RU2495240C1 - Method for adaptive control of well-drilling process - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: model is adapted to downhole conditions by means of its coefficients changing, calculation of optimal parameters and drilling of a well in optimal modes which is determined by minimum vibration frequency of drill pipe. The method envisages multiple coefficients updating for power law model by results of well measurements, calculation of optimal parameters of control against the criterion of maximum mechanical speed, performance of drilling at calculated parameters with optimum control against minimum vibration of the drill pipe. Besides drilling model the method uses flushing model for the purpose of even drilling and cleaning of wellbore from drill cuttings and also strata model characterising ability of formations for drilling.

EFFECT: increasing accuracy for control of drilling mode and increasing mechanical speed of hole making due to optimisation of control over minimum vibration of the drill pipe.

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Description

The invention relates to the field of drilling oil and gas wells and can be used for optimal process control.

A known method of regulating the drilling process according to the patent SU 1231946, ЕВВ 44/00 dated 11/27/1995, including the use of a model of the drilling process, which is an exponential trend of the mechanical penetration rate, which is obtained as a result of six or more experimental drilling data in the interval of the formation of the same drillability followed by their least squares approximation. Then, the coefficients of the drilling model are substituted into the criterion “minimum cost per meter of drilling”, containing the expression of the dependence of the drilling time t on the axial load on the bit G, its rotation speed n and the drilling fluid flow Q in the form of a polynomial of the first degree, and search for the minimum criterion using the penalty function . The obtained optimal parameters are set on the drilling rig and further drilling control is carried out at the optimal settings G, n and Q. The model is updated every 0.3 meters of penetration. At the same time, the drilling time before the bit change is calculated and the boundaries of the layers with the same drillability are determined from the confidence interval of the trend of mechanical speed. The model contains parameters representing the geology of the formation surrounding the wellbore. The downhole equipment system comprises measuring devices located above the bit on the drill pipe string. Measurement of drilling conditions includes a measurement of the evaluation of the parameters of the reservoir. Automatic adjustment allows automatic optimal control of the process of deepening wells, which can be used to predict the optimal values of the performance of the bits with heterogeneous drillability.

Disadvantages: the method requires a preliminary factor experiment to obtain a polynomial dependence of the drilling time on the load on the bit, its rotation frequency and the flow rate of the drilling fluid; uses ground-based (non-borehole) instruments to measure drilling parameters; the calculated optimal drilling mode is not confirmed by practical drilling taking into account the vibration of the drill string.

Known patent RU 2244117 C2, 09/10/2004. The way to control work in the well and the well drilling system, taken by us as a prototype.

The invention relates to the field of controlling the process of drilling for hydrocarbons, in particular to the optimized implementation of various drilling operations based on downhole measurements. The technical result is the optimization of drilling operations. The system is designed to perform well drilling operations using a computational model of the drilling process, which represents the combined effect of the conditions on the bottom hole and the operation of the drill pipe string. The model of the drilling process is continuously updated with the results of downhole measurements made during the drilling operation. Based on the updated model of the drilling process, a set of optimal drilling parameters is determined and transmitted to the ground equipment control system. In addition, the system allows the ground control system to automatically adjust the current ground control settings based on updated optimal drilling parameters. Various control scenarios are developed and executed to transfer data to the ground control system based on the current drilling mode.

Disadvantages: the method provides for the construction of an adaptive drilling model during operation in the well, which contains the parameters of the formation model and the parameters of the hydraulic flushing model, which allows it to be adjusted to the conditions at the bottom, however, the method does not take into account the vibration of the drill string to determine the optimal drilling mode.

The objective of the invention is to develop a method of adaptive optimal control of the process of drilling vertical oil and gas wells using the rotary method or using a hydraulic downhole motor.

The technical result is to increase the accuracy of control of the drilling mode and increase the mechanical speed of the well drilling due to optimization of control with the control of achieving optimum minimum vibration of the drill string.

, где М - крутящий момент на долоте, Н·м; ω - угловая скорость вращения долота, с^-1, расход бурового раствора Q обеспечивает превышение давления бурового раствора над пластовым давлением на 10-15 МПа, а контроль достижения оптимума осуществляют по минимуму частоты вибрации бурильной колонны.The technical result is achieved by the proposed method of adaptive control of the drilling process, in which a model of the drilling process is constructed, representing the interaction of the conditions in the bottom of the well with the drill string, obtaining a set of results of downhole measurements of the drilling conditions during work in the well, updating the model of the drilling process based on the results of the downhole measurements of drilling conditions and operating data of ground equipment received from the control system of ground equipment They determine the set of optimal drilling parameters on the basis of an updated model of the drilling process, transfer data on the optimal drilling parameters to the control system for ground equipment and repeatedly repeat the operations of receiving, updating, determining and transmitting during work in the well, and control is carried out according to a deterministic model of the drilling process υ _m = K _b · G ^δ n ^α · Q ^m = max, where υ _m is the mechanical speed of penetration, m / h; To _b - dimensional coefficient of rock drillability, representing a model of formations; G - axial load on the bit, N; n is the bit rotation speed, rpm; Q is the flow rate of the drilling fluid, m ³ / s; δ, α, m - exponents at G, n, Q, while the formation model is the drilling ability of the formation, which is determined by the drillability coefficient of the rocks by the formula $$K_b=\frac{n}{M\omega }$$

