US2371953A - Drilling weight control system - Google Patents

Description

March 20, 1945.

w. 51'. M. E. ,CR AKE DRILLING WEIGHT CONTROL SYSTEM 2 Sheet-Sheet 1 Filed July 24,1942

Fig. I

Fig. 111 nvm fl Wilffzd StMaur Elmorz Crakz 5g his A++ofrnzqq39\' March 20, 1945 I w. s'r. M. E. cRAkE 2,

DRILLING WEIGHT CONTROL SYSTEM Filed July 24, 1942 2 Shets- -Sheet -2 Figm lnyznkm Wilfred St Mnur- Elmore 5g his A++ornq= Patented Mar.'20, 1945 UNITED ;-s"rA'rss PATENT' OFFICE.

Wilfred St. Maur Elmore Cralre, .7 assignor to Shell Development Houston, Tex, I Company, San

.Francisco; Calif., a corporation of Delaware Application July 24, 1942, Serial No. 452,243

2 Claims.

The present inventionrelates to well drilling control systems by which the drill bit feed into the formation being drilled is controlled in accordance with the weight supported on the bit, and pertainsmore particularly to an improvement over the control. apparatus described in US. Patent 2,l33,0l6 ,iss.ued on October 11, 1938 I to Brantley.

The Brantley device operates by causing the weight of the drill stem to motivate a pump, the discharge of which pump may be throttled by means of aplurality of valves in the fluid circuit of the pump, whereby the downward speed, or the rate of penetration, of the drill bit is controlled. In a homogeneous'formation, a constant setting of the throttlingivalves will give a constant bit feed rate, and therefore a constantwelght on the drill .bit, with constant and'pump flow and rotary table speed. However, any change in rotary table speed or mud pumpspeed, or any variation in formation hardness, willlincrease or decrease the weight on the drill bit, and maintenance of a constant pressure or weight on the bit can in such case be achieved only by manual control of I the throttle valves.

It is therefore an object of this invention to provide a control'sy'stem for automatically maintaining a constant pressure or weight on the drill bit, irrespective of changes in rotary table speed, or mud pump Speed. or variations inearthformation hardness. Since aninc'rease in bit pressure over a predetermined value detracts from the useful cutting lifevof the bit considerably, such an automatic control system, in eliminating variations in pressure due to the inherent shortcomings of the manual'contrOLincreases the bit life and gives a faster. rate of penetration of the drill bit into the formation due to the increased percentage of total drilling-time during which the drill bit is engaging the earth formation at the optimum pressures The present automatic control system likewise yields straighter and better auge boreholes. ,7

With the above and other objects andad'vantages in view, theinventian hasparticular relation to certain novel features of construction;

. operation, and arrangement of parts, an example of which is givenv in this specification and 'illus-' trated in the accompanying drawings, wherein: a

Figure I is a schematic view showing the relation of the drag pump and winding drum as well as the weight indicator to the derrick and drill stem.

Figure II is an enlargement oi the weight indicator detail from Figure I, showing also the indicating dial.

Figure III is a schematic view showing the cable drum and control system including the drag pump.

Figure IVis an enlarged vertical sectional view 4 of'the pilot .valve detail of the control system.

Figure V is an enlarged vertical sectional view of the diaphragm trol system.

. Figure VI is a schematic view showing an alternate arrangement of the pilot valve part of the control system. s

Fig. VII is a cross-sectional view taken along the line VIIVII of Flg.IV.

Referring to Figures I and H ofthe drawings, adrill st'ring'ifl is suspended in the usual manner by a cable H attached tothe upper end of the drill string ID by means of the usual blocks, hook and swivel, arrangement generally shown at It.

