US3341398A

US3341398A - Offshore deep drilling method from a floating platform

Info

Publication number: US3341398A
Application number: US631715A
Authority: US
Inventors: Kingsley M Nicolson
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1956-12-31
Filing date: 1956-12-31
Publication date: 1967-09-12
Anticipated expiration: 1984-09-12

Description

4 Sheets-Sheet 1 K. M. NICOLSON OFFSHORE DEEP DRILLING METHOD FROM A FLOATING PLATFORM 31. 1956 Sept. 12, 1967 Filed Dec.

Sept. 12, 1967 K. M. NICOLSON OFFSHORE DEEP DRILLING METHOD FROM A FLOATING PLATFORM 31 J 1956 4 Sheets-Sheet 2 Filed Dec.

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/ATToRNEYs INVENTOR KINGSLEV M. N/COLSON Sept. 12, 1967 OFFSHORE DEEP K. M. NICOLSON 3,341,398 DRILLING METHOD FROM A FLOATING PLATFORM Filed Dec. 31 1956 4 Sheets-Sheet 4 K/NGSLEV M. N/COLSON United States Patent 3,341,398 OFFSHORE DEEP DRILLING METHOD FROM A FLOATING PLATFORM Kingsley M. Nicolson, Fullerton, Califi, assignor, by

mesne assignments, to Chevron Research Company, a

corporation of Delaware Filed Dec. 31, 1956, Ser. No. 631,715 3 Claims. (Cl. 175-7) The present invention relates to a method of drilling from a fully floating platform. More particularly, the invention relates to a method of drilling a vertical well bore into the underwater bottom whether or not the bottom is steeply dipping from a fully floating platform.

It is a particular object of this invention to provide a method of drilling a vertical well bore into an underwater bottom from a fully floating vessel without requiring a template or other guiding means for spudding in the well bore by suspending a drill string from the deck of a fully floating vessel with a substantial portion thereof held in tension when the lower end thereof including a drill bit and a weighted portion of said drill string touches bottom. Then, with only the weighted portion of the drill string exerting thrust on the drill bit the drill string is rotated from the working deck of the vessel. The borehole is spudded in vertically by drilling ahead with the drill bit until a consolidated rock bed or other competent formation is drilled into. Then, at least one conductor pipe is cemented in the borehole before the drill string is disconnected from the borehole.

Another object of the present invention is to provide a method for drilling into an underwater bottom from a fully floating platform without danger of contaminating the body of water with oil or gas encountered in the well bore by establishing pressure control over the borehole with a well head on bottom before the borehole penetrates potential reservoir formations. In carrying out the method, such well head is set on bottom with all work performed on the working deck of the floating vessel by maintaining continuous engagement between the underwater bottom and the floating vessel after the drill string has been first spudded without templates or other means for guiding the bit into the bottom. In said preferred method of carrying out the invention, an assembled conductor pipe is lowered into the vertical borehole formed in the underwater bottom by the drill bit, but penetration thereinto is limited by assembling a landing flange to the upper end of said pipe before it is lowered. The conductor pipe is then cemented in position through a drill string extending from the deck of the floating vessel into the borehole; said cementing being performed after a guide assembly is lowered on at least a pair of guide cables so that it slides down along the drilling string extending downward from the working deck into the borehole. The guide assembly is latched to the conductor pipe above said landing flange. Following cementing of the conductor pipe and securing of the guide cable assembly to said conductor pipe, the interconnection between the drill string and the floating vessel is broken and the guide cables slacked to permit cement around said conductor pipe to set without vertical force being applied to it through the vessel moving under wind and tide action. Pressure control equipment, including at least one blow out preventer assembly is then lowered along the guide cables after they are again drawn taut between the well head and the floating vessel. Said pressure control equipment is desirably coupled to the top of the conductor pipe by a safety joint or other quick-connect joint that requires less than one full rotation of the pressure control means, guide lines or said conductor pipe.

In the drilling of well bores to explore for oil, gas and the like through deep waters, it is necessary either to 3,341,398 Patented Sept. 12, 1967 build a platform extending from the ocean bottom to a level well above the water surface or to drill from a floating platform. It is of course uneconomical to build large fixed platforms unless there is a high probability of finding oil. Accordingly, it is desirable to be able to drill a well bore from a mobile platform such as a floating platform. The greater mobility of a fully floating platform makes this type of drilling more attractive than platforms that have a floating foundation partly submerged by vertical anchors. While such restrained floating platforms provide easier drilling conditions, the cost of vertical anchors makes their use economically unattractive.

While in general it has been proposed to anchor a vessel over a drilling site and then drill into the underwater bottom with conventional rotary equipment, such underwater bottoms are seldom level and hard so that adequate pressure control equipment can be set directly on bottom. The function of such pressure control equipment is to maintain hydrostatic pressure in the well bore that will always be greater than that of any gas or oil encountered therein. Loss of such pressure control is known as a blow out. The problem of blow outs is of course a serious one from the standpoint of explosion and fire hazards in land operations. It is even more serious in offshore operations, such as those along the California coast, where any release of oil or gas could contaminate the ocean so that marine life is destroyed and the adjacent resort beaches ruined. Accordingly, it is considered imperative that adequate and complete Well head control equipment be established before drilling is permitted in an underwater bottom where contamination of the water is possible.

