Title:
METHOD FOR AUTOMATICALLY MONITORING AND SERVICING THE DRILLING FLUID CONDITION IN A WELL BORE
United States Patent 3646808


Abstract:
This invention automatically monitors and services the drilling fluid condition of a well bore during drill pipe withdrawal by determining the amount of fluid required to replace the amount of steel removed therefrom. The required volume of fluid is then compared with the volume of fluid pumped into the borehole during the fluid refilling operation. The result of this comparison is used, among other things, to monitor kick or loss conditions which may occur during drill pipe withdrawal.



Inventors:
LEONARD LOREN W
Application Number:
05/067706
Publication Date:
03/07/1972
Filing Date:
08/28/1970
Assignee:
LOREN W. LEONARD
Primary Class:
Other Classes:
73/152.49, 175/40
International Classes:
E21B21/08; (IPC1-7): E21B47/10
Field of Search:
73/155 175
View Patent Images:
US Patent References:
2966059Indicator of drilling mud gain and loss1960-12-27Dower
2290408Exploration of boreholes1942-07-21Crites



Primary Examiner:
Myracle, Jerry W.
Claims:
What I claim is

1. A method for filling a well bore with drilling fluid to replace the volume of material withdrawn while tripping comprising the steps of:

2. A method for filling a well bore with drilling fluid to replace the volume of material withdrawn while tripping comprising the steps of:

3. The method of claim 2 wherein said volume of fluid required is determined by counting the number of pipe stands withdrawn from the well bore during each trip.

4. The method of claim 3 wherein said number of pipe stands withdrawn is multiplied by a scaling factor dependent upon the characteristics of the pipe stands withdrawn to obtain said volume of fluid required.

5. The method of claim 4 wherein said volume of fluid delivered is measured by a fluid meter positioned in the fluid fill line leading to said well bore.

6. The method of claim 5 wherein the fluid is delivered to the well bore by a circulating pump associated with the mud pit.

7. The method of claim 6 wherein said circulating pump delivers fluid to said pit and to said well bore through a three-way valve.

8. The method of claim 2 and further including the steps of:

9. A method for detecting the condition of a well by controlling, while tripping, the drilling fluid in said well and providing an early warning indication of an abnormality in said well characterized by:

10. The method of claim 9 wherein said measured volume is measured by a fluid flowmeter.

11. The method of claim 9 wherein said required volume is measured by obtaining a count of the number of units of said solid materials moved, and multiplying the count by a scaling factor dependent upon the physical characteristics of said units of solid material.

12. The method of claim 11 and monitoring said reference level in said well to obtain a first control signal, and using said first control signal to determine said measured volume.

Description:
BACKGROUND OF THE INVENTION

It has been well established that many of the blowouts that occur during drilling operations are caused by a reduction of hydrostatic pressure during drill pipe withdrawal, commonly known as a "trip". To maintain adequate hydrostatic pressure after or during each trip, it is important to pump, through the fill line of a drilling fluid (mud) circulation system, a volume of mud which is determined from the amount of steel withdrawn, which is in turn determined from the number of drill pipes and collars withdrawn.

If the amount of mud required is substantially equal to the amount of mud pumped into the borehole, the operation is assumed to be normal. If the amount of mud pumped into the borehole is less than the volume required to replace the amount of steel withdrawn, then some other fluid enters the borehole either from the formation itself or from another source. Such a gain of fluid is known as a "kick" condition. Conversely, if the volume of mud pumped into the hole is greater than the volume of mud required to replace the amount of steel withdrawn, then mud is being lost from the borehole to the formation or to another space.

SUMMARY OF THE INVENTION

It is a general object of this invention to provide an automatic mud refilling method allowing an early warning alert as to the existence of a kick or loss condition. It is a more specific object of this invention to provide a new and improved method for monitoring the condition of a well during tripping. The new method is economical, reliable in operation, and can be carried out even by a relatively unskilled driller within a minimum of time, thereby substantially reducing the cost and hazard of the trip. With the new method the driller is free to attend to chores connected with operations other than those required to refill the borehole.

