US3556218A

US3556218A - Underwater production satellite

Info

Publication number: US3556218A
Application number: US740783A
Authority: US
Inventors: William A Talley Jr; James T Dean
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1968-06-27
Filing date: 1968-06-27
Publication date: 1971-01-19
Anticipated expiration: 1988-01-19
Also published as: GB1244273A

Abstract

This specification discloses a method and apparatus for the production of subaqueous deposits of fluid minerals through a subsea satellite system. The wells are drilled in a circular pattern through a template on the marine bottom serving also as base upon which the satellite body is installed. The production and control passages of each of the wells are connected to production equipment within the satellite body by separate connector units, independently lowered into place from a surface vessel, to form portions of fluid paths between the passages within the subsea wellheads and the production equipment within the shell of the satellite. Such an installation permits production through the satellite, installed on the template base, after only one of the wells has been drilled and completed. The produced fluids are separated and/or metered within the satellite prior to being transported to storage. Flowline tools are programmed to enter the various subaqueous wells through the connector units. Hydraulic circuitry and controls are provided for pumping the tools and chemicals down through the various wells and for retrieving the tools. Also disclosed is a hot water well utilized in conjunction with the heat exchanger within the satellite for warming the separated-off gases to prevent the formation of hydrates.

Description

United States Patent [72] Inventors William A. Talley,Jr.

Dallas, Tex.; James T. Dean, Dallas, Tex. [21] Appl. No. 740,783 [22] Filed June 27, 1968 [45] Patented Jan. 19, 1971 [7 31 Assignee Mobil Oil Corporation a corporation of New York [54] UNDERWATER PRODUCTION SATELLITE 33 Claims, 8 Drawing Figs.

[52] US. Cl 166/265, l66/.5 [51] Int. Cl E2lb 39/00, E2 1 b 33/035 [50] Field of Search 166/265, 267, 5.6, 265, 315, 154

[56] References Cited UNITED STATES PATENTS 2,810,442 10/1957 Tausch 166/315X 3,366,173 l/1968 Mclntosh l66/.5 3,373,806 3/1968 Stone 166/.5 3,381,753 5/1968 Fredd 166/154X 3,396,789 8/1968 Dean 166/.5 3,422,895 1/1969 Koonce 166/79 3,444,927 5/1969 Childers et al.

Primary Examiner-Marvin A. Champion Assistant ExaminerRichard E. Favreau AttorneysWilliam J. Scherback, Frederick E. Dumoulin,

Alan G. Paul, Donald L. Dickerson and Sidney A. Johnson ABSTRACT: This specification discloses a method and apparatus for the production of subaqueous deposits of fluid minerals through a subsea satellite system. The wells are drilled in a circular pattern through a template on the marine bottom serving also as base upon which the satellite body is installed. The production and control passages of each of the wells are connected to production equipment within the satellite body by separate connector units, independently lowered into place from a surface vessel, to form portions of fluid paths between the passages within the subsea wellheads and the production equipment within the shell of the satellite. Such an installation permits production through the satellite, installed on the template base, after only one of the wells has been drilled and completed. The produced fluids are separated and/or metered within the satellite prior to being transported to storage. F lowline tools are programmed to enter the various subaqueous wells through the connector units. Hydraulic circuitry and controls are provided for pumping the tools and chemicals down through the various wells and for retrieving the tools. Also disclosed is a hot water well utilized in conjunction with the heat exchanger within the satellite for warming the separated-off gases to prevent the formation of hydrates.

PATENTEUJAN 19 I97! SHEET 1 BF 6 INVENTOR J AMES T. DEAN WILLIAM A. TALLEY,JR

azwg/ aal ATTORNEY 'PATEN EDJAMQIQII I 3.556218 SHEET 2 (IF 6 INVENTOR JAMES 1'. DEAN WILLIAM A. TALLEY, JR.

ATTORNEY PATENTEU mu 9m SHEET 3 BF 6 INVENTOR JAMES T. DEAN WILLIAM A. TALLEY; JR,

ATTORNEY P \TENTED JAN 1 9 IBYI T0 WELL 8 WELLHEAD EQUIPMENT T0 MARINE BOT TOM "m mic SHEET 5 OF 6 FIG. 6

H d SUPPLY SYSTEM :34 -Qm FLARE CLEAN, DEAD on. SUPPLY FOR TFL FLUID TO STORAGE M/ZZZ TO STORAGE OR EAD 'OIL SUPPLY FOR TLF FLUID) SUPPLY SYSTEM TO STORAGE INVENTOR JAMES T. DEAN WILLIAM A. TALLEY, JR.

ATTORNEY PATENIED JAN 1 9 I97;

sumsnse JAMES T. DEAN WILLlAM A. TALLEY, JR,

azmmwp ATTORNEY BACKGROUND OF THE INVENTION l. Field ofthe Invention j This invention relates to a subsea satellite designed to be interconnected with a group of subaqueous' wells having subsea wellheads so as to control the productiontherefrom and to provide ordinary maintenance therefor. More particularly, the invention relates to a system for inserting one or more types of tools, and/or chemicals, down through selected wells and for retrieving the tools 'upon the completion'of the respective function.

2. Description of the Prior Art Since its inception, the offshore oil and gas industry has used bottom-supportedabove-surface platforms as the principal mechanism for the installation and support of the equipment and services necessary for the production of the subaqueous mineral deposits. As the industry has developed over the years, it has extended its search for offshore minerals from its birthplace, producing oil and gas in theshallow coastal waters off California and the Gulf of Mexico into areas where, because of excessive water depth and/orother local conditions, the bottom-supported platform is not as economically or technologically feasible.

While theoretically there is no limit to the depth for which a bottom-supported platform can be designed and installed, experience to date indicates that platform costs increase almost exponentially with the increase in water" depth. Thus, the presently estimated costs of a platform to carry the production facilities for a field in 400 feet of water or more are so high as to indicate that such an installation cannot be justified economically for any but the most productivefields. Furthermore, the few bottom-supported above-surface platforms that have been designed and built for use in 300 feet or more of water depth have almost invariably suffered-leg failures of one type or another.

A possible solution is to install the production facilities on a floating platform, as is described in the H/D: Cox Pat. No. 3,111,692, issued Nov. 26, I963, which can be maintained in position in a field by either a fixed multipoint mooring system of anchors and anchor lines, or by adynamic positioning system. The above solution involves the expense'of continuous maintenanceand surveillance of the locating; system as well as the associatedproblems and expense of maintaining the multiple flexible lines connecting wellheads on the marine bottom with the continuously moving floating production platform, and the potential hazard, of this system to, the hoses, in the event of a failure of the fixed mooring or dynamic positioning systems.

Another consideration is that, in many areas of the world, local conditions other than water depth impose critical limitations on the use of bottom-supported production platforms. In arctic areas, a bottom-supported platform must be built to withstand the forces imposed by ice that forms on the water surface during the winter months of the yearQand in many such areas all year long; Furthermore, any above-water production platform is subject to the mercyofthe wind and waves, especially those occurring during hurricanes and other violent storms. In the arctic areas these storms can be exceeded by the forces exerted against the platform by movement of the thick ice layers that freeze on the surface of the water. Forexample. in Cook Inlet, Alaska, the local extremely high tidal movementson' the order of 30 feet or more cause very fast tidal currents in the Inlet, with velocities of up'to8 to miles an hour 'or more. These very rapid currents carry with themthe heavy pack ice that forms on the surface of the Inlet,

so that it bearswith tremendous force against any fixed structure, such as a production platform, that should be installed in its-path. 1-

In-still other areas it is not adverse natural,: but manmade, conditions that restrict the use of bottom-supported abovesurface production platforms. Among such conditions could be listed official and/or public objection to oil production facilities near public recreational or residential areas, and the presence of heavy-marine traffic as in harbors, channels, rivers, and other navigatable bodies of water which make it necessarily advantageous to install as much of the production equipment beneath the water surface as possible. For example, the first known use of subsea wellheads is in Lake Erie I where gas is produced from subaqueous formations beneath the heavily traveled lake.

Therefore, it would appear that where there is extremely deep water and/or adverse surface conditions, a fully subsea installation would be the most advisable solution. One method, as is shown by the J. A. Haeber Pat. No. 3,261,398, issued Jul. 19, 1966, is to locate the individual pieces of production equipment on the marine bottom. Such an installation almost necessitates the use of robots such as shown in the G. D. Johnson Pat. No. 3,099,3 l6, issued Jul. 30, 1963. However, such instrumentalities are expensive and not without their own limitations and maintenance problems. Another solution is suggested by the H. L. Shatto, Jr. et al. Pat. No. 3,221,8l6, issued Dec. 7, I965, wherein the production equipment for a plurality of wells is grouped within a satellite chamber adapted to' be raised to the surface for repair and/or maintenance.

