Rotating control head radial seal protection and leak detection systems

A system and method for reducing wear to radial seals in a rotating control device. The seals may be cooled by a thermal transfer fluid circulating through a passageway making more than one pass. Also, the differential pressure between multiple seals may be regulated and lowered, thereby increasing seal life.

STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate generally to a method and a system for a rotating control head used in a drilling operation. More particularly, the invention relates to a remote leak detection system, radial seal protection system and an improved cooling system for a rotating control head and a method for using the systems. The present invention also includes a leak detection system for a latch system to latch the rotating control device to a housing.

2. Description of the Related Art

Drilling a wellbore for hydrocarbons requires significant expenditures of manpower and equipment. Thus, constant advances are being sought to reduce any downtime of equipment and expedite any repairs that become necessary. Rotating equipment requires maintenance as the drilling environment produces forces, elevated temperatures and abrasive cuttings detrimental to the longevity of seals, bearings, and packing elements.

In a typical drilling operation, a drill bit is attached to a drill pipe. Thereafter, a drive unit rotates the drill pipe through a drive member, referred to as a kelly as the drill pipe and drill bit are urged downward to form the wellbore. In some arrangements, a kelly is not used, thereby allowing the drive unit to attach directly to the drill pipe or tubular. The length of the wellbore is determined by the location of the hydrocarbon formations. In many instances, the formations produce fluid pressure that may be a hazard to the drilling crew and equipment unless properly controlled.

Several components are used to control the fluid pressure. Typically, one or more blowout preventers (BOP) are mounted with the well forming a BOP stack to seal the well. In particular, an annular BOP is used to selectively seal the lower portions of the well from a tubular that allows the discharge of mud. In many instances, a conventional rotating control head is mounted above the BOP stack. An inner portion or member of the conventional rotating control head is designed to seal and rotate with the drill pipe. The inner portion or member typically includes at least one internal sealing element mounted with a plurality of bearings in the rotating control head.

The internal sealing element may consist of either one, two or both of a passive seal assembly and/or an active seal assembly. The active seal assembly can be hydraulically or mechanically activated. Generally, a hydraulic circuit provides hydraulic fluid to the active seal in the rotating control head. The hydraulic circuit typically includes a reservoir containing a supply of hydraulic fluid and a pump to communicate the hydraulic fluid from the reservoir to the rotating control head. As the hydraulic fluid enters the rotating control head, a pressure is created to energize the active seal assembly. Preferably, the pressure in the active seal assembly is maintained at a greater pressure than the wellbore pressure. Typically, the hydraulic circuit receives input from the wellbore and supplies hydraulic fluid to the active seal assembly to maintain the desired pressure differential.

During the drilling operation, the drill pipe or tubular is axially and slidably moved through the rotating control head. The axial movement of the drill pipe along with other forces experienced in the drilling operation, some of which are discussed below, causes wear and tear on the bearing and seal assembly and the assembly subsequently requires repair. Typically, the drill pipe or a portion thereof is pulled from the well and the bearing and seal assembly in the rotating control head is then released. Thereafter, an air tugger or other lifting means in combination with a tool joint on the drill string can be used to lift the bearing and seal assembly from the rotating control head. The bearing and seal assembly is replaced or reworked, the bearing and seal assembly installed into the rotating control head, and the drilling operation is resumed.

The thrust generated by the wellbore fluid pressure, the radial forces on the bearing assembly and other forces cause a substantial amount of heat to build in the conventional rotating control head. The heat causes the seals and bearings to wear and subsequently require repair. The conventional rotating control head typically includes a cooling system that circulates fluid through the seals and bearings to remove the heat.

Cooling systems have been known in the past for rotating control heads and rotating blowout preventers. For example, U.S. Pat. Nos. 5,178,215, 5,224,557 and 5,277,249 propose a heat exchanger for cooling hydraulic fluid to reduce the internal temperature of a rotary blowout preventer to extend the operating life of various bearing and seal assemblies found therein.

FIG. 10discloses a system where hydraulic fluid moves through the seal carrier C of a rotating control head, generally indicated at RCH, in a single pass to cool top radial seals S1and S2but with the fluid external to the bearing section B. Similarly, U.S. Pat. No. 5,662,181, assigned to the assignee of the present invention, discloses use of first inlet and outlet fittings for circulating a fluid, i.e. chilled water and/or antifreeze, to cool top radial seals in a rotating control head. A second lubricant inlet fitting is used for supplying fluid for lubricating not only the top radial seals but also top radial bearings, thrust bearings, bottom radial bearings and bottom radial seals all positioned beneath the top radial seals. (See '181 patent, col. 5, ln. 42 to col. 6, ln. 10 and col. 7, lns. 1-10.) These two separate fluids require their own fluid flow equipment, including hydraulic/pneumatic hoses.

Also, U.S. Pat. No. 5,348,107 proposes means for circulating lubricant around and through the interior of a drilling head. More particularly, FIGS. 3 to 6 of the '107 patent propose circulating lubricant to seals via a plurality of passageways in the packing gland. These packing gland passageways are proposed to be in fluid communication with the lubricant passageways such that lubricant will freely circulate to the seals. (See '107 patent, col. 3, lns. 27-65.)

U.S. Pat. Nos. 6,554,016 and 6,749,172, assigned to the assignee of the present invention, propose a rotary blowout preventer with a first and a second fluid lubricating, cooling and filtering circuit separated by a seal. Adjustable orifices are proposed connected to the outlet of the first and second fluid circuits to control pressures within the circuits. Such pressures are stated to affect the wear rates of the seals and to control the wear rate of one seal relative to another seal.

Therefore, an improved system for cooling radial seals and the bearing section of a rotating control head with one fluid is desired. If the radial seals are not sufficiently cooled, the localized temperature at the sealing surface will rise until the temperature limitations of the seal material is reached and degradation of the radial seal begins. The faster the rise in temperature means less life for the radial seals. In order to obtain sufficient life from radial seals, the rate of heat extraction should be fast enough to allow the temperature at the sealing surface to level off at a temperature lower than that of the seal material's upper limit.

Also, to protect the radial seals in a rotating control head, it would be desirable to regulate the differential pressure across the upper top radial seal that separates the fluid from the environment. Typically, fluid pressure is approximately 200 psi above the wellbore pressure. This pressure is the differential pressure across the upper top radial seal. Radial seals have a PV factor, which is differential pressure across the seal times the rotary velocity of the inner portion or member of the rotating control head in surface feet per minute. When this value is exceeded, the radial seal fails prematurely. Thus, the PV factor is the limitation to the amount of pressure and RPM that a rotating control head can be expected to perform. When the PV factor is exceeded, either excessive heat is generated by friction of the radial seals on the rotating inner member, which causes the seal material to break down, or the pressure forces the radial seal into the annular area between the rotating inner member and stationary outer member which damages the deformed seal.

