|Publication number||US3815673 A|
|Publication date||Jun 11, 1974|
|Filing date||Feb 16, 1972|
|Priority date||Feb 16, 1972|
|Also published as||CA967550A, CA967550A1|
|Publication number||US 3815673 A, US 3815673A, US-A-3815673, US3815673 A, US3815673A|
|Inventors||Bruce G, Ilfrey W|
|Original Assignee||Exxon Production Research Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (140), Classifications (14)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent [1 1 Bruce et al.
METHOD AND APPARATUS FOR CONTROLLING I'IYDROSTATIC PRESSURE GRADIENT IN OFFSHORE DRILLING OPERATIONS Inventors: George H. Bruce; William T. Ilfrey,
both of Houston, Tex.
Esso Production Research Company, Houston, Tex.
Filed: Feb. 16, 1972 Appl. No.: 226,843
McNeilI et al.
Bauer ct al.
Townsend 175/5 Ragland et a1 175/69 1 June 11, 1974 3,459,259 8/1969 Matthews 175/7 X 3,595,075 7/1971 Dower v 175/48 3,603,409 9/1971 Watkins 175/25 Primary Examiner-Henry C. Sutherland Assistant Examiner-Richard E. Favreau Attorney, Agent, or Firm-James E. Gilchrist  ABSTRACT An improved system for offshore drilling is disclosed which is particularly useful in those operations where a floating vessel is situated at the surface of a body of water and circulation of drilling fluid is accomplished by introducing drilling fluid into a drill string extending from the vessel into a borehole in the floor of the body of water and returning it through a separate conduit to the vessel. A surface detectable signal is generated which is proportional to the hydrostatic head exerted by the drilling fluid within the return conduit. Hydrostatic head of the drilling fluid within the return conduit is controlled in response to the signal, as by injecting gas into the conduit near its lower end, to regulate the hydrostatic head of the fluid in the borehole.
2 Claims, 3 Drawing Figures \PATENTEDJUN 1 1 mm DEPTH FROM WATER SURFACE IOOO FEET SHEET 10F 3 FIG.|
METHOD AND APPARATUS FOR CONTROLLING HYDROSTATIC PRESSURE GRADIENT IN OFFSHORE DRILLING OPERATIONS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an improved system for drilling from a floating vessel which involves monitoring and controlling the hydrostatic head of the drilling fluid returns to control bottom hole pressure.
2. Description of the Prior Art In recent years the search for offshore deposits of crude oil and natural gas has been extended into ever deeper waters overlying the continental shelves. With increased water depths the conduct of drilling operations from floating vessels has become more prevalent since economic considerations militate against the use of bottom-founded drilling platforms commonly used in shallow water. In these operations the drill rig and associated equipment are positioned aboard a floating vessel which is stationed over the wellsite. The drill string extends from the vessel to a wellhead situated on the floor of the body of water and a separate return conduit, normally a riser pipe, is provided to permit circulation of drilling fluid.
Control of the influx of fluid from pressurized subsurfaceformations is an important aspect of any drilling operation. If uncontrolled, fluid influx can lead to a blowout and fire, frequently with catastrophic results in terms of loss of life, damage to property, and pollution of the seaway. Conventionally, well control is established by maintaining the density of the drilling fluid and thus the hydrostatic pressure exerted on the subsurface formations at a level sufficient to overcome formation pressures. At the same time, caution is necessary to assure that the density and hence pressure gradient of the column of fluid does not exceed the natural fracture gradient of the formation, i.e., the pressure gradient necessary to initiate and propagate a fracture in the formation.
In deep water, the natural fracture gradient of shallow formations is particularly critical factor. It isdirectly related to the bulk density of the sediments resting on top of the pressurized formation and thus at the floor of the body of water is for all practical purposes the pressure gradient of water. For a formation situated 500 feet below the floor of a body of water having a depth of 2,000 feet, the natural fracture gradient will be greatly influenced by thegradient of the overlying body of water. Because of the higher bulk density of rock, however, the fracture gradient rapidly increases with the depth of penetration into the sea floor and will not represent a serious problem after the first few thousand feet of hole are drilled.
During the drilling of the surface hole (the first few thousand feet) the hydrostatic head of the drilling fluid should not greatly exceed that of a column of salt water to minimize the possibility of formation fracture. On the other hand normally pressured formations have a pressure similar to that exerted by a column of salt water corresponding to formation depth. It will therefore be apparent that in deep water, achieving a hydrostatic head high enough to control the well and yet low enough to prevent fracturing subsurface formations will require careful control of the pressure gradient of the drilling fluid.
