RU2211327C2 - Method of determination of flow string leaking in injection well equipped with tubing - Google Patents

Abstract

FIELD: oil-gas producing industry, particularly, monitoring of oil and gas deposit development, more specifically, determination of leaking of flow string in injection well equipped with tubing. SUBSTANCE: method includes registration of flow rate of fluid injected into well by flowmeter lowered below tubing funnel. Registration of flow rate of injected fluid is carried out at wellhead as well by flowmeter of same design as of that lowered into well. Flowmeter is installed on pipe length in pressure line located in interval between pumping unit and wellhead. Leaking of flow string is detected by discrepancy of flow rates of injected water registered by flowmeters. Flowmeters are used in form of electromagnetic flowmeters. Diameter of pipe length is selected equal to diameter of flow string. Fluid for injection into well is conducting one. EFFECT: higher efficiency due to confident information on well casing string leaking. 3 dwg

Description

 The invention relates to the oil and gas industry, and in particular to the field of monitoring the development of oil and gas fields, in particular to methods for assessing the tightness of the production casing of injection wells equipped with tubing (tubing).

 A known method for determining the tightness of the production casing by thermometry [1].

 The known method involves measuring and recording the temperature during the injection and the transition from the injection mode to the fluid withdrawal mode with an interval in time and comparing the obtained thermograms. In each detected temperature anomaly interval, two additional measurements are carried out, the first with a quasi-stationary temperature distribution in the barrel during the injection process. After stopping the well and stopping the injection, a second measurement is carried out over a period of not more than 2.5 minutes. The violation of the tightness of the production casing is judged by the shape of the anomaly in the first and second measurements or by the absence of the anomaly in the first and by the presence of an anomaly in the second measurement.

 The known method for its implementation requires a lot of time and labor, since it is necessary to stop the operation of the well for a long time to restore the temperature regime, as a result of which violations in the walls of the production string with injectivity much smaller in comparison with the perforation zone remain undetected. In addition, the presence of leaks in the tubing makes it difficult to obtain an unambiguous conclusion about the tightness of the production string.

 There is also a method of determining annulus flows in oil and gas wells, based on the registration of noise amplitudes [2].

 The essence of the method is as follows.

 In the frequency range of 10-1000 Hz, the amplitude of the noise is recorded in the casing in the form of graphs of the noise process by a geosensor of vertical vibrations mounted on the wellhead flange of the string.

 The method is devoid of the disadvantages inherent in the method of thermometry. However, due to various kinds of interference in the form of noise (vehicles, operation of neighboring wells, annular flows and fluid passes through the reinforcing elements of the wells), it is in many cases impossible to use it in assessing the tightness of the production string.

 A known method for assessing the tightness of the production casing of injection wells by flow metering [3,4] using flowmeters RGD-4 or RGD-5 with turntables, (see description p.227, 228 books. Technique and technology for determining the parameters of wells and reservoirs. - M .: Mineral Resources 1989).

 The essence of the method consists in the interval inspection of the production string in the process of pumping water into the well. Moreover, the equality of the flow meter readings in the studied interval indicates the tightness of the column. And the depth intervals, in which the flowmeter readings decrease, indicates the presence of absorption sites for the injected fluid, that is, places of leakage in the production string.

 The disadvantage of the method under consideration is that only the irregularities that are in the range from the top of the perforation interval to the tubing funnel, i.e. below the tubing funnel. In addition, when the RGD type flowmeter is lowered into the well or during the fluid injection process, clumps of oil or paraffin accumulated on the walls of the production string or tubing, falling on the vanes of the flowmeter turntable, significantly distort the research results.

 A known method for assessing the tightness of the production casing of an injection well equipped with tubing [5].

 The essence of the method is to register the flow rate of the injected fluid with two flow meters. One of the flow meters is lowered into the well below the tubing funnel, and the other is installed on the fluid injection line into the annulus of the well. The flow meters are pre-calibrated using a stand-alone pump unit CA-320, and the injection is carried out by the same pump unit. The tightness of the production casing is judged by the correspondence of the flow rate of the injected fluid recorded by the flow meters at the same time.

 The method allows the method of flow measurement to assess the tightness of the intervals of the columns, overlapped tubing. However, due to the possibility of clumps of oil, paraffin, debris falling on the vanes of the flowmeter turntable, the measurement results may be distorted. In addition, the readings of the same flow meter will vary in columns with different internal diameters.

 An object of the present invention is to provide a method for obtaining reliable information about a leak in a production well string.

 The problem is solved by the described method, including recording the flow rate of the fluid injected into the well by a flow meter, lowered below the tubing funnel.

 What is new is that electromagnetic flow meters are used as a flow meter, while the flow rate of the injected fluid is simultaneously carried out at the wellhead by a flowmeter of the same design as that launched into the well, on a section of the injection line located between the pump unit and the wellhead moreover, the diameter of the pipe segment with the flow meter placed is chosen equal to the diameter of the production casing of the well, while as the injected fluid into the well for research They select electrically conductive fluid, and by the mismatch of the flow rate of the injected water recorded by the flow meters, they judge the leakage of the production string.

