Control of Fluid Flow Rate During Drilling of Geological Exploration Wells
Abstract Generated abstract
This article addresses the problem of controlling flushing fluid flow during geological exploration drilling, especially in small-diameter wells where existing pumps and bypass regulation can worsen abnormal downhole conditions. It argues that available flowmeters were either unreliable or only indicative, and describes a flowmeter and alarm device developed at Tomsk Polytechnic Institute using a float sensor with electromagnetic transmission, a bridge measuring circuit, and relay-based light and sound signaling. The device is intended to measure flow over a 0 to 200 l/min range, warn when flow falls below preset minimum values, remain stable under supply voltage variation, and help reduce accidents such as tool sticking and bit burning.
Full Text
PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE
AWARDED THE ORDER OF THE OCTOBER REVOLUTION AND THE ORDER OF THE RED BANNER OF LABOR
NAMED AFTER S. M. KIROV
Vol. 252
1975
CONTROL OF FLUID FLOW RATE
DURING DRILLING OF GEOLOGICAL EXPLORATION WELLS
V. G. Khramenkov, S. S. Sutakshin, V. P. Rozhkov
(Presented by the scientific seminar of the Department of Exploration Engineering)
The intensity of flushing is one of the principal parameters of the drilling regime. At the same time, the flushing regime for different conditions must vary within strictly defined limits. Under some geological and technical conditions, with the appropriate bottom-hole tool, in order to obtain the maximum rate of deepening it is necessary to clean the bottom hole completely of the drilled cuttings; under others, such flushing intensity is required that a small portion of abrasive sludge would remain at the bottom hole for “sharpening” the bits. Finally, when drilling with shot, it is very important to regulate the flushing intensity during the run penetration with fairly high accuracy.
Recently there has been a tendency toward increasing the volume of drilling of small-diameter wells. In connection with this, special difficulties arise in controlling small flow rates of flushing fluid, explained by the following reasons: geological exploration practice uses pumps with capacities two or more times greater than required; the capacity of the pumps, more precisely the supply of flushing fluid into the well, is regulated by discharging the excess fluid into a settling tank. Under such conditions, in the event of the slightest increase in pressure losses in the well—for example, because of clogging of the bottom hole, wedging of the core, etc.—an ever larger part of the fluid is discharged, thereby aggravating the abnormal situation that has arisen in the well and ultimately leading to accidents. Such a situation often occurs in diamond drilling, when the driller cannot determine the emergency condition that has arisen in the well and that leads to burning of the bit.
One way of solving all these problems is the use of reliable and sufficiently accurate instruments that not only indicate the flow rate of the fluid entering the bottom hole, but also provide a signal about a change in flow rate. At present, flushing-fluid flowmeters EMR-2, designed by SKB MG and ON, and the ER-2 flowmeter, designed by KazIMS, have been developed.
Because of the complexity of its circuit and its low reliability in operation, the EMR-2 flowmeter is scarcely used in geological exploration practice.
The ER-2 flowmeter is more reliable in operation, simple in design and maintenance, and has become widespread in geological organizations of Kazakhstan and in some expeditions of other republics [1], but it, like the EMR-2, is only an indicating instrument and
is not intended to signal a decrease in the intensity of flushing. Geological-exploration practice as yet has no other designs of flowmeters.
Summarizing the above, the following may be noted:
1) the creation of drilling-fluid flowmeters that are simple in design and reliable in operation is a task requiring the earliest possible solution;
2) with present-day designs of flushing pumps and methods for regulating the fluid flow rate, it is necessary to develop flow-rate regulators that automatically maintain the specified flushing intensity;
3) to reduce accidents caused by a decrease in the drilling-fluid flow rate below the minimum permissible value, it is necessary to develop signaling devices for an emergency flushing mode.
This article describes a drilling-fluid flowmeter–signaling device developed at the Department of Exploration Technology of the Tomsk Polytechnic Institute. The electrical circuit of the flowmeter–signaling device is shown in Fig. 1.
The instrument consists of a sensor and a control-and-signal panel with a siren. A float-type sensor with electromagnetic transmission of readings is mounted in the discharge line after the three-way valve.
Two sections of the inductive coil of the sensor and the secondary winding of transformer Tr form a bridge circuit, in the diagonal of which, through the rectifier bridge \(D_1\)—\(D_4\), the measuring instrument IP is connected; it indicates the drilling-fluid flow rate and is calibrated in liters per minute within the range from 0 to 200 l/min. Connected in series with the measuring instrument are the trimming resistor \(R_1\) and resistor \(R_3\), from which a signal is fed to the input of the preliminary amplification stage of the electromechanical relay, consisting of an unbalanced trigger with emitter coupling and electromagnetic relay 1R.
The readings of the measuring instrument are determined by the degree of unbalance of the bridge circuit, which in turn is directly related
Fig. 1. Electrical circuit of the drilling-fluid flowmeter–signaling device.
with the flow rate of the flushing fluid, converted into displacement of the core inside a two-section inductive coil.
On the instrument panel there is a switch P (Fig. 1) with a calibrated scale of minimum flushing-fluid flow rates (25, 30, 35, 40, 50 l/min). The calculation of the resistors of switch P connected in parallel \((r_i')\) and in series \((r_i'')\) with resistor \(R_3\) was carried out from the condition of constancy of the resistance of the circuit of the measuring instrument IP and the operating condition of the trigger and relay 1R when the flow rate decreases to, and below, the value set by switch P.
If the flow rate of the flushing fluid decreases to the emergency value, the electronic-mechanical relay operates, the supply circuit (contact 1R1) of relay 2R is closed; when actuated, this relay closes, by its contacts, the supply circuit of the siren (contact 2R1), switches off the green signal lamp 1L1 (contact 2R2), and switches on the red signal lamp L2 (contact 2R3). Thus the drilling crew is given light and sound signals about the emergency condition in the well.
To adjust the instrument when drilling with flushing by various flushing fluids, a trimming resistor \(R_1\) has been introduced into the circuit.
The instrument circuit is powered from a 220 V alternating-current network. The introduction of a ferroresonant voltage stabilizer \((C_3, C_4, C_5, Dr)\) makes it possible to obtain correct readings when the network voltage varies by \(\pm 30\%\). The instrument is connected into the power circuit of the pump electric drive through a 380/220 V transformer. Then, when the pump is switched on and off, the instrument is automatically switched on and off.
Wide application of the flowmeter-signaling device will make it possible to correctly determine and regulate the intensity of flushing, will make it possible to avoid a number of accidents (sticking of the tool string, “burning” of bits), and thereby to increase labor productivity in well drilling.
REFERENCES
- Leont’ev O. P., Broitman P. M., Biletskii M. T. New instruments for monitoring the drilling process. ONTI KazIMSa. Alma-Ata, 1967.