RU2702042C1 - Method of quantitative assessment of inflow profile in low- and medium-rate horizontal oil wells with mhfr - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil production, namely, to control of development of oil deposits by field-geophysical methods (FGM). Invention can be used for long-term monitoring of inflow profile and intake capacity in low- and medium-rate horizontal oil wells with multiple hydraulic fracturing of reservoir (MHFR) for the purpose of further justification of intensification and optimization of formation. Proposed method consists in implementation of thermo-conductive principle of flow rate measurements by means of artificial heating of fiber-optic sensitive element. At the same time to increase the accuracy of the method, synchronous simultaneous determination of inflow intensity at several points of the barrel is provided, wherein heating and temperature measurement is performed simultaneously within local zones or the entire length of the distributed fiber-optic measuring system located in the wellbore in the analyzed depth interval.

EFFECT: possibility of estimating the portion of low intensity working intervals in the influx.

3 cl, 3 dwg

Description

The invention relates to oil production, namely to control the development of oil fields by field-geophysical methods (PIP). The invention can be used for long-term monitoring of the inflow and injection profile in wells with a complex completion method (horizontal wells - hydraulic wells, hydraulic wells with multiple hydraulic fracturing, multilateral wells, etc.) with the aim of further substantiating measures for stimulating and optimizing formation production.

A known method for quantitative determination of the profile of inflow (injectivity) in the well using a turbine mechanical speed sensor [1 ÷ 7]. The inflow (throttle response) is judged by the change in the length of the barrel of the flow velocity, determined by the speed of the turbine mechanical sensor (turntable). The disadvantage of this method is the low accuracy when studying small costs, especially with multiphase inflows and the presence of mechanical impurities in the stream.

Flow meters are also known, the operation of which is based on the so-called thermoconductive principle, comprising a temperature sensor heated above ambient temperature, the readings of which depend on the flow rate, the sensor and heater can either be in close proximity [8] or at a certain distance from a friend [9].

These flowmeters are more sensitive to flow, however, they have a significant drawback associated with the strong influence of the complex structure and instability of the flow on the sensitive element of the device, which has small dimensions.

The closest in technical essence to the approach proposed by the authors is a method for determining the inflow profile, which involves monitoring the temperature using a fiber-optic interferometer with a heat-sensitive element in the working shoulder. The sensing element is heated using a radiation heater. The radiation from the heater is absorbed by the thermosensitive element, increasing its temperature. The interferometer is in the stream and is sensitive to its speed (that is, the standard idea of a hot-wire anemometer with an optical output signal is actually implemented)

One of its main advantages in comparison with the analogues considered above is the ability to work with the optical output signal [10]. Another advantage of this method is that the main disadvantage of a standard hot-wire anemometer in this case is substantially leveled due to the ability to study the dynamics of the readings of the measuring element within a long time interval.

However, since in this method it is proposed to use a heated sensor of a limited length comparable with the step of geophysical recording (that is, the sensor is actually a point sensor), it also has the main disadvantage of the classic hot-wire anemometer - the negative effect of the complex structure and flow instability.

Thus, a common drawback of all of the above methods, including the prototype, is the impossibility of simultaneous simultaneous assessments of the inflow intensity at several points in the wellbore, which reduces the accuracy of solving the problem during unstable well operation, as well as in the presence of difficult conditions for measuring inflow opposite each production interval.

To eliminate this drawback in the known method, which consists in implementing the thermoconductive principle of measuring the flow velocity by means of artificial heating of a fiber optic sensing element, in order to improve the accuracy of the method, simultaneous simultaneous determination of the inflow intensity at several points of the barrel is provided, moreover, heating and temperature measurement are carried out simultaneously within local zones or the entire length of a distributed fiber optic measuring system located in the trunk wells in the studied depth interval.

Thus, synchronous flow measurements are implemented over the entire research interval or local sections of the wellbore of interest.

That is, we are talking about the implementation of a hot-wire anemometer sensor distributed along the length of the barrel. The efficiency of its work will be much higher than the standard, since it allows simultaneous estimates of the intensity of the inflow in the entire studied interval. In this case, the assessment results are more reliable, since they allow to permanently synchronously determine the characteristics of the inflow from each productive interval.

An object of the invention is to quantify the proportion in the influx of operating intervals of low intensity.

The basis for solving this technical problem is the technology proposed by the authors for continuous monitoring of the dynamics of temperature distribution along the barrel length with a heated fiber-optic sensor operating in the hot-wire anemometer mode.

To eliminate this drawback, it is proposed to carry out the heating of an extended section, under ideal conditions, comparable in length to the objects under study (productive formations, wellbore intervals).

This additionally allows providing not only a temperature measurement at a given point, but also monitoring the dynamics of changes in the nature of temperature changes along the barrel.

The implementation of the invention of a distributed sensor implies two approaches.