It has been suggested heretofore that well head controls be located on the working deck of the drilling vessel to give easy access for maintenance and to assure its recovery when drilling is completed. In this system, a conductor pipe runs from the well bore up to the control equipment located on the deck of the surface vessel. This of course requires that the conductor pipe be flexible enough to permit lateral and vertical movement of the surface vessel while drilling. One serious problem in using pressure controls at the deck is that the wind and tide forces on the vessel can put an undue strain on the conductor pipe. Such strain, of course, makes the conductor pipe more susceptible to damage that can result in complete loss of well head control. For these reasons, it is desirable to position the well head control equipment on the bottom. However, the pressure control equipment is quite expensive and therefore it is desirable that it be possible to retrieve it after the well is drilled.

While it has been suggested heretofore that well head control equipment be placed on bottom, the method of initiating, or spudding-in the borehole, landing of conductor pipe and control equipment, as well as retrieving this equipment as practiced heretofore frequently required the aid of a human diver, or other auxiliary equipment not forming part of the normal drilling equipment. The cost of diver service, in addition to rig time (i.e., rental charges on drilling equipment, drill crew wages, etc.), makes these operations unusually expensive. In general, the cost of a diver service alone may run as high as $800 to $1,000 per day. Additionally, the time that a diver can operate, even in shallow water, is greatly limited by human, physical endurance. In deep waters, it is not feasible to use a diver even if one is required. Additionally, in water bottoms having a thick bed of unconsolidated sediments, diver service cannot be used Without difficulty.

For the foregoing reasons, it is necessary and desirable that there be provided a system for drilling a vertical borehole into an underwater bottom irrespective of its slope or hardness and to a depth so that a conductor pipe can be set and cemented in a competent formation with at least an upper portion thereof extending above bottom to receive well head or pressure control equipment. (In this sense, competent means an earth formation, such as a consolidated shale bed, having sufficient compaction to give it strength and being impermeable so that the pipe can be bonded to it with cement.)

In accordance with a preferred method of carrying out the present invention, a drill bit is assembled on the lower end of a conductor pipe or surface pipe having a predetermined weight. The drill bit and conductor pipe are then connected to a drill string through a verticallyreciprocable connection; said drill string in turn is rotated by a gimbaled rotary table positioned below a supporting drill derrick mounted on the working deck of the fully floating platform. The vertically-movable connection permits the entire string to hang freely as a pendulum below the vessel so that even in deep waters only the predetermined weight of the conductor pipe is imposed on the drill bit when the bit first touches bottom. Then without further guiding thereof, the drill bit is rotated with only said predetermined weight thereon and with a substantial portion of the drill string in tension during spuddingin. By such rotation and holding said drill string in tension above the weighted section the bit and drill string is maintained vertical even on very steeply dipping bottoms. Drilling then continues until the borehole is deep enough to receive the full length of the conductor pipe. A landing flange otherwise serving as a feeler for bottom indicates when the conductor pipe has been drilled deep enough into the bottom. Desirably, this depth is preselected so the conductor pipe will be sufficiently long to assure its penetration into a competent formation. After the landing flange has engaged bottom with the conductor pipe attached thereto and extending into the borehole, cement is supplied to the annular space between the conductor pipe and the borehole while connection between the drill string and borehole is maintained. Desirably, this is done without removal of the drill string from the well bore. Alternatively, the conductor or surface pipe may be cemented in the borehole using a cement string guided into the landed conductor pipe through a guide assembly lowered on at least a pair of cables along the drill string while said drill string is still in the well bore. In either method of cementing, said guide assembly is lowered to slide down along the drill string while said string is still in the borehole and to establish a continuity of connection between the deck of the drilling vessel and the conductor pipe in the borehole before cement is injected. This continuity of interconnection between vessel and borehole just prior to the cementing operation is particularly essential to eliminate human diver service.

When the guide assembly, which desirably includes an enlarged funnel used to guide well head pressure control equipment into engagement with the conductor pipe, has been landed and interconnected, the drill string is disconnected from the borehole immediately above the landing flange. Then, the guide cables are released so that cement between the conductor pipe and the borehole may set without danger of the conductor pipe being pulled up by the cables due to action of wave and tide forces on the drilling vessel. Said conductor pipe not only serves to prevent slufling of the underwater sediments into the well bore, but also provides a firm vertical anchor for blow out prevention equipment connected thereto as drilling proceeds below the cemented section of the conductor pipe down into potential oil and gas-bearing formations.

After said conductor pipe has been cemented in the borehole in accordance with the invention, drilling proceeds to a greater depth through blow out prevention equipment, and other well head control equipment, coupled directly to the conductor pipe. Such well head equipment is assembled to the conductorpipe by again tightening the guide cables and lowering it along them. Final assembly of said well head equipment to the conductor pipe is desirably made through a quick-connect joint, otherwise known as a safety joint, which permits a fluidtight connection without requiring rotation of the guide cables, blow out preventer, drilling head or other equipment that guidably slides down along the cables. In particular, this equipment is not rotated so that thecontrol hydraulic lines and the drilling fluid return lines will not become twisted during assembly. Thus, the hydraulic control means for remotely operating the well head equipment from the vessels deck can be connected prior to lowering of said equipment along the guide cables. At the same time, said guide cables are held nearly straight and vertical between the borehole and the drilling vessel. After assembly of said well head equipment and the drilling head, drilling proceeds by guiding a drill bit and the drill string along the guide cables and into the drilling head assembly and the borehole.

