Patent Publication Number: US-11028663-B1

Title: Process and apparatus for installing a payload onto a subsea structure

Description:
RELATED U.S. APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO MICROFICHE APPENDIX 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the installation of a payload, such as hardware and other equipment, in the subsea environment. More particularly, the present invention relates to the installation of the payload onto a wellhead, a blowout preventer or a lower marine riser package (LMRP). Additionally, the present invention relates to the installation of a payload while upforce pressures from a blowing well prevent conventional installation. 
     2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98 
     As the worldwide demand for hydrocarbon fuel has increased, and known onshore reserves have not kept up with the demand, there has been increasing activity in offshore oil exploration and production. Reserves of oil known to exist in the offshore areas have steadily increased and an increasing percentage of world production is from these offshore areas. The offshore environment has presented numerous new challenges to the oil drilling industry which have been steadily overcome to allow efficient drilling and production in these areas, although the costs have been considerably higher than those of onshore operations. 
     Not only has the offshore environment made production more difficult to accomplish, it has also generally increased the risk of environmental damage in the event of a well blowout or other uncontrolled loss of hydrocarbons into the sea. As a result, known safety equipment, such as blowout preventers which have been used successfully in onshore operations, have been used in offshore operations also. In spite of safety precautions, blowouts of offshore oil wells are known to occur and will occur in the future. 
     Subsea drilling operations may experience a blowout, which is an uncontrolled flow of formation fluids into the drilling well. These blowouts are dangerous and costly, and can cause loss of life, pollution, damage to drilling equipment, and loss of well production. To prevent blowouts, blowout prevention equipment is required. This blowout prevention equipment typically includes a series of equipment capable of safely isolating and controlling the formation pressures and fluids at the drilling site. BOP functions include opening and closing hydraulically-operated pipe rams, annular seals, shear rams designed to cut the pipe, a series of remote-operated valves to allow control the flow of drilling fluids, and well re-entry equipment. In addition, process and condition monitoring devices complete the BOP system. The drilling industry refers to the BOP system as the BOP stack. 
     One of the problems associated with diverter systems for such blowout preventers is that, under certain circumstances, the pressure of the fluid released from the blowout preventer is of extremely high pressures, up to 15,000 p.s.i. Under such circumstances, if there is a release from the blowout preventer, or from the wellhead, these extreme pressure will cause boiling and turbulence in the water directly above the blowout preventer and/or wellhead. This boiling of hydrocarbons in the water directly adjacent to the oil platform is extremely hazardous. First, the amount of turbulence caused by such boiling makes it extremely difficult to carry out further repair activities. Under other circumstances, the presence of such hydrocarbons on the top of the water will create an extreme fire and explosion hazard. As such, it is extremely important so as to avoid the release of hydrocarbons from the subsea well such that the boiling action of the released hydrocarbons is diverted away from the offshore platform or from marine vessels associated therewith. 
     Whenever the pressure of the fluid released from the well is extremely high, it becomes very difficult to install payloads on the subsea structure. The blowing well will create oscillations in the payload which prevents centralization of the payload onto the subsea structure. The strong pressures will cause the payload, as it is being lowered, to vibrate and oscillate and to be deflected out of a central position above the subsea structure. As such, a need has developed so as to be able to deliver the payload to the subsea structure while compensating for the strong pressure that is released from the subsea well. 
     Whenever there is a plume of hydrocarbons, such as natural gas, at the surface of the body of water, it is important to maintain separation of the surface boil from personnel involved in the response. Furthermore, the surface boil will decrease the density of the water. This can cause vessels located within the surface boil to lose buoyancy and potentially sink. As such, when there is a plume of hydrocarbons at the surface of the body of water, vertical installation of the payload becomes virtually impossible. 
     When gas makes its way to the surface, station keeping in the surface boil becomes impossible. Vessels need to be positioned outside the perimeter of the plume. Gas expression on the surface makes the local environment hazardous for personnel. To mitigate this problem, personnel need to maintain separation of wind from the boil. 