The first approach involves the analysis of the temperature distribution profile along the length of the barrel with the allocation of sections of thermograms outside the inflow intervals. The simulation results indicate that in these areas a linear temperature distribution is distinguished along the length of the barrel, and the average rate of temperature change along the length within the linear distribution is proportional to the speed of the fluid flow in the barrel.

The second approach is also based on the analysis of the temperature distribution profile along the barrel length, but differs in that inflow intervals are distinguished by violating the monotonicity of the temperature change along the length. The simulation results show that the average rate of temperature decrease along the length of the indicated intervals depends on their share in the well flow rate, (see the figures below).

The method is illustrated in Fig. 1, which shows the results of thermal modeling of an extended linear heated optical fiber element, washed by a flow of linear symmetry fluid moving at a constant speed. Measurements are performed outside the inflow intervals.

In Fig. 1. indicated:

a) graphs of the temperature recorded on the fiber optic cable when heating its section (curve code — fluid flow rate, heating time 1020 s,

b) the amplitude of the temperature change depending on the flow rate.

From Fig. 1 it follows that not only the temperature of the sensor, but also the nature of the temperature change along its length depends on the intensity of movement of the fluid washing the sensor. In most of the length, the temperature profile has a constant slope, the magnitude of which is related to the flow rate.

An example embodiment of the invention is presented in Fig. 2.

According to the invention, a fiber optic cable is lowered into the wellbore with the possibility of local heating in the intervals of the study.

Local study intervals are selected in accordance with the features of the well and the geological structure of the formations it reveals are shown in Fig. 3.

The advantage of the described approach over classical measurement methods is that it becomes possible to synchronously quantify the inflow profile along the entire length of the wellbore under conditions of unstable inflow. An additional advantage of the present invention is the possibility of combining it with the DAS and DTS systems already in use (measuring passive acoustic signals and temperature by a distributed sensor based on fiber optics), which makes it possible to unify and exercise complete control over well operation in real time.

Due to the distributed (another option - point-distributed) continuous or cyclic heating in a permanent cable measuring system installed in the trunk of the horizontal well, the principle of "distributed thermoanemometry" (or "distributed thermoconductive flow measurement") is implemented. Thus, in practice, it becomes possible to expand the range of application of technology for distributed OVS thermal monitoring from 20% (potential current coverage for GPN facilities) to 100% (potentially improved technology allows the use of OVD distributed monitoring on any operational GS where it is technically possible to carry out a measurement descent equipment).

Literature

1. US patent 3756059, 1973, CL. 73-221

2. USSR patent 611113 G01F 1/12, published on 05/25/1978, N.Ya. Mukhortov, A.Sh. Fathutdinov, Tubine flowmeter

3. Petrov A.I. Depth instruments for well research. M., Nedra, 1980, 224 p.

4. Abrukin A.L. Flow metering of wells. M., Nedra, 1978

5. Patent 2205952 Е21В 47/10, G01F 1/12, published June 10, 2003 Anokhina E.S., Gabdullin Sh.T., Korzhenevsky A.G. Downhole flowmeter

6. Patent 2324146 G01F 1/12, published 05/10/2008 Short P.F. Turbine flowmeter

7. USSR patent SU 1079832 Е21В 47/10 published on 03.15.84 V.A. Chesnokov Turbine Flowmeter

8. Well thermoconductive flowmeter STD, I.G. Zhuvagin, S.G. Komarov, V.B. Black M., Nedra 1973.

9. USSR patent 2108457 Е21В 47/00 Е21В 47/10 published on 04/10/1998 Chesnokov V.A. Device for measuring fluid flow in a well

10. RF patent 2060504 G01P 5/10 published on 05.20.1996 Vlasov Yu.N., Maslov V.K., Silvestrov S.V. Fiber Optic Anemometer

Claims (3)

1. A method for quantifying the inflow profile in small and medium-rate horizontal oil wells with multiple hydraulic fracturing (MHF), which consists in the implementation of the thermoconductive principle of measuring flow velocity by means of artificial heating of a fiber optic sensor element, characterized in that, in order to increase the accuracy of the method, a synchronous simultaneous determination of the intensity of inflow at several points of the trunk, and heating and temperature measurement are carried out simultaneously in Roedel local zones or the entire length of the distributed fiber optic measuring system located in the wellbore in the investigated range of depths. 2. The method according to p. 1, characterized in that the profile of the temperature distribution along the length of the barrel is analyzed, sections outside the inflow intervals are identified, within which the average rate of temperature change along the length is determined, by the value of which the fluid flow rate is estimated. 3. The method according to p. 1, characterized in that the profile of the temperature distribution along the length of the well is analyzed, inflow intervals are identified for violation of the monotonicity of the temperature change along the length, the average rate of temperature decrease along the length of these intervals is determined, by which their share in the well flow rate is estimated.

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