RU2646651C1 - Method of monitoring the axial load to bit when drilling inclined well-directional wells with downhole drilling motor - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to drilling oil and gas wells. Method for monitoring the axial load on the bit when drilling obliquely directed wells, including determining the pressure at the standpipe of the drilling rig in the idle and operating modes of the screw downhole motor (bit over the face), characterized in that after starting the engine without load, when operating it in idling mode, the speed and torque are measured on the rotor M_p.x, then an axial load is applied to the bit and the rotational speed and torque are measured on the rotor M_p.p, and the actual axial load on the bit at the same speeds of rotation of the drill string under load and without load is determined by the mathematical formula given in the text of the description.

EFFECT: technical result is determination of actual axial load on the bit by calculating magnitude of friction force of drill string against borehole wall when drilling obliquely directed wells with screw downhole motors while rotating drill string.

1 cl, 1 dwg

Description

The invention relates to the drilling of oil and gas wells.

A known method of creating and controlling the necessary load on the bit when drilling horizontal and directional shafts with large displacements of the faces from the wellhead (patent RU No. 2313667, publ. 12/27/2007), including determining the working moment on the motor shaft by the magnitude of the required load bit and its specific moment, sufficient for rotation of the rock cutting tool under the necessary load on the bit. According to the characteristics of the downhole screw motor (VZD), the pressure drop across the engine is found when working with the operating moment and in idle mode, then after lowering the drilling tool with a chisel and VZD until the bottom of the well and leveling the drilling fluid parameters, the pressure on the riser of the drilling rig in the idle is recorded VZD operation mode (bit over the face), after that the necessary load on the bit is created by the unloaded weight of the drill string to the bottom until the pressure on the riser increases by Well, the pressure difference in the working and idle modes of the VZD, determined by its characteristic, after that the magnitude of the load on the bit during drilling is controlled by this value.

The disadvantage of this method is the lack of consideration of hydraulic resistance, represented by the formation of slurry pads in places of intense curvature of the well, gland formation on the bit, as well as an increase in the density of the drilling fluid in the annular space due to drill cuttings.

A known method of controlling the operation of a screw engine in downhole conditions (copyright certificate SU No. 1128646, published on 09/30/1990), which consists in measuring pressure readings in the discharge line when the engine is running on the bottomhole under load and without load, and maintaining a given speed the motor shaft is carried out by maintaining a constant difference in the measured pressure readings.

The disadvantage of this method is the lack of accounting for the wear of the working bodies of the VZD during its operation, wear of the bit or changes in the properties of rocks.

A known method of rotary drilling of wells with a downhole hydraulic motor (copyright certificate SU No. 1114777, published on 09/23/1984), which consists in determining the rotational speed of the drill string by establishing its dependence on the axial load on the rock cutting tool corresponding to the braking torque of the downhole motor, and the value the axial load corresponding to the braking torque is found by the following formula:

where M _T is the braking torque of the downhole hydraulic motor according to passport data;

M - the required working torque on the shaft of the downhole motor;

G is the axial working load on the rock cutting tool.

The disadvantage of this method is the lack of control of the rotational speed of the drilling tool due to the delay in transmitting the signal from the moment of rotation of the airway to its stop, as well as the reliable value of the axial load on the bit.

A known method of controlling the necessary load on the bit when drilling wells, including an automated control system for the drilling mode (ACS RB) (Baldenko DF, Baldenko FD, Gnoev AN Single-screw hydraulic machines: 2T. - M .: OOO IRC Gazprom. - 2007. - T2. Downhole Motors. S. 382-388), which provides control of changes in the load on the shaft of the downhole hydraulic motor (load on the bit) by changing the speed or current of the drive motor of the drilling pump unit (BNA) and bit feed regulator (RPD).

The disadvantage of this method is the lack of additional pressure when drilling directional wells, due to wear of the working bodies of the airway during its operation, an increase in the density of the drilling fluid in the annular space due to particles of drill cuttings. An additional increase in pressure due to the indicated hydraulic resistances leads to inadequate values of the established correlation of the current strength on the BNA drive and the operation of the VZD and RPD.