     Under certain circumstances, the blowout can be contained through the use of a capping stack. The capping stack is the subject of various patents by the present Applicant. For example, U.S. Pat. No. 9,080,411, issued on Jul. 14, 2015 to the present Applicant, describes a subsea diverter system for use with a blowout preventer. This apparatus diverts fluid from a subsea well. A diverter is affixed between the upper and lower portions of the blowout preventer. Each of the upper portion and lower portion of the blowout preventer has a flow passageway extending vertically therethrough. The diverter has an interior passageway extending vertically therethrough in alignment with the flow passageway of the upper and lower portions of the blowout preventer. The diverter has a flowline communicating with the interior passageway and extends outwardly therefrom. The flowline has a valve thereon which is movable between an open position and a closed position. The open position is suitable for allowing at least a portion of the fluid from the flow passageway to pass outwardly of the flowline to a location remote from the blowout preventer. 
     U.S. Pat. No. 9,038,728, issued on May 26, 2015 to the present Applicant, describes a system and method for diverting fluids from a wellhead by using a modified horizontal Christmas tree. The system has a capping stack with a connector suitable for connection or interconnection to the wellhead, a flow base fixedly positioned in the subsea environment, and a conduit connected to the outlet of a diverter line of the capping stack and connected to the inlet of an interior passageway of the flow base. The conduit is suitable for passing fluids from the capping stack toward the flow base. The flow base is a modified horizontal Christmas tree. 
     U.S. Pat. No. 8,720,580, issued on May 13, 2014 to the present Applicant, also describes a system and method for diverting fluids from a damaged blowout preventer. The system has a capping stack with a connector suitable for connection to the blowout preventer, a flowing stack, and an intervention blowout preventer connected to the connector of the flowing stack. The capping stack as a fluid passage extending from the connector. The capping stack has at least one diverter line in communication with the fluid passage. The flowing stack has an interior passageway extending to the connector at an upper end thereof. The flowing stack has at least one pipe in communication with the interior passageway. The pipe is connected with the diverter line of the capping stack such that a flow fluid passing through the diverter line passes through the pipe into the interior passageway of the flowing stack. 
     U.S. Pat. No. 9,033,051, issued on May 19, 2015 to the present Applicant, teaches a system for diversion of fluid flow from a wellhead. The system has a mudline closure mechanism suitable for attachment to the wellhead, a blowout preventer connected or interconnected to the mudline control mechanism, and a flow control line having one end connected to a diversion passageway of the mudline control mechanism and extending therefrom such that an opposite end of the flow control line is disposed away from the mudline closure mechanism. The mudline closure mechanism has a main passageway communicating with the flow passageway of the blowout preventer. The mudline closure mechanism has a valve suitable for switching fluid flow from the main passageway to the diversion passageway. The blowout preventer is positioned above the mudline closure mechanism. The flow control line is supported by a base anchored to the subsea floor away from the mudline closure mechanism. 
     U.S. Patent Application Publication No. 2017/0350210, published on Dec. 7, 2017 to the present Applicant, teaches a rapid mobilization air-freightable capping stack system. This is a method and apparatus for transporting a capping stack for use in a subsea structure. This apparatus includes a capping stack having a capping stack spool, a connector body connected to the capping stack spool and at least one diverter leg connectable to the capping stack spool. A first skid receives the capping stack spool on the floor thereof. The second skid receives the connector body on a floor thereof. A third skid receives the diverter leg thereon. The first, second and third skids are adapted to be received within an interior of an aircraft. The skids and the connected components can then be flown by the aircraft to a desired location so as to be assembled at a location near a wellhead. 
     U.S. Pat. No. 9,359,852, issued on Jun. 7, 2016 to Kebadze et al., describes a system and method for tethering subsea blowout preventers to enhance the strength and fatigue resistance of subsea wellheads and primary conductors. The system for tethering a subsea blowout preventer includes a plurality of anchors disposed about the subsea blowout preventer and secured to the seafloor. In addition, the system includes a plurality of tensioning systems. One tensioning system is coupled to an upper end of each anchor. The system includes a plurality of flexible tension members. Each tension member extends from a first end coupled to the subsea blowout preventer to a second end coupled to one of the tensioning systems. Each tensioning system is configured to apply a tensile preload to one of the tension members. 
     Of course, one difficulty associated with any attempt to install the capping stacks of the present Applicant is when the well is blowing so as to create a large plume from the wellhead up to the surface of the water. Since the gases associated with the plume are extremely explosive and toxic, it is important to be able to install the capping stack without placing personnel in a hazardous position in relation to the plume. As such, it is necessary for all personnel associated with the installation of the capping stack to reside outside the plume. Unfortunately, the blowing well is usually at the center of the plume. As such, there is been a difficulty in installing the capping stack while, at the same time, maintaining personnel away from the plume. 
