporary vessel that then could be set at one location and recovered and moved from location to location sub sea performing fluid processing until maintenance is needed. It can be used in shallow water and at depths over 6000 feet. It can be operated in fresh, brackish or saltwater environments. 
     The NEMOH™ vessel is designed to have one or more, preferably two or more pressure equalization openings oriented in an upward direction to allow potential entrained gases to escape during deployment and recovery. More openings may be used based on the size of the vessel and the type of media used in the vessel. Specific procedures are needed to safeguard that the openings are not blocked at any time during deployment and recovery, especially if sampling devices, chemical injection valves or ports, meters, screens, or a combination of these items are attached to these pressure equalization lines. These openings may be dual purpose and used during the treatment process as an inlet or outlet or may be dedicated pressure equalization openings that serve as inlets and outlets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an under sea filtration process, including a first basic oil/water separation device followed by a NEMOH™ device for separating remaining oil and/or gas contaminants from the water stream so that the water can be returned to the sea; 
         FIG. 2  is a cross-sectional side view of the NEMOH™ device of  FIG. 1 , wherein a treatment media, e.g., organophilic clay, is contained within canisters; and 
         FIG. 3  is a cross-sectional side view of the NEMOH™ device of  FIG. 1 , wherein the NEMOH™ device contains a bulk loading of treatment media. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Typical Deployment/Operation 
     The NEMOH™ remotely operated fluid stream treatment vessel is typically outfitted with a protective cage having a lifting frame, as well as a mud mat or skid incorporated into the protective lift frame weldments. One or more NEMOH™ remotely operated fluid stream treatment vessels may be put into a cage. The NEMOH™ goes through inspection and overboard preparation. This overboard preparation involves following specific overboard procedures which involve checking all valve (open) positions, adding the media into the vessel, e.g., activated carbon or organophilic clay, pre-filling the vessel and pre-soaking vessel-contained media with water, purging air out with water, and adding the treatment media, e.g., organophilic clay. The NEMOH™ apparatus is positioned so that a ship crane can lower the vessel below the ship deck until sighted with an ROV. Once in sight of the ROV, the ROV will take over direction. The ROV operators will take over the direction of the winch and the movement of the NEMOH™ to ensure that the skid has a safe landing on the bottom of the ocean. Once landed, the winch wire is disconnected and recovered to the surface. 
     The ROV will use its manipulators which can be claw like arms or can have specially designed tools attached to connect a process stream to the NEMOH™ inlet. The ROV will connect one or more conduits containing a process stream to be treated to a NEMOH™ stream inlet port, by a means such as a hot stab or quick couple hose line. Then the ROV may swim to the outlet of the NEMOH™ to connect the outlet of the NEMOH™ to additional process equipment, if necessary, such as a Pipeline End Termination (PLET) by a means such as a hot stab or quick couple connector. All NEMOH™ equalization valves are then closed so that the path of flow will be through the inlet and outlet of the NEMOH™ vessel only. Valve positions on both the outlet process such as a PLET and on the NEMOH™ will be positioned correctly. The NEMOH™ is ready to receive fluids. The same process may be done on the downstream of NEMOH™ if the valves are installed for outlets going to further processing, sampling devices, or into other equipment or pipelines. Otherwise, the NEMOH™ may have an open ended outlet, as shown in  FIG. 1 . The valves on the vessel can be fitted with traditional valves for diver operation or retrofitted with valves and hot stabs for ROV operation. In some cases to prevent inadvertent closing of valves during deployment and recovery, no valves will be installed on inlets and outlets. 
     When the treatment process is complete, the NEMOH™ may/can be recovered in a reverse process or can be disconnected or the ROV can guide the NEMOH™ using the ship winch, along the sub sea floor to another location for another application. In some applications it is preferred that clean water be flowed through the NEMOH™ before recovery. 