The drilling operation then proceeds under full pressure control of the well bore. This, of course, includes the use of drilling fluid that returns to the working deck through a mud return line connected to the borehole at a point intermediate the blow out prevention equipment and the drilling head. Upon completion of drilling, it is desirable to abandon said borehole, but prevent any possible seepage or other escape of oil or gas by setting a cement plug in the well bore of sufficient length to bond both to the uncased portion of the borehole and at least part of the cased section of the borehole. Such abandonment will of course occur where it is decided that production cannot be established, or for other reasons, it is not desired to complete a producing well through this particular borehole. After cement has been spotted in the hole, the well head control equipment is disconnected through said safety joint, or other quick-connect joint, and then lifted by a drill string to the work deck of the drilling vessel. The guide cable assembly, then in turn, is retrieved either by increasing tension on said guide cables to sever a breakable link between the cemented conductor pipe or landing flange and the guide assembly, or by interconnecting said guide assembly with a portion of a drill string to lift the guide assembly and sever the breakable link to the cemented conductor pipe.

In accordance with another method of carrying out the present invention, the conductor pipe is drilled into the underwater bottom by a concentric drill string including a plurality of drill collars directly above the bit but below the section of drill string held in tension from the work deck so that the desired load is applied to the bit when it touches bottom. In accordance with the invention, no other guiding means is used to start said well bore in the bottom. The conductor pipe then is lowered directly behind said drill string, which opens a pilot hole and then underreams it to expand the hole to a diameter large enough to let the conductor pipe pass into the borehole. The landing flange assembled to said pipe limits its depth of penetration; in this method the landing flange and guide assembly are assembled to the conductor pipe and the complete unit is lowered from the deck on the guide cables while said drill string is still in the well bore maintaining continuity of connection between the borehole and the deck.

Further objects and advantages of the present invention, both in the method of its application to drill a vertical hole into bottom without templates or other guiding means while drilling from a floating vessel and the method of remotely establishing said well head control on bottom from the working deck of a drilling vessel will become apparent from the following detailed description of the method and its mode of operation as illustrated by the various forms of apparatus shown in the accompanying drawings which form an integral part of the present specification.

FIG. 1 is a schematic elevation view of one form of apparatus for drilling into an underwater bottom from a fully floating vessel in accordance with the method of the present invention;

FIG. 2 is a vertical section of the lower end of the drill string illustrated in FIG. 1 after the landing flange has been seated on bottom and cementing of the conductor pipe has begun;

FIG. 3 illustrates the lower end of a conductor pipe, including a drill bit attached thereto, at the completion of cementing between the well bore and the conductor p p FIG. 4 is a vertical view, partly in section, illustrating the positioning of the guide assembly after it slides down the drill string and engages the conductor pipe in the borehole with the drill string still connected to the well bore;

FIG. 5 is a vertical view of the underwater Well head or pressure control equipment being lowered along the guide cabels to engage the safety joint that couples the conductor pipe to said well head equipment;

FIG. 6 illustrates an alternative method for opening a borehole into the underwater bottom with an independent drill string wherein the conductor pipe and guide assembly are preassembled concentric with said drill string for lowering therealong into the borehole as a unit and said unit is held suspended below the drilling vessel on guide cables that lower it to bottom;

FIG. 7 illustrates setting of another surface pipe to be cemented within the conductor pipe in the method illustrated in FIG. 6;

FIG. 8 illustrates a preferred method of severing the upper end of surface pipe as seen in FIGS. 6 and 7 to permit recovery of the complete safety joint with the well head control equipment when the well bore is to be abandoned.

Referring now to the drawings and in particular FIG. 1, there is illustrated a method of drilling a vertical well bore into an underwater bottom that may be steeply dipping from a fully floating vessel 10. As a first step, vessel 10 is suitably positioned and anchored over the drill site as indicated schematically by anchor lines 11. After the vessel has been positioned on the drill site, there is suspended through a central well 12 formed in vessel 10 a drill string 14 that includes an assembled section of conductor pipe 13. In the arrangement of FIG. 1, conductor pipe 13 is to be cemented in hole 15, but is an integral part of drill string 14 that also includes drill bit 17, safety joint 19 and an upwardly extending, reduced diameter section 21. Conductor pipe 13 is assembled to a predetermined length depending on the depth of the unconsolidated sediments, identified generally as 23, and the depth needed to be drilled before a competent formation is found in the solid rock 25. Conductor pipe 13 is likewise selected to have a predetermined weight that will act as the only weight on bit 17 when the bit first touches bottom and irrespective of the depth of water between the vessel and bottom. In open water, vessel 10 will be subjected to periodic rise and fall, as well as pitching and rolling, due to wave and tide action. For this reason, drill pipe 14 includes as an integral part thereof, a splined or sliding sleeve connection 43 that assures that the bit will rest on bottom with only the desired load thereon. In the arrangement of FIG. 1, drill string 14, including conductor pipe 13, is then supported by vessel 10 through a conventional derrick .27 that includes book 29, travelling block 31, cable 33 and draw works 35. In drilling, it is to be noted that templates, pipes or other guide means are not required in accordance with the invention to start and drill borehole 15 vertically into a clipping bottom where the upper end 21 of drill string 14 is held in tension so that the entire string hangs as a compound pendulum below rotary table 3-9. Drill bit 17 is rotated on bottom by rotary table 39 driven by any suitable power source such as motor 41. Preferably, motor 41 is a rotary hydraulic motor so that the motor can be driven through flexible hydraulic lines with the motor supported on the 6 gimbaled bearings of rotary table 39.. Rotary table 39 is so mounted to permit it to remain level when the vessel pitches and rolls.

