US3252528A

US3252528A - Method of drilling from a fully floating platform

Info

Publication number: US3252528A
Application number: US629937A
Authority: US
Inventors: Kingsley M Nicolson
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1956-12-21
Filing date: 1956-12-21
Publication date: 1966-05-24
Anticipated expiration: 1983-05-24

Description

y 1966 K. M. NICOLSON 3,252,528

METHOD OF DRILLING FROM A FULLY FLOATING PLATFORM Filed Dec. 21, 1956 4 Sheets-Sheet 1 7ATT0RNEY$ l y 1966 K. M. NICOLSON 3,252,528

METHOD OF DRILLING FROM A FULLY FLOATING PLATFORM Filed Dec. 21, 1956 4 Sheets-Sheet 2 K/NGSLEY M. QN/COLSON May 24, 1966 K. M. NICOLSON METHOD OF DRILLING FROM A FULLY FLOATING PLATFORM 4 Sheets-Sheet 5 Filed Dec.

INVENTOR K/NGSLEY M. N/COLSON FIG.4

May 1966 K. M. NICOLSON 3,252,528

METHOD OF DRILLING FROM A FULLY FLOATING PLATFORM Filed Dec. 21, 1956 4 Sheets-Sheet 4 INVENTOR K/NGSLEY M. N/COLSON 3,252,528 METHOD OF DRILLING FROM A FULLY FLOATING PLATFORM Kingsley M. Nicolson, Fullerton, Califi, assignor, by mesne assignments, to Chevron Research Company, a corporation of Delaware Filed Dec. 21, 1956, Ser. No. 629,937 4 Claims. (Ci. 1757) 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 wellhead 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 spndded without templates or other means for guiding the bit into the bottom. In said preferred method of carrying out the invention, an assembled con ductor 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 bones to explore for oil, gas and the like through deep waters, it is necessary either to 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 float- I ing 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 thatof 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 he 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 tpipe 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.

Whileit has been suggested heretofore that well head control equipment he placed on bottom, the method of initiating, or spudtding-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 par-t 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. Additionthat 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 thissense, 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 having a predetermined weight. The drill bit and conductor pipe are then connected to a drill string through a vertically-reciprocable 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 full 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 pipeis 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 spudding-in. 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 dip-ping 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 thewell 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 glide 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 conductor pipe by again tighteningthe guide cable and lowering it along them. Final assembly of said well head equipment tothe conductor pipe is desirably made through a quick-connect joint, otherwise known as a safety joint, which permits a fluid-tight 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 the control 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 desk 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 possi'ble seepage or other escape of oil or gas by setting a cement plug in the well bore of suflicient 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 ineluding a plurality of drill collars directly above the bit but below the section of drill string held in tension from the workdeck 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 depths 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 con ductor 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 on 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 cables 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 a 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. 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 formed of a string of drill pipe. 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, the string of drill pipe 21 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 hook 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 invention to start and drill borehole vertically into a dipping 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?. 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 After i motor so that the motor can be driven through flexible hydraulic lines with the motor supported on the 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 7.1 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 string 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 sufficient depth to enter a competent formation, landing flange 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 sideopening 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 here 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.

After the cement is placed around the conductor pipe, 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 shearable 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 pas 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 =1atch 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 belowcable drum 76. After bucket 75 of guide assembly 71 has been latched to conductor pipe 13 preferably, the upper portion or barrel section 85 of safety joint 19 is disconnected by retracting the locking sleeve 56 (shown in FIG. 2) from locking grooves in the stationary portion 77 (shown in FIG. so that the string of drill pipe 21 forming the upper section of drill string 14 can be raised and racked on the drill deck, ready :for further drilling through the lower end of the cemented casing 13. The operation of this safety joint is described more fully in my Patent No. 2,950,929.

At this time, in accordance with the preferred embodiment of 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.