In general, this PV seal problem has been addressed by limiting the RPM, pressure or both in a rotating control head. The highest dynamic, but rarely experienced, rating on a rotating control head is presently approximately 2500 psi. Some companies publish life expectancy charts which will provide the expected life of a radial seal for a particular pressure and RPM value. An annular labyrinth ring has also been used in the past between the lubricant and top radial seal to reduce the differential pressure across the top radial seal. Pressure staging and cooling of seals has been proposed in U.S. Pat. No. 6,227,547, assigned on its face to Kalsi Engineering, Inc. of Sugar Land, Tex.

Furthermore, U.S. Ser. No. 10/995,980 discloses in FIG. 14 a remote control display 1400 having a hydraulic fluid indicator 1488 to indicate a fluid leak condition. FIG. 18 of the '980 application further discloses that the alarm indicator 1480 and horn are activated based in part on the fluid leak indicator 1488 being activated for a predetermined time.

The above discussed U.S. Pat. Nos. 5,178,215; 5,224,557; 5,277,249; 5,348,107; 5,662,181; 6,227,547; 6,554,016; and 6,749,172 are incorporated herein by reference in their entirety for all purposes.

There is a need therefore, for an improved, cost-effective rotating control head that reduces repairs to the seals in the rotating control head and an improved leak detection system to indicate leaks pass these seals. There is a further need for a cooling system in a rotating control head for top radial seals that can be easily implemented and maintained. There is yet a further need for an improved rotating control head where the PV factor is reduced by regulating the differential pressure across the upper top radial seal. There is yet a further need for an improved leak detection system for the rotating control head and its latching system.

BRIEF SUMMARY OF THE INVENTION

The present invention generally relates to a system and method for reducing repairs to a rotating control head and a system and method to detect leaks in the rotating control head and its latching system.

In particular, the present invention relates to a system and method for cooling a rotating control head while regulating the pressure on the upper top radial seal in the rotating control head to reduce its PV factor. The improved rotating control head includes an improved cooling system using one fluid to cool the radial seals and bearings in combination with a reduced PV factor radial seal protection system.

A leak detection system and method of the present invention uses a comparator to compare fluid values in and from the latch assembly of the latch system and/or in and from the bearing section or system of the rotating control head.

In another aspect, a system and method for sealing a tubular in a rotating control head is provided. The method includes supplying fluid to the rotating control head and activating a seal arrangement to seal around the tubular. The system and method further includes passing a cooling medium through the rotating control head while maintaining a pressure differential between a fluid pressure in the rotating control head and a wellbore pressure.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the present invention relates to a rotating control head for use with a drilling rig. Typically, an inner portion or member of the rotating control head is designed to seal around a rotating tubular and rotate with the tubular by use of an internal sealing element and bearings. Additionally, the inner portion of the rotating control head permits the tubular to move axially and slidably through the rotating control head on the drilling rig.

FIG. 1is a cross-sectional view illustrating the rotating control head, generally indicated at100, in accord with the present invention. The rotating control head100preferably includes an active seal assembly105and a passive seal assembly110. Each seal assembly105,110includes components that rotate with respect to a housing115. The components that rotate in the rotating control head are mounted for rotation about a plurality of bearings125.

As depicted, the active seal assembly105includes a bladder support housing135mounted within the plurality of bearings125. The bladder support housing135is used to mount bladder130. Under hydraulic pressure, as discussed below, bladder130moves radially inward to seal around a tubular, such as a drilling pipe or tubular (not shown). In this manner, bladder130can expand to seal off a borehole using the rotating control head100.

As illustrated inFIG. 1, upper and lower caps140,145fit over the respective upper and lower end of the bladder130to secure the bladder130within the bladder support housing135. Typically, the upper and lower caps140,145are secured in position by a setscrew (not shown). Upper and lower seals155,160seal off chamber150that is preferably defined radially outwardly of bladder130and radially inwardly of bladder support housing135.

Generally, fluid is supplied to the chamber150under a controlled pressure to energize the bladder130. A hydraulic control will be illustrated and discussed inFIGS. 2-6. Essentially, the hydraulic control maintains and monitors hydraulic pressure within pressure chamber150. Hydraulic pressure P1is preferably maintained by the hydraulic control between 0 to 200 psi above a wellbore pressure P2. The bladder130is constructed from flexible material allowing bladder surface175to press against the tubular at approximately the same pressure as the hydraulic pressure P1. Due to the flexibility of the bladder, it also may conveniently seal around irregular shaped tubular string, such as a hexagonal kelly. In this respect, the hydraulic control maintains the differential pressure between the pressure chamber150at pressure P1and wellbore pressure P2. Additionally, the active seal assembly105includes support fingers180to support the bladder130at the most stressful area of the seal between the fluid pressure P1and the ambient pressure.

The hydraulic control may be used to de-energize the bladder130and allow the active seal assembly105to release the seal around the tubular. Generally, fluid in the chamber150is drained into a hydraulic reservoir (not shown), thereby reducing the pressure P1. Subsequently, the bladder surface175loses contact with the tubular as the bladder130becomes de-energized and moves radially outward. In this manner, the seal around the tubular is released allowing the tubular to be removed from the rotating control head100.

In the embodiment shown inFIG. 1, the passive seal assembly110is operatively attached to the bladder support housing135, thereby allowing the passive seal assembly110to rotate with the active seal assembly105. Fluid is not required to operate the passive seal assembly110but rather it utilizes pressure P2to create a seal around the tubular. The passive seal assembly110is constructed and arranged in an axially downward conical shape, thereby allowing the pressure P2to act against a tapered surface195to close the passive seal assembly110around the tubular. Additionally, the passive seal assembly110includes an inner diameter190smaller than the outer diameter of the tubular to provide an interference fit between the tubular and the passive seal assembly110.

FIG. 2Aillustrates a rotating control head200cooled by heat exchanger205. As shown, the rotating control head200is depicted generally to illustrate this embodiment of the invention, thereby applying this embodiment to a variety of different types of rotating control heads. A hydraulic control210provides fluid to the rotating control head200. The hydraulic control210typically includes a reservoir215to contain a supply of fluid, a pump220to communicate the fluid from the reservoir215to the rotating control head200and a valve225to remove excess pressure in the rotating control head200.

Generally, the hydraulic control210provides fluid to energize a bladder230and lubricate a plurality of bearings255. As the fluid enters a port235, the fluid is communicated to the plurality of bearings255and a chamber240. As the chamber240fills with a fluid, pressure P1is created. The pressure P1acts against the bladder230causing the bladder230to expand radially inward to seal around a tubular string (not shown). Typically, the pressure P1is maintained between 0-200 psi above a wellbore pressure P2.

