US3285574A - Weight regulating apparatus for submarine drilling - Google Patents

Description

Nov. M 1966 J. BERNE ET AL WEIGHT REGULATING APPARATUS FOR SUBMARINE DRILLING Filed April 10, l964 5 Sheets-Sheet 1 INVENTOR JEAN BER/YE H.946 P/Ek/QE MOI/UN (/EA/V 64575164 IV 1M ATTORNEYS Nm' 1155 1966 J. BERNE ET AL 3,285,574

WEIGHT REGULATING APPARATUS FOR SUBMARINE DRILLING Filed April 10, 1964 5 Sheets-Sheet 2 Q 3 dEA/Y Isak/vs PIERRE MOUL/N JEAN MSTERA/V BYQQ ATTORNEYj INVENTOR Nov. 15, 1966 J. BERNE ETAL WEIGHT REGULATING APPARATUS FOR SUBMARINE DRILLING Filed April l0, 1964 5 Sheets-Sheet 5 Pig 4 m m E V m JEAN BERNE PIERRE MOUL/N c/EAN C45TER/1N ATTORNEY5 Nov' 15 1966 J. BERNE ET AL 3,285,574

WEIGHT REGULATING APPARATUS FOR SUBMARINE DRILLING Filed April 10, 1964 5 Sheets-Sheet 4 Fig 6 0 m J 3 1 x INVENTOR L JEAN BERNE P/ERRE MOUL/N n dEA/Y CASTERA/V ATTORNE E Nov. 15, 1966 J. BERNE ET AL 3,285,574

WEIGHT REGULATING APPARATUS FOR SUBMARINE DRILLING Filed April 10, 1964 5 Sheets-Sheet 5 um i Un u INVENTOR dEA/V BER/YE Rig 9 PIERRE MOUL/N C/EA/V CA5 TERA N ATTORNEYS United States Patent Ofifice 3,285,574 Patented Nov. 15, 1966 7 Claims. (in. zap-172 Thi invention relates to apparatus for submarine drilling using a flexible tubing for a drill string.

In submarine drilling where a flexible tubing is employed as drill string and a turbine or an electric bottom motor for driving the drill, it is generally advantageous to control the weight on the drilling means with much greater precision than is required in the case of usual rotary drilling.

As a matter of fact, a bottom motor and particularly an electric drilling motor can only 'be used when the weight on the drilling means is not too high. Otherwise the drilling means are blocked, thus stopping the motor. But the weight on the drilling tool must not be too weak either if it is desired to advance sufliciently quickly with the drilling and to utilize the available power well.

In practice there exists an optimum weight on the drilling means which should be kept substantially constant during the drilling operation for one type of rock. This optimum weight is adjusted when the drilling progresses into layers of a different type of rock or earth.

The control of weight on the drilling means can either be effected by vertical displacement of the upper end of the drill string at a height corresponding to a portion of elongation thereof which is equivalent to make the weight exerted on the drilling means proportionately lighter, or !by the application of a constant tension to the upper end of the string.

The latter method is the simpler one since it is not necessary to constantly adjust the upper end of the string by taking into consideration the progress in drilling and the weight to be maintainedon the drilling means.

However, the application of this submarine drilling method is rendered difiicult because of the continuous movements of the ship which are caused by wind, current and big waves. The application of a constant traction force at the upper end of the string could be realized by a system of counterweights which weights are attached to a cable passing over a return pulley at the end of the string. However, the movements of the ship would have a considerable effect on the force exerted on the counterweights due to the ships own acceleration sometimes positive and sometimes negative.

It is an object of the present invention to overcome these inconveniences by a device permitting the application at the end of the string of a substantially constant force (disregarding friction) regardless of the movements of the ship.

The device according to the invention comprises at least one jack which is fed by a fluid under pressure. The force which results from the jack or jacks is applied to the upper end of the drill string. The use of one jack or several jacks has the advantage to render the traction force applied to the upper end of the string substantially independent of the vertical movements of the ship.

