RU2753327C2 - Method and device for determining bottom rod breakage/back-off in wells equipped with sucker-rod pumping units (srpu) - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to the field of transmission of downhole information from the well to the surface via an electromagnetic communication channel and can be used to monitor the operation of the well, namely: to monitor violations of rod string integrity during operation. The technical result is an increase in the reliability of determining the breakage or back-off of the rods via the electromagnetic communication channel. In particular, a method is proposed for determining breakage/back-off of the rods during the operation of downhole rod pump installations via an electromagnetic communication channel, including the excitation of an electric stabilized current in the metal string of rods using a ground-based generator, connected by one contact to the ground part of the rod string, and by another contact to the receiving electrode on the pumping and compression pipes surface, a separator of known electrical resistance dividing the metal rod string in the well into the upper and lower parts. In this case, the presence of a back-off/breakage of the rods is registered depending on the modulation of the voltage required to stabilize the direct current of the ground generator (a source of stabilized current) when the effective resistance value changes, caused by a violation of the integrity of the rod string. Also disclosed is a device for determining the breakage/back-off of rods during the operation of downhole rod pump installations, containing a ground generator connected by one contact to the ground part of the metal column of rods, and by the other contact to the receiving electrode on the surface of the pumping and compression pipes. In this case, the device contains a unit for registering the voltage of a stabilized current source, designed to determine the effective resistance of the circuit.

EFFECT: technical result is an increase in the reliability of determining the breakage or twist-off of the rods via the electromagnetic communication channel.

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Description

The proposed group of inventions relates to the field of transmission of bottomhole information from a well to the surface via an electromagnetic communication channel and can be used to monitor the well operation process, namely: to control violations of the integrity of the rod string during operation. The technical result is to increase the reliability of determining the breakage or opening of the rods through the electromagnetic channel.

Break-off of rods (OSH) today is one of the main problems in the operation of sucker rod pumps. There is a known method for detecting the lower OOS by dynamometry [1], but in many cases it is problematic to do this, since the qualitative and quantitative characteristics of the dynamometer chart practically do not differ from the dynamometer chart when the valve assemblies of the sucker rod pump pump are inoperative. In this regard, there are unnecessary costs associated with the "resuscitation" of the downhole equipment (flushing with water, hot oil, solvent), undertaken to restore the operability of the valve assemblies due to the erroneous determination of valve malfunction.

A known method of transmitting bottomhole information by exciting an electric current in a metal string in a well using a surface generator connected with one contact to the surface of the metal string, and the other contact to the receiving electrode on the surface of the well. In this case, the dielectric insert is switched, dividing the metal column in the well into the upper and lower parts. Moreover, another string of metal pipes, lowered into this well, is used as a receiving electrode. Thus, an electrical circuit is formed from a metal column in the borehole and a receiving electrode, through which a stabilized direct current from a surface generator is transmitted. In this case, obtaining information from the borehole bottom is carried out depending on the modulation of the voltage value caused by the switching of the dielectric insert. A stabilized direct current source is used as a ground generator, and a metal tubing string can be used as a receiving electrode (RF Patent No. 2494250, Bull. 27, 09/27/2013)

To detect the lower OOS, the following is proposed: to diagnose the lower OOS on the surface using a stabilized current source connected by one contact (clamp) to the ground part of the metal column of the rods, and by the other contact (clamp) to the receiving electrode at the wellhead, which is used as the column tubing (tubing), a constant stabilized current Istab is fed into the well, which creates a potential difference Usev. at the ends of an ohmic resistance, separating a metal electrical circuit and having a finite known resistance Rsection:

Udiv. = Rdiv. * Part I

In this case, the voltage at the mouth of the Umouth (at the source of the stabilized current) is equal to

where Rcol. - resistance of the string of rods, pump and tubing,

R _{plastic liquid} - resistance of the formation fluid column in the annular space between the tubing string and the rod string:

where ρ _{reservoir fluid.} - specific resistance of the produced fluid (oil + water),

D _int. and d _ext. - respectively, the diameters of the inner tubing and the outer string of rods.

H is the length of the rod string from the wellhead to the submersible pump.

Moreover, in the absence of a lower OOSh, the resistance of the entire circuit is equal to:

since Rcol. small: Rcol. << Rsection, since the tubing strings and rods are metal and have large cross-sections (more than 150 mm sq.),

and R _{plastic liquid.} large: R _{plastic liquid} >> Rsec., Since the resistivity of water-oil mixtures is close to the conductivity of oil and is greater than 10 to the power of -10 Ohm * m.

That is, when a lower TOS occurs, the electrical resistance of the "tubing-pump-separator-rod string" circuit will sharply increase, since in this case:

Rcol. → ∞,

which will cause a synchronous increase in Ujet to maintain Istab., which means:

The latter will serve as a criterion for detecting the lower EOS.