To economically package production equipment used for scheduling, measuring, separating, and otherwise performing the usual manipulations on producing oil and gas wells, it is believed to be necessary to enclose the equipment within a pressure-resistant satellite shell within which can be maintained a breathable atmosphere permitting the equipment in side to be serviced and/or maintained by personnel, not encumbered with diving suits. Single well chambers, most being removable, have been proposed and are exemplified by the J. D. Watts et al. Pat. No. 3,202,216 issued Aug. 24, I965. The

most feasible system should include a subsea satellite having therewithin production equipment servicing a number of wells and capable of maintaining life sustaining conditions therewithin.

No feasible system has been presented. to date for economically maintaining the several serviced wells in operating condition during production. This would require the periodic passing through of tools for cutting paraffin, setting chokes, removing sand, and other operations normally done with wirelines in a land or platform-supported well. A necessary part of such a maintenance system is means for detecting a malfunction in a well or in simpler installations, for instance, where frequent paraffin cutting is necessary, a timed sequence can be used. Apparatus must be provided for moving a single tool selectively through one of a number of wells and for storing one tool when one performing a different function is to be directed into a well.

While wireline tools have been used for many years to maintain wells and through-the-flowline (TFL) tools are known and have been used at least experimentally, a complete automatic system for maintaining several wells as a group is not available. The P. R. McStravick et al. Pat. No. 3,022,822 discloses a system for pumping a wireline tool down through a single subsea wellhead from a nearby above-surface location, but is not concerned with the selection of a particular tool, the timing of the operation, or the storage of the tool for a second operation. The F. H. Culver et al. Pat. No. 3,l0l,l l8 discloses a subsea wellhead to be utilized in conjunction with a wireline tool which is guided in and out of the wellhead through wide branch conduits thereof. The S. A. Bergman et al. Pat. Nos. 3,063,079 and 3,063,080 disclose launching devices for inserting pipe scraping tools or pigsinto a pipeline while the K. D; Savage Pat. No. 2,856,884 discloses a system for storing a pig in an adjacent pipe when it is not being used in the pipeline.

SUMMARY OF THE INVENTION In accordance with this invention, fluid produced from a plurality of wells, through subsea wellheads, is processed within a satellite station prior to being transported to storage. The produced fluid from the plurality of wells is combined into a single stream within the satellite station. The fluid stream is choked to reduce the wellhead pressure to that necessary to drive the fluid up to a surface installation. The fluid is then directed into a plurality of gravity separators connected in parallel. The gas taken off from the plurality separators is recombined and the main portion thereof directed to storage, utilized in a gas lift operation, or disposed of by flowing or being injected into shallow sand formations. A minor portion of the gas may be utilized to drive a turbine of a turbine-pump for pressuring up a TFL (through-the-flowline) system. The liquids, including oil and gas and sediment, are directed through the lower ends of each of the separators, the liquids being recombined and transmitted to storage. A clean oil pickup from within at least one of the separators directed oil from a point above the sediment level of the respective separator to the pump portion of the TFL system. In a storage tank forming alower portion of the satellite body, open to the sea at the lower end thereof, a well treating fluid may be stored. Alternatively, the well treating fluid can be stored in and supplied from a surface vessel moored over the site. Wherever the source of treating fluid, it is in fluid communication with a first inlet of the turbine-pump through a three-way two-position valve, the second inlet thereof being connected to the clean oil source whereby a prescribed amount of treating fluid followed by clean oil can be pumped into the TFL circuitry behind a tool whereby the TFL tool is forced through the subsea wellhead and down into the respective well to perform a desired function. In place of the turbine-pump, an electrically driven pump may be used. In this case, the clean oil pickup line is dispensed with. Where a medium or high GOR (gas-to-oil ratio) is encountered, a heat exchanger unit is necessary to prevent hydrate formation, minimize excessive paraffin deposition, and restrict emulsion formation. For a medium GOR, the unit may consist of only passing the fluid prior to expansion in close conjunction with the fluid after expansion within an insulated area. Where there is a high GOR, an outside heat source is necessary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial view of a subsea production system in accordance with the present invention;

FIG. 2 is a'partially broken away enlarged view of one of the satellite stations shown in FIG. 1, illustrating the arrangement of the equipment therewithin;

FIG. 3 is a schematic representation of a heat exchange system to be utilized within the satellite station also, but shown in less detail in FIG. 2;

FIG. 4 is a schematic diagram of the basic circuitry required to produce a plurality of oil and gas wells within a satellite station;

FIG. 5 is a schematic diagram of a modified TFL Fluid Supply System;

FIG. 6 is a schematic diagram of a modified production system for producing a field having a high gas-oil ratio;

FIG. 7 is a schematic diagram of a modified production system for producing a field having a medium gas-oil ratio; and

FIG. 8 is a schematic diagram of a modified satellite station configuration for allowing the satellite body to be installed on a base template of a satellite station prior to the completion of any of the wells through the base template.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now looking to FIG. 1, a subsea system for producing fluid minerals, in particular gas and oil, from a subaqueous field by a plurality of subsea wellheads is illustrated. A plurality of subsea production satellite stations, generally designated 10, are spaced across a marine bottom 12, each satellite station 10 comprising a satellite body centrally positioned within a circular group of closely spaced subsea wellheads 14. The

produced fluids from the subaqueous wells are directed through encircling subsea wellheads 14 into the satellite body 15 of the respective satellite station 10. The fluids being produced from the subsea wellheads 14 of each circular group are combined within the respective enclosed satellite body 15 and a first stage of separation (gravity) takes place. At least the liquid portion is then directed to a circular manifold 16 atop a central bottom-mounted storage tank 17 through a shipping line 18, one shipping line 18 extending from each satellite station 10.

A floating master station 20, having power generating and final stage separation equipment thereon, as well as being fitted out with off-loading apparatus, is in fluid and electrical communication with the bottom-supported storage tank 17 through a tensioned tether pipe 22 extending from the storage tank 17 to a point just beneath the turbulent surface zone of the body of water and fixed at this point to a large subsurface buoy 24. A flexible conduit 26, containing a plurality of electrical and fluid flow paths, extends from the upper end of the tensioned tether pipe 22 to the floating master station 20. The produced liquid, collected in the circular manifold 16, is directed to the master station through a main shipping line 27 supported along the length of the tether pipe 22, and a fluid line forming a portion of the flexible conduit 26. The produced liquid passes through the final stage separation equipment on the master station 20 where the pressure is normalized and dissolved gases are removed. The dead liquid is then transported to storage within the storage tank 17 through a line of the flexible conduit 26 connected to an axial passage in the interior of the tether pipe 22.

In the upper left-hand corner of FIG. 1 is illustrated the drilling of a well through a satellite base template, generally designated 28, which has been previously installed on a marine bottom along with a shipping line 18' for connecting a satellite station, when completed in conjunction with the template 28, with the storage tank 17. A drill string 30 is suspended from above the surface from a semisubmersible drilling vessel 32 and extends through a blowout preventer stack 33 mounted on one of a plurality of upstanding well conductor pipes 34 forming a portion of the template 28. Illustrated in the lower portion of FIG. 1 is a manned submersible work vehicle, generally designated 36, of a type to be employed at assist in the subsea operations and for the dry transfer of personnel to the satellite station 10. The submersible work vehicle 36 has a pair of articulated

arms

38 and 40 carrying a socket wrench 42 and a vise grip tool 44, respectively. The submersible work vehicle 36 is further equipped with a pivotable positioning motor 46 on each side (one shown) to assist in locating the submersible work vehicle 36 adjacent a satellite station 10 firstly when subsea operations are to be performed during the drilling operations and the installation of the satellite body 15 therewithin, and at later times during maintenance and workover operations. A lower port 48 of the submersible work vehicle 36 is connected with a rear compartment (not shown) within the shell thereof to permit a diver to be released at an installation site if one should be needed. The rear compartment is isolated from the pilots compartment, seen through the front view plate 50, so that a diver after exposure to deep water can be kept in compression in the rear compartment while the front compartment is maintained at atmospheric conditions. This general type of submersible work vehicle is well known in the artand specific vehicles of this type are more fully described in the application Ser. No. 649,959, filed Jun. 29, 1967, of Warren B. Brooks, Charles Ovid Baker, and Eugene L. Jones, and the references cited therein.