For the purpose of indicating the condition when conductor pipe 13 has been drilled to the desired depth, and to limit its penetration, a landing flange 45, formed as either a four-armed spider, or as a relatively flat plate of somewhat enlarged diameter, is clamped to the top end of conductor pipe 13. Thus, when conductor pipe 13 has been drilled to the desired depth, the driller Will immediately be notified by an increase in torque at the rotary table and/ or by a decrease in the weight supported by derrick 27 due to part of the weight of upper section 21 of drill string 14 being supported on flange 45. The drilling of the conductor pipe is desirably accomplished by using sea water as a drilling fluid. In the present arrangement this is illustrated by intake pipe 47 being interconnected to a pump 49 and to drill pipe 14 through hose 51 and swivel 53. During drilling in with sea water, there is of course no return of the cuttings to vessel 10.

In the arrangement shown in FIGS. 1 to 3, drill bit 17 has an enlarged diameter and includes a core wiper arm 54 in the center of the bit that keeps the hole open through the center of conductor pipe 13.

When the conductor pipe has been drilled to sufiicient depth to enter a competent formation, landing flange 45 touches bottom as seen in FIG. 2. The hole is then conditioned by continued circulation of sea water so that the hole is flushed of debris. After conditioning of the hole, cement is supplied by switching connections of valve 57 to pump cement from the mixing tank 59 through mud pump 49 and into drill pipe 14 through swivel 53 (FIG. 1). As best seen in FIG. 2, cement is cleared from conductor pipe 13 by dropping a ball 61 through a side-opening port or kelly cock 63 connected directly below swivel 53. When ball 61 seats on the top of cement chaser 65, pump pressure, as indicated by meter 50, will be increased to release chaser 65 from its seat in coupling 67 in the drill string lying directly above safety joint 19. Cement chaser 65 then cleans cement from the lower end of the conductor pipe as shown in FIG. 3. Core wiper 54 stops the downward travel of cement chaser 65 and prevents back flow of cement 69 from well bore 15 into conductor pipe 13. Desirably, enough cement is used so that substantially the entire length of conductor pipe 13 is cemented in the hole, but not enough is used so that cement balls up over the top of landing flange 45.

Immediately after the conductor pipe has been set in cement, a guide assembly, identified generally as 71, is lowered on a pair of guide cables identified as 73. As seen in FIG. 1, guide assembly 71, initially hangs in the well 12 of vessel 10 below the rotary table. Guide assembly 71 includes a tubular member or bucket element 75 that gives the assembly substantial weight. The assembly is free to slide down along drill pipe 21 and over the outer portion of safety joint 19 when the guide lines are slacked from cable drums 76 on the vessel. When landed adjacent to, or on top of, landing flange 45, as in FIGS. 4 and 5, bucket member 75 is latched to the lower or stationary portion 77 of safety joint 19 by a pair of latch members 78 that engage groove 72 in lower member 77. Alternatively, bucket or weight member 75 may latch directly to conductor pipe 13 or to landing flange 45 if so desired. The function of latches 78 is to connect guide assembly 71 to the upper end of conductor pipe 13 by sheerable links, such as pins 80. Pins 80 are breakable .by an upward pull on bucket 75 of a predetermined magnitude that rotates latches 78 about pivot pins 82. The respective pins 82 pass through corresponding elongated openings formed through the pivoted end portions of the latch members 78. These openings are disposed to permit the latches to slide on the pins toward and away from the latching position as well as to pivot around the pins. A respective spring biases each latch to its latching position. Thus when the bucket member 75 is lowered over the portion 77 of the safety joint the radially disposed projections on the latter displaces the latch members outwardly to permit the bucket assembly to clear such projections until the latch members are in alignment with the groove 72. When the bucket assembly reaches this position the biasing springs force the ends of the latch members into engagement with the groove. The groove-engaging end portion of the latch members are notched to form a surface complementary to that of the upper radially disposed surface of the groove. This provides a secure engagement between the groove and the latches and prevents the latch members from being displaced radially by normal working stresses, as indicated in FIG. 5. As shown in FIGS. 4 and 5, guide assembly 71 has a pair of arms 79 that extend radially outward from the center line of the borehole to anchor the lower ends of guide cables 73.

As best seen in FIG. 1, guide cables 73 are normally maintained taut between bottom and floating vessel 10 by a weight 81 hung on sheave assembly 83 below cable drum 76. After bucket 75 of guide assembly 71 has been latched to conductor pipe 13 and the cement is set, the upper portion or barrel section 85 of safety joint 19 is disconnected so that upper section 21 of drill pipe 14 can be raised and racked on the drill deck, ready for further drilling through the lower end of the cemented casing 13.

At this time, in accordance with the present invention, guide cables 73 are slacked off so that conductor pipe 13 is left standing free in the well bore and supported on flange 45 while the cement sets. Thus, cement 69 is not worked by the conductor pipe or pulled up by the guide cables while it sets.

After cement 69 has set, conductor pipe 13 is securely anchored in a competent formation along the well bore. Drilling then proceeds through the conductor pipe by drilling up ball 61 and the part of the cement at the bottom of the borehole. In accordance with the method illustrated by apparatus shown in FIGS. 1 to inclusive, the well head or pressure control equipment is coupled directly to conductor pipe 13 through safety joint 19 heretofore forming part of the drilling string. In said method, as illustrated in FIG. 4, the barrel 85 and locking sleeve 86 of safety joint 19 are assembled below a well head assembly, identified generally as 87. While the well head or pressure control assembly will vary in accordance with the pressure conditions that are expected to be met in drilling ahead, in the present arrangement it comprises a pair of gate-type blow out preventers (hereinafter called BOPs) 89 and 91 assembled in series to the upper end of safety joint barrel 85. In a preferred form of apparatus for carrying out the invention, lower BOP 89 includes a pair of shearing rams constructed in accordance with my application Ser. No. 556,685, filed Dec. 30, 1955, now Patent No. 2,919,111. As disclosed in said application, the opposite sides of the pipe-engaging rams that normally encircle a section of drill pipe, similar to those in BOP 91, as seen in FIG. 5, are provided with shearing bars that override one another. The purpose of these shearing rams is to provide a system, such that if storm or other hazardous operating conditions require, the drill pipe in the borehole can be cut off at the well head without requiring each section of the entire stiring to be raised, uncoupled and racked before the hole can be abandoned. Such action is of course drastic in that the entire length of drill pipe would need to be recovered if the hole is to be used again; such apparatus provides a method for leaving the hole, but at the same time maintains full control of well pressures while abandoning the borehole under emergency conditions.

