ELECTRONIC CONTROL AND MEASURING EQUIPMENT FOR DRILLING PROCESSES

A. A. TERESHCHENKO, V. A. KOCHEGUROV, P. P. POPOV

(Presented by the scientific seminar of the Research Institute of AEM at TPI)

One of the most important factors contributing to the growth of oil production is the further improvement of drilling equipment and drilling technology. The development of drilling technology is impossible without the broad introduction of methods and means for systematic monitoring of the drilling process and for studying the technological process. For these purposes, simple and reliable control-and-measuring instruments of a sufficiently broad range are required.

The parameters that must be monitored include: the weight of the drilling tool, the pressure, flow rate, temperature, and density of the clay mud, the angular velocity and the feed rate of the tool, etc.

The variety of quantities monitored and measured in the drilling process has led to the creation of apparatus of various types and designs in individual versions, in most cases not intended to be assembled into a complete set, which has complicated their maintenance and observation by the driller.

In addition, a number of measuring instruments produced in series are hydraulic. Such instruments operate unsatisfactorily under low-temperature conditions and do not allow their readings to be transmitted over a distance.

Below, electronic control and measuring equipment of modular construction from standardized units is described; it makes it possible to carry out continuous monitoring and to transmit instrument readings for recording.

To ensure better monitoring and control of the drilling process, a driller’s control panel is used, to which the indicating instruments of all sensors are brought out.

The panel of recording instruments, as well as the electronic part of the control and measuring equipment, may, under unfavorable climatic conditions, be installed in the driller’s cabin, since the electronic equipment is housed in a separate portable cabinet. The features of the control and measuring equipment may be considered using the circuit of a clay-mud pressure sensor as an example (Fig. 1), since the circuit design of all instruments is the same and they differ from one another only in their primary sensors.

As can be seen from Fig. 1, the electronic pressure sensor contains a primary inductive sensor and a converter unit.

The primary sensor converts the pressure of the clay mud into a proportional electrical voltage. The converter unit amplifies this voltage to the required value and transmits it to the indicating and recording instruments. In order to reduce the error of the primary sensor and improve its adjustment, provision is made ...

Fig. 1.

Visible inscriptions in the figure: “input device”; “recording meter”; “voltage recorder”; “to the recording-instrument unit”; “reduction gearbox”; \( \lambda_c \); \(B_s\); \(R_1, R_2, R_3, R_4, R_5, R_6\); \(C_1, C_2, C_3, C_4, C_5, C_6, C_7\); “\(\sim 24\) V”; “\(\sim 6.3\)”; “\(\sim 110\)”; “RA-09”; “A–A”; “A”; “\(b\)”; “\(z\)”; “\(x\)”; “\(y\)”; “\(1\)–\(6\)”.

spring 1 and four bearings, installed at points \(ABA'B'\), ensuring strictly fixed displacement of the movable core 5.

The membrane 6 of the sensor is made of heat-treated beryllium bronze Br B2, which has a hysteresis loop on the order of 0.2–0.5% [1], advantageously distinguishing it from other materials.

The sensor operates as follows.

Under the action of pressure, membrane 6 undergoes a deflection equal to [2]:

\[ f=0.17\,\frac{G R^4}{E\delta^3}, \tag{1} \]

where \(f\) is the deflection, cm;
\(G\) is the pressure in the chamber, kg/cm\(^2\);
\(E\) is the modulus of elasticity, kg/cm\(^2\);
\(R\) is the membrane radius, cm;
\(\delta\) is the membrane thickness, cm.

In this case the maximum stress arising in the membrane can be found from the expression

\[ \sigma=0.75\,\frac{G R^2}{\delta^2}. \tag{2} \]

Under the action of membrane deflection, the movable core of the inductive sensor is displaced. The displacement of the movable core of the sensor causes a proportional change in the emf \(E_{\Delta}\) induced in its secondary winding,

\[ E_{\Delta}=U\,\frac{W_0}{W}\, \frac{h_0-2h_1}{\dfrac{2Kh_1(h_0-h_1)}{S}\cos\alpha+h_0}, \tag{3} \]

where \(h_1\) is the vertical displacement of the movable core from the lower edge of the magnetic core;
\(h_0\) is the maximum possible displacement of the movable core;
\(S\) is the area of the face of the magnetic core;
\(\alpha\) is the angle of inclination of the faces;
\(U\) is the supply voltage;
\(W_0\) is the number of turns in each of the secondary windings;
\(W\) is the number of turns in the primary winding (excitation winding);
\(K\) is a coefficient that accounts for the fringing effect.

The converter unit is a follow-up system (Fig. 1) consisting of a comparison circuit, a phase-sensitive amplifier UM-239, a reversible motor (RD-09), and a feedback circuit—the measuring rheostat. For transmitting the measurement results over a distance, a selsyn sensor (SD) is used, kinematically linked with the RD-09; for recording, a recording rheostat is used, also kinematically linked with the RD-09. Resistance \(R_6\) is used to change the measurement limits of the pressure sensor.

The operating principle of the converter unit is as follows.

The output voltage of the pressure sensor \(E_{\Delta}\), proportional to the pressure, is compared with the voltage of the rheostat. The magnitude of the mismatch is amplified by the amplifier and acts on the reversible motor, which, by rotating the measuring rheostat, eliminates this mismatch. Thus the pressure of the clay slurry is converted into the angle of rotation of the output shaft of the reversible motor.

Figure 2 presents the experimental dependence of the instrument readings on the properties of the membrane and the follow-up system. Curves 4 and 2 correspond to the influence of the hysteresis loop of the membrane, recorded with a smooth increase in pressure (curve 4) and with a smooth decrease in pressure (curve 2). Curves 5 and 1 correspond to the error caused by the dead zone of the follow-up system.

Processing of the experimental data showed that the error caused by the hysteresis loop of the membrane is 0.25%, and that of the follow-up system is 0.39%.

The nonlinearity of the scale is \(\sim 2\%\).

Implementing the electronic circuit according to the principle of a follow-up system made it possible to substantially eliminate the dependence of the instrument reading on fluctuations in the supply-line voltage.

Experimental studies showed that, with fluctuations of the supply voltage within \(\pm 40\ \mathrm{V}\), the error of the instrument was on the order of \(1\%\).

Fig. 2.

The developed sensor does not require the use of low-freezing separating media, since the moving flow of clay drilling mud acts directly on the membrane, which is of substantial importance when operating the instrument under low-temperature conditions.

REFERENCES

1. L. E. Andreeva. Elastic Elements of Instruments. Matgiz, 1962.
2. L. F. Kulikovskii. Electrical Measuring Instruments for Monitoring the Drilling Process. Gostoptekhizdat, 1952.