The drill string l0 may be of any suitable such as used for rotary drilling, and an of the suitable drilling rigs may be employed. The cable H passes over the crown pulley (not shown) on derrick l3 and the live hoisting portionila of the cable I i is wound on a drum It, while the dead end llb of the cable ll is fastened to the derrick by means ofsuitable clamps II. The dead end portion Nb of the cable carries a suitable weight measuring device, such as the commonly used hydraulic diaphragm device I! connected by tube It to a weight indicating dial l9 (Figure 11) arranged in a convenient {position for inspection by the driller.

The drill bit (not shown) on the lower end of the, drill string Ill is rotated, together with said. drill string by a rotary table 2|. As the drill bit bores into the earth formation, the live end I la. of the cable It is gradually unwound from the cable drum ll to lower the drill string Ill. The

clutching means or the like for selectively con necting the pump 2! to the drum I 4.

The pump 25, which may, for example, be a multi-cylinder double acting'pump, obtains fluid.

motor valve detail of the consuch as water, oil, or the like, as shown in Figure 111, from a reservoir or storage tank 26 through a pipe 21 and discharges it through .a pipe 29 to a manifold 30, containing control valve means, such as diaphragm motor valves Sid and lib, preferit acts. The sleeve 65 is internally threaded and ably in parallel, together with suitable auxiliary shut-oi! valves 82 and ny-pass valve 33. A return pipe 35 from the manifold 3| returns to the tank or reservoir 26. A preferred form of diaphragm motor valves Ila and lib is shown in detail in Figure V and comprises a diaphragm ll connected to the valve I by means or a valve stem 42 and a spring 43 acting against the lower side of the diaphragm 40 and tending to open the valve II which may suitably be a needle valve,

asshown, a balanced type valve, etc. Preferably, the motor valve lla has a small diameter flow channel and is thus adapted for low feeding rates or high pressure feeding while the other motor valve Iib has a large diameter flow channel for high feeding rates or low pressure feeding. The valves Sla and Iib may be used singly or in parallel as desired.

The weight of the drill string ill on the cable Ila rotates the drum I4 and thus causes the Pump 28 to pump fluid from the reservoir 25, which is at atmospheric pressure, through the pipe 29 and through at least one of the control valves. iia

and Iib. By controlling the back pressure held on the pump in the pipe line 29 by closing the by pass valve 31 and partially opening at least one of the control valves 3 la and 3 ID, the load, or portion of the weight of the drill string iil, carried by the cable He can be controlled. If the valves lia and lib and 33 are shut oi!- complete- 35 ly, the pump will be stopped and the load will hang without descending. The tendency of the pump .25 to operate: due to the load applied there to through the cable lid on the drum I will cause a certain blocked pressure in the pipe line 2!. If the control valves Sid and iib are opened so that the back'pressure on the pump 25 in the line 29 is a predetermined amount lower than the closed in or blocked pressure, and maintained at this differential, the weight which is thus relieved remains constant and is transferred to the bit of the lower end of the drill string II.-

The pressure fluid, such as air, oil, or the like,

which actuates the motor valve; Sin and lib,-

passes through pipe or line to the'diaphragms as: the motor valves lie and lib from a suitable source of pressure fluid, such as a reservoir I, into which, for example, air is pumped by means of an air pump 52 having a power take-oil,

ha 2 re 55 e such as a c m mm the pump A p s 7 pump 25 is then suitably brought into operative connection'with the cable drum. ll while the sure regulator 54 of anysuitable type, such as a spring-loaded diaphragmsactuated valve in which the diaphragm is expbsed to the pressure in the conduit on the downstream side of the valve, is

preferably arranged in the line it from the reser- 00 nected to thevalve 62 in the line il by means of 7 astem l3, and a spring I} acting at on end against a bracket II on the valve stem 63 and tending to close the valve '2, which may be of any suitable type,-such as a. balanced valve, as

asripss valve opens is adjusted by means of an anally.

movable sleeve 64 surrounding the valve stem 63 and against which the other end of the spring 84 a crank 68 and gear means i! engaging the sleeve O5, asshown'in Fig. VII.