Upper blow out preventer 91 is of conventional design and may either completely close off the well bore, or grasp the sides of the drill pipe when the opposite rams 90 and 92 are actuated through hydraulic lines 93. Similar hydraulic lines 94 permit control of BOP 89 from the deck of vessel 10.

Immediately below blow out preventer 89, there is provided a mud fill-up line connection identified generally as 95. A valve 97, hydraulically operable through line 96 permits drilling fluid to be added under pressure to the well bore when drill pipe is out of the borehole. For additional safety in the operation of well head assembly 87, there is included another pressure controlled full hole blow out preventer 99 connected directly to and above BOP 91. BOP 99 is operable through lines 100. By this arrangement of

BOPs

99, 89 and 91, it is possible to hold control of the well even if control of one of said BOPs is lost by accident.

Above BOP 99, there is positioned a drilling head 101 whose function is to maintain an hydraulic seal around the rotating drill pipe; said drill pipe not only rotates but also reciprocates therein due to rise and fall of vessel 10 due to waves. Drilling head 101 likewise places a back pressure on drilling fluid returning from the borehole around the outside of drill pipe 21 and forces said drilling fluid to flow back to the deck of vessel 10 by way of mud return line 103. Control of the back pressure on drilling fluid returns is by a packing locked by hydraulic pressure applied through line 104. The returned drilling fluid of course contains the cuttings from the formation being drilled. These can be tested by conventional gas and chip analysis methods. As indicated, return mud line 103 is connected through a side-opening flange member 105 positioned directly below drilling head 101.

As indicated above, various combinations of blow out prevention equipment, either of the full hole, or drill pipe engaging types may be assembled between the top of the cemented conductor pipe and the drilling head. However, desirably this entire assembly is made on the deck of vessel 10 or in the well 12 through the vessel and then lowered on a section of drill pipe 21A, as shown in FIG. 5. In positioning this equipment through center well 12 of the drilling vessel an upper and lower pair of guide arms, indicated as 107 and 109 respectively, slidably engage the pair of guide cables 73. A spearing section of drill pipe 21A, preferably having a bull nose portion 111, extends downwardly through the entire well head assembly 87 and below safety joint barrel 85. In lowering assembly 87, rams 90 and 92 of upper BOP 91 are closed around a recessed collar portion 102 positioned a fixed distance above bull nose 111.

As indicated schematically in FIG. 5, bull nose 111 is guided along cables 73 by

guide arms

107, 109 so that even with ship 10 rising and falling in the water, the well head assembly and in particular barrel 35 of safety joint 19 is guided over mandrel 77 of safety joint 19 by funnel 113 above bucket member 75. For this purpose, a funnel arrangement 113 has a suitably enlarged diameter that is formed as an integral part of guide assembly 71. Thus, with guide cables 73 again drawn taut, well head assembly 87 slides down said guide cables while lowered by derrick 27. Through the latching of barrel to mandrel 77 of safety joint, or quick connect unit, 19 a positive connection is made between the well head assembly and the conductor pipe.

As suggested by FIG. 5, each of the

control hoses

93, 94, 95, 96, 100, 103 and 104 is connected to the well head assembly before it is lowered to engage the conductor pipe. Preferably, this is also accomplished on deck, al though it can be performed directly below the surface of the water as in well 12 in vessel 10. These control lines preferably pass over the side of the vessel 10 and are wound on a reel assembly. In their assembly, the entire bundle is passed over the side and the lower end fished up through center well 12 of vessel 10. Thus, the outer ends of each of the hoses may be attached while the assembly is in the well or on the working deck and above water; then, the entire assembly is lowered along guide cable '73.

Drilling now may proceed to any desired depth with full pressure control over the well bore and with the well head located on the ocean bottom so that if required, for

safety of vessel or personnel, the well can be abandoned temporarily without loss of pressure control in the well. In such abandonment procedure, the hoses can be severed and the guide line 73 dropped with only buoys to mark their location at the ocean surface, and if need be, the drill pipe can be severed in the hole without danger of contaminating the ocean Waters or the adjacent beaches.

As best indicated in FIG. 5, after the well head is assembled, the drill bit is assisted in entering and leaving the well head assembly by another funnel member 117 that is directly connected to upper guide arm 107. Funnel 117 and guide arm 107 are secured directly to drilling head 101. Additionally, the bit is guided by a collar arrangement, otherwise called a bit guide, that surrounds the drill pipe directly above the bit; said bit guide includes a pair of arms that engage and slide down along the guide cables to assist the bit in entering the drilling head.

There is illustrated in FIG. 6 another method of establishing well pressure control after drilling into the underwater bottom by the method of the present invention. In this embodiment, a hole opener bit arrangement, identified generally as 121, including a pilot bit 123 first touches and penetrates the bottom to open a relatively small hole.