The rotating control head200is cooled by the heat exchanger205. The heat exchanger205is constructed and arranged to remove heat from the rotating control head200by introducing a gas, such as air, at a low temperature into an inlet265and thereafter transferring heat energy from a plurality of radial seals275A and275B and the plurality of bearings255to the gas as the gas passes through the heat exchanger205. Subsequently, the gas at a higher temperature exits the heat exchanger205through an outlet270. Typically, gas is pumped into the inlet265by a blowing apparatus (not shown). However, other means of communicating gas to the inlet265may be employed, so long as they are capable of supplying a sufficient amount of gas to the heat exchanger205.

FIG. 2Billustrates a schematic view of the heat exchanger205. As illustrated, the heat exchanger205comprises a passageway280with a plurality of substantially square curves. The passageway280is arranged to maximize the surface area covered by the heat exchanger205. The low temperature gas entering the inlet265flows through the passageway280in the direction illustrated by arrow285. As the gas circulates through the passageway280, the gas increases in temperature as the heat from the rotating control head200is transferred to the gas. The high temperature gas exits the outlet270as indicated by the direction of arrow285. In this manner, the heat generated by the rotating control head200is transferred to the gas passing through the heat exchanger205.

FIG. 3Aillustrates a rotating control head300cooled by a gas. As shown, the rotating control head300is depicted generally to illustrate this embodiment of the invention, thereby applying this embodiment to a variety of different types of rotating control heads. A hydraulic control310supplies fluid to the rotating control head300. The hydraulic control310typically includes a reservoir315to contain a supply of fluid and a pump320to communicate the fluid from the reservoir315to the rotating control head300. Additionally, the hydraulic control310includes a valve345to relieve excess pressure in the rotating control head300.

Generally, the hydraulic control310supplies fluid to energize a bladder330and lubricate a plurality of bearings355. As the fluid enters a port335, a portion is communicated to the plurality of bearings355and another portion is used to fill a chamber340. As the chamber340fills with a fluid, a pressure P1is created. Pressure P1acts against the bladder330causing the bladder330to move radially inward to seal around a tubular (not shown). Typically, the pressure P1is maintained between 0 to 200 psi above a wellbore pressure P2. If the wellbore pressure P2drops, the pressure P1may be relieved through valve345by removing a portion of the fluid from the chamber340.

The rotating control head300is cooled by a flow of gas through a substantially circular passageway380through an upper portion of the rotating control head300. The circular passageway380is constructed and arranged to remove heat from the rotating control head300by introducing a gas, such as air, at a low temperature into an inlet365, transferring heat energy to the gas and subsequently allowing the gas at a high temperature to exit through an outlet370. The heat energy is transferred from a plurality of radial seals375A and375B and the plurality of bearings355as the gas passes through the circular passageway380. Typically, gas is pumped into the inlet365by a blowing apparatus (not shown). However, other means of communicating gas to the inlet365may be employed, so long as they are capable of supplying a sufficient amount of gas to the substantially circular passageway380.

FIG. 3Billustrates a schematic view of the gas passing through the substantially circular passageway380. The circular passageway380is arranged to maximize the surface area covered by the circular passageway380. The low temperature gas entering the inlet365flows through the circular passageway380in the direction illustrated by arrow385. As the gas circulates through the circular passageway380, the gas increases in temperature as the heat from the rotating control head300is transferred to the gas. The high temperature gas exits the outlet370as indicated by the direction of arrow385. In this manner, the heat generated by the rotating control head300is removed allowing the rotating control head300to function properly.

In an alternative embodiment, the rotating control head300may operate without the use of the circular passageway380. In other words, the rotating control head300would function properly without removing heat from the plurality of radial seals375A and375B and the plurality of bearings355. This alternative embodiment typically applies when the wellbore pressure P2is relatively low.

FIGS. 4A and 4Billustrate a rotating control head400cooled by a fluid mixture. As shown, the rotating control head400is depicted generally to illustrate this embodiment of the invention, thereby applying this embodiment to a variety of different types of rotating control heads. A hydraulic control410supplies fluid to the rotating control head400. The hydraulic control410typically includes a reservoir415to contain a supply of fluid and a pump420to communicate the fluid from the reservoir415to the rotating control head400. Additionally, the hydraulic control410includes a valve445to relieve excess pressure in the rotating control head400. In the same manner as the hydraulic control310, the hydraulic control410supplies fluid to energize a bladder430and lubricate a plurality of bearings455.

The rotating control head400is cooled by a fluid mixture circulated through a substantially circular passageway480on an upper portion of the rotating control head400. In the embodiment shown, the fluid mixture preferably consists of water or a water-glycol mixture. However, other mixtures of fluid may be employed, so long as, the fluid mixture has the capability to circulate through the circular passageway480and reduce the heat in the rotating control head400.

The circular passageway480is constructed and arranged to remove heat from the rotating control head400by introducing the fluid mixture at a low temperature into an inlet465, transferring heat energy to the fluid mixture and subsequently allowing the fluid mixture at a high temperature to exit through an outlet470. The heat energy is transferred from a plurality of radial seals475A and475B and the plurality of bearings455as the fluid mixture circulates through the circular passageway480. The fluid mixture is preferably pumped into the inlet465through a fluid circuit425. The fluid circuit425is comprised of a reservoir490to contain a supply of the fluid mixture and a pump495to circulate the fluid mixture through the rotating control head400.

FIG. 4Billustrates a schematic view of the fluid mixture circulating in the substantially circular passageway480. The circular passageway480is arranged to maximize the surface area covered by the circular passageway480. The low temperature fluid entering the inlet465flows through the circular passageway480in the direction illustrated by arrow485. As the fluid circulates through the circular passageway480, the fluid increases in temperature as the heat from the rotating control head400is transferred to the fluid. The high temperature fluid exits out the outlet470as indicated by the direction of arrow485. In this manner, the heat generated by the rotating control head400is removed allowing the rotating control head400to function properly.

FIGS. 5A and 5Billustrate a rotating control head500cooled by a refrigerant. As shown, the rotating control head500is depicted generally to illustrate this embodiment of the invention, thereby applying this embodiment to a variety of different types of rotating control heads. A hydraulic control510supplies fluid to the rotating control head500. The hydraulic control510typically includes a reservoir515to contain a supply of fluid and a pump520to communicate the fluid from the reservoir515to the rotating control head500. Additionally, the hydraulic control510includes a valve545to relieve excess pressure in the rotating control head500. In the same manner as the hydraulic control310, the hydraulic control510supplies fluid to energize a bladder530and lubricate a plurality of bearings555.

The rotating control head500is cooled by a refrigerant circulated through a substantially circular passageway580in an upper portion of the rotating control head500. The circular passageway580is constructed and arranged to remove heat from the rotating control head500by introducing the refrigerant at a low temperature into an inlet565, transferring heat energy to the refrigerant and subsequently allowing the refrigerant at a high temperature to exit through an outlet570. The heat energy is transferred from a plurality of radial seals575A and575B and the plurality of bearings555as the refrigerant circulates through the circular passageway580. The refrigerant is preferably communicated into the inlet565through a refrigerant circuit525. The refrigerant circuit525includes a reservoir590containing a supply of vapor refrigerant. A compressor595draws the vapor refrigerant from the reservoir590and compresses the vapor refrigerant into a liquid refrigerant. Thereafter, the liquid refrigerant is communicated to an expansion valve560. At this point, the expansion valve560changes the low temperature liquid refrigerant into a low temperature vapor refrigerant as the refrigerant enters inlet565.