Now looking at FIG. 2, the interior of the satellite body 15, as well as the satellite base template 28, are illustrated in more detail. The internal equipment comprises that necessary for a high gas-oil ratio, high pressure field. The base template 28 comprises an outer ring 51 to which are rigidly connected the plurality of upstanding vertical well conductor pipes 34 through which subaqueous wells have been drilled. As shown, I

a dual completion wellhead 14 is mounted on the upper end of each of the well conductor pipes 34 in completing each of the respective subaqueous wells. The satellite body is installed after the completion of all of the wells drilled through the respective base template 28. The satellite body 15 is shown to be cradled in a plurality of radially extending spaced arms 41 fixed to the base template 28. Threaded detent rods 43 extend through each of the arms 41 and through the shell of the satellite body 15 into receivers 45 fixed to the inner wall of the shell. The detent rods can be screwed into and out of engagement with the receivers by means of the socket wrench 42 of the submersible work vehicle 36. A hex nut 53, terminating in a conical guide, is affixed to the outer endofeach detent rod 43. Support frames 47, having pillow boxes 49 in which the detent rods 43 are journaled, allow the use of long detent rods 43 extending radially out beyond the well conductor pipes 34.

A water well 52 is shown as having been drilled through the center of the base template 28 and is necessarily completed prior to the installation of the satellite body 15. After all of the wells, including the water well 52, have been completed, the satellite body 15 is lowered into place and is leveled and locked into the base template 28 in any suitable manner. There would be no reason why one water well could not be drilled through one of the well conductor pipes 34 on the ring 51 of the base template 28, if this should prove more convenient. The only disadvantage would be the elimination of one possible producing well. The W. F. Manning patent applications Ser. Nos. 663,799 and 663,798 entitled Subsea Satellite Foundation Unit and Method for Installing a Satellite Body Within said Foundation Unit, and Subsea Satellite F oundation Unit and Method for Installing a' Satellite Body Therewithin, respectively, disclose alternate leveling and locking nieans as well as means for registering the installed satellite with respect to encircling wellheads.

The water well 52 is designed to providea heat source for a heat exchanger unit (to be discussed below)to warm the produced fluids after a pressure cut has been taken. The well water may also be directed through radiators in the portions of the satellite body 15 in which personnel are present to raise the interior temperature of that portion of the satellite body 15 above the ambient temperature at the marine bottom. In deep water the temperature at the marine bottom isin the range of 35 F. to 45 F., too cold for a man towork. for long periods unless he is heavily clothed.

Each of the submerged dual completion wellheads 14 has a pair of upstanding tubing nipples (not shown), each being in fluid communication with a producing zone. Each of the pairs of tubing nipples is adapted to telescope into complementary passages of stabover connector unit, generally designated 54, comprising a pair of downwardly curving tubing sections 56 extending radially outward from within the shell of satellite body 15 and terminating in vertical lubricator sections 58. By

means of the stabover connector units 54, the production and control passages extending through the subaqueous wells are connected to manifolds within the satellite body 15 for the combining of the produced fluids through the satellite body 15 and/or for the injection of lift gas, or other fluids utilized in secondary recovery procedures, from the satellite body 15, to allor selected ones of the subaqueous wells; As shown in the embodiment of FIG. 2, the stabover connector units 54 are permanently fixed with respect to the satellitebody 15. Therefore, the satellite body 15 must be radially positioned quite precisely so that the stabover connector units 54 can register with and telescope over the upstanding tubing nipples of the respective wellheads l4. 1

An escape hatch 60 is formed within the upper end of the satellite body 15 to permit the entry of an operator 62 from a diving bell or travel chamber, as shown in the Townsend application Ser. No. 521,745, filed Jan. 19, 1966, ora submersible work vehicle 38. The upper portion of the interior of the satellite body 15, within which the operator 62 is shown sitting at a panel 64, comprises a control section, generally designated 66, from which various operations, not normally programmed,

may be controlled and from which stored information can be retrieved. Below the control section 66 is a production section, generally designated 68, containing the various equipment necessary to separate and meter the produced fluids as I 5 well as to pump treating fluids and tools through the various I in one or more operations. Although some plumbing extends through the storage section 70, it is substantially uncluttered to permit the storage of a large quantity of well treating fluid.

Centrally located, within the production. section 68, is a cylindrical heat exchanger unit 74. Equiangularly spaced around the heat exchanger unit 74 are a plurality of spherical separators 72. The produced fluids normally flow through the shell of the satellite body 15 by way of the tubing section 56 of the connector units 54. From a tubing section 56 the fluid is directed by a branch conduit 76 through an expansion valve (shown in FIG. 3 and to be discussed with respect thereto) into an upper heat exchanger manifold 78 located within the upper end of an insulated jacket 79 of the heat exchanger unit 74. Fluids, exiting from the manifold 78, flow down through a central pipe 80, leaving the heat exchanger unit 74 near the lower end thereof by means of conduits 82 (one shown) which lead the produced fluids into the individual separators 72.

The separators 72 in the satellite station 10 are of the gravity type to permit the separation of the gas from the oil without a substantial temperature drop in the separators, avoiding hydrate and paraffin deposition problems therewithin. A loss of 7 F. to 8 F. would be normal with such equipment. With a one-minute retention time within the separator, all of the free gas will be removed, only the gas, dissolved in the liquid at the separator pressure, remaining for the secondary, or final,

separation stage. While the separators planned for this installation have no water knockout feature, provision for removal of water from the oil could be provided if it was desirable at this stage of production. The pressure at which the separators 72 are designed to function may be governed by the depth at which the satellite station 10 is located since it is desirable to have sufficient pressure to lift the oil from the marine bottom to the master station 20 on the surface. [in very deep water the produced oil may have to be lifted, at least in part, by powerdriven pumps. Where the satellite is connected into a truck pipeline, rather than being transported away by tanker, the output pressure of the separators would be governed by the line pressure in the pipeline. Where the wells are producing with a wellhead pressure of, for example, 1,500 p.s.i. and the 5 satellite station 10 is located in 2,000 feet of water, a 900- pound pressure drop will be taken, prior to introducing the produced fluid into the separators 72, to obtain a pressure of approximately 600 p.s.i., which would be that'necessary to drive the oil from the marine bottom to the surface.

Taking a pressure drop of 900 p.s.i. lowers the temperature of the produced fluids by more than 50 F. When considering a 10,000-foot well in which the produced fluids at the wellhead would be at from F. to F., at 50 F. the resultant temperature would be well within the formation tem- 5 perature of hydrates and paraffms.

70 a heat source to increase the temperature: of the mixed oil and gas on the downstream side of the choke 84 where a pressure out has been taken, to prevent hydrate formation, minimize excessive paraffin deposition in the equipment, and restrict emulsion formation. The heat exchanger unit 74 depends 5 upon well water obtained from the previously mentioned water well 52 (shown only in FIG. 2). The water is produced through a normal type of oil well completion and then flows through a variable choke 86 that regulates the flow and downstream pressure. In an example, using a 10,000-foot water well, the water at the upper end of the heat exchanger will also be in the range of 150 F. to 170 F. The water from the well 52 is directed upward through a conduit 88, entering the insulated cylindrical jacket at 79 of the heat exchanger unit 74, through the upper end thereof. The water travels down through the interior of the heat exchanger jacket 79, emerging from the lower end thereof in outlet line 90 from which the water is dumped into the sea. As the cold produced fluid passesinto the manifold 78 within the upper end of the heat exchanger unit 74, after passing through the expansion choke 84 and a one-way valve 92, the fluid comes into indirect contact with the warmer water flowing around the manifold 78. From the manifold 78, the produced fluid flows through a helical coil 94 extending axially through the heat exchanger unit 74 and into a'heat exchanger manifold (not shown) in the lower end thereof, and then out of the jacket 79 through conduits 82, each connected between one of the separators 72 and the lower heat exchanger manifold. A temperature sensor 96 is installed in at least one of the outlet lines 82 to act as a flow indicator and monitor mechanism to control the increase or decrease of the water flowing into the heat exchanger unit 74. By increasing or decreasing the size of the choke 80, the water flow is regulated to maintain the required temperature of the produced fluids entering the separators 72 (FIG. 2). Such a system also acts as a resource conservation in that large use of produced oil and/or gas to fire such heater equipment as would be otherwise needed is not required.

Looking back to FIG. 2, the liquids leave the separators 72 through respective liquid outlet lines 98, connecting the separators 72 with liquid output manifold 100 centrally positioned around the lower end of the heat exchanger unit 74. The combined produced liquid from the plurality of separators 72 is directed from the manifold 100 through a main oil outlet line 102 which is connected to the input end of a respective shipping line 18.