A known method of controlling the axial load on the bit when drilling horizontal and directional wells VZD (patent RU No. 2361055, publ. 07/10/2009), which includes determining the pressure on the riser of the rig in idle operation of the VZD (bit over the face), creating the necessary the load on the bit by the unloaded weight of the drill string to the bottom until the pressure on the riser increases by the magnitude of the pressure difference in the operating and idle operating modes of the engine, determined by its characteristic. After the engine is started (over the face), when it is idling, the drill string is rotated by the rotor (or the top drive of the drilling rig), followed by the measurement of the magnitude of M _p.x (torque on the rotor in idle mode), after this creates an axial load on the bit and rotate the drill string with the rotor (or the top drive of the drilling rig), followed by measuring the magnitude of the moment on the rotor M _rp (moment on the rotor in the operating mode of the engine).

Moreover, the actual axial load on the bit is determined by the expression:

Н

N

where G _{oc. GTI} - axial load on the bit at the station of geological and technical research, N;

M _r.kh - the moment on the rotor in the operation mode of the IDR at idle, Nm;

M _r.r - the moment on the rotor in the operating mode of the VZD, Nm;

D _well - well diameter, m

The disadvantage of this method is the lack of a parameter of the mechanical drilling speed, the rotational speed of the drill string and the rate of its movement relative to the axis of the well.

A known method of controlling axial load on a bit when drilling horizontal and directional wells VZD (MV Dvoinikov / Technology for drilling oil and gas wells with modernized downhole screw motors. Diss. Doctor of Engineering. Tyumen 2011. - S. 215-219) adopted for the prototype, including determining the pressure on the riser of the drilling rig, turning the drill string with subsequent measurement of the magnitude of the moment M _rx (torque on the rotor in the operation mode of the _{air intake} at idle). After creating an axial load on the bit, the operating mode of the VZD is determined by the pressure on the riser of the drilling rig and the drill string is rotated with subsequent measurement of the moment M _rp (torque on the rotor in the operating mode of the VZD). Knowing the magnitude of the moments M _rx and M _rp , determine the friction force on the rock and the actual load on the bit according to the formula:

where G _{oc. GTI} - axial load on the bit at the station GTI, N; M _r.kh - the moment on the rotor in the operation mode of the IDR at idle, Nm; M _r.r - the moment on the rotor in the operating mode of the VZD, Nm; D _SLE - well diameter, m; υ _p - the speed of movement of the drill string along the wall of the well; ω _SLE - the angular velocity of rotation of the drill string relative to the axis of the well.

The disadvantage of this method is that the method does not take into account the displacement of the drill string relative to the axis of the borehole and the moment of resistance to friction of the drill string against the borehole wall, taking into account the loss of stability, taking into account the Young's modulus and the polar moment of inertia, which determine its rigidity when the stress-strain state changes.

The technical result is to increase the efficiency of drilling directional wells, the reliability of the VZD and rock cutting tools by improving the quality of control of the axial load on the bit with the simultaneous rotation of the drill string.

The technical result is achieved by the fact that after starting the engine without load, when operating in idle mode, the speed and moment on the rotor M _{r.x are measured} , then the axial load on the bit is created and the speed and moment on the rotor M _r are measured _{. p} , and the actual axial load on the bit at the same rotational speed of the drill string under load and without load is determined by the formula:

Н

N

where G _OS.GTI - axial load on the bit at the GTI station, G _OS.GTI = G _bk -G _d , H;

G _bq - the weight of the drill string on the hook of the rig, N;

G _d - the load on the bit, N;

M _r.kh - the moment on the rotor in the operation mode of the IDR at idle, N⋅m;

M _r.r - the moment on the rotor in the operating mode of the VZD, N⋅m;

D _SLE - well diameter, m;

ϑ - mechanical drilling speed, m / s;

ω _well - rotational speed of the drill string relative to the borehole wall, rad / s;

м; a is the movement of the drill string along the axis of the well,

m;

- зазор между бурильной колонной и стенками скважины,

м;

- the gap between the drill string and the walls of the well,

m;

м;t is the pitch of the helix of the drill string relative to the axis of the well in 2π,

m;

E is Young's modulus, Pa;

I - polar moment of inertia of the drill string, m ⁴ .