In offshore operations controlling the density of the fluid as it is pumped into the well is not an entirely satisfactory approach since at normal drilling rates the drill cuttings suspended in the returning drilling fluid may sufficiently increase its density to yield a gradient exceeding normal fracture gradient. Heretofore, the only available system to assure a balanced condition in these circumstances was to greatly increase drilling fluid circulation rate or to reduce the rate of penetration; both practices are economically unattractive. A need therefore exists for a system for controlling the hydrostatic head of the drilling fluid within close limits without either increasing drilling fluid circulation rate or reducing the penetration rate.
SUMMARY OF THE INVENTION The present invention permits close control over the pressure gradient of the drilling fluid at no sacrifice of penetration rate and with no increase in circulation rate and thus alleviates the difflculties encountered in deep water drilling which are outlined above. In accordance with the present invention the hydrostatic pressure exerted by the drilling fluid within the drilling riser or other return conduit is monitored and its density is regulated to control the hydrostatic head of the mud column and thereby assuresufficient hydrostatic pressure to counterbalance formation pressures without exceeding their fracture gradients.
The system of the present invention is particularly applicable to drilling operations wherein a floating vessel is situated at the surface of a body of water above a wellhead positioned on the floor thereof. Drilling fluid is introduced into a drill string that extends between the vessel and wellhead and is returned through a separate conduit. The apparatus of the invention includes a means mounted on the conduit for generating a signal proportional to the pressure therein and detectable at said vessel. The method involves monitoring the hydrostatic head of the fluid flowing within the conduit and regulating its density to control the hydrostatic head of the column of drilling fluid acting on subsurface formations. The pressure gradient of the fluid within the return conduit can be reduced by injecting gas into the conduit. The rate of gas injection is controlled in response to the pressure within the riser to maintain the hydrostatic head at a substantially constant level, thereby assuring the proper hydrostatic head will be maintained on formations exposed to the borehole.
It will theerefore be apparent that the present invention will permit the hydrostatic pressures exerted by drilling fluids and entrained .cuttings to be closely controlled without any substantial reduction in drilling rate or-increase in circulation rate. The present invention thus permits control of pressurized formations during normaldrilling operations while reducing the danger of exceeding their fracture gradients and offers significant advantages over systems existing heretofore.
BRIEF DESCRIPTION or THE DRAWINGS FIG. 1 depicts typical curves relating fracture gradient to formation depths beneath the water surface. I
FIG. 2 is an elevation view, partially in'section, of a floating drilling vessel provided with apparatus necessary to carry out the method of the invention.
FIG. 3 is a schematic flow diagram of a system for monitoring and regulating the hydrostatic head of the drilling fluid within the return conduit in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plot of formation depth in thousands of feet versus the natural fracture gradient expressed both in psi/ft and as an equivalent mud density in lbs/gal (ppg). The curves shown are for a particular geographic area but illustrate the general relationship between water depth and formation fracture gradient. It will be apparent from an inspection of FIG. 1 that for any particular depth from the water surface, the fracture gradient decreases markedly as water depth increases.
Curve A relates the fracture gradients of formations encountered onshore to depth. These range from 0.60 psi/ft at 1,000 ft up to about 0.69 psi/ft at 3,000 ft. Curve B is for similar strata at a water depth of 750 ft. The fracture gradient is thus that of sea water, about 0.44 psi/ft, for depths to 750 ft. A formation buried under 1,000 ft of sediments is 1,750 ft below the water surface and will be noted to have a fracture gradient-on the order of 0.54 psi/ft. The gradient at 3,000 ft beneath the sea floor (3,750 ft below the water surface) is 0.64 psi/ft. Curve C represents identical sediments under l,500 ft of water. The natural fracture gradient for a formation under 1,000 ft of sediments corresponds to a depth of 2,500 ft and will be noted to be 0.51 psi/ft, corresponding to a mud weight just under ppg. At 3 ,000 ft of penetration, the fracture gradient is 0.61 psi/ft. It will therefore be apparent that for any particular depthof penetration into the substrata, the fracture gradient decreases as water depth increases.
The importance of the decrease in fracture gradient with water depth can be demonstrated by an example comparison of the hydrostatic pressure required to maintain well control to that which will fracture the formation. A normally pressured subsurface formation can be anticipated to have a formation pressure equivalent to the pressure exerted by a column of salt water having'a height equal to formation depth. A gas formation 1,000 ft beneath the floor of a 1,500 ft body of water could therefore be expected to have a pressure equal to the product of the salt water gradient and the depth of the formation beneath the water surface or about 1,1 10 psi and a drilling fluid having a salt water gradient (0.445 psi/ft, or about 8.5 ppg) could be expected to balance the formation pressure. It is normally desirable to drill with a fluid having a degree of overbalance, i.e., exerting a hydrostatic head greater than formation pressure. On the other hand, the fracture gradient at this depth is 0.51 psi/ft, which corresponds to a bottom hole pressure of 1,275 psi. Thus the pressure exerted by the mud must be kept between 1,110
- could of course be overcome by drillingat reduced rates and simultaneously increasing the rate of circulation, thereby assuring that the drilling fluid density remains within the critical range. This approach is however economically very unattractive in view of the daily expense of maintaining drilling equipment at the wellsite.