FIG. 5Billustrates a schematic view of the vapor refrigerant circulating in the substantially circular passageway580. The circular passageway580is arranged in an approximately 320-degree arc to maximize the surface area covered by the circular passageway580. The low temperature vapor refrigerant entering the inlet565flows through the circular passageway580in the direction illustrated by arrow585. As the vapor refrigerant circulates through the circular passageway580, the vapor refrigerant increases in temperature as the heat from the rotating control head500is transferred to the vapor refrigerant. The high temperature vapor refrigerant exits out the outlet570as indicated by the direction of arrow585. Thereafter, the high temperature vapor refrigerant rejects the heat to the environment through a heat exchanger (not shown) and returns to the reservoir590. In this manner, the heat generated by the rotating control head500is removed allowing the rotating control head500to function properly.

FIG. 6illustrates a rotating control head600actuated by a piston intensifier circuit610in communication with a wellbore680. As shown, the rotating control head600is depicted generally to illustrate this embodiment of the invention, thereby applying this embodiment to a variety of different types of rotating control heads. The piston intensifier circuit610supplies fluid to the rotating control head600. The piston intensifier circuit610typically includes a housing645and a piston arrangement630. The piston arrangement, generally indicated at630, is formed from a larger piston620and a smaller piston615. The pistons615,620are constructed and arranged to maintain a pressure differential between a hydraulic pressure P1and a wellbore pressure P2. In other words, the pistons615,620are designed with a specific surface area ratio to maintain about a 200 psi pressure differential between the hydraulic pressure P1and the wellbore pressure P2, thereby allowing the P1to be 200 psi higher than P2. The piston arrangement630is disposed in the housing645to form an upper chamber660and lower chamber685. Additionally, a plurality of seal members605,606are disposed around the pistons615,620, respectively, to form a fluid tight seal between the chambers660,685.

The piston intensifier circuit610mechanically provides hydraulic pressure P1to energize a bladder650. Initially, fluid is filled into upper chamber660and is thereafter sealed. The wellbore fluid from the wellbore680is in fluid communication with lower chamber685. Therefore, as the wellbore pressure P2increases more wellbore fluid is communicated to the lower chamber685creating a pressure in the lower chamber685. The pressure in the lower chamber685causes the piston arrangement630to move axially upward forcing fluid in the upper chamber660to enter port635and pressurize a chamber640. As the chamber640fills with a fluid, the pressure P1increases causing the bladder650to move radially inward to seal around a tubular (not shown). In this manner, the bladder650is energized allowing the rotating control head600to seal around a tubular.

A fluid, such as water-glycol, is circulated through the rotating control head600by a fluid circuit625. Typically, heat on the rotating control head600is removed by introducing the fluid at a low temperature into an inlet665, transferring heat energy to the fluid and subsequently allowing the fluid at a high temperature to exit through an outlet670. The heat energy is transferred from a plurality of radial seals675A and675B and the plurality of bearings655as the fluid circulates through the rotating control head600. The fluid is preferably pumped into the inlet665through the fluid circuit625. Generally, the circuit625comprises a reservoir690to contain a supply of the fluid and a pump695to circulate the fluid through the rotating control head600.

In another embodiment, the piston intensifier circuit610is in fluid communication with a nitrogen gas source (not shown). In this embodiment, a pressure transducer (not shown) measures the wellbore pressure P2and subsequently injects nitrogen into the lower chamber685at the same pressure as pressure P2. The nitrogen pressure in the lower chamber685may be adjusted as the wellbore pressure P2changes, thereby maintaining the desired pressure differential between hydraulic pressure P1and wellbore pressure P2.

FIG. 7Aillustrates an alternative embodiment of a rotating control head700in an unlocked position. The rotating control head700is arranged and constructed in a similar manner as the rotating control head100shown onFIG. 1. Therefore, for convenience, similar components that function in the same manner will be labeled with the same numbers as the rotating control head100. The primary difference between the rotating control head700and rotating control head100is the active seal assembly.

As shown inFIG. 7A, the rotating control head700includes an active seal assembly, generally indicated at705. The active seal assembly705includes a primary seal735that moves radially inward as a piston715wedges against a tapered surface of the seal735. The primary seal735is constructed from flexible material to permit sealing around irregularly shaped tubular string such as a hexagonal kelly. The upper end of the seal735is connected to a top ring710.

The active sealing assembly705includes an upper chamber720and a lower chamber725. The upper chamber720is formed between the piston715and a piston housing740. To move the rotating control head700from an unlocked or relaxed position to a locked or sealed position, fluid is pumped through port745into an upper chamber720. As fluid fills the upper chamber720, the pressure created acts against the lower end of the piston715and urges the piston715axially upward towards the top ring710. At the same time, the piston715wedges against the tapered portion of the primary seal735causing the seal735to move radially inward to seal against the tubular (not shown). In this manner, the active seal assembly705is in the locked or sealed position as illustrated inFIG. 7B.

As shown onFIG. 7B, the piston715has moved axially upward contacting the top ring710and the primary seal735has moved radially inward. To move the active seal assembly705from the locked position to the unlocked position, fluid is pumped through port755into the lower chamber725. As the chamber fills up, the fluid creates a pressure that acts against surface760to urge the piston715axially downward, thereby allowing the primary seal735to move radially outward, as shown onFIG. 7A.

FIG. 8illustrates an alternative embodiment of a rotating control head800in accord with the present invention. The rotating control head800is constructed from similar components as the rotating control head100, as shown onFIG. 1. Therefore, for convenience, similar components that function in the same manner will be labeled with the same numbers as the rotating control head100. The primary difference between the rotating control head800and rotating control head100is the location of the active seal assembly105and the passive seal assembly110.

As shown inFIG. 8, the passive seal assembly110is disposed above the active seal assembly105. The passive seal assembly110is operatively attached to the bladder support housing135, thereby allowing the passive seal assembly110to rotate with the active seal assembly105. The passive seal assembly110is constructed and arranged in an axially downward conical shape, thereby allowing the pressure in the rotating control head800to act against the tapered surface195and close the passive seal assembly110around the tubular (not shown). Additionally, the passive seal assembly110includes the inner diameter190, which is smaller than the outer diameter of the tubular to allow an interference fit between the tubular and the passive seal assembly110.