Valve 12 continuously bleeds pressure from line 50 at a predetermined slow rate in order to prevent excessive build-up of pressure from line" and also to exhaust the pressure from line when valve 52 is closed ofi.

In one preferred embodiment of the P11858111? invention, the weight supported by the drill bit is maintained constant by holding the back pres sure on the pump 25 in the line 25 at a predeter 25 mined constant value. This is achieved by exposing the diaphragm iii of th pilot valve "to the V An increase in the backfpressure acting on the diaphragm SI of the pilot pressure in line 29.

valve it closes the valve 62 and the decreased pressure on the diaphragm II of the motor valves tin and lib caused by bleeding of pressure from line SI through valve 12, causes the valve elements ll of said throttling valves Sid and iib therein to be opened further, releasing the excess pressure in line 29 and allowing the drum ii to rotate faster. Likewisea decrease in the back pressure on line 28 acting on the diaphragm ll of the pilot valve Si opens valve 62 and permits pressure fluid from line 13 to enter line so and in- 7 4,0 creasethe pressure on diaphragm I in valves flu and lit. This causes the motor valves tic and lib to close, permitting the back pressure to increase and further restraining the unwinding of the cable iia from the drum il, so that the drill 5 string is lowered at a decreased rate.

In operation of the above described embodiment of the control system of' the present invention, the drill string 10 is lowered into the borehole until the drill bit reaches within a fewfeet of the so bottom. The circulation of drilling fluid and rotation of the rotary table are started at whatever operating speeds are desired and then the weight supported by the cable ii indicated on the weight indicator H, which may be caller! the full hanging load, is noted. The drag or restraining throttling valves 3i and by-pass valve 33 are in closed position. The pilot valve Gil is adjusted by means of parts "-69 inclusive so that the back pressure on the pump 25 in the line 29 act. ing on diaphragm 6i, which actuates the valve 82, causes the valve to just close. The supply of pressure fluid through line SI acting on the as diaphragm Iii of the throttling valves 3la and iib being cut oflrthe valve elements ll of said throttling valves lie and Si?) open slightly due to action or the spring 43, allowing the fluid to circulate through the fluid circuit comprising the pump 25, pipe 29, motor valvesiia and tlb, rehim line 35, reservoir 28, etc. The pump 2' is thus able to operateslowly and the load, comprising the drill string ID, on "the cable, starts to move downward very slowly, while the backpresshowninl 'igure IV, a tapered needle valve, or the sure on the pump 2! is practically q al to the reduced blocked pressure under full hanging load conditions. The compression in the spring 64 ofthe pilot valve 60 is further released by slowly moving the sleeve 65'upwardly until a lowered reading on weight indicator ll shows that the back pressure has been reduced sufliciently to allow the load or weight of the drill string In on the suspending cable II to be reduced from the previously noted full hanging load by the amount'oi weight desired to be'maintained on the drill bit.

It will be seen that the back pressure held on the pump 25 by the throttling valves 3 la and 3lb will be reduced by an amount proportional to the load or weight supported on the drill bit, and the control system will maintain this pressure constantly. Thus, in case the back pressure tends to decrease due to a slower rate of penetration of the earth formation by the bit as a result, for ex 'ample, of increased hardness of formation,.the

diaphragm-6| of the pilot valve 60 will be forced downwardly by the action of the compressed spring 64 and the valve 62 thereby caused to open. The increased pressure on the diaphragms 40 of the throttling valves 3m and 3lb by the fluid pressure through line 50 and opened valve 62 causes the valves 4| connected to diaphragms 40 to be moved toward closed position, whereby the fluid circuit is more tightly throttled, that is, fluid circulates therethrough more. difiiculty, and thus the back pressure on pump -is raised by the required increment back to the predetermined nor.- mal value. The weight on the drill bit will thus be controlled automatically to a constant value, re-

gardless of the speed of circulation of drilling fluid, the rotary table speed, both of which have a buoyant efiect, or .the' hardness of the earth formation being penetrated.