An alternative approach is to drill at a rapid penetration rate and at the same time reduce the bottom hole pressure of the drilling fluid by injecting gas orother low density material into the riser to lighten the mud. At the same time, however, a gas injection program undertaken in deep water requires careful control to assure that the hydrostatic head of the drilling fluid remains between that necessary to control the well and that which would result in a fracturing of the formation.
It is therefore an important aspect of the present inven-.
tion to monitor the'pressure exerted by the drilling fluid within the return conduit and to adjust the density of r the fluid therein to control bottom hole pressure. Control of fluid density is preferably accomplished by injecting gas into the riser near the lower end at a rate regulated in response to the pressure therewithin to' maintain the total hydrostatic head of the drilling fluid acting on a subsurface formation within the range necessary to assure control of the well without fracturing the formation.
FIG. 2 shows a drilling vessel 11 floating on a body of water 13 and equipped to carry out the method of the present invention. A wellhead 15 is positioned on the floor 17 of the body of water. A drill string 19 is susand 1,275 psi. This in turn dictates a mud density bepended from derrick 21 mounted on the vessel and extends between it and the wellhead. Drilling fluid is pumped down the string of drill pipe through the bit and into the borehole and returns to the vessel via a return condit shown as drilling riser 23. A high pressure gas source 25 is situated aboard the vessel. Injection conduit 31 extends from the control valve down the length of the riser to a level near the wellhead. One or preferably a plurality of gas lift valves 33 are positioned between the injection line and the drilling riser. The lift valves are normally preset to open at a given differenf tial pressure. A pressure sensor 35 is shown positioned near the lower end of the drilling riser and arranged to sense riser internal pressure. It may for example be a pressure transducer which generates an electrical signal proportional to pressure within the return'conduit.
The signal is conducted to the surface by means of elec trical .conductor 37 extending between the pressure transducer and the drilling vessel.. It may be directed to controller 39 which controls the position of routing valve 29 in response to the amplitude of the pressure signal to regulate the rate at which gas is introduced into the lower portion of the drilling riser. By properly adjusting the response characteristics of the valve controller, the pressure gradient of the fluid within the drilling riser can be closely controlled.
FIG. 3 is an exemplary flow diagram of apparatus which can be used to implement the method of the invention. An inert gas source is designated by numeral 41 and is preferably engine exhaust gas or the product from an inert gas generator. Exhaust gas is routed through conduit 43 to gas treater 45. Nitrogen oxide and water are separated from the source gas and the residue, which consists primarily of nitrogen, carbon dioxide and water, is piped through conduit 47 to compressor 49. The gas is then compressed through stages, as required, to sufficiently increase its pressure. For depths of l,000-2,000 ft, 1,500 psi will normally suffice. The high pressure gas is conveyed to cooler 53 which condenses any residual water and cools the compressed gas to about 100F. Normally, the dry, high pressure gas passes from treating unit 53 via line 27 to routing valve 29. In the event of excess pressure, however, release valve 55 opens and discharges the gas through exhaust line 57, returning the inert gas to the atmosphere. Under normal pressure conditions, the release valve remains closed and routing valve 29 diverts part of the gas down injection line 31 to lighten the drilling fluid and recycles the remainder through conduit 59 leading back to the compressor. The percentage of gas diverted into the riser is controlled by valve controller 39 in response to a surface detectable signal proportional to pressure within the riser which is generated from pressure sensor 35 situated near the base of the riser and may, for example, be conducted to the vessel by means of electrical conductor 37 leading to the valve controller. The signal could alternatively be transmitted acoustically, pneumatically or by other means as well.
High pressure gas routed into injection conduit 31 travels downwardly and into the riser through differential-pressure actuated gas lift valves 33. These valves are preferably vertically spaced to assist in unloading the riser whenever drilling operations have been interrupted for a period of time. Gas is injected into the interior of the conductor pipe in the annulus surrounding the drill pipe and the lift gas and drilling fluid flow upwardly to rotating drilling head 61 which diverts the gas-mud mixture away from the drill floor. Both gas and mud are diverted through conduit 63 to separator 65 wherein the inert gas is separated from the mud as by means of gravity segregation. The gas is exhausted to the atmosphere via exhaust conduit 57 while the mud is returned through line 67 to the mud pits for recirculation.