The liquid is removed, at the lower end of each of the separators 72, by the respective line 98 so as to also drain off all the water, entrained sand, and other impurities with the oil. These impurities might otherwise impede the action of the separator 72 and cause a premature malfunction thereof. A shutoff valve 104 in each of the liquid outlet lines 98 is controlled in conjunction with a float (not shown) within each of the separators 72, to regulate the levels of the liquid within the separators 72. As shown, a mechanical linkage is utilized between the float and the valve 104. One of the electromechanical systems, well known in the art, could be substituted for the mechanical linkage. A clean oil line 108 is con nected at a first end thereof into at least one of the separators 72, above the lower end thereof, to pick up oil from above the sediment level and below the low level of the liquid to provide substantially clean oil (with dissolved gas) for pumping a tool into and down through a selected well. Line 108, at the other end thereof, is connected to a first inlet of three-way two-position valve 110, the outlet of which is connected to the inlet of a gas-driven turbine-pump 112 to provide the clean oil under pressure to the TFL system. A second inlet of the three-way two-position valve 110 is also connected to a line 114 having a pickup head 1 16 in the fluid storage section 70 of the satellite body to provide a source of treating fluid for the turbinepump 112. Gas under pressure, for driving the turbine portion of the turbine-pump 112, is provided through a turbine gas supply line 118 extending from an auxiliary turbine (not shown in this view) which is supplied with produced fluid tapped off, through lines 1 l9, upstream of the chokes 84. The clean oil under pressure from the pump portion of the turbinepump 112 is fed into a manifold (not shown in this view). From this last-mentioned manifold, the oil is pumped out, being selectively directed into one or more pressure lines 122, each pressure line 122 being connected into a bypass conduit section 124 just behind a TFL tool 126 stored therein. Each bypass conduit 124 is directly connected to a curved tubing portion 56 of a connector unit 54 for pumping the TFL tool 126 therein into the connected wellhead 14 and down a passage of the respective well. The separated-out gas, leaving a separator 72 through an upper pipe or gas outlet line 120, is combined with the separated-out gas from the other separators 72 in a ring manifold unit 128 encircling the insulated jacket 79 of the heat exchanger unit 74.

The separated-out gas can be, in various instances, utilized in production procedures, stored for eventual transportation to shore, or disposed of at the site of the offshore production field. A main outlet line 130, from the ring manifold 128, is shown directing the gas out of the satellite station 10 for disposal through one or more distant gas disposal wells (not shown) where the gas will be injected into shallow sands underlying the marine bottom. A safety regulator valve 132 is connected in the main outlet line to allow gas to be bled off through a flare line 134 to the master floating station 20, if the pressure in the main outlet line 130 should rise above a predetermined value. If the gas obtained in the primary stage of separation is to be either disposed of by flaring or is to be stored for future transportion-to-shore facilities, it is conducted to the master station 20 by shipping line (not shown), as described with respect to the produced oil. At the master station 20, the gas obtained from the primary stage of separation is combined with the gas obtained from the secondary or final stage of separation on the master station 20. If the gas is to be flared, a flare stack is erected above the master station 20. If the gas is to be stored, it is first compressed at the master station 20 and then is pumped down to a portion of the storage tank 17 or to a separate storage tank (not shown) nearby. As noted above, the gas from the primary separation stage may also be utilized in production procedures, the most common of these procedures being the utilization of the gas under pressure to provide lift pressure in the producing formations. A gas injection well for this purpose may be one of the wells drilled through the ring 51 of the template 28, in which case a separated-out gas is fed into the wellhead 14 through a respective one of the curved tubing sections 56 of a stabover connector unit 54, or the injection well may be located at a distance from the satellite station 10, in which case an interconnecting flowline having a pressure regulator valve and a flare line, as described above with respect to injecting the gas into shallow sand formations, will be utilized.

FIG. 4 illustrates, in schematic form, a complete system, with the exception of a storage means, for the production of a low gas-oil ratio low pressure field. The fluid is produced in the portion of the system designated as Well and Wellhead Equipment at the TD (total depth) 136 of a representative well, generally designated 138. In the well 138 is a storm choke 140 placed at approximately a 3,000-foot depth, below the normal lower limit of paraffin deposition, for safety purposes. Quarter-turned manually operated valves 142 are mounted on the wellhead 14 outside the satellite body 15 where they are easily accessible for operation by a man, robot, or a manned craft such as the underwater submersible work vehicle 36 illustrated in FIG. 1. In some instances, it may be desirable to utilize remotely actuatable valves in place of the manually operated valves 142. A highlow safety valve 144, also mounted on the wellhead 14 outside the satellite body 15, will automatically close should the pressure in the well 138 exceed a specified high pressure or drop below a specified low pressure.

From the upper end of the wellhead 14, the fluid is directed through connector unit 54 to the portion of the wellhead equipment within the satellite body 15 where one or more TFL tools are stored in a storage chamber, designated by block 146. (A TFL storage device and a paraffin cutting tool, designed to be stored therewithin, are fully described in the patent application Ser. No. 579,571 of James T. Dean, entitled Storage System for TFL Tools, filed Sept. 15, 1966, now US. Pat. No. 3,396,789. In FIG. 3 of the Dean patent, the incorporation of the described Roiagje device in a fluid circuit for automatically maintaining a subset! well is shown.) The TFL storage chamber 146 is located in the previously described bypass conduit section 124, as is a TFL tool control valve 148, which remains closed except during TFL maintenance and/or testing. The branch conduit 76 contains a pressure indicator 150, an orifice metertlSZfand a production wing valve 154. The production wing' valve 154 is normally open while the well 138 is producingand closed during TFL. operations. The branch conduit 76 through which the produced fluid generally flows, provides a, path around the TFL storage chamber 146, and the'closedcontrol valve 148. When the well 138 is producing, the fluids flew from TD'point 136, up through the storm choke 140, and the series of

valves

142 and 144, of the wellhead 14, into the'branch conduit 76. The pressure and flow rate of the fluid. at the wellhead 14 are monitored at alltimes by the pressure indicator 150 and the orifice meter 152, respectively, and representative signals are transmitted to, and recorded within, the control section=66 of the satellite station 10. l

The produced fluid flowing through the branch conduit 76,

past the interconnectionwith the bypass conduit section 124, leaves the portion of the system designated'in the schematic diagram asWellhead and Wellhead Equipment and enters the portion designated Production Systemthrough a rotary variable choke 156. As the fluid passes through thevariable choke 156, the pressure is lowered from that'at the wellhead 14 to a pressure just above that necessary to drive .the fluid from the marine bottom to the surface. From the rotary choke 156, the produced fluid is directed through a check valve 157 into a collector manifold 158. Branch conduits'76',:each having a check valve 157', also shown as leading into the collector manifold 1' 5 8 ,'are connected to the wellhead equipment of the various wells encircling the satellite station 10. A pressure sen- .sor 160 is mounted inthe collector manifold 158 to monitor the pressure ,therewithin, a signal representative of which is transmitted to and recorded within the control portion of the satellite station 10. The rotary variable choke 156 is controlled in response to the pressures indicatedby the

pressure sensors

150 and 160. Three gravity separators 72 areconnected, in parallel, to thecollectorinanifold 158through inlet lines 162, each having a shutoff valve 163 therewithin. The liquids, including oil and water, exit for the most part through lines 98 which empty into a liquid collector manifold 164. This manifold corresponds to the circular manifold 100 shown in FIG. 3. From the liquid collector'manifold164, the oil exits through the 'outlet line 102 and ,is'tran'sferred to storage through shipping line 18 after passing through a flow meter 166. A clean oil outlet line 108, as pre vi'ously discussed, extends from a point within each of the separators 72, from where substantially clean pure oil can be :obtained, to a manifold 175, which empties in turn into the upstream end of a line 174 connected at its downstream end to an inlet port of a three-way two-position valve 181) inthe TFL Fluid Supply System. The gas accumulating in the separators 72 passes out througha high liquid shutoff valve 168 located in the upper end of each of the separators 7 2, into a gasoutlet line 120, which empties into a gas collector manifold .170. The major portion of the gas leaves-the-manifold 170 through the main gas outlet line 130, passing through an orificemeter 172, and is transferred to storage or disposal means. By disposal means is meant fflaring" or shallow sand injecting as previously discussed. The fluid pressure supply lin'e, 1 191 is connected between the bypass conduit 124; at-one -end,thereof, and a manifold 159 at the other end. Lines '1 19' connect the bypass.