 Preliminary patent research on the “novelty” and “inventive step” of the proposal was carried out by the patent fund of the TatNIPIneft Institute. The absence of similar technical solutions with such a combination of significant differences allows us to conclude that the claimed object meets the criteria of "novelty" and "inventive step".

 The following drawings explain the essence of the invention, where in FIG. 1 shows a well with wellhead fittings equipped with tubing and electromagnetic flow meters, one of which is lowered into the well on a geophysical cable, and the other is placed in a pipe segment with a diameter equal to the diameter of the production string and installed in the discharge line between the pump unit and wellhead fittings.

 In FIG. 2 is a view of an electromagnetic electromagnetic flowmeter with an electronic unit in a partial longitudinal section.

 In FIG. 3 is a view of a II schematic illustration of an electronic unit.

 In the method, the electromagnetic flowmeter used comprises a housing 1 (see Fig. 2), inside of which are placed electromagnets 2 and 3 with field windings 4 and 5, electrodes 6 and 7 of a magnetically permeable screen 8 made, for example, of caprolon, as well as an electronic unit 9 (see Figs. 2 and 3).

 Electromagnetic flowmeters have the following advantages over traditional ones, namely: independence of indications from viscosity and density of the measured liquid flow rate, the possibility of use in pipes of any diameter, the absence of pressure loss, linearity of the scale, high speed, the ability to measure aggressive, abrasive and viscous liquids, and also the lack of moving or rotating parts.

 The method is carried out in the following sequence.

First, electromagnetic flowmeters (EMR) 10 and 11 are calibrated using an autonomous pumping unit, for example, a cementing unit ЦА-320М, taking into account the injectivity of the injection well to be investigated (the pumping unit is not shown in Fig.), Then one of the flowmeters 10 on the geophysical cable 12 lowered into the well 13 through the tubing 14 and set it about 2-3 m below the funnel 15, and another EMR 11 of the same design is mounted in the discharge line 16 of the pump unit, located in the gap between the last and the wellhead in the well ZEC pipe 17 with a diameter equal to the diameter of the borehole, i.e., production casing (see Fig. 1). Next, the discharge line 16 of the pump unit is connected to the pipe or annular space of the well and put it into operation. Liquid injection is continued until the operating mode is established, which is judged by the stabilization of the operating mode of the EMRs. Then simultaneously with each EMR, the flow rate of the injected conductive fluid is recorded for 5-10 minutes. During the specified period of time, 0.5-1 m ^{3 of} liquid is pumped.

 Mineralized water can be used as such a liquid.

 When the electromagnetic field interacts with a moving fluid, an electromotive force is induced in it - EMF of electromagnetic induction, the amplitude of which is proportional to the fluid velocity and current in the field windings ОВ1 and ОВ2, which is ensured by the presence of a magnetically permeable shield 8. In the composition of housing 1, the EMF is removed by electrodes E1 and E2, amplified by a differential amplifier UM1 and fed into the circuit of an analog-to-digital converter - ADC, where it is converted into code perceived by the processor included in the controller. After preliminary processing, the processor generates a signal in the form of a serial code at the output. This signal is supplied to the power amplifier UM2 and through the core of the cable 12 is perceived by ground equipment, for example, "HECTOR".

 The processor of the downhole tool also generates a magnetic field excitation voltage, which, through the current exciter, enters the windings of the exciter OV1 and OB2.

 The output signals EMR10 and EMR11 from "HECTOR" are transmitted to a computer, the software of which provides the formation of a diagram recording the reading of EMRs. If there is a difference in readings, the production casing is considered leaky.

 According to the results of studies, if the production casing turns out to be leaky, the team of wells overhaul using the geophysical lot will specify the place of damage and carry out further repair work.

 The technical and economic advantage of the proposal is as follows.

 The method provides the accuracy of determining leakage of the production string. Accelerates research regardless of the depth of the well and the type of fluid located there. At the application filing date, the method was tested in the oil fields of NGDU Almetyevneft, the results are positive.

Sources of information
1. RF patent 2121572, 6 E 21 B 47/00, BI 31, 98. A method for researching injection wells.

 2. Patent on application 94041117, 6 Е 21 В 47/00, publ. BI 28, 96.

 3. Prince Satellite oil field geologist. Reference book under the editorship of I.P. Chalovsky. - M .: Nedra, 1989.

 4. Prince Technique and technology for determining the parameters of wells and reservoirs. - M .: Nedra, 1989.

 5. RU 2168622 C1, cl. E 21 B 47/00, 47/10, publ. 06/10/2001, 5 p. A method for assessing the tightness of the production casing of an injection well equipped with tubing (options).

Claims (1)

 A method for determining the leakage of a production well string equipped with tubing, which includes recording the flow rate of the fluid injected into the well with a flow meter lowering the tubing funnel, and recording the flow rate of the injected fluid simultaneously at the wellhead with a flowmeter of the same design as lowered into the well, on a pipe segment in the injection line, located in the gap between the pump unit and the wellhead, and due to the mismatch s injected water, registred flowmeters, leakage is judged on the production string, characterized in that the flow meters using electromagnetic action, and the diameter of the tube segment is selected equal to the diameter of the column of the production well, at the same time as the injected liquid in the well is selected conductive liquid.

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