Pilot bit 123 is then followed by an underreamer bit 125. In this system of drilling in, a desired length of conductor pipe or casing 127 is supported below the ships center well 12 and is assembled to a landing flange assembly 129 and guide assembly 131, so that entire assembly can be hung on guide cables 73 by arms 133. As shown in FIG. 6, the guide assembly 131 is secured by links 135 directly to landing flange assembly 129, rather than to the conductor pipe, but in the present case flange assembly 129 is welded to conductor pipe 127. The conductor pipe 127, landing flange assembly 129, and guide assembly 131 are all assembled below the rotary table prior to spudding in of the well, and as shown drill string 122 is lowered through conductor pipe 127.

After the borehole has been opened and underreamed to a sufiicient assembled length of conductor pipe 127, said conductor pipe and guide assembly 131 are lowered along the drill string in the same manneras guide assembly 71 is lowered along drill string 21 in the arrangementof FIGS. 1, 4 and 5. With the conductor pipe set in the well bore and guide assembly 131 connected to the vessel through cables 73, drill string 122 can be withdrawn to substitute a cement shoe for bit 121. However, if desired said drill string can include a cement shoe so that the drill need not be re- .moved from the borehole to cement conductor pipe 127 in the borehole. The conductor pipe is cemented in the .well bore in much the same manner as illustrated in FIG. 2. Where a cement tool is used, it is guided into the conductor pipe by a bit guide sliding down the guide cables 73 and into the borehole by funnel is of course added to fill the annular space between the side of the well bore and the conductor pipe. Desirably, only enough cement is added at this stage so that the cement does not rise to the top of the conductor pipe as shown in FIG. 7. As will be explained later in connection with FIG. 7, this permits ports 141 in landing flange 129 to act as cement openings when another pipe or liner 143 is cemented within conductor pipe 127.

In accordance with the method disclosed in the arrangement of FIGS. 6, 7 and 8, the well bore is drilled to a greater depth before setting of blow out preventers or other well head control means. Such an operation is usu ally undertaken when a knowledge of the geology of the underwater bottom indicates that gas and oil under pressure will not be encountered during the first few hundred feet of drilling. Accordingly, drilling can proceed through through the bottom of cemented conductor pipe 127, after that pipe is set to prevent debris or unconsolidated sediments from sloughing into the boreholerIn practice, the

depth and diameter to receive the pre- 137. Sufficient cement end of surface pipe conductor pipe will be set to a depth of about 50 to 75 feet, the depth of surface casing 143 may be of the order of 300 feet, and usually is deep enough so that a competent formation, such as a thick bed of impervious shale or other non-porous rock is encountered by the borehole. By going deeper into the earth before cementing surface casing 143, a much greater depth and higher pressures can be withstood by the pressure control equipment without danger of high pressure oil and gas accumulations blowing out.

There is illustrated in FIG. 7 a preferred method of assembling the blow out prevention equipment, as well as the preferred method of cementing the surface easing into the deepened well bore. As there shown, surface casing 143 extends downwardly to about 300 feet and is run into the well through conductor pipe 127. The upper 143 preferably includes a cement sleeve 145 that extends axially along the upper end of surface casing 143. Sleeve 145 is tapered at its lower end 147 so that it can be sealed by welding to the outer surface of the surface casing. The upper end of sleeve 145 frictionally engages coupling 149 on the mandrel 277 of a safety joint 219. The purpose of cement sleeve 147, as best seen in FIG. 7 is to permit the upper end of surface casing 143. Sleeve 145' is tapered at its lower 127, but to leave an annular space 159 that will not be filled with cement.

As further distinguished from the arrangement of FIGS. 4 and 5, a conically tapered portion of mandrel 277 of safety joint 2.19 seats within a conical section 157 of landing flange 129 that serves as a tubing hanger for surface casing 143. In this way, casing 143 is supported throughout its length until it is cemented into the well bore as illustrated in FIG. 7. In the present embodiment, surface pipe 143 is hung in the well bore on safety joint 219 so that the drill string thereabove can be disconnected after cement has been set through cement shoe 151 at the lower end of pipe 143. Pipe 143 is guided into the hole by bit guide 221 that will pass the barrel of safety joint 219 to let it rest above guide arms 133 of guide assembly 131. The upper end of mandrel 277 is sealed against cement by O-rings 161.

Deep drilling is then possible under full pressure control by landing well head equipment, identical to that of FIG. 5, on safety joint 219. This couples the blow out preventers and the drilling head to axially cemented section of surface casing 143. After the desired depth is drilled, it may be desirable to abandon the well bore. When it is desired to leave the well, the surface casing will normally be left in the well bore with cement spotted therein to prevent any possible blow out from the borehole. Then, the entire assembly of Well head equipment is recovered by severing the upper portion of surface casing 143 opposite annular section 159 between cement sleeve 145 and the casing. FIG. 8 represents a preferred manner of severing casing 143 with a shaped explosive charge. The tubing can also be cut by a milling cutter run into the casing. Upon severance of the upper end of casing 143, the complete safety joint 219 and the well head equipment secured thereto can be withdrawn from within flange 129. After release of the well head equipment, the guide assembly 131 can also be recovered in much the same manner as that illustrated in FIGS. 4 and 5. That is, the lines or cables 73 can be tightened to sever pins 163 that hold links 135 to flange 129. Desirably, guide assembly 131 is pulled free from landing flange 129 by a special tool run into guide assembly 131 on a drill string. As indicated in FIG. 8, weight or bucket element 165 of the guide assembly has a pair of diametrically op- 'posed J-slots 167 formed in its upper, inner surface. Slots 167 can be engaged by the lifting tool so that the drill derrick hoist can apply the necessary force to shear pins 163. In this way, only the cemented casing and landing flange 129 are left on bottom.