A preferred method of this invention comprises: obtaining an electric count of the number of pipe stands pulled during each trip, multiplying the count by a scaling factor dependent upon the particular well characteristics to obtain the volume of fluid required, comparing the volume required with a metered quantity of fluid pumped into the fill line in order for the fluid in the borehole to reach a normal reference fluid level, and using the result of this comparison to obtain an indication with respect to kick and loss conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of a suitable system for carrying out the preferred method of this invention; and

FIG. 2 illustrates the use of a manual counter for providing a scaling factor into the system of FIG. 1.

FIG. 1 illustrates a conventional well being drilled which typically includes a conductor casing 10, a wellhead 12, and conventional blowout preventers 14 and 16. A pump 18, which can conveniently be the circulating centrifugal pump of the existing mud system that circulates the fluid or mud in a mud tank or pit 22 through a circulating fluid line 24, is selected to refill the borehole with mud. Accordingly, the fill line 25 is connected to a three-way valve 30 of the type manufactured by Rockwell Manufacturing Company, Model 3464. Ordinarily valve 30 establishes fluid communication between ports 26 and 27 in line 24 and upon becoming actuated by a line 28, which can be an electric line or an air line, valve 30 breaks fluid communication between ports 26 and 27 and establishes fluid communication between ports 26 and 29. Since the construction and operation of such a three-way valve 30 is well known in the art, no further description thereof is believed necessary.

To measure the amount of fluid pumped through the fill line 25 for passage downwardly through the casing 10, there is provided in fill line 25 a conventional fluid meter 32, the readout of which is preferably an electric signal fed via line 33 as hereinafter described. One such fluid meter is manufactured by the Foxboro Company and known as a Magnetic Flow Transmitter, another is manufactured by Rotron, Inc., and known as a Velocity Flowmeter. A return line 34 returns the fluid back to the mud tank 22 in conventional fashion. Mounted on the derrick floor 36 are a rotary table 37 of conventional design and a suitable monitoring and alarm system, generally designated as 40.

System 40 is preferably a digital system to provide faster response and greater versatility. It will be understood however that this invention is not limited to any particular system and that an analog rather than a digital system could be equally employed, as will be apparent to those skilled in the art. The components forming system 40 can be purchased from various manufacturers, such as Foxboro, Co., Atek Inc., Master Specialties Co., etc.

Above the derrick floor 36 are the elevators 42, which are coupled on one hand to the drill stand, generally designated as 44, desired to be withdrawn, and to a hook 46 on the other hand. Hook 46 is carried by a block 48 in conventional manner. As will be understood by those skilled in the art, each pipe stand 44 normally comprises a number, say three, of drill pipe joints 45.

To count the number of pipe stands 44 withdrawn by block 48, there is provided a stand detector 50 which detects the passage and removal of each stand and provides an appropriate electric signal onto line 51 to advance the count in a stand counter 52. The stand detector 50 may be a mechanical system, an electromechanical system, or an optical system employing a light beam and photocells. The electromechanical system would include microswitches for closing an electric circuit after the passage of each pipe stand. Whichever system is employed for the stand detector 50, line 51 can be made to receive a number of pulses equal to the number of pipe stands withdrawn. This number, illustrated as 3, is displayed in the window of the stand counter 52.

A volume required counter 56, which may be solid-state, electronic, digital multiplier device, manually receives a scaling factor through a knob 57, which is determined from the parameters of the particular well being refilled. Counter 56 multiplies this scaling factor by the number or count of stands pulled. The count of stands pulled is received on a line 58 from the stand counter 52. The number illustrated in the window of counter 56 is 1.77 barrels for the three stands pulled by the block 48.

This volume required is the volume of fluid necessary to fill the borehole up to a reference level, which is detected by a normal mud level detector 60, in order to replace the volume of steel withdrawn from the borehole. If after pump 18 delivers to the fill line 25 an amount of fluid equal to the volume required and the fluid level in the borehole is still below the normal level required, the pump will continue to deliver fluid into the borehole and an alarm or warning signal will be given as hereinafter described. If, after the pump has delivered the required volume of fluid into the borehole, the fluid in the borehole suddenly rises above the normal level a high-level, detector 61 will detect the rise in the fluid level to also provide a warning signal.