     Under certain circumstances, it is necessary to precisely and accurately control the installation of the capping stack onto the blowout preventer or the wellhead. This is quite difficult under those circumstances where a plume is created in the water. Under certain circumstances, the installation of the capping stack cannot be done from directly above the wellhead. The oscillations created by the pressures from the well onto the capping stack make centralization of the capping stack onto the mandrel of the blowout preventer or the lower marine riser package nearly impossible. As such, a need has developed to provide a process and apparatus whereby the capping stack can overcome the forces of the hydrocarbon release and also to centralize the capping stack upon the mandrel of the blowout preventer. 
     A particular problem occurs during the installation of capping stacks onto blowout preventers when the upthrust from the blowing well exceeds the mass of the capping stack. As such, any attempt to lower the capping stack from a surface location directly onto the top of the blowout preventer is thwarted because of the force of the plume of hydrocarbons being released from the blowing well. In any event, it is difficult to achieve precise alignment of the capping stack with the mandrel of the blowout preventer under these circumstances. As such, a need has developed so as to provide a way of accurately and controllably drawing the capping stack into position over the blowout preventer while the well is blowing. 
     It is an object of the present invention to provide a process and apparatus for offset positioning and drawdown installation of payloads upon subsea structures. 
     It is another object of the present invention to provide a process and apparatus whereby a payload can be effectively installed upon a wellhead, a blowout preventer or an LMRP by personnel away from the plume associated with a subsea blowing well. 
     It is still a further object of the present invention to provide a process and apparatus whereby the payload can be installed upon the wellhead, the blowout preventer or the LMRP without risk to the safety and health of workers associated with the subsea installation operation. 
     It is a further object of the present invention to provide a process and apparatus which stabilizes and centralizes the payload during the lowering of the payload in the plume. 
     It is still a further object of the present invention to provide a process and apparatus which avoids damage to the payload and to the subsea structure to which the payload is employed. 
     These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is a process for installing a payload onto a subsea structure. The process comprising the steps of: (1) forming an adapter spool having a plurality of sheaves in spaced relation to each other and in which the adapter spool is adapted to lock onto the subsea structure; (2) affixing the adapter spool onto the subsea structure; (3) extending a plurality of slings respectively through the plurality of sheaves; (4) deploying a plurality of winches at opposite sides of the subsea structure on the seabed; (5) connecting an end of each of the plurality of slings to the plurality of winches; (6) connecting an opposite end of the plurality of slings to the payload; (7) lowering the payload in a direction toward the subsea structure; (8) actuating the plurality of winches so as to draw the payload in a position on the subsea structure; and (9) locking the payload to the subsea structure. 
     The adapter spool has a collar positioned between the plurality of sheaves. The collar locks onto the mandrel of the subsea structure. Each of the plurality of slings has a hookup connector at one end thereof. This hookup connector connects to a line extending from the winch. 
     In the present invention, the step of deploying can be from a barge or other vessel positioned in proximity over the subsea structure. The plurality of winches can be a pair of winches located approximately 180° apart relative to the subsea structure. The plurality of winches are deployed onto the seabed approximately one hundred feet away from the subsea structure. If necessary, more than two winches can be used so as to further enhance stabilization and guided lowering of the payload. 
     In the present invention, the subsea structure is a blowout preventer. The payload is a capping stack. The blowout preventer is affixed to a blowing well. An upthrust of the blowing well can be greater than the mass of the capping stack. The plurality of winches are positioned along a line perpendicular to a direction of approach by the barge or vessel. The step of actuating includes paying in the line of the winches and the plurality of slings so as to draw the line around the pair of sheaves so as to move the payload toward the subsea structure. The payload is moved toward the subsea structure with a remotely-operated vehicle (ROV). 
     The present invention is also an adapter spool for use with a subsea structure. The adapter spool includes a body having a collar formed centrally thereof, a first sheave positioned on one side of the collar, and a second sheave positioned on the collar away from the first sheave. The collar is adapted to engage with a mandrel of the subsea structure. Each of the first and second sheaves are rotatable about an axis transverse to a longitudinal axis of the collar. 
     In the adapter spool of the present invention, a first sling is received over the first sheave and a second sling is received over the second sheave. Each of the first and second slings has a hookup connector at an end thereof. 