The nature of the present invention will be more completely understood with reference to the accompanying specification taken in connection with the drawings in which:

FIG. 1 is a schematic view showing the principle of the invention;

FIGS. 1A, 1B and 1C illustrate the relative displacement of the device and the ship when the ship moves vertically;

FIG. 2 shows a guiding system for the flexible tub- FIG. 3 shows in simplified fashion a control device for the tension of the flexible tubing, having only one vertical jack;

FIG. 4 illustrates schematically a first embodiment of the device according to the invention;

FIG. 5 shows a modification of the device illustrated in FIG. 4;

FIG. 6 portrays schematically a second embodiment of the device according to the invention;

FIG. 7 is a schematic view indicating the respective positions of different elements of a device as illustrated in FIG. 6;

FIG. 8 shows schematically the feeding of a jack in a device according to the invention, by oil under pressure starting from an oleopneu-matic storage battery with thepossibility of injecting oil into the hydraulic circuit;

FIG. 9 shows the variation of pressure in the hydraulic circuit as a function of the volume of oil for the feeding system illustrated in FIG. 8.

In FIG. 1 which schematically shows the principle of the invention, .a jack is utilized which is fed by a pressure being substantially constant and acting upon the upper end A of the drill string.

The force exerted by the jack is independent of the position of piston P in the cylinder C as long as the displacements of the upper end E of the jack do not attain the limits allowed by the geometrical stroke of the piston P (FIG. 1). The upper end A of the drill string is The displacements of the ship caused by rolling and pitching will be substantially neutralized, for example, by maintaining the flexible tubing in aguide mean-s which may consist in pulleys, Pt .an Pt as shown in FIG. 2. Under these conditions, only the vertical component of these movements remains to be taken care of. It is absorbed by the jack in the same manner as the vertical displacements of the ship, the amplitude of which is much larger.

A simplified form of embodiment of a control device for the tension of the flexible tubing having a vertical jack is illustrated by way of example in FIG. 3.

The flexible tubing 1 passes over a pulley 2, and from there between the jaws of a conveyor means 3 mounted on the ship at a distance L from the vertical passing through the axis of the pulley 2. The distance L is chosen as large as possible with respect to the maximum height h of the of the variations of the angle a when the maximum value of this angle remains small, by adding a force G of the vertical jack which is substantially constant and a force F of the inclined jack which is also substantially constant.

However, in order to make the force exerted by the inclined jack substantially constant, it is necessary that it maximum volume be small as compared to v If S is the section of the jack 6 and x its stroke, its volume v is equal to:

If this jack is being fed at the same time as the first one from the capacity v on, it is necessary to choose it with a volume relatively small as compared to that of the first jack, since its stroke does not vary proportionate- 1y to a.

The sections S and S of the two jacks are related by the equation:

wherefrom the preceding equation is deducted. As can be seen, the preceding equation is not independent of the value v. The ratio of the sections S2/S1 is therefore calculated for the maximum value of v corresponding to the greatest amplitude of the vertical displacement of the ship.

For this maximum value of v the equality of G+F =F is substantially attained (the terms of the second and third order are negligible).

On the other hand, for a value of zero for v, P will be zero and F will be equal to T.

If v is zero, then there is G=S p =T. Under these conditions, the equality G+F =F will be maintained.

It is therefore only in the interval between a value zero and the maximum value of v that an error is introduced for the value of F, which differs slightly from FG.

The absolute importance of said error is small because it only applies to the complementary value F, and is maximal for a value of P not being at its maximum.

In order to reduce the forces on the slide 10, it may be advantageous, as shown in FIG. 5, to substitute two inclined jacks 7 and 8 for the jack 6. These inclined jacks 7 and 8 are symmetrical with respect to the slide, :and the rods of the pistons 11 and 12 have a common articulation 13 which can glide in the slide 10.

In another embodiment of the invention (FIG. 6) a single jack 14 is used which is inclined with respect to the horizontal and articulated in the plane defined by the vertical of the pulley and that portion of the flexible tubing which is comprised between the pulley and the entrance of the conveyer means. The piston of this jack acts upon the axis of the pulley, which is subject to being displaced in the vertical slide 10.

If it is not possible, as described above, to exert constant traction upon the drilling means with a single vertical jack connected to a pneumatic accumulator, then it is possible under certain conditions to obtain this result by using a sole jack which is articulated around a horizontal axis and is inclined with respect to the horizontal.