As depicted, the active seal assembly105includes the bladder support housing135mounted on the plurality of bearings125. The bladder support housing135is used to mount bladder130. Under hydraulic pressure, bladder130moves radially inward to seal around a tubular such as a drilling tubular (not shown). Generally, fluid is supplied to the chamber150under a controlled pressure to energize the bladder130. Essentially, a hydraulic control (not shown) maintains and monitors hydraulic pressure within pressure chamber150. Hydraulic pressure P1is preferably maintained by the hydraulic control between 0 to 200 psi above a wellbore pressure P2. The bladder130is constructed from flexible material allowing bladder surface175to press against the tubular at approximately the same pressure as the hydraulic pressure P1.

The hydraulic control may be used to de-energize the bladder130and allow the active seal assembly105to release the seal around the tubular. Generally, the fluid in the chamber150is drained into a hydraulic reservoir (not shown), thereby reducing the pressure P1. Subsequently, the bladder surface175loses contact with the tubular as the bladder130becomes de-energized and moves radially outward. In this manner, the seal around the tubular is released allowing the tubular to be removed from the rotating control head800.

FIG. 9illustrates another alternative embodiment of a rotating control head, generally indicated at900. The rotating control head900is generally constructed from similar components as the rotating control head100, as shown inFIG. 1. Therefore, for convenience, similar components that function in the same manner will be labeled with the same numbers as the rotating control head100. The primary difference between rotating control head900and rotating control head100is the use of two passive seal assemblies110, an alternative cooling system using one fluid to cool the radial seals and bearings in combination with a radial seal pressure protection system, and a secondary piston SP in addition to a primary piston P for urging the piston P to the unlatched position. These differences will be discussed below in detail.

WhileFIG. 9shows the rotating control head900latched in a housing H above a diverter D, it is contemplated that the rotating control heads as shown in the figures could be positioned with any housing or riser as disclosed in U.S. Pat. Nos. 6,138,774, 6,263,982, 6,470,975, U.S. patent application Ser. No. 10/281,534, filed Oct. 28, 2002 and published Jun. 12, 2003 under U.S. Patent Application No. 2003-0106712-A1, or U.S. patent application Ser. No. 10/995,980, filed Nov. 23, 2004, all of which are assigned to the assignee of the present invention and incorporated herein by reference for all purposes.

As shown inFIG. 9, both passive seal assemblies110are operably attached to the inner member support housing135, thereby allowing the passive seal assemblies to rotate together. The passive seal assemblies are constructed and arranged in an axially-downward conical shape, thereby allowing the wellbore pressure P2in the rotating control head900to act against the tapered surfaces195to close the passive seal assemblies around the tubular T. Additionally, the passive seal assemblies include inner diameters which are smaller than the outer diameter of the tubular T to allow an interference fit between the tubular and the passive seal assemblies.

FIG. 11discloses a cooling system where air enters a passageway, formed as a labyrinth L, in a rotating control head RCH similar to the passageway shown inFIGS. 2A and 2Bof the present invention.

FIG. 12discloses a cooling system where hydraulic fluid moving through inlet I to outlet O is used to cool the top radial seals S1and S2with a seal carrier in a rotating control head RCH.

Turning now toFIGS. 9,13and14, the rotating control head900is cooled by a heat exchanger, generally indicated at905. As best shown inFIGS. 13 and 14, heat exchanger905is constructed and arranged to remove heat from the rotating control head900using a fluid, such as an unctuous combustible substance. One such unctuous combustible substance is a hydraulic oil, such as Mobil 630 ISO 90 weight oil. This fluid is introduced at a low temperature into inlet965, thereafter transferring heat from upper top radial seal975A and lower top radial seal975B, via seal carrier982A and its thermal transfer surfaces982A′ and a plurality of bearings, including bearings955, to the fluid as the fluid passes through the heat exchanger905and, as best shown inFIG. 14, to outlet970.

In particular, the top radial seals975A and975B are cooled by circulating the hydraulic fluid, preferably oil, in and out of the bearing section B and making multiple passes around the seals975A and975B through a continuous spiral slot980C in the seal housing982B, as best shown inFIGS. 9,13and14. Since the hydraulic fluid that passes through slot passageway or slot980C is the same fluid used to pressure the bearing section B, the fluid can be circulated close to and with the radial seals975A and975B to improve the heat transfer properties. Although the illustrated embodiment uses a continuous spiral slot, other embodiments are contemplated for different methods for making multiple passes with one fluid adjacent to and in fluid contact with the radial seals.

As best shown inFIG. 14, the passageway of the heat exchanger905includes inlet passageway980A, outlet passageway980B, and slot passageway980C that spirals between the lower portion of inlet passageway980A to upper outlet passageway980B. These multiple passes adjacent the radial seals975A and975B maximize the surface area covered by the heat exchanger905. The temperature hydraulic oil entering the inlet965flows through the passageway in the direction illustrated by arrows985. As the oil circulates through the passageway, the oil increases in temperature as the heat from the rotating control head900is transferred to the oil. The higher temperature oil exits the outlet970. In this manner, the heat generated about the top radial seals in the rotating control head900is transferred to the oil passing through the multiple pass heat exchanger905. Moreover, separate fluids are not used to cool and to lubricate the rotating control head900. Instead, only one fluid, such as a Mobil 630 ISO fluid 90 weight oil, is used to both cool and lubricate the rotating control head900.

Returning toFIG. 9, it is contemplated that a similar cooling system using the multiple pass heat exchanger of the present invention could be used to cool the bottom radial seals975C and975D of the rotating control head900.

Returning now toFIG. 13, the top radial seals975A and975B are staged in tandem or series. The lower top radial seal975B, which would be closer to the bearings955, is a high flow seal that would allow approximately two gallons of oil per minute to pass by seal975B. The upper top radial seal975A, which would be the seal closer to the atmosphere or environment, would be a low flow seal that would allow approximately 1 cc of oil per hour to pass by the seal975A. A port984, accessible from the atmosphere, is formed between the radial seals975A and975B. As illustrated in bothFIGS. 13 and 15B, an electronically-controlled valve, generally indicated at V200, would regulate the pressure between the radial seals975A and975B. Preferably, as discussed below in detail, the pressure on upper top radial seal975A is approximately half the pressure on lower top radial seal975B so that the differential pressure on each radial seal is lower, which in turn reduces the PV factor by approximately half. Testing of a Weatherford model 7800 rotating control head has shown that when using a Kalsi seal, with part number 381-6-11, for the upper top radial seal975A, and a modified (as discussed below) Kalsi seal, with part number 432-32-10CCW (cutting and gluing), for the lower top radial seal975B, has shown increased seal life of the top radial seals.

