EP2816194A1 - Method for performing a deep drilling process - Google Patents

Abstract

The invention relates to a method for performing a deep drilling operation, wherein a drill pipe is used, which is rotated by a drive, which is suspended from a cable, and which carries at its lower end a drill head. To improve the quality of control, a multi-variable controller (4) is used in a control device (3) on which at least the traction force (FH) exerted by the drill pipe on the cable pull and the feed speed (v) of the drill pipe are guided as controlled variables. As manipulated variables, the speed (s) of rotation of the drill pipe and a brake quantity (B) for the cable are advantageously output by the multivariable controller (4). Thus, lateral influences can be taken into account in the control. Particularly advantageous is the use of a multi-variable controller (4) in which a business management and / or energy optimization of the stationary operating point is integrated. This minimizes the cost of drilling.

Description

The invention relates to a method for performing a deep drilling operation, wherein a drill pipe is used, which is suspended from a cable and carries at its lower end a drill head. The drill string is rotated by a drive.

Geological drilling operations, commonly referred to as deep drilling operations, are very energy and cost intensive. For example, in the exploration and production of oil and / or natural gas such drilling operations are carried out at great expense. The cost of operating a derrick is $ 6 per day, and for a rig it can be millions of dollars per day. Improvements in deep drilling operations are therefore of significant economic importance.

In practice, a manual procedure of drilling operations has hitherto been customary, in which an experienced plant operator controls the drilling process by means of various control interventions, e.g. Example by adjusting the speed of the drill or the braking torque to a cable drum on which a rope is wound to suspend the drill string. The operator observes, among other things, the feed rate of the drill string, which is referred to in the literature as "Rate Of Penetration", ROP, the hook load, which is adjustable in a cable winch with rope drum by their braking torque, and vibrations on the drill string. In addition, the recirculated rinsing fluid is often examined by other employees for rocks that are washed to the surface, or on contained gas bubbles. This information may be taken into account when determining the driving style by the system operator. Because the costs for the drilling process are often billed in daily rates, the cost consideration is predominantly time-related and the goal of the plant operator is the minimization of the time required to reach the desired drilling depth.

From the WO 2009/062725 A2 is a method for performing a deep well known in which motors are arranged for feed and rotation of the drill head and thus at the lower end of the drill string. For the drilling operation, a control is provided in which, in a first mode of operation, the speed of rotation of the bit, often referred to as "RPM," and the drilling pressure are controlled so that the power at the bit is a predetermined maximum, and at which, in a second mode of operation, regulate the same quantities so that the depth of cut (DOC) is kept at a predetermined value. Possible interactions between the two manipulated variables are disadvantageously disregarded.

From the WO 2012/080812 A2 is a derrick with a hydraulic motor on the drill head known. When performing a drilling operation, an iterative optimization of the driving style is performed, which is based on an approximation of characteristics of the hydraulic motor.

In the DE 601 21 153 T2 For example, the detailed structure of a derrick is described as an example of an apparatus for performing a deep drilling operation. For further details on the structural design of drilling devices, reference is therefore made to this document. There, an optimization of the feedrate (ROP) is proposed using one of several possible manipulated variables, the one that best correlates with the feedrate. In this case, a range of the feed rate is sought, in which their slope is almost zero and thus a local maximum of the feed rate.

For a description of an example of suspension of a drill string by means of a cable pull and cable drum on the WO 2005/113930 A1 directed. A PID controller provides there for a defined rotational speed of the cable drum by engaging a mechanical brake, which generates a braking torque on the cable drum. As long as the rope is taut, its elasticity and the effective drum diameter variable with the length of the wound rope are neglected, the rotational speed of the cable drum correlates with the feed rate of the drill head.

The invention has for its object to improve the efficiency in performing a deep drilling operation.

To solve this problem, the new method for performing a deep drilling operation on the features specified in claim 1. Advantageous developments of the invention are described in the dependent claims, in claim 6 a computer program, in claim 7 a digital storage medium and in claim 8 a control device for carrying out the method are described.