     This foregoing Section is intended to describe, with particularity, the preferred embodiments of the present invention. It is understood that modifications to this preferred embodiments can be made within the scope of the present claims. As such, this Section should not to be construed, in any way, as limiting of the broad scope of the present invention. The present invention should only be limited by the following claims and their legal equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view showing the plume released from a blowout preventer associated with a subsea blowing well. 
         FIG. 2  shows a perspective view of an initial step of the process of the present invention. 
         FIG. 3  is a perspective view showing a subsequent step of the process of the present invention. 
         FIG. 4  is a perspective view showing of further step in the process of the present invention. 
         FIG. 5  is perspective view showing the adapter spool as positioned over the mandrel of a blowout preventer. 
         FIG. 6  is perspective view showing a further step in the installation of the adapter spool sling setup in accordance with the present invention. 
         FIG. 7  is a perspective view showing a still further step in the process of installing the adapter spool sling setup of the present invention. 
         FIG. 8  is a still further view showing the installation of the adapter spool sling setup of the present invention. 
         FIG. 9  of is a perspective view showing the drawing of the blowout preventer into proximity of the mandrel of the blowout preventer. 
         FIG. 10  is a perspective view showing the step of the process of the present invention in which the payload is located directly over the top of the mandrel of the blowout preventer in the plume. 
         FIG. 11  is a perspective view showing the drawing of the payload onto and in position onto the blowout preventer of the blowing well. 
         FIG. 12  is the final step in the process of the present invention in which the payload is secured to the mandrel of the blowout preventer. 
         FIG. 13  is a perspective view of a capping stack with spider adapters mounted to the capping stack above the connector. 
         FIG. 14  is a perspective view of an adapter spool as position on the mandrel of a subsea structure. 
         FIG. 15  is a perspective view of the subsea winch in accordance with the present invention. 
         FIG. 16  shows an alternative embodiment for the installation of a payload onto a subsea structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , it can be seen that there is a wellhead  10  that is blowing. In particular, a blowout preventer  12  is affixed to the wellhead  10 . The blowout preventer is open so that a plume  14  of hydrocarbons is released from the upper end of the blowout preventer  12 . The plume  14  is released in such a manner so as to spread out in a conical manner. As such, the surface of the body of water in which the blowout preventer  12  is positioned will have a large amount of boiling hydrocarbons. 
     In normal operations, it is important for workers to avoid any activities located within the danger zone of the plume at the surface of the body of water. As such, a need has developed whereby a payload can be installed onto the blowout preventer by personnel located away from the plume. For example, a series of barges can extend in a linear fashion into the plume and then a downline can extend from the end of the plurality of barges so as to allow for a installation of equipment onto the blowout preventer  12 . However, under certain circumstances, the force of the hydrocarbon release in the plume  14  will prevent this vertical installation technique. In other words, the force of the upthrust of the plume  14  will prevent the payload from being placed directly in its desired location upon the blowout preventer. As such, the present invention provides a technique for the installation of a payload onto a subsea structure from a location away from the plume. The present invention also overcomes the forces of the released hydrocarbons upon the payload. The present invention also centralizes the payload relative to the mandrel of the subsea structure. 
       FIG. 2  shows an initial step in the process of the present invention. In  FIG. 2 , a subsea winch  16  has been lowered onto the seabed  18 . The subsea winch  16  will have a clump weight  20  at the bottom thereof. A cable  22  can be used to lower the winch  16  to the seabed  18 . The winch  16  will have a line thereon which, as will be described hereinafter, can be extended so as to perform the operation required by the present invention. The winch  16  will be positioned on one side of the blowout preventer  12 . The winch  16  will be approximately one hundred feet away from the wellhead  10 . 
       FIG. 3  shows the next step of the process of the present invention. In  FIG. 3 , it can be seen that there is a second winch  24  that has a clump weight  26  at the bottom thereof. The second winch  24  is lowered to the seabed  22  by a cable  28 . Winch  24  is positioned on an opposite side of the blowout preventer  12  and also approximately one hundred feet from the wellhead  10 . Winches  16  and  24  will be on a line that is perpendicular to the direction of approach of the barge at the surface of the body of water. The winches  16  and  24  can be lowered from the barge or can be lowered from other vessels positioned outside of the plume at the surface of the body of water. Winch  24  will also have a line that can be utilized in the process of installing the capping stack. 