It is seen in FIG. 6 that the force applied to the axis There is:

6 D of the pulley for realizing the traction T on the drilling means, is:

5 F 2T cos i 8 being the angle formed by the strands of the tubing passing over the pulley (5=90a).

The vertical component of this force is:

F,,=T(l+cos 6) The jack 14 develops the force wherein p is the pressure exerted upon the piston,

S is the section of the jack,

V is the total volume of fluid V=v +v(v being the Volume of the tank and v the variable volume of the jack),

K is the constant value of the product pV" proportional to the quantity of compressible fluid.

The vertical component of the force G is expressed as follows:

G =G sin B=% sin 5 with )3 being the inclination of the jack with respect to the horizontal.

The vertical components F and G must also be as close to each other as possible when a, and therefore 6, vary between their extreme values.

By going back to the above expressions of F, and G it is found that when 5 increases, F decreases; whereas the sense of variation of G is less evident since G appears as the product of a function sin 8 which is decreasing when 6 increases (,8 and 6 vary in the opposite sense) and of a function SK/ V which increases with the angle a (V decreases when 8 increases, therefore the function SK/ V increases).

Now two equations are considered:

S sin 6 )+vol wherein v is the capacity of the fluid tank, d is the distance between the axis D of the pulley and the articulation axis I of the jack, and e is the difference between d and the stroke x of the jack for the angle 6(x=de).

The two functions are, respectively, the product of the constant quantities T and K by functions of angle 6.

The value of K can be easily adjusted to that of T,

since,

is a function of the quantity of fluid.

The identity of the factors S sin 6 cannot be realized in an absolute manner from the point of view of mathematics since there are two functions 8 irreducible one toward the other, but it will be sufficient to obtain the equality of the two functions in certain points.

For each equality which is to be realized (6 given), an equation is obtained whose unkown values are the parameters namely S, v e, L, m and n. L is the distance between the vertical slide and the entrance I of the conveyor means (vertex of the angle a), m and n are the coordinates of the articulation I of the jack in the system of rectangular coordinates admitting for respective axes a horizontal passing through I and the vertical of the slide (FIG. 7 where the limits of displacement of the pulley D in the slide which depend on and 1+cos 6 the vertical movements of the ship, are designated by D and D1)- If one would dispose of n parameters one could cause the function G to assume for n values of 5 the value of F for the same values.

In practice it is always necessary to deal with a certain number of inequalities which reflect certain conditions of location (length L, coordinates in and n) or of technology (length 2, volume v section S).

On the other hand, the identity of the functions G and F need only be determined by approximation. Keeping in mind the variations which must be accepted for T, it is preferred in general to set the functions G and F to be equal for three values of 5 only. This furnishes only a number of equations which is smaller than the number of parameters to be determined. There is still the possibility to use supplementary relations between these parameters, for example, by minimizing the difference F G between the horizontal components of the forces F and G.

This allows in particular to diminish friction forces of the axis of the pulley along the slides, thus considerably improving the functioning of the device at a'constant tension and making it possible to have a lighter overall construction.

Other embodiments are possible whereby numerous jacks are introduced of which the outer end of the drill string is articulated on the axis of the pulley. The base of the cylinder is articulated at different points of the ship which are or not situated in the vertical plane of symmetry defined by the two strands of the flexible drill string positioned partly on one and partly on the other side of the pulley.

This arrangement ofifers two advantages. The first one is that the available parameters are more numerous to realize the identity two by two of the functions F and F and of the functions 26;; and EG ZG and 26 being respectively the sum of the horizontal and vertical components of the forces exerted by the different jacks on the axis of the pulley. The second advantage is that it becomes possible under certain circumstances to omit the slide completely. The curve described by the axis of the pulley can be a straight vertical, resulting not anymore from a slide, but from mechanical or pneumatic arrangements between said axis and the jack-s.

In the various preceding embodiments the jack or the jacks are being fed from a tank with gaseous fluid under pressure (pneumatic accumulator).

The control during the functioning of the constant tension T assured by the device according to the invention is then obtained by introducing or drawing oif of considerable quantities of gaseous fluid.

In practice it is diflicult for effecting such control to use another gas than air. However, compressed air is dangerous when its pressure exceeds 200 kg./cm. in case oil deposits are present in the jacks (inflammation).