The invention has the advantage that due to the use of a multi-variable controller, the two controlled variables feed rate and hook load on the cable are controlled simultaneously. Since these sizes are highly dependent on each other, this is of particular advantage. The speed of rotation of the drill pipe, which is also referred to as shaft speed below, is consistent with the drill speed when no additional motor is provided at the bottom of the shaft for the drill bit. For example, even if at the lower end of the shaft, a hydraulic motor causes additional rotation of the drill head relative to the shaft, a change in shaft speed will affect the drill speed and thus primarily the feed rate, but will also indirectly affect the hook load, ie, those due to the drill string the cable tension exerted. The brake size for the cable, for example, when using a cable drum required for the operation of the drum brake Actuator corresponds primarily affects the hook load, but has a significant effect on the feed rate (ROP) on the contact pressure of the drill head ("Weight On Bit", WOB). These interactions or cross influences are taken into account in an advantageous manner by the multi-variable controller in the control of the respective control variable feed rate or hook load. Thus, control performance and efficiency in performing the deep drilling operation are improved.

A suitable multi-variable controller has at least as many inputs as controlled variables and at least as many outputs as manipulated variables. The couplings between the different sizes are taken into account in a uniform controller concept. The design of the multivariable controller takes place via a matrix / vector calculation.

The choice of the feed rate (ROP) as a controlled variable has the advantage that it is easily measurable and of great importance for the time required to achieve the desired drilling depth. The hook load is also easily measurable and representative of the contact pressure of the drill head (WOB), which is crucial for the fragmentation of the rock. A use of the contact pressure as a control variable, however, would have the disadvantage that their measurement would be associated with considerable difficulties, since they u. a. depends on the frictional forces on the walls of the borehole and the buoyancy of the drill string in the rinsing liquid, which can be subject to strong fluctuations.

The manipulated variables used shaft speed and braking size for the cable advantageously correspond to the previously used by the operator for manual control intervention. In this case, the multi-variable controller significantly relieves the operator of manual control actions compared to the conventional manual mode, which has been described above, achieved. The closed-loop multi-variable controller responds faster and more reproducibly to disturbances, which can occur, for example, by changes in the rock formations during the drilling process. The control keeps the feed speed and pressure more precisely at preset values, thus improving the service life of drill heads.

In a particularly advantageous embodiment, a model-based predictive controller ("MPC") is used as the multi-variable controller. In such regulators, a discrete-time dynamic model of the process to be controlled serves to calculate the future states of the process in dependence on the input signals and to select suitable input signals based on this prediction. This allows the calculation of the optimum in terms of a quality function input signal with the simultaneous consideration of input and state constraints.

During the drilling operation, the drive torque, which is required to achieve the desired shaft speed, and / or the return temperature of a rinsing fluid used during the drilling operation can be advantageously monitored for maintaining predetermined upper limits in an advantageous manner. This can disturbances, z. As an overload of the drive or overheating of the drill head can be avoided.

A regulation of the speed of a pump for the rinsing liquid could be useful in addition to the above-described multi-variable control. As long as sufficient removal of drill cuttings and sufficient cooling of the drill head is ensured, however, the pump speed does not have a significant transverse influence on the other controlled variables of the multiuser controller described above. The control of the pump speed can therefore be done either by a separate size controller or integrated into a correspondingly extended multi-variable controller. In any case, by using the pump speed as a further manipulated variable, which is predetermined as a function of at least the return temperature of the washing liquid by a controller, an optimization of the pump performance while ensuring adequate cooling achievable.