conduits of the other wells, which flow through the satellite station 10, with the manifold 159. The inlet-of an auxiliary separator 161, where only a small pressure cut is taken, is in fluid connection with the manifold 159 through a high pres;

are designed so that any two area" that are required to process the total amount of fluid passing through the satellite station 10. With the same rate'of flow of gas through the oriface meter 172, and liquid through the flow meter 166.11 signal warning of an increase in pressure will be transmitted to the control portion 66 of the satellite station 10 from the sensor 160 in the manifold 158, indicating that there is a problem. Furthermore, the closing of avalve 168 can be made to actuate an electric switch, which in turn will provide a signal indicating which separator is malfunctioning. The production stream through the plugged separator 72 would then be cutoff by closing the respective shutoff valve 163 so that the respective separator 72 can be serviced by personnel within the satellite station 10. a

The portion of the schematic diagram designated as the TFL Fluid Supply System contains a-fluiid storage means 178, which corresponds to the open-bottomed fluid storage section 70 of the satellite station 10 as shown in FIG. 2. Thestorage means 178 is connected to a first inlet port of the three-way two'position valve. 180 through a line 190 having a salt water sensor 188 therein to provide a signal in the control section of the satellite station 10 indicating that the storage means 178 is empty of treating fluid and now contains only salt water. The other inlet port of the three-way two-position valve 180, as previously discussed, is connected to asource of clean oil through the line 174 extending from the manifold 175 in the Production System portion of the schematic diagram. The outlet of the three-way two-position valve is operatively connected to the inlet of the pump portion of the turbine-pump 112, the outlet of the pump portion of the turbine-pump 112 being connected to an inlet of a manifold 182 through a conduit 184 The power for driving the. pump portion of the turbine-pump 112 is provided by gas under pressure obtained through the line 118 from the auxiliary separator 161 which is outlined. By opening and closing a'valve 176 in the line 118,

the operation of the turbine-pump 112 may be controlled. From the manifold 182 the clean oil and/or the treating fluid, under pressure, is pumped through one or more of the outlet lines192 at a time, each of the outlet lines192 having a check valve 194 and a selectively actuated cutoff valve 196 therein from which the fluid is directed throughthe respective line 122 into the Well and Wellhead Equipment portion of the schematic diagram where it is directed into the bypass conduit 124 between the TFL tool storage chamber 146 and the shutoff valve 148. Outletlines 192', each having a one-way check valve 194' and a shutoff valve 196 therein, are connected to the bypass conduits of the Well and Wellhead Equipment portions of the other wells (not shown) producing through the respective satellitestation 10. I i

To commence a TFL maintenance and/or testing procedure,

valves

148 and 154 in the Well and Wellhead Equipment portion would both be closed. .The shutoff valve 176, in the TFL Fluid Supply System, connected to the input I of the turbine-pump ll2would be open to activate the turbine sure line 165. The turbine gas supply line 118is connected between the gas outlet of the auxiliary separator 161 and the inlet of the turbine of the turbine pump 112 of the TFL. Fluid Supply System to supply high pressure gas to thepump portion portion. For paraffin removal, for instance, a paraffin solvent and corrosion inhibitor stored in the storage means 178 would first be drawn into the input of the pump section of the turbine-pump 112 by the proper positioning of the valve 180.

After pumping approximately one barrel of treating fluid through the valve 180, the position of the valve would be changed so that the oil from line 174 would then be supplied to the pump portion of the turbine-pump 112. One or more of the

valves

196, 196 would be open to permit the fluid driven by the turbine-pump 112 to exit from the header 182 through a line 122 to apply fluid pressure inithe section of the bypass conduit 124, of the Well and Wellhead Equipment portion, between the valve 148 and the storage means 146. With the valve 148 closed, the fluid driven through line 122 into the bypass conduit 124, behind the storage means 146, will cause a paraffin cutting tool 126 positioned within the storage means 146 to be propelled down through the curved tubing section 56 of the connector unit 54 and down through the wellhead 14 of the respective well 138. The piston section of the tool 126 is not completely sealed within the tubing of the well 138 in which it moves so that by the time the tool is down in the well, at the lower end of the paraffin deposition zone, all of the treating fluid is in the well ahead of the tool. When the tool 126 reaches the end of its travel, above the storm choke 140, the valve 176, in the TFL Fluid Supply System portion, controlling the turbine-pump 112, would be shut causing the turbine-pump 112 to cease operation. The shutoff valve 148 in the bypass conduit 124 is then opened causing the TFL tool 126 to be returned up the well 138 by the fluid being produced, which now is directed into the downstream portion of the branch conduit 76 through the bypass conduit 124. When the TFL tool 126 has reentered the storage chamber 146, an indication of this condition will be given in the control section 66. A switching means for providing this function is shown in the Dean patent US. Pat. No. 3,396,789 discussed above. At this time, the valve 148, in the bypass conduit 124, will be shut and the valve 154, in the branch conduit 76, will be reopened, returning the well to production through the branch conduit 76. All of the previously described steps can be sequentially performed by an operator'in the control section 66 of the satellite station 10, by remote control from the floating master station 20, or by a programmed computer, or by a combination of the aforementioned methods.

FIG. illustrates a modification in which an electric motor 198 is utilized for driving a pump 200. With the substitution of the electric motor 198 and the pump 200 for the turbinepump 112 (shown in FIG. 4), the ga's'line 118 is eliminated and the only exit line from the manifold 170 is the line 130.

The remainder of the TFL Fluid'Supply System (shown in FIG. 5) is identical to that shown in FIG. 4, therefore being a storage means 178 connected to one inlet of a three-way two position valve 180' through a line 190' having a salt water sensor 188 therein. The other inlet of the three-way two-position valve 180' is connected to the line 174 as shown in FIG. 4

which is connected at the other end thereof to a clean oil source in the separators 72. The outlet of thethree-way twoposition valve 180' is operatively connected to the inlet of the pump 200. The outlet of the pump 200 is in turn connected, through the line 184, to the header 182, as shown in FIG. 4. The identical procedure would be followed with the exception that electrical power would be used to operate the-electric motor 198 to drive the pump 200.

FIG. 6 shows the modified Production'System to be used with the typical high gasoil ratio high pressure well. This modified Production System is utilized with the Well and Wellhead Equipment portion and TFL Fluid Supply System portion of the schematic diagram of FIG. 4. As the produced fluid is directed from the branch conduit'76 through a variable choke 156' and a check valve 157, it is collected in a primary manifold 202 (generally similar to the-manifold 78 shown in FIG. 2). The produced fluid in the manifold 202, having a high gas content, is now quite cold due to expansion in the choke 156. This cold fluid passes out of the manifold 202 through a line 204 extending through a heat exchanger unit 206 (corresponding to the heat exchanger unit 74 of FIG. 2). The fluid, warmed up in theheat exchanger-unit 206, enters a secondary manifold 208 from which it is directed into three separators 72. A pressure sensor 209 and a temperature probe 238 are located in the secondary manifold 208. From-the separators 72' the major part of the produced liquid is collected in the manifold 164' after which it is removed through a line 1,02

