GB2057694A - Drilling rig monitoring system - Google Patents

Abstract

In a drilling rig, parameters of interest (e.g. rate of penetration and drill bit location, number of stands, monkey board position) are calculated and displayed by a unified electronic system. A weight transducer measures the load of the drill string on the rig. A movement sensor provides information on movement of the hook. An internal clock provides time signals. The relevant parameters are calculated, using a microprocessor, from at least the first two of these three factors.

Description

SPECIFICATION Drilling rig monitoring system This invention relates to a system for acquiring operational data in a drilling rig.

In conventional oil drilling rigs, data is acquired and displayed by separate instruments for the various parameters of interest. The instruments used are electromechanical or purely mechanical, and they have poor accuracy and low reliability in the arduous conditions usually present in drilling rigs.

An object of the invention is to provide a significant improvement on such known arrangements, and to provide an integrated electronic system with no (or very few) moving parts. A further object is to provide drilling data which cannot be obtained by existing instruments.

The invention accordingly provides a system for monitoring drilling rig parameters, comprising: a weight transducer mounted to provide a weight signal which is a function of the loading of the drill string on the rig; sensing means arranged to provide a signal representative of the load of the entire drill string calculating means connected to receive the weight signal and the movement signal and arranged to calculate therefrom one or more further parameters of interest.

The further parameters may include weight on bit and depth of bore and the number of drill pipe joints going into or coming out of the borehole which was previously carried out by manual recording means. The calculating means is suitably provided in the form of a microprocessor.

The system also provides detection of approach of the elevator (travelling block) to a fixed part of the rig structure, such as the monkey platform, and the crown block and to an alarm in response thereto.

The invention will now be described in more detail, referring to the accompanying drawings, in which: Figure 1 is a block diagram illustrating one embodiment of the invention; Figure 2 is a side view of a crown block assembly carrying a sensor used in the system of Figure 1; Figure 3 is an end view of the crown block assembly of Figure 2; and Figure 4 illustrates a drillfloor unit used in the system of Figure 1.

Referring to Figure 1, the system is based on a computer 10 utilising a microprocessor of known type, suitably a Z80 microprocessor by Zilog. The computer 10 receives signals from a crown block sensor 12 and a weight sensor 14, and processes these to provide drilling data to output peripherals.

The computer 10 may optionally also receive signals from speed sensors 16, 1 8 and 20.

The weight sensor 14 may suitably be a strain gauge, and is mounted so as to give a signal representative of the load of the entire drill string acting on the drilling rig. Thus the sensor 14 may, for example, be attached to the crown block support or to the hook assembly. These parts of the drilling rig are not herein illustrated since they are extremely well known in the art, as are strain gauges.

The crown block sensor is illustrated in greater detail in Figures 2 and 3. The crown block assembly includes a base 22 secured to the drilling derrick, and pulleys 24 independently rotatable on a pulley shaft 26 journalled in the base 22, as is conventional. The sensor 12 is secured to the base 22 adjacent the fast line pulley 24a, and comprises three magnetic proximity detectors, or photo-cell mark detectors, 28, 30, 32 which produce output pulses when passed by mild steel pieces 34 secured to the adjacent face of the fast line pulley 24a.There are suitably eight pieces 34 equispaced about the pulley 24a, the positioning being such that the distance D1 = 2 x D2 x sin 22.5 ; the distance D2 is not critical and can conveniently be 400-500mm. 8 strips of white paint are used as marks in place of mild steel pieces when using the photo-cell marker detector.

The centre detector 30 is used to provide datum pulses which can be switched with the pulses from the detectors 28, 32 to distinguish forward and reverse movement. Thus the sensor 12 provides an output to the computer 10 comprising (1) a signal distinguishing forward and reverse, and (2) a pulse signal wherein each pulse indicates a unit of distance travelled by the travelling block, and the pulse rate indicates the speed of movement.

A duplicate sensor 1 2a is provided as a standby.

These signals are processed by techniques known per se in the computer 10, together with time signals generated by an internal clock, to generate parameters of interest as detailed below.

(1) True drilling depth is derived by reading movement of the crown block pulley and accumulating the total for downward movement only. The total depth thus derived is a nominal depth equal to the unstretched length of the drill string. The microprocessor of the present apparatus is provided with memory and program data to allow a corresponding algorithm to be performed to calculate true depth for immediate display. The memorised data is suitably provided in an EPROM, which can readily be set up initially with information relevant to the specific rig.