Where only a single pipe is cemented in the well bore, as in the apparatus shown in FIGS. 1 to 5, the conductor pipe also desirably has a cement sleeve surrounding its upper end. This is best seen in FIG. 5, where the details of the connection between safety joint 19 and conductor pipe 13 are shown in vertical section. In this arrangement sleeve 88 is welded to conductor 13 at its lower end and slips over the lower coupling end of mandrel 77 of safety joint 19. In this embodiment, severance of conductor 19 within the cement sleeve allows recovery of landing plate 45 as well as safety joint 19.

In the foregoing detailed description of two forms of apparatus for carrying out the method of the present invention, it will be apparent that various modifications and changes can be made in both said method and the apparatus without departing from the present invention. Accordingly, all such modifications and changes falling with in the scope of the appended claims are intended to be included therein.

I claim:

1. The method of drilling and working in a well bore in an underwater bottom from a floating vessel which comprises positioning said vessel over an underwater drilling site, suspending an assembled conductor pipe of a predetermined length from said vessel and above the underwater bottom, connecting a landing flange to the upper end of said conductor pipe, assembling in axial alignment with and as an integral part of said conductor pipe and landing flange assembly a tubular guide assembly having aflixed thereto at least a pair of guide cables, inserting a drill string with a radially expandable and contractible drill bit attached to the lower end thereof axially through said conductor pipe from said vessel and into contact with said underwater bottom, radially expanding said drill bit to a diameter greater than that of said conductor pipe and rotating said drill string by means on said vessel while lowering said drill string from said vessel to drill into said underwater bottom a bore hole having a diameter and depth to permit said conductor pipe to be received therein to permit said landing flange to seat on said underwater bottom, lowering said conductor pipe, said landing flange and said guide assembly from said vessel along said drill string and guiding said conductor pipe into said bore hole with said drill string to position said landing flange on said underwater bottom, radially contracting said drill bit to a diameter smaller than that of said conductor pipe and retracting said drill string and said drill bit from said conductor pipe while maintaining a flexible connection between said conductor pipe and said vessel with said guide cables, lowering from said vessel along said guide cables and to said tubular guide assembly a string of cement tubing having a guide member attached thereto and cooperating with said guide cables, guiding the lower end of said string of cement tubing into said conductor pipe by said guide cables and said tubular guide assembly, introducing cement from said vessel through said string of cement tubing into said bore hole and cementing said conductor pipe in said bore hole, retracting said string of cement tubing from said conductor pipe and slacking said guide ca'bles while said cement sets.

2,. The method of drilling and working in a submerged well from a floating vessel which comprises anchoring a floating drilling vessel above a submerged well site on an underwater bottom, suspending a drill string from a working platform of said vessel, said drill string including a radially expandable and contractible drill bit aflixed to the lower end thereof and rotatable by power transmitted thereto by said drill string, assembling a conductor pipe concentric with said drill string, securing a half part ofan automatically engaging connector to and concentric with the upper end of said conductor pipe, suspending said conductor pipe from said working platform on at least a pair of cables so that the lower end of said conductor pipe is above the underwater bottom to be drilled into by said drill bit, lowering said drill string into contact with said underwater bottom, radially expanding'said drill bit to a diameter greater than that of said conductor pipe and rotating said drill bit while lowering said drill string from said working platform to drill a bore hole into said underwater bottom of a diameter and to a depth to permit said conductor pipe to be inserted therein with the upper end of said conductor pipe 'held adjacent said underwater bottom by a landing flange secured thereto and contacting the said underwater bottom, lowering said concentric conductor pipe along said drill string by means of said cables and guiding the lower end of said conductor pipe into said bore hole with said drill string, lowering said conductor pipe into said bore hole by means of said cables to land said landing flange on said underwater bottom, introducing cement into said bore hole through said drill string and forcing said cement between the outer wall of said conductor pipe and the wall of said bore hole, radially contracting said drill bit to a diameter smaller than that of said conductor pipe and withdrawing said drill bit and drill string from said conductor pipe, slacking said cables while said cement sets, retightening said cables and lowering from said working platform blowout prevention equipment adapted to receive a drill string in fluid-tight slidable relationship and having the other half part of said automatically engaging connector secured to and extending from the bottom thereof and having a guide member attached thereto and co-operating with said cables along said cables and into contact with the upper portion of said conductor pipe, afiixing said blowout prevention equipment to the upper portion of said conductor pipe by said automatically engaging connector to provide a seal between the upper end of said conductor pipe and a drill string passing through said blowout prevention equipment.

3. The method of drilling and working in a submerged well from a floating vessel which comprises anchoring a floating drilling vessel above a submerged well site on an underwater bottom, suspending a drill string from a working deck of said vessel, said drill string including a radially expandable and contractible drill bit afiixed to the lower end thereof and rotatable by power transmitted thereto by said drill string, assembling a conductor pipe concentric with said drill string, securing a half part of an automatically engaging connector to and concentric with the upper end of said conductor pipe, suspending said conductor pipe from said working deck on at least a pair of cables so that the lower end of said conductor pipe is above the underwater bottom to be drilled into by said drill bit, lowering said drill string into contact with said underwater bottom, radially expanding said drill bit to a diameter greater than that of said conductor pipe and rotating said drill bit while lowering said drill string from said working deck to drill a bore hole into said under-water bottom of a diameter and to a depth to permit said conductor pipe to be inserted therein with the upper end of said conductor pipe held adjacent said underwater bottom by a landing flange secured thereto and contacting the said underwater bottom, lowering said concentric conductor pipe along said drill string by means of said cables and guiding the lower end of said conductor pipe into said bore hole with said drill string, lowering said conductor pipe into said bore hole by means of said cables to land said landing flange on said underwater bottom, radially contracting said drill bit to a diameter smaller than that of said conductor pipe and withdrawing said drill bit and drill string from said conductor pipe, lowering from said working deck along said guide cables and to said upper end of said conductor pipe a string of cement tubing having a guide member attached thereto and co-operating with said cables, guiding the lower end of said string of cement tubing into said conductor pipe by said guide cables, introducing cement from said working deck through said string of cement tubing and cementing said conductor pipe in said bore hole, retracting said string of cement tubing from said conductor pipe and slacking said cables while said cement sets, retightening said cables and lowering from said working deck blowout prevention equipment adapted to receive a drill string in fluid-tight slidable relationship and having the other half part of said automatically engaging connector secured to and extending from the bottom thereof and having a guide member attached thereto and co-operating with said cables along said cables and into contact With the upper portion of said conductor pipe, aflixing said blowout prevention equipment to the upper portion of said conductor pipe by said automatically engaging connector to provide a seal between the upper end of said conductor pipe and a drill string passing through said blowout prevention equipment.

