Rapid deployable floating production system

A floating production system includes a jacket and a deck supported by the jacket. The jacket includes a plurality of legs and a plurality of braces connected between the plurality of legs. The plurality of braces are connected between the legs along substantially the entire length of each leg to provide a stiffened space frame. Two or more of the plurality of legs may further include a longitudinally oriented launch cradle.

FIELD OF THE INVENTION

The present invention generally relates to the production of petroleum from offshore reserves and more particularly, but not by way of limitation, to a floating production system capable of rapid deployment.

BACKGROUND OF THE INVENTION

For many years, petroleum has been recovered from subterranean reservoirs through the use of drilled wells and production equipment. Petroleum hydrocarbons may be produced in a variety of forms, including liquid crude oil, natural gas and light condensates. The discovery of significant offshore petroleum reserves has lead to the development of an industry dedicated to the design, manufacture and operation of sophisticated drilling and production equipment.

The production of petroleum from offshore reserves typically involves the placement of equipment on a floating structure above the subsea well. There are currently four basic floating hull forms utilized by the deepwater offshore industry: ship-shape, tension leg platforms (TLP), semi-submersibles, and spars. When utilized for the production of petroleum products, each of these types of floating structures can be regarded as a “floating production system.”

In many cases, a floating production system is designed and manufactured for a specific installation. The floating production system is sized and designed to support the maximum production from the producing field. Over time, however, as production from the field diminishes, the floating production system may only use a small fraction of its maximum capacity. In this way, the significant cost of the large-scale floating production system cannot be efficiently recovered while the system is operating at a less-than-optimal capacity. When the cost of operating the large-scale floating production system cannot be adequately offset by the declining production, the field is often abandoned.

There is, therefore, a need for a method for more cost-effectively and completely producing hydrocarbons from offshore reservoirs after a decline in the production. It is to these and other objects that the present invention is directed.

SUMMARY OF THE INVENTION

In preferred embodiments, the present invention provides a floating production system that includes a jacket and a deck supported by the jacket. The jacket includes a plurality of legs and a plurality of braces connected between the plurality of legs. The plurality of braces are connected between the legs along substantially the entire length of each leg to provide a stiffened space frame. Two or more of the plurality of legs may further include a longitudinally oriented launch cradle.

In another aspect, the preferred embodiments include a method for moving the floating production system on a body of water. The jacket of the floating production system is constructed on skid ways, loaded onto a launch barge, transported offshore and horizontally launched at site. The jacket is then rotated to vertical using controlled ballasting of select ballast compartments. The mooring system is then attached holding the jacket in place and the topside is lifted and set on the jacket completing the installation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring toFIG. 1, shown therein is a floating production system100constructed in accordance with a presently preferred embodiment. In preferred embodiments, the floating production system100is particularly well suited for use in connection with the production of oil and gas from marginal (small) reservoirs and end-of-life reservoirs. It will be appreciated, however, that although the floating production system100includes features that permit the use of the floating production system100in certain small-scale applications, the floating production system100will also find utility in larger production environments. The floating production system100is also well suited for the rapid deployment to offshore locations for assisting with test wells.

The floating production system100includes a jacket102, a deck104and surface facilities106mounted on the deck104. The surface facilities106may include, for example, pumps, process vessels, storage tanks, generators, living quarters, cranes, helipads and other resources and equipment typically found on offshore floating production systems. The surface facilities are preferably installed on the deck104and placed onto the jacket102after the jacket102has been moved into a production position. The deck104includes a plurality of deck legs105that support the deck104and surface facilities106on the jacket102.

The jacket102generally includes a plurality of large diameter vertical legs108and interconnecting bracing110. In the particularly preferred embodiment depicted inFIG. 1, the jacket102includes four vertical legs108. The combination of the vertical legs108and bracing110creates a rigid frame space across the entire height of the jacket102. Thus, unlike prior art systems that only include braces at discrete locations between vertical legs, the jacket102includes rigid bracing110along the length of the jacket102.

Each of the legs108includes one or more hard tank joint cans112and one or more soft tank joint cans114. Each of the hard tank joint cans112are connected by hard tank leg sections116. Each of the soft tank joint cans114are connected by soft tank leg sections118. The hard tank joint cans112and soft tank joint cans114are preferably reinforced to support the loading forces exerted by the bracing110. The collection of hard tank joint cans112or soft tank joint cans114disposed at the same depth on the legs108are referred to as a “level” of hard tank joint cans112or soft tank joint cans114. Thus, as depicted inFIG. 1, there are hour levels of hard tank joint cans112and two levels of hard tank joint cans114.

Each of the hard tank joint cans112preferably includes a horizontally disposed watertight bulkhead120. The hard tank joint cans112and hard tank leg sections116create a substantially watertight, buoyant chamber within the leg108. In contrast, each of the soft tank joint cans114and soft tank leg sections118are configured to be flooded. In a particularly preferred embodiment, the hard tank joint cans112, hard tank leg sections116, soft tank joint cans114and soft tank leg sections118near the bottom of the jacket102are longer than the corresponding hard tank joint cans112, hard tank leg sections116, soft tank joint cans114and soft tank leg sections118near the surface.

In the particularly preferred embodiment depicted inFIG. 1, the jacket102further includes a ballast chamber122positioned at the bottom of each leg108. In this way, when loaded with the deck104and surface facilities106, the jacket102establishes a center of gravity for the floating production system100that is below the center of buoyancy. The jacket102provides a stable, self-righting platform for the deck104. The jacket102preferably includes mooring lines124that extend downward from the floating production system100to maintain the position of the floating production system100over the targeted subsea structures.