Alternatively the drill string may remain connected to the conductor pipe after the cement is placed around the latter, the sliding connection 43 functioning to isolate the vertical motion of the vessel from the conductor casing while the cement 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, in a manner to be explained hereinafter, 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 5 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. 5, the barrel 85, including locking sleeve 86 illustrated in FIG. 2, 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 Patent No. 2,919,111, filed December 30, 1955. As disclosed in said application, the opposite sides of the pipeengaging 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 string 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 maintainsfull control of well pressures while abandoning the borehole under emergency conditions. 7 I

Upper blow out preventer 91 is of conventional design and many either completely close off the well bore, or grasp the sides of the drill pipe when the opposite rams 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 39, 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 line 100. By this arrangement of

BOPs

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

Above BOP 99, there is positioned a drilling head 191 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 161.

As indicated above, various combinatons of blow out prevention equipment, either of the full hole, or drill pipe engaging types may be assembledbetween 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 169 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, 199 so that even with ship '10 rising and falling in the water, the well head assembly and in particular barrel 85 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 85 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, 163 and 1114 is connected to the well head assembly before it is lowered to engage the conductor pipe. Preferably, this is also accomplished on deck, although it can be performed directly below the i 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. After the well-head assembly is connected to the conductor pipe in the manner explained hereinbefore, the rams 9i) and 92 of BOP 91 are opened to release the drill pipe 21A, and the latter, together with the attached bullnose portion 111, is raised from the assembly and returned aboard the drilling vessel.

Drilling may now 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. Fun nel 117 and guide arm 107 are secured directly to drilling head 101. Additionally, the bit is guided by a coilar 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 assembiy 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 driil string 122 is lowered through conductor pipe 127.

After the borehole has been opened and underreamed to a sufficient depth and diameter to receive the preassembled length of conductor pipe 127, said conductor pipe and guide assembly 131 are lowered along the drill string in the same manner as guide assembly 71 is lowered along drill string 21 in the arrangement of 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 removed 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 137. Sufficient cement 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 usually 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 the bottom of cemented conductor pipe 127, after that pipe is set to prevent debris or unconsolidated sediments from sloughing into the borehole. In practice, the conductor pipe will be set to a depth of about to 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 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 casing 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 end of surface pipe 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 145, as best seen in FIG. 7 is to permit the upper end of surface casing 143 to be cemented into conductor pipe 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 219 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 a-bove 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 land the drilling head to axially cemented section of surface casing 143. After the desireddepth 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 cementspotted 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 opposed 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 13 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 within the scope of the appended claims are intended to be included therein. 7

I claim:

1. The method of drilling and working in a submerged bore hole from a floating vessel which comprises positioning said vessel on the surface of a body of water over an underwater drilling site, suspending from said vessel a conductor pipe of a predetermined length by means of a string of drill pipe detachably connected in concentric relationship to the upper end of said conductor pipe, said conductor pipe having a drill bit of larger diameter than said conductor pipe aflixed to the bottom end thereof and a flange of larger diameter than said drill bit aflixed adjacent the upper end thereof, lowering said conductor pipe vertically through said body of water by extending said string of drill pipe downwardly from said vessel to place said drill bit in contact with the submerged land, rotating said string of drill pipe and said conductor pipe by means aboard said vessel while continually lowering said conductor pipe to thereby drill a bore hole into said submerged land until said flange is in contact with said submerged land, subsequently lowering from said vessel along and in concentric relationship with said string of drill pipe a guide assembly to which is attached at least a pair of guide members yieldabiy connecting said guide assembly with said vessel, connecting said guide assemblyto the top portion of said conductor pipe by an automatioally engaging connector, flowing'cement from said vessel down through said string of drill pipe and said conductor pipe and into the annulus between the outer wall of said conductor pipe and the wall of said bore hole, and subsequently disconnecting said string of drill pipe from the upper end of said conductor pipe and reducing the tension in said guide members while said cement sets.