References Cited UNITED STATES PATENTS Smith.

Wigle 166-27 X Kinniear 16627 McNeill 2552.5 Bauer et al. 255-2.5 Bauer et al 175-7 10 CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, WALTER BISLOWITZ, HAR- RISON R. MOSELEY, Examiners.

15 R. E. FAVREAU, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,341,398 September 12, 1967 Kingsley M. Nicolson ears in the above numbered pat- It is hereby certified that error app d Letters Patent should read as ent requiring correction and that the sai corrected below.

Column 5, line 18, for "cabels" read cables column 7, line 61, for "stiring" read string column 9, line 73, strike out "through"; column 10, line 25, for "143. Sleeve 145 is tapered at its lower" read 143 to be cemented into conductor pipe Signed and sealed this 3rd day of December 1968.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

Claims

1. THE METHOD OF DRILLING AND WORKING IN A WELL BORE IN AN UNDERWATER BOTTOM FROM A FLOATING VESSEL WHICH COMPRISES POSITIONING SAID VESSEL OVER AN UNDERWATER DRILLING SITE, SUSPENDING AN ASSEMBLED CONDUCTOR PIPE OF A PREDETERMINED LENGTH FROM SAID VESSEL AND ABOVE THE UNDERWATER BOTTOM, CONNECTING A LANDING FLANGE TO THE UPPER END OF SAID CONDUCTOR PIPE, ASSEMBLING IN AXIAL ALIGNMENT WITH AND AS AN INTEGRAL PART OF SAID CONDUCTOR PIPE AND LANDING FLANGE ASSEMBLY A TUBULAR GUIDE ASSEMBLY HAVING AFFIXED THERETO AT LEAST A PAIR OF GUIDE CABLES, INSERTING A DRILL STRING WITH A RADIALLY EXPANDABLE AND CONTRACTIBLE DRILL BIT ATTACHED TO THE LOWER END THEREOF AXIALLY THROUGH SAID CONDUCTOR PIPE FROM SAID VESSEL AND INTO CONTACT WITH SAID UNDERWATER BOTTOM, RADIALLY EXPANDING SAID DRILL BIT TO A DIAMETER GREATER THAN THAT OF SAID CONDUCTOR PIPE AND ROTATING SAID DRILL STRING BY MEANS ON SAID VESSEL WHILE LOWERING SAID DRILL STRING FROM SAID VESSEL TO DRILL INTO SAID UNDERWATER BOTTOM A BORE HOLE HAVING A DIAMETER AND DEPTH TO PERMIT SAID CONDUCTOR PIPE TO BE RECEIVED THEREIN TO PERMIT SAID LANDING FLANGE TO SET ON SAID UNDERWATER BOTTOM, LOWERING SAID CONDUCTOR PIPE, SAID LANDING FLANGE AND SAID GUIDE ASSEMBLY FROM SAID VESSEL ALONG SAID DRILL STRING AND GUIDING SAID CONDUCTOR PIPE INTO SAID BORE HOLE WITH SAID DRILL STRING TO POSITION SAID LANDING FLANGE ON SAID UNDERWATER BOTTOM, RADIALLY CONTRACTING SAID DRILL BIT TO A DIAMETER SMALLER THAN THAT OF SAID CONDUCTOR PIPE AND RETRACTING SAID DRILL STRING AND SAID DRILL BIT FROM SAID CONDUCTOR PIPE WHILE MAINTAINING A FLEXIBLE CONNECTION BETWEEN SAID CONDUCTOR PIPE AND SAID VESSEL WITH SAID GUIDE CABLES, LOWERING FROM SAID VESSEL ALONG SAID GUIDE CABLES AND TO SAID TUBULAR GUIDE ASSEMBLY A STRING OF CEMENT TUBING HAVING A GUIDE MEMBER ATTACHED THERETO AND COOPERATING WITH SAID GUIDE CABLES, GUIDING THE LOWER END OF SAID STRING OF CEMENT TUBING INTO SAID CONDUCTOR PIPE BY SAID GUIDE CABLES AND SAID TUBULAR GUIDE ASSEMBLY, INTRODUCING CEMENT FROM SAID VESSEL THROUGH SAID STRING OF CEMENT TUBING INTO SAID BORE HOLE AND CEMENTING SAID CONDUCTOR PIPE IN SAID BORE HOLE, RETRACTING SAID STRING OF CEMENT TUBING FROM SAID CONDUCTOR PIPE AND SLACKING SAID GUIDE CABLES WHILE SAID CEMENT SETS.