Another solution is .to feed the jack or the jacks not with gas under pressure, but with oil under pressure which comes from an oleopneumatic accumulator. The oil serves as transmission agent for the jacks by means of pressure of an inert gas like nitrogen which is contained in the oleopneumatic accumulator where the oil is separated from the. nitrogen by a membrane allowing equilibrium of pressure between liquid and gas Without the possibility of explosive contact.

Such an oleopneumatic accumulator is characterized by the pressure w at which is maintained the gaseous inert atmosphere when the gas occupies the entire available Volume of the accumulator, designated hereinafter by the term calibrating pressure.

These accumulators are constructed in such a manner as to operate with a constant quantity of inert gas, and it is diificult to modify this gas quantity in such a way that tl'E'tension T of the flexible tube is changed because it 8 needs an expensive gas feeding system to the accumulator.

It is preferable to control the value of the tension T by introducing or drawing 01f a certain quantity of oil in the oil transfer tubing between the jack and the oleopneumatic accumulator.

A device according to the invention for controlling the tension in a flexible feeding tubing will now be considered which utilize-s one or several jacks supplied by oil under pressure from an oleopneumatic accumulator.

The tension on the flexible tubing is maintained constant at an initial value'T by a construction of the device in which the number, the kind and operation of the jacks, the kind of oleopneumatic accumulator and the quantity of introduced oil are suitably chosen.

The pressure of the accumulator varies between 11- and W when the piston of the jack is displaced between its two extreme positions, under the effect of the movements of the ship (the pressures 1r and 1r are both superior to the calibrating pressure 1ro of the accumulator).

If it is desired to regulate the device for a new tension T to be maintained substantially constant on the flexible tubing, the total quantity of oil will be changed so that the pressure in the accumulator will vary between the pressures 1r' and 11" which are different, respectively, from 1r and r for the same displacement of the piston of the jack between its extreme positions. It will now be proved that the mechanical device calculated to ensure a constant tension T is still valid without modification to maintain a constant tension T if the relative variation A1r/1r of the oil pressure as a function of the variation AU of the inert gas volume in the oleopneumatic accumulator is in the form of:

1r 'y=constant Where 'y is the polytropic coeflicient of the gas. The preceding relations (1) and (2) are incompatible. A solution of this problem consists according to the invention in the utilization of a plurality of oleopneumatic accumulators having increasing calibrating pressures feeding in parallelthe jacks.

FIG. 8 shows schematically such an embodiment where a jack 15 articulated at I can be supplied by oil under pressure 16 from one, two or three oleopneumatic accumulators 17, 18 and 19 which are characterized by their pressure and volume of expansion of the inert gas: respectively 1r U 1r U and 1r" U" with 1r 1r' 1r" Each of said accumulators is put in communication with the jack 15 when the pressure 1r in the oil circuit attains or exceeds the calibrating pressure of the respective accumulator, either by introduction of oil which is intended to adjust the tension T on the flexible string, or by the normal play of the piston in the jack. Thereby the accumulators 17 (calibrated at the pressure T 18(1r' 19(1r" are successively put in communicatio with the jack when the pressure rises.

The variation of the pressure 1r in the oleopneumatic accumulators 17, 18 and 19 with respect to the volume of the inert gas, i.e. U U' U" respectively, is shown in FIG. 9 by means of the curves 20, 21 and 22.

U is the volume of oil in the oil supply circuit from the accumulator to the jack 15. The pressure 1r of the oil follows the broken curve marked by an arrow if, when the pressure remains between ar and 11" the accumulator 17 is alone in communication with the jack and if, when the pressure attains 'lr' the accumulator 18 is also put in service which leads to the utilization of a portion of the curve obtained by forming the sum of the curves 20 and 21.

Putting the accumulator 19 into service also leads to a portion of the curve resulting from the sum of the three curves 20, 21 and 22.