What is claimed is:
1. In a method of drilling wherein a floating vessel is situated at the surface of a body of water and drilling fluid is introduced into a drill string extending from the vessel into a borehole in the floor of the body of water and returned to the vessel through a separate conduit which conduit is provided with means for injecting a gas thereinto near its lower end, the improvement comprising measuring the hydrostatic pressure of the drilling fluid within said return conduit beneath the gas injection point and adjusting the pressure gradient of the fluid contained within the return conduit to maintain the hydrostatic pressure of the drilling fluid within the borehole at a level sufficient to counterbalance formation pressure without exceeding its fracture gradient.
2. The method of claim 1 wherein said gas is an inert gas.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2726063 *||May 10, 1952||Dec 6, 1955||Exxon Research Engineering Co||Method of drilling wells|
|US2808230 *||Jan 17, 1955||Oct 1, 1957||Continental Oil Co||Off-shore drilling|
|US2923531 *||Apr 26, 1956||Feb 2, 1960||Continental Oil Co||Drilling|
|US3434550 *||Jun 6, 1966||Mar 25, 1969||Mobil Oil Corp||Method and apparatus for lightening the load on a subsea conductor pipe|
|US3459259 *||Sep 9, 1966||Aug 5, 1969||Mobil Oil Corp||Mudline suspension system|
|US3595075 *||Nov 10, 1969||Jul 27, 1971||Warren Automatic Tool Co||Method and apparatus for sensing downhole well conditions in a wellbore|
|US3603409 *||Mar 27, 1969||Sep 7, 1971||Regan Forge & Eng Co||Method and apparatus for balancing subsea internal and external well pressures|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3976148 *||Sep 12, 1975||Aug 24, 1976||The Offshore Company||Method and apparatus for determining onboard a heaving vessel the flow rate of drilling fluid flowing out of a wellhole and into a telescoping marine riser connecting between the wellhouse and the vessel|
|US4046191 *||Jul 7, 1975||Sep 6, 1977||Exxon Production Research Company||Subsea hydraulic choke|
|US4091881 *||Apr 11, 1977||May 30, 1978||Exxon Production Research Company||Artificial lift system for marine drilling riser|
|US4099583 *||Apr 11, 1977||Jul 11, 1978||Exxon Production Research Company||Gas lift system for marine drilling riser|
|US4135841 *||Feb 6, 1978||Jan 23, 1979||Regan Offshore International, Inc.||Mud flow heave compensator|
|US4210208 *||Dec 4, 1978||Jul 1, 1980||Sedco, Inc.||Subsea choke and riser pressure equalization system|
|US4282939 *||Jun 20, 1979||Aug 11, 1981||Exxon Production Research Company||Method and apparatus for compensating well control instrumentation for the effects of vessel heave|
|US4291772 *||Mar 25, 1980||Sep 29, 1981||Standard Oil Company (Indiana)||Drilling fluid bypass for marine riser|
|US4440239 *||Sep 28, 1981||Apr 3, 1984||Exxon Production Research Co.||Method and apparatus for controlling the flow of drilling fluid in a wellbore|
|US5875848 *||Apr 10, 1997||Mar 2, 1999||Reading & Bates Development Co.||Weight management system and method for marine drilling riser|
|US6102673 *||Mar 25, 1999||Aug 15, 2000||Hydril Company||Subsea mud pump with reduced pulsation|
|US6105689 *||May 26, 1998||Aug 22, 2000||Mcguire Fishing & Rental Tools, Inc.||Mud separator monitoring system|
|US6216799 *||Sep 24, 1998||Apr 17, 2001||Shell Offshore Inc.||Subsea pumping system and method for deepwater drilling|
|US6230824||Mar 25, 1999||May 15, 2001||Hydril Company||Rotating subsea diverter|
|US6263981 *||Sep 24, 1998||Jul 24, 2001||Shell Offshore Inc.||Deepwater drill string shut-off valve system and method for controlling mud circulation|
|US6276455 *||Sep 24, 1998||Aug 21, 2001||Shell Offshore Inc.||Subsea gas separation system and method for offshore drilling|
|US6325159||Mar 25, 1999||Dec 4, 2001||Hydril Company||Offshore drilling system|
|US6328107||Jul 27, 2000||Dec 11, 2001||Exxonmobil Upstream Research Company||Method for installing a well casing into a subsea well being drilled with a dual density drilling system|