Particularly advantageous is the use of a multi-variable controller in which a business management and / or energy optimization of the stationary operating point is integrated during the drilling process. For example, the function block for model-based predictive multi-variable control integrated in the SIMATIC PCS 7 process control system contains such an optimization as of PCS 7 V8.0 (December 2012). As a quality criterion, any linear combination of all manipulated variables and controlled variables of the multivariable controller can be formulated. Secondary conditions for the controlled variables are specified in the form of tolerance ranges for the setpoints. The optimizer delivers setpoints within the tolerance ranges that are optimal in terms of the quality criterion. In this case, the current value of the quality criterion, z. As the resulting costs or the specific energy consumption, the system operator displayed on an operator station to strengthen the energy and cost awareness. In particular, when performing deep drilling operations, the operating point optimization in the multi-variable controller has the advantage that each manipulated variable and controlled variable can be evaluated with a cost factor. This achieves an objective cost optimization that can deviate significantly from the purely subjective assessment of the system operator. This objective cost optimization is of considerable advantage over a "blind" maximization of the feed rate (ROP), because in the range of the maximum achievable feed rate experience has shown that undesirable side effects already occur, for example a smearing of the drill head, unwanted vibrations, excessive wear or energy waste. The limits that can be specified for each manipulated or controlled variable, arise due to technological constraints, eg. As the maximum available drive power, the state of wear of the drill head or the prevention of vibration. The preliminary considerations for the specification of the quality criterion also support the definition of alarm limits, e.g. B. with regard to a required replacement of the drill head.

The above object is also achieved with a control device for controlling a deep drilling operation, which comprises means for carrying out the method according to claim 1. The invention is preferably implemented in software or in software and firmware. On the one hand, the invention is thus also a computer program with program code instructions executable by a computer and, on the other hand, a storage medium with such a computer program, ie a computer program product with program code means, and finally also a control device, in whose memory such a computer program is used as means for carrying out the method and its embodiments loaded or loadable.

Annex of the drawing, in which an embodiment of the invention is shown, the invention and refinements and advantages are explained in more detail below.

The single FIGURE shows a block diagram of a deep drilling device 1 with the essential components drill 2 and control device 3. The drill 2 is for example a derrick, which is equipped with measuring means for detecting current measured values and with adjusting means for influencing the drilling process. The control device 3 is realized for example by an automation device, in which a function block 4 is loaded for a multi-variable controller with integrated operating point optimization. The automation device includes a processing unit and a memory in which a computer program is loaded, which is executed during operation of the automation device for controlling the deep drilling operation by the processing unit. As an automation device comes, for example, a SIMATIC S7, as a function block 4, for example, the model-based predictive multi-variable controller ModPreCon, which is known from the SIEMENS catalog ST PCS 7, is used.

In deep drilling operations, a drill pipe is used which is composed of several segments and carries at its lower end a drill head, which, as soon as it is worn, must be replaced with complete removal of the linkage. The feed rate v (ROP) and the wear of the drill head are mainly dependent on the rock type G, which can be determined for example by a laboratory sample of emerging from the borehole mud, from the contact pressure of the drill head (WOB) against the rock and the drill speed n (RPM).

At the lower end of the drill string, the drill head may be preceded by a hydraulic motor, which causes an additional rotation of the drill head relative to the linkage. In this case, the bit rotation speed is increased from the shaft speed by a substantially constant offset, which, however, is insignificant for the behavior of the control, so that in the following between the terms shaft speed and drill speed need not be distinguished.

The various primary effects and interactions exerted on the measured variables by the manipulated variables given on the drill 2 are indicated in the figure by arrows which are drawn with broken lines into the block representing the drill 2. Thus, the drill speed n (RPM) has a primary effect on the feed rate v (ROP) and the amount of braking B applied to the drill string of the drill pipe suspension, a primary effect on the measured hook load FH. However, between drill speed n and hook load FH and between brake size B and feed speed v, there is additionally a strong interaction, which has hitherto been neglected, now being advantageously taken into account in the control by the new multi-variable controller. With the new method for performing a deep drilling process thus feed speed v and hook load FH are kept much more precise than previously on specified or predefinable setpoints.