The Kalsi seals referred to herein can be obtained from Kalsi Engineering, Inc. of Sugar Land, Tex. The preferred Kalsi 381-6-11 seal is stated by Kalsi Engineering, Inc. to have a nominal inside diameter of 10½″, a seal radial depth of 0.415″±0.008″, a seal axial width of 0.300″, a gland depth of 0.380″, a gland width of 0.342″ and an approximate as-molded seal inside diameter of 10.500″ (266.7 mm). This seal is further stated by Kalsi to be fabricated from HSN (peroxide cured, high ACN) with a material hardness of Shore A durometer of 85 to 90. While the preferred Kalsi 432-32-10CCW seal is stated by Kalsi Engineering, Inc. to have a nominal inside diameter of 42.375″, a seal radial depth of 0.460″±0.007″, a seal axial width of 0.300″, a gland width of 0.342″ and an approximate as-molded seal inside diameter of 42.375″ (1,076 mm), this high flow seal was reduced to an inside diameter the same as the preferred Kalsi 381-6-11 seal, i.e. 10½″. This high flow seal975B is further stated by Kalsi to be fabricated from HSN (fully saturated peroxide cured, medium-high ACN) with a material hardness of Shore A durometer of 85±5. It is contemplated that other similar sizes and types of manufacturers' seals, such as seals provided by Parker Hannifin of Cleveland, Ohio, could be used.

Startup Operation

Turning now toFIGS. 15A to 25along with below Tables 1 and 2, the startup operation of the hydraulic or fluid control of the rotating control head900is described. Referring particularly toFIG. 25, to start the power unit, button PB10on the control console, generally indicated at CC, is pressed and switch SW10is moved to the ON position. As discussed in the flowcharts ofFIGS. 16-17, the program of the programmable logic controller PLC checks to make sure that button PB10and switch SW10were operated less than 3 seconds of each other. If the elapsed time is equal to or over 3 seconds, the change in position of SW10is not recognized. Continuing on the flowchart ofFIG. 16, the two temperature switches TS10and TS20, also shown inFIG. 15B, are then checked. These temperature switches indicate oil tank temperature. When the oil temperature is below a designated temperature, e.g. 80° F., the heater HT10(FIG. 15B) is turned on and the power unit will not be allowed to start until the oil temperature reaches the designated temperature. When the oil temperature is above a designated temperature, e.g. 130° F., the heater is turned off and cooler motor M2is turned on. As described in the flowchart ofFIG. 17, the last start up sequence is to check to see if the cooler motor M2needs to be turned on.

Continuing on the flowchart ofFIG. 16, the wellbore pressure P2is checked to see if below 50 psi. As shown in below Table 2, associated alarms10,20,30and40, light LT100on control console CC, horn HN10inFIG. 15B, and corresponding text messages on display monitor DM on console CC will be activated as appropriate. Wellbore pressure P2is measured by pressure transducer PT70(FIG. 15A). Further, reviewingFIGS. 15B to 17, when the power unit for the rotating control head, such as a Weatherford model 7800, is started, the three oil tank level switches LS10, LS20and LS30are checked. The level switches are positioned to indicate when the tank634is overfull (no room for heat expansion of the oil), when the tank is low (oil heater coil is close to being exposed), or when the tank is empty (oil heater coil is exposed). As long as the tank634is not overfull or empty, the power unit will pass this check by the PLC program.

Assuming that the power unit is within the above parameters, valves V80and V90are placed in their open positions, as shown inFIG. 15B. These valve openings unload gear pumps P2and P3, respectively, so that when motor M1starts, the oil is bypassed to tank634. Valve V150is also placed in its open position, as shown inFIG. 15A, so that any other fluid in the system can circulate back to tank634. Returning toFIG. 15B, pump P1, which is powered by motor M1, will compensate to a predetermined value. The pressure recommended by the pump manufacturer for internal pump lubrication is approximately 300 psi. The compensation of the pump P1is controlled by valve V10(FIG. 15B).

Continuing review of the flowchart ofFIG. 16, fluid level readings outside of the allowed values will activate alarms50,60or70(see also below Table 2 for alarms) and their respective lights LT100, LT50and LT60. Text messages corresponding to these alarms are displayed on display monitor DM.

When the PLC program has checked all of the above parameters the power unit will be allowed to start. Referring to the control console CC inFIG. 25, the light LT10is then turned on to indicate the PUMP ON status of the power unit. Pressure gauge PG20on console CC continues to read the pump pressure provided by pressure transducer PT10, shown inFIG. 15B.

When shutdown of the unit desired, the PLC program checks to see if conditions are acceptable to turn the power unit off. For example, the wellbore pressure P2should be below 50 psi. Both the enable button PB10must be pressed and the power switch SW10must be turned to the OFF position within 3 seconds to turn the power unit off.

Latching Operation System Circuit

Closing the Latching System

Focusing now onFIGS. 9,15A,18A,18B,23and24, the retainer member LP of the latching system of housing H is closed or latched, as shown inFIG. 9, by valve V60(FIG. 15A) changing to a flow position, so that the ports P-A, B-T are connected. The fluid pilot valve V110(FIG. 15A) opens so that the fluid on that side of the primary piston P can go back to tank634via line FM40L through the B-T port. Valve V100prevents reverse flow in case of a loss of pressure. Accumulator A (which allows room for heat expansion of the fluid in the latch assembly) is set at 900 psi, slightly above the latch pressure 800 psi, so that it will not charge. Fluid pilot valve V140(FIG. 15A) opens so that fluid underneath the secondary piston SP goes back to tank634via line FM50L and valve V130is forced closed by the resulting fluid pressure. Valve V70is shown inFIG. 15Ain its center position where all ports (APBT blocked) are blocked to block flow in any line. The pump P1, shown inFIG. 15B, compensates to a predetermined pressure of approximately 800 psi.

The retainer member LP, primary piston P and secondary piston SP of the latching system are mechanically illustrated inFIG. 9(latching system is in its closed or latched position), schematically shown inFIG. 15A, and their operations are described in the flowcharts inFIGS. 18A,18B,23and24. Alternative latching systems are disclosed in FIGS. 1 and 8 and in U.S. patent application Ser. No. 10/995,980, filed Nov. 23, 2004.

With the above described startup operation achieved, the hydraulics switch SW20on the control console CC is turned to the ON position. This allows the pump P1to compensate to the required pressure later in the PLC program. The bearing latch switch SW40on console CC is then turned to the CLOSED position. The program then follows the process outlined in the CLOSED leg of SW40described in the flowcharts ofFIGS. 18A and 18B. The pump P1adjusts to provide 800 psi and the valve positions are then set as detailed above. As discussed below, the PLC program then compares the amount of fluid that flows through flow meters FM30, FM40and FM50to ensure that the required amount of fluid to close or latch the latching system goes through the flow meters. Lights LT20, LT30, LT60and LT70on console CC show the proper state of the latch. Pressure gauge PG20, as shown on the control console CC, continues to read the pressure from pressure transducer PT10(FIG. 15B).