|US6378628 *||Jun 16, 2000||Apr 30, 2002||Mcguire Louis L.||Monitoring system for drilling operations|
|US6401823 *||Feb 8, 2001||Jun 11, 2002||Shell Oil Company||Deepwater drill string shut-off|
|US6408948||Jul 14, 1999||Jun 25, 2002||Deep Vision Llc||Tubing handling for subsea oilfield tubing operations|
|US6415877||Jul 14, 1999||Jul 9, 2002||Deep Vision Llc||Subsea wellbore drilling system for reducing bottom hole pressure|
|US6470975||Mar 1, 2000||Oct 29, 2002||Weatherford/Lamb, Inc.||Internal riser rotating control head|
|US6505691||Aug 6, 2001||Jan 14, 2003||Hydril Company||Subsea mud pump and control system|
|US6530437||Jun 5, 2001||Mar 11, 2003||Maurer Technology Incorporated||Multi-gradient drilling method and system|
|US6571873||Feb 20, 2002||Jun 3, 2003||Exxonmobil Upstream Research Company||Method for controlling bottom-hole pressure during dual-gradient drilling|
|US6578637||Jul 27, 2000||Jun 17, 2003||Exxonmobil Upstream Research Company||Method and system for storing gas for use in offshore drilling and production operations|
|US6648081||Mar 8, 2002||Nov 18, 2003||Deep Vision Llp||Subsea wellbore drilling system for reducing bottom hole pressure|
|US6662885 *||Oct 24, 2001||Dec 16, 2003||Precision Drilling Technology Services Group, Inc.||Method and apparatus for providing a stream of pressurized substantially inert gas|
|US6668943||May 31, 2000||Dec 30, 2003||Exxonmobil Upstream Research Company||Method and apparatus for controlling pressure and detecting well control problems during drilling of an offshore well using a gas-lifted riser|
|US6745857 *||Sep 19, 2002||Jun 8, 2004||National Oilwell Norway As||Method of drilling sub-sea oil and gas production wells|
|US6802379||Feb 21, 2002||Oct 12, 2004||Exxonmobil Upstream Research Company||Liquid lift method for drilling risers|
|US6854532||Nov 17, 2003||Feb 15, 2005||Deep Vision Llc||Subsea wellbore drilling system for reducing bottom hole pressure|
|US6957698||Jun 23, 2003||Oct 25, 2005||Baker Hughes Incorporated||Downhole activatable annular seal assembly|
|US6981561||Sep 2, 2003||Jan 3, 2006||Baker Hughes Incorporated||Downhole cutting mill|
|US7096975||Mar 25, 2004||Aug 29, 2006||Baker Hughes Incorporated||Modular design for downhole ECD-management devices and related methods|
|US7114581||Feb 20, 2004||Oct 3, 2006||Deep Vision Llc||Active controlled bottomhole pressure system & method|
|US7174975||Sep 9, 2004||Feb 13, 2007||Baker Hughes Incorporated||Control systems and methods for active controlled bottomhole pressure systems|
|US7185705 *||Mar 18, 2003||Mar 6, 2007||Baker Hughes Incorporated||System and method for recovering return fluid from subsea wellbores|
|US7261164||Jan 18, 2005||Aug 28, 2007||Baker Hughes Incorporated||Floatable drill cuttings bag and method and system for use in cuttings disposal|
|US7270185||Jul 9, 2002||Sep 18, 2007||Baker Hughes Incorporated||Drilling system and method for controlling equivalent circulating density during drilling of wellbores|
|US7353887||Sep 8, 2005||Apr 8, 2008||Baker Hughes Incorporated||Control systems and methods for active controlled bottomhole pressure systems|
|US7513310 *||Mar 12, 2004||Apr 7, 2009||Ocean Riser Systems As||Method and arrangement for performing drilling operations|
|US7677329 *||Nov 24, 2004||Mar 16, 2010||Agr Subsea As||Method and device for controlling drilling fluid pressure|
|US7806203||Jun 16, 2006||Oct 5, 2010||Baker Hughes Incorporated||Active controlled bottomhole pressure system and method with continuous circulation system|
|US7836946||Mar 2, 2006||Nov 23, 2010||Weatherford/Lamb, Inc.||Rotating control head radial seal protection and leak detection systems|
|US7926593||Apr 19, 2011||Weatherford/Lamb, Inc.||Rotating control device docking station|
|US7934545||Oct 22, 2010||May 3, 2011||Weatherford/Lamb, Inc.||Rotating control head leak detection systems|
|US7938190 *||Nov 2, 2007||May 10, 2011||Agr Subsea, Inc.||Anchored riserless mud return systems|