In order to prevent a rapid falling of the load, 1. e. the drill string In, etc., in case the drill bit penetrates into a cavity, either or both of the auxiliary values 32 are set by hand prior to the setting of the pilot valve 60 so that with the throttling valves 31a and 3| b wide open, the auxiliary valves 32 throttle the flow so that the rate of fall of the load is fixed to a reasonable maximum greater than the maximum at which it is expected to drill.

It will be seen that in the above described embodiment the control system will maintain a constant load on the drill bit as long as the cable Ila on the hoist drum I 4 unreels from the constant drum radiusat which the back pressure is set. In the event that the cable Ila unwinds a whole layer during the drilling for a depth equal to the length of one section or stand of drill pipe and thus drops to a smaller radius, the torque on the hoist-drum M which is connected to the pump 25 is reduced and the weight on the drill bit will be unless corrected by re-setting the pilot valve 60 which controls the back pressure on the 'pump 25.

the dead end llb of the cable I! in parallel and identical to the regular weight indicator II. If desired, the pipe ll may be tapped into the pressure fluid line 18 of the weight indicator shown in Figure II.

When the back pressure on the pump 25 is set by adjustment of the pilot valve 60 to give the desired weight on the drill bit, as shown by the weight indicator, the back pressure 'on the pump 25 will be automatically controlled by the cooperating effects of weight indicator Ma and pilot valve 60 to give a constant load oppressure on the drill bit regardless of the radius of the cable H a on the hoist drum l4, since the unwinding speed of the cable I la and thus the downward speed of the drill string [0 is directly controlled by the weight on the dead end llb of cable M through the weight indicator Ila.

It will be apparent that the above described embodiments of the control system of the present invention may undergo various modifications and.

.60, respectively, spring-controlled plungers or pistons, or the like, may be used. I laim as my invention:

1. A control system for well drilling apparatus.

comprising a drill stem adapted to penetrate the ground, a rotatable drum, a cable suspending saidstem and wound around said drum, whereby said drum is rotatably driven as the stem penetrates the ground, a pump, a speed multiplying mechanism to drive said pump by the rotation of said drum, 2. closed fluid circuit between the high and the low sides of said pump, diaphragm controlled valve means in said fluid circuit adapted to throttle the fluid flow therein, thereby maintaining on the pump a back pressure to oppose the unwinding of said cable from said drum, and a pressure fluid-control system comprising a, source of pres- This contingency is overcome by using a modification or the present invention illustrated by Figure VI. Insteadoi the diaphragm SI of the pilot valve being exposed to the back pressure in the line 29, the pilot valve 60 is controlled directly by the weight or load on the cable 6|, preferably by the weight on the dead end llb of the cable. For this purpose, a pipe H communicates from the pressure-responsive side of the diaphragm GI- 01' the pilot valve ill to the fluid pressure side oi. the diaphragm oi. a weight indicator, such as an auxfliary indicator Ila, attached to and actuated by sure fluid; means for adjusting the pressure in said control fluid to a predetermined value, and means responsive to variations in the suspended weight of said drill stem and cooperating with the dead end of said drill stem-supporting cable for applying the pressure of the control fluid to the diaphragms of the valve means in the pump circuit,thereby throttling the fluid flow in said circuit and maintaining the back pressure in said circuit at a predetermined value.

2. A control system for well drilling apparatus comprising a drill stem adapted to penetrate the ground, a rotatable drum, a cable suspending said stem and wound around said drum, whereby said drum is rotatably driven as the stem penetrates the ground, a pump driven by the rotation of said drum a closed fluid circuit between the high and low sides of said pump, pressure-responsive valve means in said fluid circuit adapted to throttle the fluid flow therein, thereby maintaining on the a pump a back pressure to oppose the unwinding of WILFRm) s'r. mun melanomas;

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