where M is the torque on the bit, N · m; ω is the angular velocity of rotation of the bit, s ^-1 , the flow rate of the drilling fluid Q ensures that the drilling fluid pressure exceeds the reservoir pressure by 10-15 MPa, and the optimum is controlled by minimizing the vibration frequency of the drill string.

The deterministic drilling model has a power-law character, represents the interaction of the bit with the rock at the bottom of the well, and during the process constantly adapts to the change in the drillability of the rocks drilled by the bit. Adaptation is carried out by changing the values of the coefficients of the model, continuously updated according to the operational results of downhole measurements. Since the power-law model does not have inflection points, the determination of the optimum is made by minimizing the vibration frequency of the drill string. The method provides for multiple updating of the model coefficients according to the results of downhole measurements, calculation of optimal control parameters by the criterion of "maximum mechanical speed", performing drilling on the calculated parameters with the control of achieving the optimum to minimize vibration of the drill string.

The method is implemented by means of a ground-based computerized drilling equipment control system and a downhole system for measuring downhole parameters interconnected by a communication channel.

The list of figures of graphic images:

Figure 1 - Drilling Management System

Figure 2 - Finding the optimum υ _m = max minimum frequency f _{vib min}

Figure 3 - Example of a mechanical log curve

The ground control system consists of ground equipment 1, control computer 2, pressure sensor 3, vibration sensor 4 and other ground sensors 5 with ADC for measuring wellhead drilling and flushing parameters. A downhole measuring system consists of a measuring module with downhole sensors 6 located in the downhole assembly of the drill pipe string 7 above the bit 8. The module contains sensors, analog-to-digital converters (ADCs) and an electronic block for generating downhole information frames. The module contains a deformation sensor for measuring the axial load on the bit, a bit rotation speed sensor, a torque sensor on the bit, and a mud flow sensor through the bit. The signals from the sensors are converted into digital form by means of the ADC and transmitted via the communication channel 9 to the downhole electronic unit, which accumulates the binary bits corresponding to the measurement results by the sensors and forms data frames from them, into which additional bits can be added for synchronization and detection and correction mistakes. The composition of the sensors can be expanded to control other downhole parameters.

The control computer 2 with the software is connected with the ground equipment of the drilling 1 and controls its operation (a drive of rotation of the pipe string, mud pumps to control the flow of drilling fluid, a winch drive to control axial load, etc.).

The signal from the electronic block of the downhole system is transmitted through the drilling fluid through the hydro-pulse communication channel 9 and enters a pressure sensor 3 located on the riser, which responds to changes in the pressure of the drilling fluid and generates the corresponding signals. The output of the pressure sensor is converted by the ADC into digital form and processed by the control computer. Communication with downhole tools can also be made in other ways, for example, through a drill string with wireline communications.

In addition to the drilling model, the method uses a flushing model, with the help of which equilibrium drilling and cleaning of the wellbore from drilled rock is ensured, as well as a formation model that characterizes the ability of the rocks to drill.

Management is performed by the objective function

$${\upsilon }_m=K_b\cdot G^{\delta }\cdot n^{\alpha }\cdot Q^{{}_m}=\max ,(\mathrm{one})$$

where υ _m is the mechanical speed of penetration, m / h;

K _b - dimensional coefficient of rock drillability;

G - axial load on the bit, N;

n is the bit rotation speed, rpm;

Q is the flow rate of the drilling fluid, m ³ / s;

δ, α, m - exponents for G, n, Q.

The model is updated by adjusting to the conditions at the bottom of the parametric coefficients K _b , δ, α, m.

The achievement of the optimum is controlled by the minimum vibration frequency of the drill string f _{vib min} , determined by the vibration sensor. A minimum of vibrations means achieving the optimum mode of rock destruction by a bit - the axial load on the bit provides the necessary depth of penetration of the teeth of the bit into the rock, and the speed of rotation of the bit provides the necessary torque for the shift / destruction of the rock by the teeth, i.e. there are no jams or slipping of the teeth of the bit along the face due to excessive or insufficient penetration into the rock for a given bit rotation speed. In addition, the vibration sensor determines the moment of contact of the bit with the face when lowering the column.