Notably, unlike prior art spars, the jacket102does not include an outer skin around the hard tank. The absence of an external skin reduces the impact of wave, current and wind forces on the jacket102.

Turning toFIG. 2, shown therein is a perspective view of the jacket102ofFIG. 1. The bracing110generally include horizontal peripheral braces126, horizontal interior braces128and diagonal peripheral braces130. Each of these bracing110is preferably welded or otherwise affixed to a hard tank joint can112or soft tank joint can114.

Each horizontal peripheral brace126extends substantially horizontally between two hard tank joint cans112or soft tank joint cans114located on adjacent legs108within the same level. In contrast, each horizontal interior brace128extends substantially horizontally between two hard tank joint cans112or soft tank joint cans114located on opposite legs108within the same level. The diagonal peripheral braces130extend between hard tank joint cans112and/or soft tank joint cans114between adjacent levels.

In the particularly preferred embodiment depicted inFIG. 2, each level of hard tank joint cans112and soft tank joint cans114includes four horizontal peripheral braces126and one horizontal interior brace128. The horizontal interior brace128preferably alternates position between adjacent levels within the jacket102. The preferred embodiment includes four diagonal peripheral braces130between each level. In the particularly preferred embodiment depicted inFIG. 2, the angular orientation of the diagonal peripheral braces130are the same between two particular levels, but alternate angular orientation at each level of hard tank joint cans112and soft tank joint cans114. The jacket102preferably includes two intersecting horizontal interior braces128between two or more levels within the jacket102. In a particularly preferred embodiment, there are two intersecting horizontal interior braces128between the uppermost level of hard tank joint cans112.

Referring now toFIGS. 3-9, shown therein are plan views of the legs108and bracing110at various depths along the jacket102. Beginning withFIG. 3, shown therein is a plan view of the legs108above the uppermost level of hard tank joint cans112near the deck104. Each leg102includes a chain jack132which can be used in connection with the mooring lines124to stabilize the floating production system100. The deck legs105of the deck104are preferably connected and supported by the interior surface of the legs108.

Turning toFIG. 4, shown therein is a top plan view of the legs108at the first level of hard tank joint cans112. As depicted inFIG. 4, the floating production system100includes a plurality of pull tubes134. The pull tubes134may include, for example, incoming flow lines, export lines, umbilicals and future flow lines. The jacket102may optionally include a plurality of guides136extending between the legs108and the horizontal interior brace128. The guides136prevent the pull tubes134from exhibiting an unacceptable level of lateral displacement.

Turning toFIGS. 4-7, shown therein are plan views of the first, second, third and fourth levels of the hard tank joint cans112.FIGS. 6-9illustrate plan views of the fifth and sixth levels which constitute soft tank joint cans114in the preferred embodiment. As illustrated in these drawings, at least two of the legs108each include a longitudinally oriented launch cradle138. The launch cradle138provides a reinforced base to support the weight of the jacket102in a horizontal position. The launch cradle138is preferably configured to facilitate the sliding movement of the jacket102during launch. Turning toFIG. 10, the ballast chambers122each include a flood port140that permits water to enter the ballast chambers122and soft tank joint cans114and soft tank leg sections118.

Although the structure of the jacket102has been described with reference to the structures depicted inFIGS. 1-10, it will be understood that the present invention is not so limited. Preferred embodiments may include alternative configurations of the legs108and bracing110.

Turning toFIG. 11, shown therein is a depiction of the jacket102resting on a transportation barge142. The transportation barge preferably includes a selectively tilting launch platform (or rocker arm)144. The launch cradles138support the jacket102on the transportation barge142. Unlike prior art spar systems, the presence of bracing110along the length of the jacket102provides enough rigidity to permit the floating production system100to be transported on and launched from the transportation barge142. The ability to move the jacket102on the transportation barge142presents a significant improvement over prior art spar systems that must be towed horizontally through the water due to a lack of rigidity.

When the transportation barge142has been towed to the desired location, the transportation barge142is ballasted down on the stern and the jacket102is forcibly moved down the transportation barge142to the stern. The jacket102may be moved with winches, jacks or other equipment suitable for inducing movement of the jacket102down the transportation barge142.

As the jacket102is moved to the stern of the transportation barge142, the stern of the transportation barge142and the upper portions of the jacket drop in the water. The jacket102will eventually achieve self-sustained movement in the stern direction without the assistance. When the center of gravity of the jacket102passes over the launch platform144, the launch platform144will rock about its pivot point and allow the aft portion of the jacket102to lift from the transportation barge142. The jacket102will then slide from the launch platform144into the water. Once the jacket102has separated from the transportation barge142, the jacket102will rise to the surface and float horizontally.

Once the jacket102is floating in the water, the selective flooding of the soft tank joint cans114and soft tank leg sections118causes the jacket102to orient in a vertical position where the center of gravity is below the center of buoyancy. The mooring lines124are then attached to hold the jacket102in place. Slurried magnetite or other fixed ballast can then be pumped or otherwise transferred into the ballast chambers122. Once the jacket102has been stabilized, the deck104can be then lifted and set on top of the jacket102.

Thus, in a broad sense, the floating production system100includes an improved jacket102that includes a unique bracing system and launch cradles138that provide sufficient structural rigidity and support to permit the floating production system100to be transported on horizontally and launched from a floating barge.

It is clear that the present invention is well adapted to carry out its objectives and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments of the invention have been described in varying detail for purposes of disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention disclosed and as defined in the appended claims.