(2) Rate of penetration (ROP) is derived by dividing the drilling depth signal by time.

(3) Drilling bit location is derived by accumulating both upward and downward movement of the crown block pulley when under load.

(4) Trip speed (i.e. the speed of the drill string while being removed from the drill hole) is derived by dividing the upward movement of the crown block pulley by time, during upward movement under load.

(5) The ton/mile reading of the drill line is derived from the total travel of the cable of the travelling block/crown block assembly and the weight on the travelling block. Thus total work done on the cable is measured, which is vital for evaluation of the safe life of the cable.

(6) Hook load indication comes directly from the drill string transducer signal.

(7) Weight on bit (WOB) is developed by storing total hook load before the bit is at bottom and subtracting from this the instantaneous hook load.

(8) Digital timer and stop watch functions are supplied by the clock circuit. The system also enables the information from the crown block sensor to.be used to generate safety signals, by initially storing in the memory of the computer 10 data representing the position of the elevator relative to the monkey board and the permissible range of movement of the (travelling block) elevator relative to the crown block. Thus: (9) A signal representing the relative position of the elevator to the crown block and to the monkey board is developed from the movement of the crown block pulley and activates an alarm if the travelling block approaches within a safe limit from the crown block.

The parameters derived by the computer 10 can be output to a range of peripherals as shown in Figure 1, such as a local VDU 50, a remote VDU 52, a printer 54, a recorder 56 (e.g. a chart plotter or a multi-track tape recorder or magnetic tape/disc recorder), and a drillfloor unit 58. The drillfloor unit, shown in greater detail in Figure 4, is positioned on the drillfloor for use by the drilling crew. The rate of operation is displayed by a meter 60 since this accords with traditional drillfloor practice, and the other parameters on digital displays.

The availability of the computer 10 permits the monitoring of other functions to be easily added.

For example, as shown in Figure 1, the additional sensors 16, 18, 20 may supply the computer with speed date for the rotary table and two mud pumps, respectively, for suitable display or recording.

The invention thus allows the parameters of interest to be derived from a limited number of sensors entirely without moving parts, thus giving improved reliability and low maintenance costs.

Since the system replaces a number of conventional instruments, the initial cost is also competitive.

Claims (10)

1. A system for monitoring drilling rig parameters, comprising: a weight transducer mounted to provide a weight signal which is a function of the weight of the drill string on the rig; sensing means arranged to provide a signal representative of movement of the drill string; and calculating means connected to receive the weight signal and the movement signal and arranged to calculate therefrom one or more further parameters of interest.

2. The system of claim 1, in which the sensing means detects rotation of a drill pipe hoisting pulley.

3. The system of claim 2, in which the sensing means detects movement of the crown block fast line pulley.

4. The system of claim 3, in which the sensing means comprises pieces of predetermined magnetic characteristics equispaced about said pulley, and a sensor unit responsive to passage of said pieces to produce a pulse signal representative of movement and speed and a signal indicative of direction of movement.

5. The system of claim 3, in which sensing means comprises paint markings equispaced about said pulley, and a paint mark photocell detector unit responsive to the passage of said marks to produce a pulse signal representative of movement and speed, and a signal indicative of direction of movement.

6. The system of any preceding claim in which the calculating means includes a clock, and is arranged to produce from the distance travelled by the drill string and time an output representing rate of penetration as one said further parameter.

7. The system of any preceding claim, in which the calculating means accumulates upward and downward movement of the drill string separately, thereby to produce outputs representing drill bit location and depth of drilling and number of joints of-drill pipe in or out of the drilled hole.

8. The system of any preceding claim, in which the calculating means comprises a microprocessor and a memory storing predetermined data representing the relationship between the length of the drill string and weight of the drill string thereof; whereby the microprocessor may comprise from the movement signal a true depth signal.

9. The system of any preceding claim, including detecting the movement of the elevator and supplying a signal representative thereof to the calculating means, the latter being arranged to produce an alarm signal if the elevator approaches unduly closely to a fixed part of the structure.

10. A drill monitoring system substantially as hereinbefore described with reference to the drawings.