|US7950463||Apr 7, 2009||May 31, 2011||Ocean Riser Systems As||Method and arrangement for removing soils, particles or fluids from the seabed or from great sea depths|
|US7972555||Oct 16, 2008||Jul 5, 2011||Exxonmobil Upstream Research Company||Method for fabricating compressible objects for a variable density drilling mud|
|US7997345||Aug 16, 2011||Weatherford/Lamb, Inc.||Universal marine diverter converter|
|US8011450||Jul 21, 2006||Sep 6, 2011||Baker Hughes Incorporated||Active bottomhole pressure control with liner drilling and completion systems|
|US8076269||Oct 16, 2008||Dec 13, 2011||Exxonmobil Upstream Research Company||Compressible objects combined with a drilling fluid to form a variable density drilling mud|
|US8088716||Oct 16, 2008||Jan 3, 2012||Exxonmobil Upstream Research Company||Compressible objects having a predetermined internal pressure combined with a drilling fluid to form a variable density drilling mud|
|US8088717||Jan 3, 2012||Exxonmobil Upstream Research Company||Compressible objects having partial foam interiors combined with a drilling fluid to form a variable density drilling mud|
|US8113291||Mar 25, 2011||Feb 14, 2012||Weatherford/Lamb, Inc.||Leak detection method for a rotating control head bearing assembly and its latch assembly using a comparator|
|US8286734||Oct 23, 2007||Oct 16, 2012||Weatherford/Lamb, Inc.||Low profile rotating control device|
|US8322432||Dec 21, 2009||Dec 4, 2012||Weatherford/Lamb, Inc.||Subsea internal riser rotating control device system and method|
|US8322439 *||Dec 4, 2012||Ocean Riser Systems As||Arrangement and method for regulating bottom hole pressures when drilling deepwater offshore wells|
|US8347982 *||Jan 8, 2013||Weatherford/Lamb, Inc.||System and method for managing heave pressure from a floating rig|
|US8347983||Jul 31, 2009||Jan 8, 2013||Weatherford/Lamb, Inc.||Drilling with a high pressure rotating control device|
|US8353337||Jan 15, 2013||Weatherford/Lamb, Inc.||Method for cooling a rotating control head|
|US8403059 *||Mar 26, 2013||Sunstone Technologies, Llc||External jet pump for dual gradient drilling|
|US8408297||Mar 15, 2011||Apr 2, 2013||Weatherford/Lamb, Inc.||Remote operation of an oilfield device|
|US8590629||Feb 16, 2009||Nov 26, 2013||Pilot Drilling Control Limited||Flow stop valve and method|
|US8636087||Jan 7, 2013||Jan 28, 2014||Weatherford/Lamb, Inc.||Rotating control system and method for providing a differential pressure|
|US8701796||Mar 15, 2013||Apr 22, 2014||Weatherford/Lamb, Inc.||System for drilling a borehole|
|US8714240||Jan 14, 2013||May 6, 2014||Weatherford/Lamb, Inc.||Method for cooling a rotating control device|
|US8752630||Oct 18, 2012||Jun 17, 2014||Pilot Drilling Control Limited||Flow stop valve|
|US8770297||Aug 29, 2012||Jul 8, 2014||Weatherford/Lamb, Inc.||Subsea internal riser rotating control head seal assembly|
|US8776887||Apr 8, 2013||Jul 15, 2014||Pilot Drilling Control Limited||Flow stop valve|
|US8776894||Jul 6, 2012||Jul 15, 2014||Halliburton Energy Services, Inc.||Offshore universal riser system|
|US8826988||Feb 6, 2009||Sep 9, 2014||Weatherford/Lamb, Inc.||Latch position indicator system and method|
|US8833488||Mar 19, 2012||Sep 16, 2014||Halliburton Energy Services, Inc.||Automatic standpipe pressure control in drilling|
|US8844652||Sep 29, 2010||Sep 30, 2014||Weatherford/Lamb, Inc.||Interlocking low profile rotating control device|
|US8863858 *||Jan 7, 2013||Oct 21, 2014||Weatherford/Lamb, Inc.||System and method for managing heave pressure from a floating rig|
|US8881831||Jul 6, 2012||Nov 11, 2014||Halliburton Energy Services, Inc.||Offshore universal riser system|
|US8887814||Nov 7, 2007||Nov 18, 2014||Halliburton Energy Services, Inc.||Offshore universal riser system|
|US8939235||Feb 24, 2014||Jan 27, 2015||Weatherford/Lamb, Inc.||Rotating control device docking station|
|US8973676||Jul 28, 2011||Mar 10, 2015||Baker Hughes Incorporated||Active equivalent circulating density control with real-time data connection|
|US9004181||Sep 15, 2012||Apr 14, 2015||Weatherford/Lamb, Inc.||Low profile rotating control device|