The method is illustrated in FIG. 1 is a graph of the actual load of the bit on the rotational speed of the drill string.

The method is as follows. When drilling directional wells using a CDD as a rock cutting tool, an effective drilling mode is selected to ensure reliable operation of the rock cutting tool. To this end, on the drill string, the VZD with the bit fixed on it, is lowered into the well. Before reaching the bottom, the drilling fluid is supplied through the drill pipe string into the VZD. After starting the engine without load, when it is idling, the pressure on the riser of the drilling rig is determined. Then, the drill string is rotated without load, with subsequent measurement of the magnitude of the moment M _r.x (torque on the rotor in the _IZD idle mode) and the rotational speed of the drill string.

Then the drill string with the motor and the bit is fed down to the contact with the face and then the axial load on the bit is smoothly created. The operating mode of the VZD is determined by the pressure on the riser of the rig, after which the drill string is rotated under load, followed by the measurement of the moment M _rp (torque on the rotor in the operating mode of the VZD) and the rotational speed of the drill string under load.

Due to the load on the bit and the presence of torsional vibrations, the stability of the drill string is lost. As a result, the drill string experiences both tensile and compressive stresses. With the increase in weight on bit (G _bc reduction and increasing G _d) sliding friction between the drill string and the borehole wall becomes rolling friction. In this case, the drill string rotates around its own axis in a clockwise direction, as well as figurative motion (planetary) relative to the axis of the well ω _borehole. .

Knowing the magnitude of the moments in M _rx and M _rp , as well as the rotational speed of the drill string, taking into account the stress-strain state, determine the friction force on the rock, which prevents its progressive movement along the axis of the well.

The friction force of the drill string against the borehole wall, directed opposite to the created axial load on the bit, is defined as

Knowing the axial load at the GTI station G of the _GTI , calculated only by the change (loss) in weight on the hook of the rig using GIV indicators (hydraulic weight indicator), the actual axial load on the bit is determined.

Moreover, the actual axial load on the bit, taking into account the stress-strain state of the drill string, is determined by the formula:

Н

N

where G _{oc. GTI} - axial load on the bit at the GTI station, G _ax . _GTI = G _bk -G _d , N;

G _bq - the weight of the drill string on the hook of the rig, N;

G _d - the load on the bit, N;

M _r.kh - the moment on the rotor in the operation mode of the IDR at idle, N⋅m;

M _r.r - the moment on the rotor in the operating mode of the VZD, N⋅m;

D _SLE - well diameter, m;

ϑ - mechanical drilling speed, m / s;

ω _well - rotational speed of the drill string relative to the borehole wall, rad / s;

м; a is the movement of the drill string along the axis of the well,

m;

- зазор между бурильной колонной и стенками скважины,

м;

- the gap between the drill string and the walls of the well,

m;

м;t is the pitch of the helix of the drill string relative to the axis of the well in 2π,

m;

E is Young's modulus, Pa;

I - polar moment of inertia of the drill string, m ⁴ .

The results of the analysis of practical data on drilling wells with a complex profile showed that the actual axial load on the bit differs significantly from the load measured at the GTI station. As a result, when drilling wells, the mechanical speed decreases, and the wellbore is formed with the formation of large caverns and ledges that impede the BHA advancement, and the intensity of the curvature and the radius of the sections of the set and fall of the zenith angle do not correspond to the allowable strength characteristics of the drill pipes. It is almost impossible to carry out drilling of such sections using only a motor as a drive of a bit. This is primarily due to the large friction between the BC and the rock. As a technological technique for increasing the efficiency of drilling, for example, with a downhole screw motor (VZD), simultaneous periodic or constant rotation of the drill string using a rotor or top drive is used. Manufacturers call this method combined. Its use allows drilling wells of various depths with different types of profiles, a wide range of changes in the type and properties of flushing fluids, parameters of the drilling mode, as well as using different designs and sizes of rock cutting tools.