Drill speed n and brake magnitude B additionally have an effect on a torque M of the drive motor which rotates the shaft of the drill string and a measured return temperature T of the rinse medium pumped into the borehole. In the case of the variables torque M and return temperature T, their monitoring would be sufficient in principle to comply with predetermined limits, so that disturbances due to impermissible elevations are avoided. The setting of a return quantity Q of the rinsing agent is carried out to optimize the Spülmittel- and energy consumption with a separate controller 5 in the control device 3, which specifies a pump speed nP as a function of the measured return temperature T and possibly in dependence of the determined rock type G as a manipulated variable. In a modification of the embodiment shown, this controller may additionally be implemented in the multi-variable controller, so that instead of a 2 × 2 multi-variable control, it is then a 3 × 3 multi-variable control by the functional module 4.

As further variables which influence the drilling process carried out by the drill 2, exemplary rock properties R, z. As the rock hardness, and a weight FG of the introduced into the borehole drill string drawn. The weight FG of the drill string loads, reduced by the bucket caused by the Spülmittelstand and the hook load FH, on the drill head. The contact force of the drill head (WOB) differs during the drilling process only by an offset of the hook load FH, so measured on the hook load changes, apart from dynamic effects and friction in the borehole, in an advantageous manner for the control of the changes in the contact pressure of the drill head ,

The described integration of a working point optimization in the function module 4 and thus in the multi-variable controller has the advantage that an economic optimization of the drilling operation can be carried out, which has the goal to minimize the total costs for a borehole at a location with specific rock properties R and a predetermined depth H. , For this purpose, a quality criterion can be specified, which is formed on the basis of the costs. Total costs KG for the borehole are made up of costs KA for the plant, costs KM for the maintenance during the drilling process and costs KE of the energy used. The following applies: $$\mathrm{KG}=\mathrm{KA}+\mathrm{KM}+\mathrm{KE}\mathrm{,}$$

mit $$\begin{array}{ll}\mathrm{H}& -\mathrm{Tiefe},\\ \mathrm{v}& -\mathrm{Vorschubgeschwindigkeit\; und}\\ \mathrm{tDO}& -\mathrm{Stillstandszeit},\mathrm{englisch}:"\mathrm{Down\; Time}"\mathrm{.}\end{array}$$

The investment costs KA are time-related costs and result from the costs for the equipment leasing and for the personnel. This costs per day costs dK. The time requirement tDR for the entire drilling process, English: "drilling time", can be calculated to $$\mathrm{tDR}=\mathrm{H}/\mathrm{v}+\mathrm{tDO}.$$

With $$\begin{array}{ll}\mathrm{H}& -\mathrm{depth}.\\ \mathrm{v}& -\mathrm{Feed\; rate\; and}\\ \mathrm{tDO}& -\mathrm{Downtime}.\mathrm{English}:"\mathrm{Down\; time}"\mathrm{,}\end{array}$$

The system costs KA can then be calculated to: $$\mathrm{KA}=\mathrm{dK}*\mathrm{tDR}\mathrm{,}$$

mit
N - Anzahl der Bohrköpfe und
tR - Zeitbedarf eines Bohrkopftauschs, englisch: "Replacement Time".The hook load FH affects the wear of the drill head and thus the maintenance costs via the contact pressure of the drill head (WOB). The replacement of a drill head causes material costs KB. N drill heads are required for the entire drilling operation, with the number of drill heads being the ratio of the tDR time requirement for the entire drilling operation and the average life of a drill bit results. The drill head change has a double effect on the costs. On the one hand, the downtime tDO increases according to the formula: $$\mathrm{tDO}=\left(\mathrm{N}-\mathrm{1}\right)*\mathrm{tR}$$

With
N - number of drill heads and
tR - Time required for a drill head exchange, in English: "Replacement Time".

mit
KB - Kosten eines Bohrkopfs, englisch: "Bit".On the other hand, maintenance costs accrue to KM according to the formula: $$\mathrm{KM}=\mathrm{N}*\mathrm{KB}$$

With
KB - costs of a boring head, English: "Bit".

mit
KC - Energiefixkosten und
KF - ein drehzahlbezogener Kostenfaktor.For example, when using a cable with cable drum and friction brake to generate a braking torque caused by the brake wear no significant cost. The shaft speed n, on the other hand, has an effect on the frictional forces on the drill head and linkage and correlates to a first approximation with energy costs KE for driving the drill, which are calculated as: $$\mathrm{KE}=\mathrm{KC}+\mathrm{KF}*\mathrm{n}$$

With
KC - energy costs and
KF - a speed-related cost factor.