|US9016381 *||Mar 17, 2011||Apr 28, 2015||Hydril Usa Manufacturing Llc||Mudline managed pressure drilling and enhanced influx detection|
|US9051790||Jul 6, 2012||Jun 9, 2015||Halliburton Energy Services, Inc.||Offshore drilling method|
|US9085940||Jul 6, 2012||Jul 21, 2015||Halliburton Energy Services, Inc.||Offshore universal riser system|
|US9127511||Jul 6, 2012||Sep 8, 2015||Halliburton Energy Services, Inc.||Offshore universal riser system|
|US9127512 *||Jul 6, 2012||Sep 8, 2015||Halliburton Energy Services, Inc.||Offshore drilling method|
|US9157285 *||Jul 6, 2012||Oct 13, 2015||Halliburton Energy Services, Inc.||Offshore drilling method|
|US9175542||Jun 28, 2010||Nov 3, 2015||Weatherford/Lamb, Inc.||Lubricating seal for use with a tubular|
|US9222320||Dec 19, 2011||Dec 29, 2015||Halliburton Energy Services, Inc.||Subsea pressure control system|
|US9260927 *||Oct 17, 2014||Feb 16, 2016||Weatherford Technology Holdings, Llc||System and method for managing heave pressure from a floating rig|
|US9334711||Jan 24, 2014||May 10, 2016||Weatherford Technology Holdings, Llc||System and method for cooling a rotating control device|
|US20030062199 *||Sep 19, 2002||Apr 3, 2003||Gjedebo Jon G.||Method or drilling sub-sea oil and gas production wells|
|US20030066650 *||Jul 9, 2002||Apr 10, 2003||Baker Hughes Incorporated||Drilling system and method for controlling equivalent circulating density during drilling of wellbores|
|US20030075332 *||Oct 24, 2001||Apr 24, 2003||Krill Ross Michael||Method and apparatus for providing a stream of pressurized substantially inert gas|
|US20040031623 *||Mar 18, 2003||Feb 19, 2004||Baker Hughes Incorporated||System and method for recovering return fluid from subsea wellbores|
|US20040069504 *||Jun 23, 2003||Apr 15, 2004||Baker Hughes Incorporated||Downhole activatable annular seal assembly|
|US20040074637 *||Jul 28, 2003||Apr 22, 2004||Krill Ross Michael||Method for providing a stream of pressurized substantially inert gas|
|US20040074673 *||Jul 28, 2003||Apr 22, 2004||Krill Ross Michael||Apparatus for providing a stream of pressurized substantially inert gas|
|US20040112642 *||Sep 2, 2003||Jun 17, 2004||Baker Hughes Incorporated||Downhole cutting mill|
|US20040124008 *||Nov 17, 2003||Jul 1, 2004||Baker Hughes Incorporated||Subsea wellbore drilling system for reducing bottom hole pressure|
|US20040206548 *||Feb 20, 2004||Oct 21, 2004||Baker Hughes Incorporated||Active controlled bottomhole pressure system & method|
|US20040256161 *||Mar 25, 2004||Dec 23, 2004||Baker Hughes Incorporated||Modular design for downhole ECD-management devices and related methods|
|US20050098349 *||Sep 9, 2004||May 12, 2005||Baker Hughes Incorporated||Control systems and methods for active controlled bottomhole pressure systems|
|US20050252685 *||Jan 18, 2005||Nov 17, 2005||Baker Hughes Incorporated||Floatable drill cuttings bag and method and system for use in cuttings disposal|
|US20060065402 *||Jul 9, 2002||Mar 30, 2006||Baker Hughes Incorporated||Drilling system and method for controlling equivalent circulating density during drilling of wellbores|
|US20060124352 *||Sep 8, 2005||Jun 15, 2006||Baker Hughes Incorporated||Control systems and methods for active controlled bottomhole pressure systems|
|US20060169491 *||Mar 12, 2004||Aug 3, 2006||Ocean Riser Systems As||Method and arrangement for performing drilling operations|
|US20070007041 *||Jun 16, 2006||Jan 11, 2007||Baker Hughes Incorporated||Active controlled bottomhole pressure system and method with continuous circulation system|
|US20070119621 *||Nov 24, 2004||May 31, 2007||Agr Subsea As||Method and device for controlling drilling fluid pressure|
|US20070235223 *||Apr 26, 2006||Oct 11, 2007||Tarr Brian A||Systems and methods for managing downhole pressure|
|US20090084604 *||Oct 16, 2008||Apr 2, 2009||Polizzotti Richard S||Compressible objects having partial foam interiors combined with a drilling fluid to form a variable density drilling mud|