It is possible to choose the characteristics 1T0, Ugo, vr' U' o, 0, U in such a manner that the broken curve marked by arrows is as close as possible to the theoretical dashed curve which corresponds to Under these conditions the substantially constant tension T exerted by the device can be controlled by simple injection of oil under pressure through the pipe 23 (FIG. 8) in a whole interval depending on the mechanical characteristics of the device. The connection between the jack or the jacks and each oleopneumatic accumulator will be carried out automatically when the pressure of the oil attains the value of the calibrating pressure of the accumulator in question and, inversely, the communication will be interrupted when the pressure in the oil circuit becomes smaller than the calibrating pressure of this jack.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed as this invention is:

1. An apparatus for regulating the weight that is exerted on an underwater drilling tool suspended from a floating installation by a flexible conduit which passes, on this installation, from a return pulley to a means for maneuvering said conduit, said apparatus comprising at least one jack sustaining the axis of the pulley and articulated on the floating installation, said jack 'being inclined to the vertical plane of the axis of the pulley and communicating with at least one reservoir containing fluid under pressure.

2. An apparatus for regulating the weight that is exerted on an underwater drilling tool suspended from a floating installation by a flexible conduit which passes, on this installation, from a return pulley to a means for maneuvering said conduit, said apparatus comprising a guideway in which the axis of the pulley is slidable, at least one jack sustaining this axis and articulated on the floating installation, said jack being inclined to the vertical plane of the axis of the pulley and communicating with at least one reservoir containing fluid under pressure.

3. An apparatus for regulating the weight that is exerted on an underwater drilling tool suspended from a floating installation by a flexible conduit which passes, on this installation, from a return pulley to a means for maneuvering said conduit, said apparatus comprising an approximately vertical guideway in which the axis of said pulley can slide, at least one vertical jack and at least one complementary jack sustaining this axis, said complementary jack being articulated on the floating installation and inclined to the guideway, the jacks communicating with at least one reservoir containing fluid under pressure.

4. An apparatus for regulating the weight that is exerted on an underwater drilling tool suspended from a floating installation by a flexible conduit which passes, on this installation, from a return pulley to a means for maneuvering said conduit, said apparatus comprising at least two jacks sustaining the axis of said pulley, these two jacks being articulated on the floating installation and symmetrically inclined to the vertical plane of the axis of the pulley, said jacks communicating with at least one reservoir containing fluid under pressure.

5. The apparatus of claim 1, in which the reservoir of fluid under pressure is constituted of an oleopneumatic accumulator.

6. The apparatus of claim 1, in which the reservoir of fluid under pressure is constituted of an oleopneumatic accumulator containing an inert gas.

7. An apparatus for regulating the weight that is exerted on an underwater drilling tool suspended from a floating installation by a flexible conduit which passes, on this installation, from a return pulley to a means for maneuvering said conduit, said apparatus comprising at least one jack sustaining the axis of the pulley and articulated on the floating installation, said jack being inclined to the vertical plane of the axis of the pulley and reunited by the intermediary of a hydraulic circuit to a battery of pneumatic oil accumulators connected in parallel to said circuit, each of said accumulators having a calibrating pressure, said circuit containing a hydraulic fluid and being adapted to have any one of its accumulators put into communication with said jack when the pressure of the hydraulic fluid in the circuit is at least equal to the calibrating pressure of said one accumulator, said means including also one supply conduit for delivering hydraulic fluid under pressure to said circuit.

References Cited by the Examiner UNITED STATES PATENTS 3,151,686 10/1964 Krammerer 254172 3,158,208 11/1964 Krammerer 1755 3,208,728 9/1965 Parks 254-172 SAMUEL F. COLEMAN, Primary Examiner.

EVON C. BLUNK, Examiner.

H. C. HORNSBY, Assistant Examiner.

Claims (1)

1. AN APPARATUS FOR REGULATING THE WEIGHT THAT IS EXERTED ON AN UNDERWATER DRILLING TOOL SUSPENDED FROM A FLOATING INSTALLATION BY A FLEXIBLE CONDUIT WHICH PASSES, ON THIS INSTALLATION, FROM A RETURN PULLEY TO A MEANS FOR MANEUVERING SAID CONDUIT, SAID APPARATUS COMPRISING AT LEAST ONE JACK SUSTAINING THE AXIS OF THE PULLEY AND ARTICULATED ON THE FLOATING INSTALLATION, SAID JACK BEING INCLINED TO THE VERTICAL PLANE OF THE AXIS OF THE PULLEY AND COM-

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