having a flow meter 166 therein, the outlet of the flow meter 166 being connected to the inlet of a shipping line 18 connecting the satellite station 10 with a distant storage facility. Again, clean oil is picked up by lines 108' and is directed through line 174 to the clean oil supply inlet of the three-way two-position valve, as shown in FIG. 4. The gas exiting from the separators 72, through lines is collected in the manifold 170' from which it is, in the main, transmitted through a line 210 from the orifice meter 172, through a safety popoff valve 214, to a gas injection well 212, for disposal in shallow sand formations. The gas enters the injection well 212 through the wellhead 216 thereof having a high-low fail-safe valve 218 and a manually operated valve 220. There is also a storm choke 222 beneath the marine bottom in the injection well 212. If the back pressure in the shallow sand formations being used for disposal should rise above a preset limit of the popoff safety valve 214, the gas will be directed instead through a line 134' to the surface where it will be flared. To heat the cold fluids within the heat exchanger unit 206, warm water, at F. to F is obtained from the TD 228 of a water injection well 226 producing through a wellhead 227 comprising a manual valve 230 and an automatic setting valve 232, and a rotary choke 234 having a pressure differential indicating device 236 located thereacross. The warm water flows through the heat exchanger unit 206, past a series of coils 205, in the line 204. From the heat exchanger unit 206, the then cooled water is directed out through line 240 into the surrounding water near the marine bottom. The rotary choke 234 is operated automatically in response to a temperature signal obtained from the temperature probe 238 previously described as located in the primary manifold 208 downstream of the heat exchanger unit 206. As the temperature sensed by the temperature probe 238 decreases, the choke 234 is opened further. If the temperature indicated reaches a specified low level, the satellite station 10 is completely shut FIG. 7 is a schematic diagram of another modification of the Production System of FIG. 4, for a typical medium gas-oil ratio, medium pressure well. A well is produced in the same manner as in the previous two examples utilizing the. same type of well and wellhead equipment. In this modification the fluid, entering the Production System portion through a branch conduit 76, is directed through a one-way valve 241 into a heat exchanger conduit 242 which traverses a heat exchanger unit 244. The produced fluid having been produced from a TD of 10,000 feet makes its first pass through the heat exchanger unit 244 at a temperature of 150 F. to 170 F. Upon exiting from the heat exchanger unit 244, a pressure cut is taken through a variable choke 245.'The now cold fluids are passed back through the heat exchanger unit 244 by the traversing heat exchanger conduit 245 to raise the temperature in the expanded fluid to a prescribed minimum to prevent hydrate formation and wax deposition. From the conduit 245 the fluid passes into a collector manifold 246 containing a pressure sensor 238 and temperature probe 209'. In collector manifold 246, the fluid from the heat exchanger conduit is combined with the pressure cut fluid from the other wells of the satellite stations through heat exchanger lines 245'. The fluid from each well has previously been directed through the heat exchanger unit 244, had a pressure cut taken and then been passed back through the heat exchanger unit 244 through separate conduits. The combined fluid in the collector manifold 246 is directed out through a conduit 247, making a final pass across the heat exchanger unit 244 into another collector manifold 248. From the manifold 248, the fluid is divided into separate streams and directed into separators 72 through lines 249. The remainder of the fluid system is identical to that already discussed with respect to FIG. 4. If the temperature indicated by the temperature probe 209' decreases below a specified value, all the wells of the satellite station 10 are shut in. I i v g The schematic diagrams of FIGS. 4-47 Illustrate examples of systems to be used in specific cases. However, the features the production wells through the ring li ofthe base template 28'. In this embodiment. instead of using cradling arms as illustrated in FIG. 2, the satellitetbody isfheld in the satellite base 28 by a central sleeve 250 depending from the lower end of the satellite body -15 andautomatic spring-loaded latches (not shown) over theupper end of thetwell' conductorv pipe ofthe water well 52. The latches can:be disabled by ahydraulic pressure appliedthroughthe conduit 25 2 extendingbetween a manifold 25d,tforrning a,portion of the framing of the base template 28', at the inner end, and a ,quick-disconnect coupling section 2 56, at thetouterend. The-outer end of the conduit is supported by askeletalframe 2 58to displace the coupling section 256 outward of the well conductor pipes 34. The arrangement of the equipment withinthe satellitebody 15' is substantially the same asthe arrangernent within the satellite body 15 of the earlier discussed embodiment with the exception of the orientation of the TFL tool 126 and the associated hydraulic circuitry. in ,thisinstanceathe connector units 54 are not permanently attached to the satellite body 15 but instead are stabbed-overttubingnipples 26 0 extending vertically out of theupperend of the satellitetbody ,ISuWhen a wellis to be completed -through oneof the upstandingwell conductor pipes 34, a wellhead 14' is firstmounted on the respective well conductor pipe 34. Aconnector unit 55 is later lowered from the surface to make the connection betweenthe wellhead jflandthe satellitebodyjlS. ,Tihecon- ,nectorunit 54' consistsof mount d @tubingtsection Sti'and a venicaltlubricator section 58'. The lower end of thejlubricator section 58' is stabbed over-the tub ingtnotshownyextending vertically out of the ripper end of thewellhead- 514", .while the outer vertical free ends of the curved tubing section 54 stabs over the respective ones of the upstanding [tubing nipples 260 extending out of ,the upperendofthe satellite .body lnthis manner, with each v connector section Sgl' being individually engaged between the wellhead .14 and the respeictivenpstanding tubingnipples 260, greater tolerances can'gbe allowedjn installing the satellitebody l5. Furthermore,an individual ,well can be produced through the satellite station while the remaining wells are still being drilled and completed. The verticalorientationof the tubing nipples260 extending vertically into the satellite body ;l 5' presents no problem, each of the TFL storage chambersltt 6" is reoriented into;a vertical position so as to be coaxial with therespectiye-tubing nipples 260. The vertical positionof the storage chamber 146' permits the TFL tool 126' stored therewithin ,to move easily into respective tubing nipples .so that it can be pumped, under fluid pressure, through afull 1, 80 bend in the ,tubin gsections 5,6'.of the connector unit 54' .Suchabend, of 180 will not present any insurmountable problems requiring vonly that the .wells be spaced out far enoughfrom the satellite body to obtain a 5-foot radius bend in the conduit. Staboverconnections, as discussed in this application, are more -fullydescribed in the Manning applicationSer. No. 663,799. Althoughthe present invention has been described in connection with details of the specific embodiments thereof, it is to be understood that such details are not intended to limit the scope of the invention. The terms and expressions employed are used .in a descriptive and not a limiting senseand there is no intention of excluding such equivalents in'the invention ,described as fall within the scope of the claims-. Now having described the apparatus and methods herein disclosed, reference should be had to the claims which follow.

We claim: j i

1. A system for maintaining a plurality of submerged wells from a central station comprising: a central station comprising a submergible, watertight shell and having a first manifold therewithin; first conduit means providing separate fluid connections between production passages of each of said plurality of wells and said first manifold, each of said first conduit means having parallel fluid flow paths including a first flow path for production flow and a second flowpath for inserting well maintenance tools intoa respective production passage of the respective well; a first shutoff valve insaid first flownpath; means within said shell, for insertingatool into said respective production passage being connected in series in said second flow path; and a second shutoffvalve in said second flow path, said second shutoff valvebeing located between said tool-in serting means and said first manifold.

2. Aisystem for maintaining a;plurality of wells from a central station, as recited in claim 11, comprisingra source of, fluid underpressure for pumping awell maintenancetool fromsaid tool-inserting means into said respective production'passage tagainstwell pressure; and second conduit means fluidly connecting said source of fluid underpressure with said second flow pathbetween said tool-inserting means and said second shutoffvalve.

3. A system formaintaining aplurality of wells from a central station comprising: a central station having a first manifold .therewithin; first conduit means providing separate fluid connections between,productionpassages of each of said ,plurality of wells and said first manifold,,each of said first conduit means having parallel fluid flow ,paths includinga first flow path ,for production flowand a second flow pathfor inserting ,well maintenance tools into a respective production passage of the respectivewelh a-first shutoff valve in said first flow path; means for inserting a tool into said respective production ,passage being connected .in series in said second. =.flow,path; a second shutoff valve in said secondflow path, said second shutoffvalvebeing located between said tool-inserting ,rneansandsaidfirst manifold; asource of fluid underpressure for p umping a well maintenance tool from said tool-inserting \means ,into said respective production passage against well pressure second conduitmeansfluidly connecting said source of fluid under pressure with said second flow ,path between said-tool-inserting means and said second shutoff valve; and a pressure-reducing means locatedin each first conduit just upstream of said first manifold.

Aisystem for-maintainingaplurality of wells froma central station, as recitedi in claim 3, comprising: a source of fluid under pressure for pumping a tool from said tool-inserting means into said respective production passage against well pressure; second conduit meansfor connectingsaid source of fluid under pressure with said second flow path between said tool-inserting means and said second shutoff valve; said source of fluid under pressure :being a turbine-pump; a third conduit connected into said first conduit upstream of said pressurereducing means in at least one of saidsecond flow paths for supplying gas under pressure from said] at least one second flow path to the turbine portion of said turbine-pump; and means for exhausting waste gas from said turbine portion of said turbine-pump.

5. Asystem for maintaining a plurality of wells froma central station, as recited in claim 4, wherein there is means for disposing of waste gas that has been used to drive said turbine portion ,of said turbine-pump; said waste gas disposal means including a fourth conduit fluidly connecting the outletof said turbine portion of said turbine-pump with a gas manifold downstream of said pressure-reducing means downstream of saidfirst manifold, inlets of a plurality of separators connected in parallel to outlets of said first manifold; gas outlets of said plurality of separators connected in parallel to said gas manifold; and a gas outlet line connected to an outlet of said gas manifold for directing the separated-out produced gas from said central station.

6. A system for maintaining a plurality of wells from a central station, as recited in claim 4, wherein said third conduit means includes first and second fluid lines and an auxiliary of said first fluid line of said third conduit means; and said second fluid line of said third conduit means being connected between a gas outlet of said auxiliary separator and an inlet to said turbine portion of said turbine-pump.