Curve 1 has a power-law character and grows infinitely, i.e. does not have an inflection point (maximum point) 3 (figure 2), therefore, the calculated maximum of function (1) falls on the border of the domain of definition of the function (shaded) - v.2. The experimental determination of the optimum point f _{vibp min} no to the minimum of vibrations allows us to find the optimum inside the domain of definition of the function.

The method of optimal adaptive drilling control is implemented as follows:

1 At the beginning of drilling, according to the data specified by the project (or from the experience of the driller), the optimal values of G are calculated using model (1)_opt, n_wholesale and Q_opt To achieve maximum mechanical speed υ_M= max;

2 The optimal parameters are set on the drilling equipment and drilling is performed for 10 minutes. while controlling the vibration of the pipe string. The parameters at which the minimum vibration of the column is achieved are considered optimal;

3 The obtained values of the control parameters G, n and Q are measured during drilling and transmitted to the computer via the feedback channel;

4 The computer recalculates the values of the coefficients K _b , δ, α and m of model (1) for the new G, n and Q, thereby it adapts to the actual conditions at the bottom;

5 For a model with new coefficients, a maximum is determined, new G _opt , n _opt and Q _opt are installed on the rig, they are re-drilled and the vibration level of the column is monitored for 10 minutes. etc.

To obtain a reservoir model, the optimal values of C _opt , n _opt , Q _opt and vibration frequency f _{vib min} are recorded in a computer database for each Kb as a function of the depth of the well, together with the bit used and the obtained drilling speed for subsequent use when drilling similar intervals in this well and while drilling other wells of the field.

The second option for optimal control of mechanical speed is a preliminary calculation for the type of bit used G _opt , n _opt and Q _opt for each rock from the reservoir model with the same K _b and their corresponding frequencies f _{vib min} at the stage of development of a well construction project.

The flushing model is the pressure in the riser, which determines the sum of the pressure losses on all elements of the circulation system of the well, the properties and flow rate Q of the drilling fluid, which ensure equilibrium drilling with a 10-15 MPa excess of the drilling fluid pressure above the reservoir pressure and high-quality cleaning of the bottom and well bore from cuttings.

The reservoir model characterizes the drillability of the underlying reservoirs - their ability to drill and is the result of mechanical logging - the dependence of the drillability coefficient of rocks K _b from the depth of the well (Figure 3). The drillability coefficient is the mechanical coefficient of performance (efficiency) of the process of rock destruction by a bit assigned to a unit axial load and is determined by the formula:

$$K_b=\frac{n}{M\omega }$$

where M is the torque on the bit, N · m;

ω is the angular velocity of rotation of the bit, s ^-1 .

The formation model is used in model (1) as a drillability coefficient K _b . In addition, using the formation model, it is possible at the design stage to calculate the optimal values G _opt , n _opt and Q _opt for a given bit diameter D _d for each passable rock.

Obtaining a model of mechanical drillability of formations does not require expensive types of logging - electrical, acoustic, gas, thermal, radioactive, and is the most practically necessary characteristic of the ability of rocks to fracture. In addition, it is carried out in the process of drilling a well without the use of additional special equipment.

The technical result is to increase the accuracy of control of the drilling mode and increase the mechanical speed of the well drilling due to optimization of control with the control of achieving optimum minimum vibration of the drill string.

Claims (1)

A method of adaptive control of a drilling process, in which a drilling process model is constructed that represents the interaction of the conditions in the bottom of the well with the drill string, obtaining a plurality of downhole measurements of the drilling conditions while working in the well, updating the drilling process model based on the results of downhole measurements of the drilling conditions and operating data of ground equipment received from the ground control system, determine the set of optimal parameters drilling on the basis of an updated model of the drilling process, transferring data on the optimal drilling parameters to the control system of ground equipment and repeating the operations of receiving, updating, determining and transmitting while working in the well, characterized in that the control is carried out according to a deterministic model of the drilling process υ _m = K _b · G ^δ · n ^α · Q ^m = max, where υ _m is the mechanical speed of penetration, m / h; K _b - dimensional coefficient of rock drillability, representing a model of formations; G - axial load on the bit, N; n is the bit rotation speed, rpm; Q is the flow rate of the drilling fluid, m ³ / s; δ, α, m - exponents at G, n, Q, while the formation model is the drilling ability of the formation, which is determined by the drillability coefficient of the rocks by the formula $$K_b=\frac{n}{M\omega }$$

where M is the torque on the bit, N · m; ω is the angular velocity of rotation of the bit, s ^-1 , the flow rate of the drilling fluid Q ensures that the drilling fluid pressure exceeds the reservoir pressure by 10-15 MPa, and the optimum is controlled by minimizing the vibration frequency of the drill string.

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