2. The method of drilling and working in a bore hole from a floating vessel which comprises positioning said vessel over an underwater drilling site, suspending below said vessel and above the underwater bottom a conductor pipe by means of a string of drill pipe detacha bly connected in concentric relationship to the upper end. of said conductor pipe, said conductor pipe having a drill bit of larger diameter than said conductor pipe aflixed tothe bottom end thereof and a flange of larger diameter than said drill bit affixed adjacent the upper end thereof, lowering said conductor pipe vertically from said vessel to place said drill bit in contact with the submerged land, rotating said string of drill pipe by means aboard said vessel while continually lowering said string of drill pipe to thereby drill a bore hole into said submerged land until said flange is in contact with said submerged land, subsequently securing a guide assembly to the submerged upper end of said conductor pipe and adjacent said flange, said guide assembly including at least a pair of guide cable members yieldably connecting said vessel with said guide assembly and disposed in symmetrical relationship around the axis of said conductor pipe, flowing cement from said vessel through said string of drill pipe and said conductor pipe downwardly to the bottom of said. conductor pipe and upwardly between the outer wall of said conductor pipe and the wall of said bore hole, disconnecting said string of drill pipe from the upper end of said conductor pipe and reducing the tension in said guide cable members while the cement sets, subsequently increasing the tension in said guide cable members and then lowering a drilling head assembly having a guide member attached thereto and co-operating withsaid guide cable members along said guide cable members to the submerged said upper end of said conductor pipe, guiding said drilling head assembly into concentric relationship with the said upper end of said conductor pipe by means of said guide assembly and securing said drilling head assembly to said upper end of said conductor pipe by an automatically operating connector, said guide as sembly being adapted to receive a drill string in concentric slidable relationship, guiding a drill bit aifixed on the lower end of a second drill string having a guide member attached thereto and co-operating with said guide cable members downwardly from said vessel along said guide cable members and into concentric relationship with said drilling head assembly, lowering said second drill string from said vessel to project said second drill string and drill bit through said drilling head assembly and through said conductor pipe and into contact with the subterranean formations at the bottom of said bore hole, and rotating said second drill string by means aboard said vessel while continually lowering said sec ond drill string to drill said bore hole to a desired depth.

3. The method of drilling and working in a submerged well bore from a floating vessel which comprises anchoring a drilling vessel on the surface of a body of water over a submerged drilling site, suspending an assembled conductor pipe of a predetermined length from said vessel and above the underwater bottom, connecting a radially extending landing flange adjacent the upper end of said conductor pipe, detacha'bly connecting the lower end of a string of drill pipe to said upper end of said conductor pipe and supporting the upper end of said drill pipe on said vessel, drilling said conductor pipe into said underwater bottom by rotating said conductor pipe and said landing flange as a portion of the lower end of a drill string which includes a drill bit of larger diameter than said conductor pipe aflixed to the lowermost end of said conductor pipe while lowering said drill pipe from said vessel until said landing flange engages said underwater bottom, subsequently lowering from said vessel along said drill pipe a guide assembly concentric with said drill pipe and including at least a pair of guide cables, said guide assembly having a guide member attached thereto and cooperating in sliding relationship with said guide cables, guiding said guide assembly into concentric relationship with the upper portion of said conductor pipe and securing said guide assembly to the said upper portion of said conductor pipe by an automatically engaging connector, circulating cement through said drill pipe and said conductor pipe and into the annulus between the outer wall of said conductor pipe and the wall of the bore hole drilled thereby in said underwater bottom, disengaging said drill pipe from said upper end of said conductor pipe while said cement sets, and maintaining a flexible connection between said upper portion of said conductor pipe and said vessel by means of said guide cables.