       FIG. 4  shows a further step of the process of the present invention in which an adapter spool  30  is lowered by a cable  32  toward the blowout preventer  12 . An ROV  34  can be employed so as to suitably grasp the adapter spool  30  for the purposes of moving the adapter spool toward the blowout preventer  12 . The ROV  34  can be controlled from a surface location by signals through a tether or umbilical  36 . The adapter spool  30 , as will be described hereinafter, is to be installed onto the mandrel of the blowout preventer  12 . The adapter spool  30  has at least two sheaves in spaced relation around the outer diameter of the adapter spool  30 . At least a pair of soft slings are pre-wired through the sheaves. The two soft slings have hook-up connectors at each end. Suitable oceangoing barges, as described hereinbefore, can be utilized so as to facilitate the installation of the adapter spool. 
       FIG. 5  shows the adapter spool  30  of the present invention. The adapter spool  30  includes a collar  40  formed centrally thereof. A first sheave  42  is located on one side of the collar  40 . Another sheave  44  is located on an opposite side of the collar  40 . If necessary, additional sheaves can be utilized on the adapter spool  30 . The collar  40  is adapted to be locked onto the mandrel  50  of the blowout preventer  12 . The body of the adapter spool  30  has a bore  52  formed centrally thereof. Bore  52  is illustrated as being open so that the plume  14  can pass therethrough when the adapter spool  30  is secured to the mandrel  50  of the blowout preventer  12 . As such, the bore  52  should be open during installation. The collar  40  can have an automatic locking feature so that the adapter spool  30  is secured to the mandrel  50  upon engagement therewith. Otherwise, the ROV can be used so as to properly manipulate and lock the collar  40  in its proper position.  FIG. 5  further shows that the sheaves  42  and  44  have an axis of rotation that is transverse to the longitudinal axis of the collar  40 . 
       FIG. 6  shows a further step in the process of installation. In  FIG. 6 , it can be seen that the adapter spool  30  is moved by the ROV into the plume  14 . In  FIG. 4 , the adapter spool  30  is positioned outside of the plume  14 . In  FIG. 6 , the ROV  34  has moved the adapter spool  30  into the plume and into a position above the blowout preventer  12 . Cable  32  (extending from the barge at the surface location) will support the adapter spool  30  in its proper position both within the plume  14  and over the blowout preventer  12 . Since the bore  52  of the adapter spool  30  is open, hydrocarbons in the plume  14  will pass freely therethrough even when the adapter spool  30  is supported above the mandrel of the blowout preventer  12 . 
       FIG. 7  illustrates that the ROV  34  has manipulated the adapter spool  30  so as to clamp onto the mandrel  50  of the blowout preventer  12 . The slings  60  and  62  are pre-wired through the sheaves of the adapter spool  30 . Sling  60  has a hook-up connector  68  at an end thereof. Similarly, sling  62  will have a hook-up connector  70  at an end thereof. 
       FIG. 8  shows that the line  72  extending from the first winch  16  has an end that is joined to the hook-up connector  68  of the sling  60 . Similarly, the second winch  24  has line  74  connected to the hook-up connector  70  of sling  62 . This connection can be made by the operation of the ROV  34 . In this position, the line  74  is strongly secured to the sling  62  and the line  72  is secured to the sling  60 . 
       FIG. 9  illustrates that there is a payload  80 , such as a capping stack, that is supported by a cable  82  extending from a surface location (such as the barge at the surface of the body of water). Sling  66  extends through the sheave  42  and connects to one side of the payload  80 . The winch  16  can be operated so as to pay out the line  72  so as to accommodate the joining of the sling  66  the payload  80 . Similarly, the sling  62  is connected to an opposite side of the payload  80 . Sling  62  extends through the sheave  44 . The line  74  is payed out from the winch  24 . The ROV  34  can manipulate the payload  80  so as to be in a proper position over the mandrel of the blowout preventer  12 . 
       FIGS. 10 and 11  show that the winches  16  and  24  are actuated so as to pay in the respective lines  72  and  74 . This will tension the slings  66  and  62  in the respective sheaves  42  and  44 . As such, the payload  80  is forcefully drawn into a precise position over the mandrel of the blowout preventer  12 . The payload  80 , because of the tension produced by the winches  16  and  24 , can be properly installed despite the upthrust forces of the plume  14 . Because of the precise positioning of the sheaves  42  and  44  and the fastening of the collar of the adapter spool  30  onto the mandrel of the blowout preventer  12 , the payload  80  can be accurately and precisely aligned with the mandrel of the blowout preventer  12 . The tension created by the winches also centralized the payload and minimizes oscillations in the payload. 