When using a quality criterion determined in this way, a business optimization of the deep drilling operation automatically takes place automatically.

In addition to the business optimization, the specific mechanical energy MSE (English: "Mechanical Specific Energy") can be calculated and displayed for the drilling process. This is proportional to the energy consumption related to the feed rate v and is calculated according to the formula: $$\mathrm{MSE}=\mathrm{WOB}*\mathrm{n}/\mathrm{v}\mathrm{,}$$

After multiplication with a wellhead efficiency typically between 30 and 40% and unit conversion, the specific mechanical energy can be compared to the so-called "Rock Compressive Strength", a measure of the physical properties of the rock. If the rock properties are known from laboratory investigations, it can be used to verify the efficiency of the drilling process.

The proposed method for performing a deep drilling operation is universally applicable to drilling rigs on land or on oil rigs, ie on-shore or off-shore, regardless of design details of the drilling rig. It can be used in particular for electric or hydraulic main drive drills, directly on a shaft mounted drill head, for downhole hydraulic drilling machines or downhole electric drilling machines, or for drills with cable drag systems, mechanical or electrodynamic depending on the brake type corresponding, predetermined by the multi-variable controller braking effect. In this case, no special downhole sensor technology is required in an advantageous manner. The adaptation to a concrete drilling rig is made by data-based process identification for the model-based predictive controller and possibly by specification of the quality criterion for the optimization from a business or energy point of view. As stated above, a largely exact cost definition for the quality criterion is possible. at This can be done by empirical estimates, eg. B. for the service life of the drill head to be supplemented.

Claims (8)

Method for carrying out a deep drilling operation,
a drill string is used which is rotated by a drive suspended from a cable and which carries a drill head at its lower end,
wherein at least the tensile force (FH) exerted on the cable pull by the drill pipe and the feed rate (v) of the drill pipe are measured and fed as controlled variables to a common controller (4) for regulation to a predetermined or predefinable nominal value,
wherein the controller (4) outputs as manipulated variables at least the rotational speed (s) of the rotation of the drill string and a braking amount (B) for the cable and
wherein the controller (4) for taking into account the respective influences of the rotational speed (s) of the drill string on the feed rate (v) and on the tensile force (FH) and to take into account the respective influences of the braking amount (B) on the feed rate (v) and the tensile force (FH) is designed as a multi-variable controller (4). Method according to claim 1, characterized in that
in that a model-based predictive controller is used as the multivariable controller (4). A method according to claim 1 or 2, characterized in that the drive torque (M) and / or the return temperature (T) of a rinsing fluid used in the drilling operation are monitored for compliance with predetermined upper limits. Method according to claim 3, characterized
that is output as a further correcting variable a rotational speed (nP) of a pump for the washing liquid depending on at least of the return temperature (T) of the rinsing liquid through the regulator (4) or a further controller (5). Method according to one of the preceding claims, characterized
that in the multi-variable controller (4) is integrated a business management and / or energy optimization of the stationary operating point during the drilling process. A computer program or computer program product having program code means stored on a computer-readable medium and arranged to carry out all the steps of a method according to at least one of claims 1 to 5 when the program is executed on a controller for controlling a deep drilling operation. Digital storage medium with electronically readable control signals, which can cooperate with a programmable controller for controlling a deep drilling operation such that a method according to at least one of claims 1 to 5 is executed. Control device for controlling a deep drilling operation with a processing unit and a memory in which a computer program according to claim 6 is loaded, which is executed by the processing unit during operation of the control device (3).

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