|US20090090558 *||Oct 16, 2008||Apr 9, 2009||Polizzotti Richard S||Compressible Objects Having A Predetermined Internal Pressure Combined With A Drilling Fluid To Form A Variable Density Drilling Mud|
|US20090090559 *||Oct 16, 2008||Apr 9, 2009||Polizzotti Richard S||Compressible objects combined with a drilling fluid to form a variable density drilling mud|
|US20090091053 *||Oct 16, 2008||Apr 9, 2009||Polizzotti Richard S||Method for fabricating compressible objects for a variable density drilling mud|
|US20090114443 *||Nov 2, 2007||May 7, 2009||Ability Group Asa||Anchored riserless mud return systems|
|US20090140444 *||Oct 8, 2008||Jun 4, 2009||Total Separation Solutions, Llc||Compressed gas system useful for producing light weight drilling fluids|
|US20090143253 *||Nov 26, 2008||Jun 4, 2009||Smith Kevin W||Drilling fluids containing microbubbles|
|US20090188721 *||Jul 30, 2009||Smith Kevin W||Membrane method of making drilling fluids containing microbubbles|
|US20090200037 *||Apr 7, 2009||Aug 13, 2009||Ocean Riser Systems As||Method and arrangement for removing soils, particles or fluids from the seabed or from great sea depths|
|US20100006297 *||Jul 31, 2007||Jan 14, 2010||Agr Subsea As||Pipe string device for conveying a fluid from a well head to a vessel|
|US20100018715 *||Nov 7, 2007||Jan 28, 2010||Halliburton Energy Services, Inc.||Offshore universal riser system|
|US20110036591 *||Feb 16, 2009||Feb 17, 2011||Pilot Drilling Control Limited||Flow stop valve|
|US20110168399 *||May 4, 2009||Jul 14, 2011||Jean Francois Saint-Marcoux||Mid water gas lift|
|US20110253445 *||Apr 16, 2010||Oct 20, 2011||Weatherford/Lamb, Inc.||System and Method for Managing Heave Pressure from a Floating Rig|
|US20110278014 *||May 12, 2010||Nov 17, 2011||William James Hughes||External Jet Pump for Dual Gradient Drilling|
|US20120067590 *||Nov 29, 2011||Mar 22, 2012||Ocean Riser Systems As||Arrangement and method for regulating bottom hole pressures when drilling deepwater offshore wells|
|US20120234550 *||Mar 17, 2011||Sep 20, 2012||Hydril Usa Manufacturing Llc||Mudline Managed Pressure Drilling and Enhanced Influx Detection|
|US20120292106 *||Nov 22, 2012||Halliburton Energy Services, Inc.||Offshore universal riser system|
|US20120292107 *||Jul 6, 2012||Nov 22, 2012||Halliburton Energy Services, Inc.||Offshore universal riser system|
|US20130118806 *||Jan 7, 2013||May 16, 2013||Weatherford/Lamb, Inc.||System and Method for Managing Heave Pressure from a Floating Rig|
|US20150034326 *||Oct 17, 2014||Feb 5, 2015||Weatherford/Lamb, Inc.||System and Method for Managing Heave Pressure from a Floating Rig|
|USRE43199 *||Sep 10, 2002||Feb 21, 2012||Ocean Rider Systems AS||Arrangement and method for regulating bottom hole pressures when drilling deepwater offshore wells|
|WO2000004269A3 *||Jul 15, 1999||Apr 20, 2000||Deep Vision Llc||Subsea wellbore drilling system for reducing bottom hole pressure|
|WO2000075477A1||Jun 1, 2000||Dec 14, 2000||Exxonmobil Upstream Research Company||Controlling pressure and detecting control problems in gas-lift riser during offshore well drilling|
|WO2001020120A1 *||Sep 6, 2000||Mar 22, 2001||Exxonmobil Upstream Research Company||Method and system for storing gas for use in offshore drilling and production operations|
|WO2001094740A1 *||Jun 8, 2001||Dec 13, 2001||Maurer Technology Incorporated||Multi-gradient drilling method and system|
|WO2002068787A2 *||Feb 20, 2002||Sep 6, 2002||Exxonmobil Upstream Research Company||Method and apparatus for controlling bottom-hole pressure during dual-gradient drilling|
|WO2002068787A3 *||Feb 20, 2002||Feb 20, 2003||Exxonmobil Upstream Res Co||Method and apparatus for controlling bottom-hole pressure during dual-gradient drilling|
|WO2006118920A2 *||Apr 27, 2006||Nov 9, 2006||Shell Internationale Research Maatschappij B.V.||Systems and methods for managing downhole pressure|
|U.S. Classification||166/359, 175/7, 175/72, 175/25|
|International Classification||E21B21/08, E21B7/12, E21B7/128, E21B21/00|
|Cooperative Classification||E21B7/128, E21B21/001, E21B21/08|
|European Classification||E21B7/128, E21B21/00A, E21B21/08|