Primary Latching System Opening

Similar to the above latch closing process, the PLC program follows the OPEN leg of SW40as discussed in the flowchart ofFIG. 18Aand then the OFF leg of SW50ofFIG. 18Ato open or unlatch the latching system. Turning toFIG. 15A, prior to opening or unlatching the retainer member LP of the latching system, pressure transducer PT70checks the wellbore pressure P2. If the PT70reading is above a predetermined pressure (approximately 50 psi), the power unit will not allow the retainer member LP to open or unlatch. Three-way valve V70(FIG. 15A) is again in the APBT blocked position. Valve V60shifts to flow position P-B and A-T. The fluid flows through valve V110into the chamber to urge the primary piston P to move to allow retainer member LP to unlatch. The pump P1, shown inFIG. 15B, compensates to a predetermined value (approximately 2000 psi). Fluid pilots open valve V100to allow fluid of the primary piston P to flow through line FM30L and the A-T ports back to tank634.

Secondary Latching System Opening

The PLC program following the OPEN leg of SW40and the OPEN leg of SW50, described in the flowchart ofFIG. 18A, moves the secondary piston SP. The secondary piston SP is used to open or unlatch the primary piston P and, therefore, the retainer member LP of the latching system. Prior to unlatching the latching system, pressure transducer PT70again checks the wellbore pressure P2. If PT70is reading above a predetermined pressure (approximately 50 psi), the power unit will not allow the latching system to open or unlatch. Valve V60is in the APBT blocked position, as shown inFIG. 15A. Valve V70then shifts to flow position P-A and B-T. Fluid flows to the chamber of the secondary latch piston SP via line FM50L. With valve V140forced closed by the resulting pressure and valve V130piloted open, fluid from both sides of the primary piston P is allowed to go back to tank634though the B-T ports of valve V70.

Bearing Assembly Circuit

Continuing to reviewFIGS. 9,15A,15B,18A and18B and the below Tables 1 and 2, now reviewFIGS. 19 to 22describing the bearing assembly circuit.

Valve positions on valve V80and valve V90, shown inFIG. 15B, and valve V160, shown inFIG. 15A, are moved to provide a pressure in the rotating control head that is above the wellbore pressure P2. In particular, the wellbore pressure P2is measured by pressure transducer PT70, shown inFIG. 15A. Depending on the wellbore pressure P2, valve V90and valve V80(FIG. 15B) are either open or closed. By opening either valve, pressure in the rotating control head can be reduced by allowing fluid to go back to tank634. Also, depending on pressure in the rotating control head, valve V160will move to a position that selects a different size orifice. The orifice size, e.g. 3/32″ or ⅛″ (FIG. 15A), will determine how much back pressure is in the rotating control head. By using this combination of valves V80, V90and V160, four different pressures can be achieved.

During the operation of the bearing assembly circuit, the temperature switches TS10and TS20, described in the above startup operation, continue to read the oil temperature in the tank634, and operate the heater HT10or cooler motor M2, as required. For example, if the oil temperature exceeds a predetermined value, the cooler motor M2is turned on and the cooler will transfer heat from the oil returning from the bearing section or assembly B.

Flow meter FM10measures the volume or flow rate of fluid or oil to the chamber in the bearing section or assembly B via line FM10L. Flow meter FM20measures the volume or flow rate of fluid or oil from the chamber in the bearing section or assembly B via line FM20L. As discussed further below in the bearing leak detection system section, if the flow meter FM20reading is greater than the flow meter FM10reading, this could indicate that wellbore fluid is entering the bearing assembly chamber. Valve V150is then moved from the open position, as shown inFIG. 15A, to its closed position to keep the wellbore fluid from going back to tank634.

Regulating Pressure in the Radial Seals

ReviewingFIGS. 13,14,15B,22and23along with the below Tables 1 and 2, pressure transducer PT80(FIG. 15B) reads the amount of fluid “seal bleed” pressure between the top radial seals975A and975B via port984. As discussed above, proportional relief valve V200adjusts to maintain a predetermined pressure between the two radial seals975A and975B. Based on the well pressure P2indicated by the pressure transducer PT70, the valve V200adjusts to achieve the desired “seal bleed” pressure as shown in the below Table 1.

The flowcharts ofFIGS. 18A and 18Bon the CLOSED leg of SW40and after the subroutine to compare flow meters FM30, FM40and FM50, describes how the valves adjust to match the pressures in above Table 1.FIGS. 19 to 22describes a subroutine for the program to adjust pressures in relation to the wellbore pressure P2.

Alarms

During the running of the PLC program, certain sensors such as flow meters and pressure transducers are checked. If the values are out of tolerance, alarms are activated. The flowcharts ofFIGS. 16,17,18A and18B. describe when the alarms are activated. Below Table 2 shows the lights, horn and causes associated with the activated alarms. The lights listed in Table 2 correspond to the lights shown on the control console CC ofFIG. 25. As discussed below, a text message corresponding to the cause is sent to the display monitor DM on the control console CC.

Latch Leak Detection System

Usually the PLC program will run a comparison where the secondary piston SP is “bottomed out” or in its latched position, such as shown inFIG. 9, or when only a primary piston P is used, such as shown inFIG. 1, the piston P is bottomed out. In this comparison, the flow meter FM30coupled to the line FM30L measures either the flow volume value or flow rate value of fluid to the piston chamber to move the piston P to the latched position, as shown inFIG. 9, from the unlatched position, as shown inFIG. 1. Also, the flow meter FM40coupled to the line FM40L measures the desired flow volume value or flow rate value from the piston chamber. Since the secondary piston SP is bottomed out, there should be no flow in line FM50L, as shown inFIG. 9. Since no secondary piston is shown inFIG. 1, there is no line FM50L or flow meter FM50.

In this comparison, if there are no significant leaks, the flow volume value or flow rate value measured by flow meter FM30should be equal to the flow volume value or flow rate value, respectively, measured by flow meter FM40within a predetermined tolerance. If a leak is detected because the comparison is outside the predetermined tolerance, the results of this FM30/FM40comparison would be displayed on display monitor DM on control console CC, as shown inFIG. 25, preferably in a text message, such as “Alarm90—Fluid Leak”. Furthermore, if the values from flow meter FM30and flow meter FM40are not within the predetermined tolerance, i.e. a leak is detected, the corresponding light LT100would be displayed on the control console CC.

In a less common comparison, the secondary piston SP would be in its “full up” position. That is, the secondary piston SP has urged the primary piston P, when viewingFIG. 9, as far up as it can move to its full unlatched position. In this comparison, the flow volume value or flow rate value, measured by flow meter FM30coupled to line FM30L, to move piston P to its latched position, as shown inFIG. 9, is measured. If the secondary piston SP is sized so that it would block line FM40L, no fluid would be measured by flow meter FM40. But fluid beneath the secondary piston SP would be evacuated via line FM50L from the piston chamber of the latch assembly. Flow meter50would then measure the flow volume value or flow rate value. The measured flow volume value or flow rate value from flow meter FM30is then compared to the measured flow volume value or flow rate value from flow meter FM50.