4. The method of drilling and casing and working in a well bore in an underwater bottom comprising positioning a floating vessel on the surface of a body of water over a submerged drilling site, suspending a Vertically disposed casing string from said vessel by a string of drill pipe detachably connected at its lower end to the upper end of said casing string and supported on said vessel by means which permits said string of drill pipe to be lowered through said body of water from said vessel, drilling a well bore into the underwater bottom of sufiicient depth and diameter to receive said casing string by drilling apparatus which includes said string of drill pipe, said casing string, a drill bit afiixed to the lower end of said casing string and means on said vessel to rotate said string of drill pipe while continually lowering said string of drill pipe from said vessel to maintain said drill bit in contact with the subterranean formations of said underwater bottom, afiixing an underwaterbottom-engaging member to the upper portion of said casing string to limit the penetration of said casing string into said well bore, drilling said casing string into said subterranean formations of said underwater bottom until said underwaterbottom-engaging member is in contact with said underwater bottom, cementing at least a portion of said casing string in said well bore by cement introduced from said vessel into said string of drill pipe and said casing string and forced into the annulus between said casing string and the wall of said well bore, subsequently lowering from said vessel and connecting by an automatically engaging connector flexible guide means between said vessel and said upper portion of said casing string and symmetrically disposed around the longitudinal axis of said casing string, and detaching said string of drill pipe from its connection to said upper end of said casing string and retracting said string of drill pipe onto said vessel while maintaining a connection between said vessel and said upper portion of said casing string by said flexible guide means.

References Cited by the Examiner UNITED STATES PATENTS 987,266 3/ 1-9 1 1 Smith. 2,606,003 8/1952 McNeill 2552.5 2,808,229 10/ 1957 Bauer et al. 255-2.'5 2,891,770 6/1959 Bauer et al. 255-25 X 2,923,531 2/1960 Bauer et al. 255-25 CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, WALTER BERLOWITZ,

Examiners. R. E. FAVREAU, Assistant Examiner.

Claims

4. THE METHOD OF DRILLING AND CASTING AND WORKING IN A WELL BORE IN AN UNDERWATER BOTTOM COMPRISING POSITIONING A FLOATING VESSEL ON THE SURFACE OF A BODY OF WATER OVER A SUBMERGED DRILLING SITE, SUSPENDING A VERTICALLY DISPOSED CASING STRING FROM SAID VESEEL BY A STRING OF DRILL PIPE DETACHABLY CONNECTED AT ITS LOWER END TO THE UPPER END OF SAID CASING STRING AND SUPPORTED ON SAID VESSEL BY MEANS WHICH PERMITS SAID STRING TO DRILL PIPE TO BE LOWERED THROUGH SAID BODY OF WATER FROM SAID VESSEL, DRILLING A WELL BORE INTO THE UNDERWATER BOTTOM OF SUFFICIENT DEPTH AND DIAMETER TO RECEIVE SAID CASING STRING BY DRILLING APPARATUS WHICH INCLUDES SAID STRING OF DRILL PIPE, SAID CASING STRING, A DRILL BIT AFFIXED TO THE LOWER END OF SAID CASING STRING AND MEANS ON SAID VESSEL TO ROTATE SAID STRING OR DRILL PIPE WHILE CONTINUALLY LOWERING SAID STRING TO DRILL PIPE FROM SAID VESSEL TO MAINTAIN SAID DRILL BIT IN CONTACT WITH THE SUBTERRANEAN FORMATIONS OF SAID UNDERWATER BOTTOM, AFFIXING AN UNDERWATER-BOTTOM-ENGAGING MEMBER TO THE UPPER PORTION OF SAID CASING STRING TO LIMIT THE PENETRATION OF SAID CASTING STRING INTO SAID WELL BORE, DRILLING SAID CASING STRING INTO SAID SUBTERRANEAN FORMATIONS OF SAID UNDERWATER BOTTOM UNTIL SAID UNDERWATERBOTTOM-ENGAGING MEMBER IS IN CONTACT WITH SAID UNDERWATER BOTTOM, CEMENTING AT LEAST A PORTION OF SAID CASING STRING IN SAID WELL BORE BY CEMENT INTRODUCED FROM SAID VESSEL INTO SAID STRING OF DRILL PIPE AND SAID CASING STRING AND FORCED INTO ANNULUS BETWEEN SAID CASING STRING AND THE WALL OF SAID WELL BORE, SUBSEQUENTLY LOWERING