     In the preferred embodiment, NEMOH™ is used as a secondary separation device, for example for separating oil from water that was previously removed from the recovered crude oil via a primary separation device and method, such as by gravity or centrifuge. Oil that is recovered from below a sea bed generally contains water as a primary contaminant and the water is separated via phase separation, gravity separation, centrifugal separation, or some other primary process that is remotely operated from ship, platform or shore. The separated water phase contains a quantity of oil that cannot be discharged to the ocean and meet EPA regulations. The NEMOH™ device described herein is remotely operated via ROV to remove almost all of the oil remaining in the water phase so that the water can be discharged to the ocean and meet EPA regulations. The oil separated from the water phase is captured in a media contained within the NEMOH™ apparatus and periodically the oil-laden media is replaced with fresh media. The media of choice in this preferred embodiment is an organophilic clay that can be contained in bulk or may be contained within cartridges, as shown in  FIG. 2 , and in the assignee&#39;s issued patents, for example U.S. Pat. No. 6,398,966, hereby incorporated by reference. Another preferred media is activated carbon. 
     Canister media, as shown in  FIG. 2 , is useful for long term applications where extra inventory can be stored on a ship/boat to change out media with out having to send a media vessel in for maintenance. 
     Media can be made up of various materials depending on the constituents to be removed, oxidized, coalesced, neutralized or a combination of these processes. 
     The typical medias may be Granulated Activated Carbon (GAC), a mixed media bed, organo-clay CrudeSorb™, polymeric media, cellulose media, silica based media or a combination of the medias mixed or layered in bulk or in canisters. Bulk media may be contained with large screens, plates with small holes or diverters on the inlet, outlets and equalization ports. When screens and such items are utilized, additional equalization openings are used in case of inadvertent blockage of these screens after usage. This is especially important for during vessel recovery. A critical aspect of the vessel design is to allow degassing of the media during descent and ascent journeys. 
     The NEMOH™ media host objective is to remove, oxidize, coalesce, neutralize, react or making less or not harmful, or a combination of these processing steps to treat or remove contaminant or undesirable substances that are dissolved or suspended in the fluid being treated. The fluid stream may treated through the NEMOH™ apparatus in an open ended process, where the contaminant, e.g., water can be released to the ocean or NEMOH™ can be connected in a sub sea process where the fluid stream is flowing in a closed system that includes the NEMOH™ apparatus. 
     For discharges open to the environment, typical contaminant materials found in oil and/or gas production, drilling and commissioning activities that the media be utilized to remove, oxidize, coalesce, neutralize to include the following: arsenic; antioxidants (hindered phenols based, phenyl diamine); biocides (such as glutaraldehde, tetrakis(hydroxymethyl)phosphonium sulfate), or materials that have inherent biocidal characteristics; BTEX components (benzene, toluene, ethylbenzene, and xylene); corrosion inhibitors (organic acid based, imidazoline, cationic amines, nitate based, sulfonates, filmers that are surfactant based, amine based such as ethylenediamine, imidazoline, cationic amines, and phosphate ester based); demulsifiers, and emulsion breakers (such as oxalkylated resins and poly glycols, alkylaryl sulfonate based); dyes (fluoresine, xanthene); oxygen scavengers (ammonium bisulphate); suspended and water soluble organics; metals (such as zinc, lead, mercury); refined products (such as diesel, gasoline, hydraulic oil, lubricant oil, triethylamine); hydrocarbons (such as crude oil and condensate); residual equipment treatment (such as point in filmers); storage fluids/preservations fluids (fluids containing glycol, methanol in combination with other chemicals); other chemical treatment such as but not limited to hydrate inhibitors (alkyl ether and alkylpyridine based), paraffin inhibitors, pour point depressants (ethylvinyl acetate copolymers, High MW ester based, methylethyleneketone), asphaltene inhibitors; dispersants and surfactant (such as alcohol ethoxylates, glycol ether, and dodecylbenzenesulfonic acid based); passivators; cleaning products (such as succamide based, sodium hypochlorite, d-lemonene); acid; caustic; viscosity improvers (such as polyisobutylene, olefin and polymethacrylate based); waste stream products. 
     The media may be designed to treat or remove a specific contaminant or fluid stream component, or a combination of constituents depending on the application and the media used. Different media may be utilized in series to treat a specific contaminant or a combination of contaminants. 