Accidental short-circuits of the rod string during bending (in particular, during the downward stroke), and, accordingly, the drop in resistance to almost zero,

Rcol. → 0,

do not affect the reliability of determining the lower OOS with this method, since the synchronization unit included in the wellhead unit is configured to register an increase in the circuit resistance much more than Rsection.

Thus, the observation of the voltage value Ujet (that is, the measurement of the effective value of the resistance of the circuit) allows you to reliably determine the absence (f. (3)) or the presence (4) of the lower OOS.

A device for implementing the method is claimed, comprising a surface DC generator connected by one contact to the surface of the metal column, and by the other contact to the receiving electrode on the surface of the well, an ohmic resistance separating the metal column in the well into upper and lower parts. The top of the metal string and tubing are isolated from each other.

Figure 1 shows a device for implementing the method.

The essence of the method. When operating a well, a string of metal rods is lowered into the metal tubing, on which a deep pump is installed to pump out the fluid. During operation, it is necessary to obtain information about the technical condition of the rod string. To do this, on the surface using a stabilized current source connected by one contact (clamp) to the ground part of the metal column, which can be a column of metal rods, and the other contact (clamp) to the receiving electrode at the wellhead, which is used as another metal pipe, for example, tubing, a constant stabilized current I _{stab is fed into the well.} , which, passing along a metal column (a column of metal rods), creates a potential difference Usev. at the ends of the ohmic resistance:

Udiv. = Rdiv. * Part I

where I _section. - current flowing through the dielectric separator:

where I _stab. - stabilized current of the ground generator,

To determine the lower OOS along the electromagnetic channel, the measuring unit measures the resistance of the direct current circuit created by the stabilized current source Istab. The integrity of the rod string is determined by the change in the specified resistance within (Ohm) 0 (the rod string is closed on the tubing) to the value of ≈Rdiv. (the rod column is in good order). When the rod string is broken (turned away), the change in the indicated resistance lies within (Ohm) 0 (the circuit is closed on the tubing) to the value of Rplastic fluid >> Rsection. (column of rods in a cliff).

Thus, a useful signal is the change in voltage at the terminals of the current source, which maintains a constant (stabilized) current, the value of which is determined by the transmission conditions - the integrity of the electrical circuit, which includes the rod string.

The implementation of the method can be carried out by the presented device.

The device (Fig. 1) contains a stabilized current source 1, connected by one contact 2 to the ground part of the column of metal hollow rods (metal column) 3, and by the other contact to the receiving electrode 4 of the metal tubing 5 (another metal column), in which it is concentrically installed a string of metal rods 3. Between these contacts, a voltage change recording unit is installed 6. The metal string 3 in the well is divided by a separator of the known electrical resistance 7 into upper and lower parts. The lower part of the rod string and the tubing string are electrically closed by the metal of the deep pump 8 for pumping out the fluid. At the wellhead, the metal string 3 and tubing 5 are separated by a gland 9 made of a dielectric material. Pos. 10 - dielectric scraper-centralizer. The dashed line shows the electrical circuit being created.

The ground generator 1 generates a constant value-stabilized current, which, passing through the metal column 3, separated by a dielectric insert 7, creates a potential difference across the separator.

The measuring unit monitors and determines the resistance value of the "tubing string-pump-separator-rod string" chain.

If the integrity of the rod string is violated, the value of the indicated resistance is within (Ohm) 0 ... Rsep., In the case of a break (breakaway) of the rod string, the change is within (Ohm) 0 ... Rplast.sid.

LITERATURE

1. Andreev V.V., Urazakov K.R., Dalimov V.U. Oil Production Handbook / Ed. K.R. Urazakov. - M .: Nedra-Business Center, 2000 .-- 374 p.

2. RF patent No. 2494250, Bul. 27, 27.09.2013

Claims (2)

1. A method for determining the breakage / breakaway of rods during the operation of downhole sucker rod pump installations via an electromagnetic communication channel, including the excitation of an electric stabilized current in a metal rod string using a ground generator connected with one contact to the ground part of the rod string, and the other contact to the receiving electrode on surface of tubing pipes, a separator of known electrical resistance, separating the metal string of rods in the well into upper and lower parts, characterized in that the presence of a flap / break of rods is fixed depending on the modulation of the voltage value required to stabilize the direct current of the ground generator (source of stabilized current) with a change in the effective resistance value caused by a violation of the integrity of the rod string. 2. A device for detecting breakage / breakaway of rods during the operation of sucker rod pump installations, containing a surface generator connected with one contact to the surface of the metal string of rods, and with the other contact to a receiving electrode on the surface of the tubing, characterized in that it contains a block registering the voltage of the stabilized current source, configured to determine the effective resistance of the circuit.

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