However, with the current technology of combined drilling, problems are noted associated with the instability of the VZD, their stops, as well as accidents (lapels, destruction of the elements of the VZD) layout of the drill string (BK). The main disadvantage of using the simultaneous rotation of the VZD and the drill string in the areas of stabilization of the zenith angle is the ability to adjust the trajectory of the well profile during the posting of obliquely straight (tangential) sections.

In the case of drilling subsequent intervals located after the stabilization section, for example, plots of set or reduction of the zenith angle, it is practically impossible to use the CDW without rotating the BC. This is due to the action of additional frictional forces between the drilling tool and the rock. Friction forces prevent the required load on the bit, reduce operational management and control the trajectory of the well profile.

The most effective technical solution to this problem, aimed at improving the quality of the design of well trajectories and monitoring the actual load on the bit, is to use the calculation of the displacement of the drill string relative to the axis of the borehole, the moment of resistance to friction of the drill string against the borehole wall, taking into account the loss of stability, as well as rigidity tool when changing its stress-strain state.

The implementation of the method is made by the example of drilling a section of stabilization of the zenith angle using drill pipes with a diameter of 127 mm and a bit with a diameter of 215 mm. The mechanical drilling speed varied from 20 to 28 m / h. Immediately before drilling, the following parameters were calculated: rotational speed of the drill string; moments on the rotor in idle and operating modes of the VZD; displacement indicators and the pitch of the helix of the drill string relative to the axis of the well in 2π

The difference of the moments on the rotor during the operation of the IDR in idle mode and operating mode is 5 kN⋅m with the measured M _x.x = 5 kN⋅m, M _r.x = 10 kN⋅m. The rotational speed of the drill string relative to the borehole wall varies from 5.3 to 14.1 rad / s (with rotation from 30 to 80 rpm). The movement of the drill string relative to the borehole axis a is 3.48 × 10 ^-3 m. The pitch of the helical string of the drill string relative to the borehole axis in 2π is 54.2 m. The axial load on the bit according to the GTI station is 10 kN.

Analysis of the calculation results showed that the value of the actual load on the bit does not coincide with the value of the load on the bit at the GTI station (Fig. 1). At a drill string rotation frequency of 5.1 rad / s (30 rpm), the load on the bit does not reach 7.8 kN. With an increase in the rotational speed to 14.1 rad / s (80 rpm), the load on the bit increases and amounts to 9.2 kN.

Determination of the actual axial load will increase the efficiency of drilling directional wells with downhole motors with simultaneous rotation of the drill string, will also reduce the likelihood of an emergency during uncontrolled rotation without taking into account the stress-strain state.

Claims (15)

A method for controlling the axial load on a bit when drilling directional wells, including determining the pressure on the riser of a drilling rig in idle and operating modes of a downhole screw motor (bit above the bottom), characterized in that after starting the engine without load, when operating in idle mode , the speed and moment on the rotor M _{r.x are measured} , then the axial load on the bit is created and the speed and moment on the rotor M _{r.r are measured} , and the actual axial load on the bit is At the same rotational speed of the drill string under load and without load is determined by the formula:

where G _OS.GTI - axial load on the bit at the GTI station, G _OS.GTI = G _bk -G _d , N; G _bq - the weight of the drill string on the hook of the rig, N; G _d - the load on the bit, N; M _r.kh - the moment on the rotor in the operation mode of the IDR at idle, N⋅m; M _r.r - the moment on the rotor in the operating mode of the VZD, N⋅m; D _well - well diameter, m; ϑ - mechanical drilling speed, m / s; ω _well - rotational speed of the drill string relative to the borehole wall, rad / s; a - the movement of the drill string along the axis of the well,

, m;

- the gap between the drill string and the walls of the well,

, m; t is the pitch of the helix of the drill string relative to the axis of the well in 2π,

, m; E - Young's modulus, Pa; I - polar moment of inertia of the drill string, m ⁴ .

Images