     The NEMOH™ apparatus can be used for removal or treatment of any of the above listed contaminants also in a closed loop system to protect an oil and/or gas formation such as for re-injection; as part of a process to protect downstream equipment, or simply to treat a process stream, sub sea or on land 
     NEMOH™ may be operated as a stand alone vessel (single pass) or in combination in series (multi-pass) with additional vessels for fluid with high levels or multiple constituents desired to be processed. 
     Rates, Capacity and Sizes 
     NEMOH™ contaminate capacity (to remove, oxidizing, coalescing, neutralizing or making less or not harmful constituents) is variable and is based on the material makeup, concentration, flow rate for treatment time. 
     Example 1 
     For a bulk granulated activated carbon (GAC) loaded host, it is expected that a (GAC) absorbs 5%-20% by weight of the GAC in the vessel in a 1 barrel per minute (BPM) flow rate is expected for the removal of typical new pipeline chemically treated fluids is expected. 
     Example 2 
     For a bulk CrudeSorb™ media loaded host, it is expected to adsorb 1%-50% by weight of the CrudeSorb™ media in the vessel of a line containing suspended total petroleum hydrocarbons less than 200 ppm at rates less than 1 BPM. 
     The NEMOH™ can be of various sizes dependent on the application. The typical NEMOH™ size: 
                                                     Dry               Oper.       Item   Weight   Length   Width   Height   Weight                   OS 72   4,000   4′4″   4′4″   7′5″   6,400       (Loaded - 2000# media)                    
This size has been selected for the ease of operation during deployment for a boat crane and for boat space footprint. The flow rate is typically 1-2 barrel per minute and is dependant on the media, fluid quality and composition.
 
     Multiple NEMOHs™ can be manifolded together to address higher flow rates or a larger vessel can be used. 
     Most Common NEMOH™ Applications 
     Pressure testing: Some typical applications for NEMOH™ for pressure testing equipment. During installation of new equipment, the equipment integrity needs to be verified. Connections, seals, valves, and lines all need to be checked for leaks. This is routinely done by pressure testing the lines. This is accomplished by filling the equipment up with water which often is chemically treated to protect the equipment from corrosion. These chemicals (biocides, corrosion inhibitors, oxygen scavengers) can be inherently toxic to the environment. There are strict regulations in the Gulf of Mexico as well as other EPA—controlled waterways, strictly limiting contaminants carried by the pressure treatment water being discharged to the ocean water. Each state has regulations for inland waters and for federal waters there are the EPA regulations. 
     After this equipment is filled, additional water is pumped into the equipment until a desired pressure is held. The pressure is held and charted for variances. If all is well the equipment is depressurized. This excess fluid can be captured and treated through a NEMOH™ to ensure there is no harmful release to the environment that is not treated. 
     This hydrostatic testing can be done for risers, pipelines, manifolds and other equipment that needs to be integrity tested. This is typically done during new installation or if maintenance has had to be done on a process section where a new component needs to be evaluated in a system. In cases where the equipment has been in use there may be additional contaminants such as oil and grease, entrained gas, production chemicals, maintenance chemicals, or the like. 
     Over Flushing 
     When equipment is being replaced, repaired, or modified, preservation fluids may be in place. As the system is opened on purpose or inadvertently (such as hurricane damage) sea water my enter the line or system. The sea water may then be pumped out of the sea water-containing equipment while ensuring that all sea water is displaced with preservation fluids, oil or other fluid. The pumped out fluids may then be collected and/or processed. 
     Turning now to  FIG. 1  there is shown an underwater oil/water well pipe  12  that is initially directed through a gravity separation tank  14  for gravity separation of a lower level of water  18  from a floating layer of oil  20 . The water  18 , containing hydrocarbon (oil) and/or other contaminants is conveyed through a separation tank water outlet conduit  32  disposed near a bottom of the separation tank  14 . 
     In accordance with an important feature of the present invention, water outlet conduit  32  is remotely connected by ROV to be in fluid communication with an inlet  45  of one or more NEMOH™ treatment vessels  44  containing a volume of treatment media, for example, an oil adsorbent, particularly an organophilic clay. The separated water flows through separation tank  14  water outlet conduit  32  and is conveyed through conduit  32  into treatment vessel  44  at the treatment vessel inlet conduit  45 . The organophilic clay within treatment vessel  44  adsorbs the hydrocarbons, oil and other organic materials entrained with the water flowing through conduit  32  for essentially complete hydrocarbon removal (less than about 10 parts per million, preferably less than about 1 part per million organics after organophilic clay treatment). The treated water flows through treated water exit opening  46  in the treatment vessel  44  and through exit conduit  46 A back to the ocean water  14 . 