       FIG. 12  shows the final step in the affixing of the payload  80  onto the blowout preventer  12 . In particular, the lines  72  and  74  have been pulled to their furthest extent so that the automatic locking mechanism of the payload  30  securely engages with the mandrel of the blowout preventer  12 . The payload  80 , such as the capping stack, is now in operation for diverting fluids from the blowing well or by closing the well in the manner described in the previous patents to the present Applicant. 
     In this configuration, the installation allows personnel to operate outside of the plume and the danger zone of the plume. The winches can be operated remotely so that is not necessary for personnel to be within the plume of hydrocarbons released from the blowing well. All of the lowering of the various components of the process of the present invention can be carried from a barge located within the plume (and without personnel thereon). The arrangement of the adapter spool assures that the capping stack can be applied onto the blowout preventer despite the upthrust forces from the plume released from the blowing well. The adapter spool assures a precise alignment during installation. As such, the capping stack can be properly installed while avoiding danger to personnel located near the plume at the surface of the body of water. 
     Referring to  FIG. 13 , there shown a capping stack  100  which serves as the payload to the process of the present invention. Capping stack  100  has a wellhead connector  102  at its bottom. So as to facilitate connection of the capping stack  100  to the slings, a spider adapter  104  is secured around the low diverter spool flange  106  of the capping stack  100 . In particular, a spider adapter  104  is secured around the low diverter spool flange  106  of the capping stack  100  wellhead connector  102 . Multiple spider adapters  110 ,  112  and  114  are bolted to the ring and extend outwardly therefrom. The arms  110 ,  112  and  114  have a U-shaped hooks  116 ,  118  and  120  at the ends thereof. These hooks  116 ,  118  and  120  serve to establish tie-in points for the stabilizer system. In an alternative embodiment of the present invention, the stabilizer and slings are installed prior to subsea deployment. 
       FIG. 14  shows an alternative in embodiment of the adapter spool  124  as used on the subsea structure  126  of the present invention. In particular, it can be seen that there is a ring  128  that is secured around the mandrel  130  of the subsea structure  126 . A plume  132  is being released from they bore and through the mandrel  130 . Sheave assemblies  134 ,  136  and  138  extend outwardly from ring  128 . In particular, the sheave assemblies  134 ,  136  and  138  are shown with the sheaves  140  at a bottom thereof. In other words, each of the slings will thread through a funnel  142  and over the sheaves  140 . In this embodiment, the slings can be pre-installed prior to subsea deployment. 
       FIG. 15  shows one of the winches  150  as used in the present invention. The winch  150  is a subsea hydraulic winch. In particular, winch  150  has a API 17H Class 5 or 6 rotary torque bucket and gearbox. There is a mechanical wave gear on the drum with a gear ratio of 13.75 to 1. A chain-driven lever wind assists in slang winding. The winch  150  has a seventeen ton tension capacity as a drawdown forced. Two five inch hydraulic cylinders serve to create the final tension and lock in of the payload to the subsea structure. The sling  150  has a swivel base  152  to adjust the drum  154  and sling  156  heading. There is a 0 to 90° fleet angle for the sling  156 . The clump  158  is a 40 ton concrete-filled clump with a mudmat. 
       FIG. 16  shows this alternative embodiment of the present invention. In particular, the system  200  has a subsea structure  202  and a payload  204 . Slings  206 ,  208  and  210  are affixed to the spider adapters on the low diverter spool flange (as shown in  FIG. 13 ) of the payload  204 . The installation of the adapters onto the payload flange occurs on the surface location prior to subsea deployment. The adapter spool  212  (as shown in  FIG. 14 ) receives the slings  206 ,  208  and  210  through the respective sheaves thereof. Winches  214 ,  216  and  218  are located at the seafloor  220 . Winch  214  serves to pay in slung  206 . Winch  216  serves to pay in sling  208 . Winch  218  serves to pay in sling  210 . As the various lines are being payed in, the payload  204  is being drawn to the mandrel of the subsea structure  202  (in the manner described herein previously). The slings  206 ,  208  and  210  are pre-loaded into the payload  204  and pre-loaded through the adapter the sheaves of the adapter spool  202  and to the winches  214 ,  216  and  218  prior to deployment. 
     The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated and the construction and described method can be made is the scope of the present claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.