As previously mentioned, the readout of the fluid meter 32 is an electrical signal on line 33 applied to a volume pumped counter 62 which indicates the volume of fluid actually delivered downwardly into the borehole through the fill line 25. This delivered volume is displayed in the window of counter 62. With the figures previously selected and assuming normal operation, the volume delivered is also 1.77 barrels.

A suitable comparator 64 receives the count from the volume required counter 56 on line 66 and the count from the volume pumped counter 62 on line 68. Comparator 64 compares the counts received on lines 66 and 68. The result of that comparison will be a zero output which will be indicated by a "normal" indicating device 70, in the event that the volume required is substantially equal to the volume pumped. If the volume pumped is greater than the volume required, comparator 64 will provide an output signal to a "loss" indicating device 72. If the volume pumped is less than the volume required, a "kick" indicating device 74 will become actuated.

Referring now to FIG. 2, to facilitate the driller to obtain the required scaling factor for manual insertion by knob 57 in the volume required counter 56, there is provided a simple, convenient, hand-operated counter 80 having a rotatable drum 82 which is rotated manually by a knob 84. The operator selects in window 86 the particular physical parameters for the pipe stands being pulled. After selecting the proper parameters, say 41/2 inch-OD pipe having 16.60 lbs./ft., the proper scaling factor will appear opposite to the number of feet of pipe pulled. In the example illustrated, for 93 feet of drill pipe pulled, which corresponds to one stand, the required volume will be 0.59 barrels. It is this amount which is the scaling factor to be inserted into the volume required counter 56.

In operation, the circulating centrifugal pump 18 ordinarily circulates continuously the mud in the mud pit 22 through line 24. Pump 18 is a relatively low-pressure, high-volume pump as compared to the relatively high-pressure, high-volume, extremely bulky stroke pump (not shown) conventionally employed to fill the borehole. Prior to starting operations, the operator selects, in the manner previously described, the suitable scaling factor and inserts it into the volume required counter 56. After the operator initiates the stand withdrawal operation, the stand detector 50 detects the passage of each stand and the count in the stand counter 52 increases by one. After stand detector 50 has detected three stands, the reading in the window of the stand counter 52 will be 003 and the reading in the volume required counter 56 will be 1.77.

For the numbers illustrated, after the stand counter 52 has counted 003, a signal will be supplied from the volume required counter 56 via a line 53 to a valve control mechanism 55 for suitably actuating the three-way valve 30. This actuation is effected via line 28 and causes the three-way valve 30 to break fluid communication between ports 26 and 29, thereby commencing the refilling operation through the fill line 25 and the metering operation by the fluid meter 32.

Assuming that the refilling operation is normal, after the fluid meter 32 has measured a volume pumped equal to the volume required, the fluid level in the borehole will be at the reference level, as detected by the normal level detector 60. If the volume pumped to reach the reference level is greater than the volume required as determined by the comparator 64, the loss warning light 72 will become actuated. If the volume pumped is less than the volume required, a kick lamp 74 will become actuated. Finally, if the volume required is equal to the volume pumped, the normal lamp 70 will become actuated. After pump 18 delivers the required volume of fluid downwardly into the borehole up to the reference level, the normal level detector 60 will provide a signal via line 63 to the valve control device 55 for actuating the three-way valve 30, thereby breaking fluid communication between ports 26 and 29, and reestablishing fluid communication between ports 26 and 27. Counters 52, 56 and 62 will then begin the next withdrawal cycle and cumulate the counts. On the other hand, it will be appreciated that the counters can be arranged to become reset after each cycle of operation.

If after the three-way valve 30 has switched back to its normal condition, whereby fluid communication is established between ports 26 and 27, there should occur a sudden rise in the fluid level above the reference level, the high-level detector 61 will provide a signal to a warning lamp 71 via line 73.

While in the above description of system 40 and of the mud filling system, specific reference was made to particular component parts and subassemblies, it will be appreciated that variations are possible. For example, pump 18 need not be the mud circulating pump of the mud pit 22. Instead, a pump independent of the mud circulation system can be employed for pumping fluid from pit 22 into casing 10 and, hence, the three-way valve 30 can be eliminated. Also, other means can be used to measure the volume of steel withdrawn which determines the volume of fluid required. The means 50 for counting the pipe stands are positioned preferably on the sidewall of the derrick at a distance above the derrick floor 36 substantially equal to a pipe stand.