     As shown in the embodiment of  FIG. 2  the treatment vessel  44  includes an outer, fluid-impermeable housing  48  having a process stream inlet  45  and valve  49  interconnected through the housing  48  so that the process stream, e.g., contaminated water, enters the treatment vessel  44  and then, as shown in  FIG. 2 , enters individual organophilic clay-containing vessels or cartridges  55 , from outside surfaces of the cartridges  55 . Alternatively, as shown in  FIG. 3 , the vessel  44  can be filled with bulk treatment media  56 . The organophilic clay-containing cartridge  55  is water-permeable by virtue of having water flow apertures (not shown) that are sized sufficiently small such that organophilic clay granules do not pass therethrough. Water entering the treatment vessel  44  through water inlet conduit  45  flows radially inwardly into longitudinal, axial, central conduits  50 ,  51 ,  52 ,  53  and  54 , each containing treated water exit openings for the organophilic clay-treated water. Organophilic clay contained in cartridges  55  adsorbs any oil and organics contained in the water and the clean water exits through exit openings  59 ,  61 ,  63 ,  65  and  67  in each stack of cartridges  55  and the clean water collectively exits the treatment vessel  48  through exit opening  46  and flows through valve  47  and conduit  46 A and may be returned to the ocean, as shown in  FIG. 1 , or the outlet conduit  46 A may be connected to another process device, e.g., another NEMOH™, via ROV for further processing. 
     In accordance with one embodiment of the underwater processing methods and apparatus described herein, the treatment media functions excellently when loaded into the treatment vessel  44  in bulk, as shown in  FIG. 3 . As described above, before submerging the treatment vessel  44 , the NEMOH™ vessel  44  is charged with bulk treatment media, e.g., organophilic clay  56 , and the vessel and its treatment media is thoroughly wetted with shore drain valve  69  ( FIGS. 2 and 3 ) closed so that any gas contained with the vessel will rise to escape through inlet conduit  45 , disposed at the highest point of a top  48 A of the NEMOH™ vessel  44 . Some gas may also escape through the treated stream outlet opening  46  since valve  47  in outlet conduit  46 A is opened during wetting of treatment media and degassing of the NEMOH™ treatment vessel  44  prior to submerging the vessel  44 . A fine mesh screen or filter cap  49  is fitted over outlet opening  46  in conduit  46 A to prevent bulk treatment media from being lost through the outlet opening  46  and conduit  46 A. Alternatively, a fine mesh plate or screen  60  ( FIG. 3 ) can be secured to an inside circumference along a horizontal plane inside the vessel  44 , above the outlet opening  46  in conduit  46 A to prevent treatment media  56  from being lost through the outlet opening  46  in conduit  46 A. 
     The wetted and de-gassed NEMOH™ treatment vessel  44 , on planar skid  53 , and preferably protected from ROV collision damage by frame structure  70 , then is lowered by cable from ship or platform down to the waterway, e.g., ocean, floor, as shown in  FIG. 11 , with the valves  49  and  47  in uppermost conduit  45  and outlet conduit  46 , respectively, open to allow for the escape of gas and for water to enter the NEMOH™ vessel  44  during its downward journey into deeper water so that gases are released through conduits  45  and  46 , and pressure is equalized within the outside of the NEMOH™ vessel, regardless of its depth. 
     Surprisingly, the treatment media  56  does not escape from the NEMOH™ vessel through open vessel inlet conduit  45  while the NEMOH™ vessel descends to the ocean floor. It is theorized that the substantial water pressures placed on the treatment media  56  during the descent of the NEMOH™ vessel  44  densifies the treatment media at the lower portion  48 B of the NEMOH™ vessel  44  enabling the treatment process described herein, at great depths, since the process is carried out at ambient conditions at the ocean or lake floor.