7. A system for maintaining a plurality of wells from a central station, as recited in claim 6. wherein said inlet of said auxiliary separator is fluidly connected to an outlet of a third manifold by a third fluid line of said third conduit means; and a first portion of said second fluid line of said third conduit means is fluidly connected to each of said second flow paths of said plurality of wells of said central station to inlets of said second manifold.

8. A system for maintaining a plurality of wells from a central station, as recited in claim 3, comprising: a power-driven pump for supplying fluid under pressure for pumping a tool from said tool-inserting means into said respective production passage against well pressure; and second conduit means for operatively connecting an outlet of said pump with said second flow path between said tool-inserting means and said second shutoff valve, said pressure-reducing means being located between said second shutoff valve and said first manifold.

9. A system for maintaining a plurality of wells from a central station, as recited in claim 8, wherein a means for driving said power-driven pump is an electric motor.

10. A system for maintaining a plurality of wells from a central station, as recited in claim 8, wherein there is means for selectively connecting the inlet of said power-driven pump to either a source of well treating fluid or a source of substantially clean, dead oil.

1]. A system for maintaining a plurality of wells from a central station, as recited in claim 8, wherein there is a three-way two-position valve, the outlet port of said three-way two-position valve being connected to the inlet of said power-driven pump; a first inlet port of said three-way two-position valve being connected to a source of well treating fluid; and a second inlet port of said three-way two-position valve being connected to a source of substantially clean, dead oil.

12. A system for maintaining a plurality of wells from a central station, as recited in claim 8, wherein said second conduit means comprises: first and second fluid lines and a second manifold; said first fluid line of said second conduit means being connected between the outlet of said power-driven pump and an inlet of said second manifold, a plurality of second fluid lines of said second conduit means being connected between outlets of said second manifold and each of said plurality of second flow paths.

13. A system for maintaining a plurality of wells from a central station, as recited in claim 12 wherein there is a shutoff valve in each of said second fluid lines of said second conduit means.

14. A system for maintaining a plurality of wells from a central station, as recited in claim 8, wherein there is a source of substantially clean, dead oil; fifth conduit means for fluidly connecting said source of substantially clean, dead oil to an inlet of said power-driven pump.

15. A system for maintaining a plurality of wells from a central station, as recited in claim 14, wherein said source of substantially clean, dead oil is at least one separator means for fluidly connecting an inlet of said at least one separator with an outlet of said first manifold, said separator comprising: a first outlet for separated-out gas; a second outlet, at the lower end of said separator, for a separated-out mixture of fluids and solids in suspension therein; and a third outlet, above said second outlet, for separated-out substantially clean, dead oil.

16. A system for maintaining a plurality of wells from a central station, as recited in claim 3, wherein there are a plurality of separators fluidly connected in parallel with said first manifold; a fourth manifold for collecting produced gas; means for fluidly connecting gas outlets of said plurality of separators in parallel with said fourth manifold; a gas outlet line for directing produced gas from said fourth manifold and out of said'central station; a fifth manifold for collecting produced liquids; means for fluidly connecting liquids outlets of said plurality of separators in parallel with said fifth manifold; and a liquids outlet line for direction produced liquids from said fifth manifold and out of central station.

17. A system for maintaining a plurality of wells from a central station, as recited in claim 16, wherein there is a sixth manifold for collection clean, dead oil; means for fluidly connecting clean, dead oil outlets of said plurality of separators, above said liquids outlets of said respective separators, in parallel with said sixth manifold for supplying clean, dead oil for pumping well maintenance tools into the production passages of said respective wells.

18. A system for maintaining a plurality of wells from a central station, as recited in claim 16, wherein said gas outlet line, downstream of said fourth manifold, is in fluid connection with a means for injecting gas into at least one underground formation.

19. A system for maintaining a plurality of wells from a central station, as recited in claim 18, wherein said at least one underground formation is an underground formation from which fluids are being produced through at least one of said wells whereby said underground formation can be repressurized.

20. A system for maintaining a plurality of wells from a central station, as recited in claim 18, wherein said at least one underground formation is a shallow, low pressure porous formation, not being produced, whereby waste gas can be disposed of.

21. A system for maintaining a plurality of wells from a central station, as recited in claim 3, wherein each of said pressure-reducing means is a choke whereby the produced fluid is expanded downstream of each of said chokes; and means for heating the expanded fluid just downstream of said chokes to hinder the formation of hydrates and emulsions and to prevent the deposition of paraffin in the equipment.

22. A system for maintaining a plurality of wells from a central station, as recited in claim 21, wherein the source of heat for said heating means is outside of said produced fluid.

23. A system for maintaining a plurality of wells from a central station, as recited in claim 22, wherein said heating means is an indirect heat exchanger unit; a first fluid line portion of each of said first conduit means, upstream of said chokes, for directing the produced fluid, under pressure, in a first pass through said indirect heat exchanger unit; and a second fluid line portion of each of said first conduit means, between the respective choke, and said first manifold, for directing the produced fluid, now expanded, in a second pass through said heat exchanger unit whereby heat is exchanged between said first and said second passes to warm the expanded fluids downstream of said chokes.

24. A system for maintaining a plurality of wells from a central station, as recited in claim 23, wherein there is a third pass through said heat exchanger unit fluidly connected at the upstream end to the single outlet of said first manifold.

25. A system for maintaining a plurality of wells from a central station, as recited in claim 24, wherein the downstream end of said third pass through said heat exchanger is in fluid connection with a seventh manifold; and means for fluidly connecting each of a plurality of separators in parallel with said seventh manifold.

26. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of said well, said production passage of said well being a fluid connection with equipment in a distant production facility through a first conduit means; said first conduit means having parallel fluid paths including afirst path connected to a first manifold for production flow and a second path for insert ing said well maintenance tool into a respective production passage of a respective well; a first shutoff valve in said first flow path; a tool storage means being connected in series in said second flow path; a second shutoff valve in said second flow path, said second shutoff valve being located between said tool storage means and said first manifold; a source of clean, dead oil for pumping said well maintenance tool down said respective well production passage against well pressure; a source of well treating fluid; and means for selectively fluidly connecting a second conduit means between said source of clean, dead oil and said second flow path between said tool storage means and said second shutoff valve, said selective connecting means is operable to selectively alternately connect said second conduit to said source of clean, dead oil or to said source of well treating fluid, including the following steps:

a. shutting said first shutoff valve while leaving said second shutoff valve closed as it is positioned during production of fluid from said respective production passage;

. selectively fluidly connecting said source of well treating fluid with said second conduit means;

. pumping a prescribed amount of well treating fluid behind said well maintenance tool;

d. selectively fluidly connecting said source of clean, dead oil with said second flow path through said second conduit means; and

e. pumping clean, dead oil from said source through said second conduit means whereby a well maintenance tool in said storage means is pumped out of said storage means and down through said production passage of said respective well.

27. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 26, wherein said well treating fluid is a paraffin dissolving agent and said well maintenance tool is a paraffin scraping tool.

28. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 26, including the following additional steps to be performed for the retrieval of said well maintenance tool from said production passage by the pressure of fluids being produced through said well:

f. shutting off the supply of fluid under pressure through said second conduit;

g. opening said second shutoff valve so that well fluids are produced through said second flow path;

h. closing said second shutoff. valve when said well maintenance tool has been driven up said production passage and into said storage means by the produced fluids; and

i. opening said first shutoff valve after said well maintenance tool is again within said storage means whereby well production continues thereafter through said first flow path of said first conduit into said production facility.

29. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 26, including the following additional steps:

j separating the produced fluids into liquid and gaseous components;

k. drawing off clean, dead oil from the upper portion of said liquid component which could include oil, water, and/or solids; and

l. directing said clean, dead oil to the inlet of a power-driven pump, the outlet of said power-driven pump being connected to said second conduit means.

30. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage ofa well, as recited in claim 26, wherein the means for pumping said oil is a gas'driven turbine-pump, including the following additional steps:

m. separating the produced fluid into liquid and gaseous components;

n. drawing off at least a portion of the gaseous component;

and

o. directing said gaseous component, drawn off, into the inlet of the turbine portion of said turbine-pump to drive the turbine.

31. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recitedin claim 26, whe rein th re are a plurality of wells spaced from said production facilityQsaid production facility being a satellite station located in the field being exploited, including the following additional step:

p. collecting the produced fluids from said plurality of wells in a first manifold.

32. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into production passage of a well, as recited in claim 31, including the following additional step:

q. choking the flow of produced fluid in the first conduit means just prior to the collecting of said produced fluids in said first manifold whereby the pressure in said produced fluids is reduced in said first manifold.

33. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 32, including the following additional step: t

r. heating said produced fluids subsequent to reducing the pressure thereof by choking the flow of said produced fluids.