If the compared FM30/FM50values are within a predetermined tolerance, then no significant leaks are considered detected. If a leak is detected, the results of this FM30/FM50comparison would be displayed on display monitor DM on control console CC, preferably in a text message, such as “Alarm100—Fluid Leak”. Furthermore, if the values from flow meter FM30and flow meter FM50are not within a predetermined tolerance, the corresponding light LT100would be displayed on the control console CC.

Sometimes the primary piston P is in its full unlatched position and the secondary piston SP is somewhere between its bottomed out position and in contact with the fully unlatched piston P. In this comparison, the flow volume value or flow rate value measured by the flow meter FM30to move piston P to its latched position is measured. If the secondary piston SP is sized so that it does not block line FM40L, fluid between secondary piston SP and piston P is evacuated by line FM40L. The flow meter FM40then measures the flow volume value or flow rate value via line FM40L. This measured value from flow meter FM40is compared to the measured value from flow meter FM30. Also, the flow value beneath secondary piston SP is evacuated via line FM50L and measured by flow meter FM50.

If the flow value from flow meter FM30is not within a predetermined tolerance of the compared sum of the flow values from flow meter FM40and flow meter FM50, then the corresponding light LT100would be displayed on the control console CC. This detected leak is displayed on display monitor DM in a text message.

Measured Value/Predetermined Value

An alternative to the above leak detection methods of comparing measured values is to use a predetermined or previously calculated value. The PLC program then compares the measured flow value in and/or from the latching system to the predetermined flow value plus a predetermined tolerance.

It is noted that in addition to indicating the latch position, the flow meters FM30, FM40and FM50are also monitored so that if fluid flow continues after the piston P has moved to the closed or latched position for a predetermined time period, a possible hose or seal leak is flagged.

For example, alarms90,100and110, as shown in below Table 2, could be activated as follows:

Alarm90—primary piston P is in the open or unlatched position. The flow meter FM40measured flow value is compared to a predetermined value plus a tolerance to indicate the position of piston P. When the flow meter FM40reaches the tolerance range of this predetermined value, the piston P is indicated in the open or unlatched position. If the flow meter FM40either exceeds this tolerance range of the predetermined value or continues to read a flow value after a predetermined time period, such as an hour, the PLC program indicates the alarm90and its corresponding light and text message as discussed herein.

Alarm100—secondary piston SP is in the open or unlatched position. The flow meter FM50measured flow value is compared to a predetermined value plus a tolerance to indicate the position of secondary piston SP. When the flow meter FM50reaches the tolerance range of this predetermined value, the secondary piston SP is indicated in the open or unlatched position. If the flow meter FM50either exceeds this tolerance range of the predetermined value or continues to read a flow value after a predetermined time period, such as an hour, the PLC program indicates the alarm100and its corresponding light and text message as discussed herein.

Alarm110—primary piston P is in the closed or latched position. The flow meter FM30measured flow value is compared to a predetermined value plus a tolerance to indicate the position of primary piston P. When the flow meter FM30reaches the tolerance range of this predetermined value, the primary piston P is indicated in the closed or latched position. If the flow meter FM30either exceeds this tolerance range of the predetermined value or continues to read a flow value after a predetermined time period, such as an hour, the PLC program indicates the alarm110and its corresponding light and text message as discussed herein.

Bearing Leak Detection System

A leak detection system can also be used to determine if the bearing section or assembly B is losing fluid, such as oil, or, as discussed above, gaining fluid, such as wellbore fluids. As shown inFIG. 15A, line FM10L and line FM20L move fluid to and from the bearing assembly B of a rotating control head and are coupled to respective flow meters FM10and FM20.

If the measured fluid value, such as fluid volume value or fluid rate value, from flow meter FM10is not within a predetermined tolerance of the measured fluid value from flow meter FM20, then alarms120,130or140, as described below in Table 2, are activated. For example, if the measured flow value to the bearing assembly B is greater than the measured flow value from the bearing assembly plus a predetermined percentage tolerance, then alarm120is activated and light LT90on control console CC is turned on. Also, a text message is displayed on display monitor DM on the control console CC, such as “Alarm120—Losing Oil.” For example, this loss could be from the top radial seals leaking oil to the atmosphere, or the bottom radial seals leaking oil down the wellbore.

If the measured flow value from the bearing assembly read by flow meter FM20is greater than the measured flow value to the bearing assembly read by flow meter FM10plus a predetermined percentage tolerance, then alarm130is activated, light LT90is turned on and a text message such as “Alarm130—Gaining Oil” is displayed on display monitor DM.

If the measured flow meter FM20flow value/measured flow meter FM10flow value is higher than the alarm130predetermined percentage tolerance, then alarm140is activated, light LT90is turned on and a horn sounds in addition to a text message on display monitor DM, such as “Alarm140—Gaining Oil.”

An alternative to the above leak detection methods of comparing measured values is to use a predetermined or previously calculated value. The PLC program then compares the measured flow value in and/or from the bearing assembly B to the predetermined flow value plus a predetermined tolerance.

Additional methods are contemplated to indicate position of the primary piston P and/or secondary piston SP in the latching system. One example would be to use an electrical sensor, such as a linear displacement transducer, to measure the distance the selected piston has moved.

Another method could be drilling the housing of the latch assembly for a valve that would be opened or closed by either the primary piston P, as shown in the embodiment ofFIG. 1, or the secondary piston SP, as shown in the embodiment ofFIGS. 9,26and27. In this method, a port PO would be drilled or formed in the bottom of the piston chamber of the latch assembly. Port PO is in fluid communication with an inlet port IN (FIG. 26) and an outlet port OU (FIG. 27) extending perpendicular (radially outward) from the piston chamber of the latch assembly. These perpendicular ports would communicate with respective passages INP and OUP that extend upward in the radially outward portion of the latch assembly housing. Housing passage OUP is connected by a hose to a pressure transducer and/or flow meter. A machined valve seat VS in the port to the piston chamber receives a corresponding valve seat, such as a needle valve seat. The needle valve seat would be fixedly connected to a rod R receiving a coil spring CS about its lower portion to urge the needle valve seat to the open or unlatched position if neither primary piston P (FIG. 1embodiment) nor secondary piston SP (FIGS. 9,26and27embodiments) moves the needle valve seat to the closed or latched position. An alignment retainer member AR is sealed as the member is threadably connected to the housing H. The upper portion of rod R is slidably sealed with retainer member AR.

If a flow value and/or pressure is detected in the respective flow meter and/or pressure transducer communicating with passage OUP, then the valve is indicated open. This open valve indicates the piston is in the open or unlatched position. If no flow value and/or pressure is detected in the respective flow meter and/or pressure transducer communicating with passage OUP, then the valve is indicated closed. This closed valve indicates the piston is in the closed or latched position. The above piston position would be shown on the console CC, as shown inFIG. 25, by lights LT20or LT60and LT30or LT70along with a corresponding text message on display monitor DM.