@fifi UFHTED STATES PATENT OFFHHE CERTIFICATE OF CORRECTION Patent No. 3,556,218 Dated January 19, 1971 Invenuns) William A. Talley, Jr. and James T. Dean It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 51, -a--has been omitted before "stabover".

Column 16, Claim 16, line 3, "direction" should be "directing line 4, --said-- has been omitted before "central".

Claim 17, line 7, "collection" should be --collect:

Claim 26, line 66, before "fluid" "a" should be ca1 and --in--inserted.

Column 18, Claim 32, line 33, --a-- has been omitted before "production".

Signed and sealed this 25th day of May 1971.

(SEAL) Attest:

EDWARD M.FLETCH5R,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents

Claims

1. A system for maintaining a plurality of submerged wells from a central station comprising: a central station comprising a submergible, watertight shell and having a first manifold therewithin; first conduit means providing separate fluid connections between production passages of each of said plurality of wells and said first manifold, each of said first conduit means having parallel fluid flow paths including a first flow path for production flow and a second flow path for inserting well maintenance tools into a respective production passage of the respective well; a first shutoff valve in said first flow path; means within said shell for inserting a tool into said respective production passage being connected in series in said second flow path; and a second shutoff valve in said second flow path, said second shutoff valve being located between said toolinserting means and said first manifold.

2. A system for maintaining a plurality of wells from a central station, as recited in claim 1, comprising: a source of fluid under pressure for pumping a well maintenance tool froM said tool-inserting means into said respective production passage against well pressure; and second conduit means fluidly connecting said source of fluid under pressure with said second flow path between said tool-inserting means and said second shutoff valve.

3. A system for maintaining a plurality of wells from a central station comprising: a central station having a first manifold therewithin; first conduit means providing separate fluid connections between production passages of each of said plurality of wells and said first manifold, each of said first conduit means having parallel fluid flow paths including a first flow path for production flow and a second flow path for inserting well maintenance tools into a respective production passage of the respective well; a first shutoff valve in said first flow path; means for inserting a tool into said respective production passage being connected in series in said second flow path; a second shutoff valve in said second flow path, said second shutoff valve being located between said tool-inserting means and said first manifold; a source of fluid under pressure for pumping a well maintenance tool from said tool-inserting means into said respective production passage against well pressure; second conduit means fluidly connecting said source of fluid under pressure with said second flow path between said tool-inserting means and said second shutoff valve; and a pressure-reducing means located in each first conduit just upstream of said first manifold.

4. A system for maintaining a plurality of wells from a central station, as recited in claim 3, comprising: a source of fluid under pressure for pumping a tool from said tool-inserting means into said respective production passage against well pressure; second conduit means for connecting said source of fluid under pressure with said second flow path between said tool-inserting means and said second shutoff valve; said source of fluid under pressure being a turbine-pump; a third conduit connected into said first conduit upstream of said pressure-reducing means in at least one of said second flow for supplying gas under pressure from said at least one second flow path to the turbine portion of said turbine-pump; and means for exhausting waste gas from said turbine portion of said turbine-pump.

5. A system for maintaining a plurality of wells from a central station, as recited in claim 4, wherein there is means for disposing of waste gas that has been used to drive said turbine portion of said turbine-pump; said waste gas disposal means including a fourth conduit fluidly connecting the outlet of said turbine portion of said turbine-pump with a gas manifold downstream of said pressure-reducing means downstream of said first manifold, inlets of a plurality of separators connected in parallel to outlets of said first manifold; gas outlets of said plurality of separators connected in parallel to said gas manifold; and a gas outlet line connected to an outlet of said gas manifold for directing the separated-out produced gas from said central station.

6. A system for maintaining a plurality of wells from a central station, as recited in claim 4, wherein said third conduit means includes first and second fluid lines and an auxiliary separator, an inlet of said auxiliary separator being operatively fluidly connected to an outlet of said first fluid line of said third conduit means; and said second fluid line of said third conduit means being connected between a gas outlet of said auxiliary separator and an inlet to said turbine portion of said turbine portion of said turbine-pump.

7. A system for maintaining a plurality of wells from a central station, as recited in claim 6, wherein said inlet of said auxiliary separator is fluidly connected to an outlet of a third manifold by a third fluid line of said third conduit means; and a first portion of said second fluid line of said third conduit means is fluidly connected to each of said second flow paths of said plurality of wells of said central station to inlets of said second manifold.

11. A system for maintaining a plurality of wells from a central station, as recited in claim 8, wherein there is a three-way two-position valve, the outlet port of said three-way two-position valve being connected to the inlet of said power-driven pump; a first inlet port of said three-way two-position valve being connected to a source of well treating fluid; and a second inlet port of said three-way two-position valve being connected to a source of substantially clean, dead oil.

13. A system for maintaining a plurality of wells from a central station, as recited in claim 12 , wherein there is a shutoff valve in each of said second fluid lines of said second conduit means.

16. A system for maintaining a plurality of wells from a central station, as recited in claim 3, wherein there are a plurality of separators fluidly connected in parallel with said first manifold; a fourth manifold for collecting produced gas; means for fluidly connecting gas outlets of said plurality of separators in parallel with said fourth manifold; a gas outlet line for directing produced gas from said fourth manifold and out of said central station; a fifth manifold for collecting produced liquids; means for fluidly connecting liquids outlets of said plurality of separators in parallel with said fifth manifold; and a liquids outlet line for direction produced liquids from said fifth manifold and out of central station.

26. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of said well, said production passage of said well being a fluid connection with equipment in a distant production facility through a first conduit means; said first conduit means having parallel fluid paths including a first path connected to a first manifold for production flow and a second path for inserting said well maintenance tool into a respective production passage of a respective well; a first shutoff valve in said first flow path; a tool storage means being connected in series in said second flow path; a second shutoff valve in said second flow path, said second shutoff valve being located between said tool storage means and said first manifold; a source of clean, dead oil for pumping said well maintenance tool down said respective well production passage against well pressure; a source of well treating fluid; and means for selectively fluidly connecting a second conduit means between said source of clean, dead oil and said second flow path between said tool storage means and said second shutoff valve, said selective connecting means is operable to selectively alternately connect said second conduit to said source of clean, dead oil or to said source of well treating fluid, including the following steps: a. shutting said first shutoff valve while leaving said second shutoff valve closed as it is positioned during production of fluid from said respective production passage; b. selectively fluidly connecting said source of well treating fluid with said second conduit means; c. pumping a prescribed amount of well treating fluid behind said well maintenance tool; d. selectively fluidly connecting said source of clean, dead oil with said second flow path through said second conduit means; and e. pumping clean, dead oil from said source through said second conduit means whereby a well maintenance tool in said storage means is pumped out of said storage means and down through said production passage of said respective well.

28. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 26, including the following additional steps to be performed for the retrieval of said well maintenance tool from said production passage by the pressure of fluids being produced through said well: f. shutting off the supply of fluid under pressure through said second conduit; g. opening said second shutoff valve so that well fluids are produced through said second flow path; h. closing said second shutoff valve when said well maintenance tool has been driven up said production passage and into said storage means by the produced fluids; and i. opening said first shutoff valve after said well maintenance tool is again within said storage means whereby well production continues thereafter through said first flow path of said first conduit into said production facility.

29. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 26, including the following additional steps: j. separating the produced fluids into liquid and gaseous components; k. drawing off clean, dead oil from the upper portion of said liquid component which could include oil, water, and/or solids; and l. directing said clean, dead oil to the inlet of a power-driven pump, the outlet of said power-driven pump being connected to said second conduit means.

30. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 26, wherein the means for pumping said oil is a gas-driven turbine-pump, including the following additional steps: m. separating the produced fluid into liquid and gaseous components; n. drawing off at least a portion of the gaseous component; and o. directing said gaseous component, drawn off, into the inlet of the turbine portion of said turbine-pump to drive the turbine.

31. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 26, wherein there are a plurality of wells spaced from said production facility, said production facility being a satellite station located in the field being exploited, including the following additional step: p. collecting the produced fluids from said plurality of wells in a first manifold.

32. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into production passage of a well, as recited in claim 31, iNcluding the following additional step: q. choking the flow of produced fluid in the first conduit means just prior to the collecting of said produced fluids in said first manifold whereby the pressure in said produced fluids is reduced in said first manifold.

33. A method for maintaining a well in conjunction with a well maintenance tool that can be pumped into a production passage of a well, as recited in claim 32, including the following additional step: r. heating said produced fluids subsequent to reducing the pressure thereof by choking the flow of said produced fluids.