SU711280A1 - Method of determining depth inside well - Google Patents

Description

(54) METHOD FOR DETERMINING DEPTH IN THE WELL

The invention relates to the field of geophysical work in oil, gas and other wells and can be used for various work related to the exact determination of the distance to hard-to-reach objects. The most widely used depth determination method is to measure the length of a cable that is lowered into the well l. According to this method, the depth is measured by the counter of revolutions of the swivel roller (approximate depth determination) and by the number of intervals between the marks applied to the cable. Cable marks are applied on a permanently marking tool with simulated resilient cable tension in a well or directly on a well in the process of recording curves. However, this method is inaccurate. When determining the depth of a stationary cable, errors can occur up to 5-6 m at a depth of 7 km. Taking into account that the error grows in proportion to the square of the depth, in ultra-deep wells (up to 15 km) one should expect errors calculated in tens of meters. The introduction of amendments to the depth, which would take into account the elastic and thermal elongation of the cable, may be subjective. In addition, there is always an error in determining the depth, due to the error in the marking itself and reaching for the wells of 7 km depth about one and a half meters, as well as possible significant errors due to residual elongation of the cable. All of these factors are often caused in wells over 4 km deep to an error exceeding the allowable one. The closest in technical essence to the invention is a method of measuring the distance to an object by means of directing a coherent radiation beam to an object, for example, a laser beam, recording reflection of pulse objects and determining the distance from the object to

signal propagation speed and time 2.

This method provides exceptional measurement accuracy. However, it is suitable for measuring the depths in wells, since the washing liquid practically does not transmit electromagnetic waves and, in addition, squalls have a significant curvature.

The purpose of the present invention is to improve the accuracy of the depth measurement.

This goal is achieved by the fact that the squash delivers fiber-optic link and the depth is determined by two signals, one of which is excited in the communication line at the mouth of the link, and the other is directed from the end of the link to the surface Of the earth.

And also by the fact that the depth is determined by two signals that excite in the communication line at the wellhead.

The drawing shows the implementation of the method.

The delivery of a fiber-optic line to a well can be accomplished by lowering a cable of a cable with fiber-guided fiber cables connected to it. The latter should have a small attenuation coefficient (a few dB / km) and therefore be suitable for transmitting signals no greater than a distance. By the speed and timing of the propagation of one of the signals sent from the end of the communication line on the surface of the Earth to the well to the back, the length of the entire cable (both the well and the lift jack) and the other signal’s direction and length The distance between the values found is the length of the cable, in the squash, or the depth

In the cable, in addition to conventional optical fibers, optical fibers with active additives, such as phosphors, with a rather short luminescence time (10– or less) can be used. If at the same time we suck up a sufficiently intense intensity in the fibers near the well head, then we can refuse the signal that is wiped from the end of the cable on the surface of the Earth. In this case, the depth of the well is determined by the time of propagation of two signals from the flash point — one to the lift, and the other to the well and back to the winch collector, the lift

Different methods can be used to excite signals from the surface of the cable near the wellhead, depending on the optical fibers used, the cable construction and the measured depths. Such methods include: electromagnetic, thermal, or other effects on lumen-resistant fibers; backscattering of light in conventional (without activators) fibers, in particular, on hypersound waves under the action of a heat pulse, a pulsed change in the intensity of incoming light by acoustic waves when using optical fibers with a step change in the refractive index and a small aperture. Depending on the method used, the signal may be the same as the intensity of the incoming light, a partial reflection of the transmitted light, a flash of light directly excited in the fibers of the cable.

To allow a signal across the entire cable, a laser LED is used with a filter, if this allows the attenuation of the used optical fibers and the value of the determined depths.

When using this method, the best depth is corrected, taking into account the distance from the reflector in the well to the point where the curves are recorded, the location of the signal eosbulodeia section in the cable, and so on.

5 The application of the method almost completely solves the problem of accurately determining the depths in. So, random error, depth measurement, caused by the photoelasticity of the material of optical fibers in

the operation time of the cable, in particular the gfI, of its multilayer winding on the drum of the winch is of the order of several cm / km (Hereinafter, the error estimate is given for cables that have them.

5 quartz fibers).

Claims (2)

Approximately the same error occurs as a result of mode variance. The latter is particularly small for single mode fiber cables. The error caused by the performance of the receiver, the light gate, the heterogeneity of the material of Vologkon, etc., depends on the choice of the latter and can be quite small. Regarding the error caused by the cable unwinding in the well and changing the fiber length, it will be insignificant if certain conditions are met in the choice of cable design. All other errors are generally systematic in nature and, if necessary, can be taken into account (for example, as well as from the borehole curve and the temperature extension of the cable). These include: the error of increasing the signal path through the fibers, if the latter have a corner angle: error due to a change in the dielectric constant of the fiber material from the temperature in the well. The first of these errors may be absent if the fibers intended for determining the depths are arranged in the cable parallel to its center line or with a slight deviation from this position. The second error, which is important only for accurate tracking of the depth of the formations over the area, can be insignificant if the average temperature gradient over the area changes little, which is often observed. The error caused by the change in dielectric constant temperature; there may be an occasional error in determining the depth in the same well. Such an error will be observed due to the fluctuating average temperature in squamine. On average, it is also on the order of a few cm / km. The scheme that implements the proposed method (see drawing) includes (mirror) 1 optical signals in or near the downhole tool, an electro-optical logging cable 2, block .3 for exciting signals from the cable lateral surface, a collector 4 on the elevator winch drum, adapted for receiving and inputting optical signals, an additional optical cable 5 and unit 6- consisting of transmitting and receiving systems, as well as a data processing system. In cable 2 from the laser of the block b, a signal of a nanosecond duration is applied. This signal after reflection in the squash returns to block 6. The length of the entire cable at a given time is determined by the time it passes. The second signal is excited in the cable optical fibers near the wellhead by block 3. If the cable is armored and the method of exciting the signal is chosen to influence the cable with high-frequency sound or a heat pulse, then the first signal simultaneously causes B1X light in the form of weak backscatter enters the receiver unit 6. Depending on the laser frequency, the attenuation of the fibers to etc. Avalanche photodiode or {| UTO multiplier can be used as a receiver. In block 6, similar to the well-known range-finder systems, the signals received determine the depth in the well and its values shift to a logging station to the logging perforation receiver. If the cable is unarmoured and, moreover, luminescent fibers are used in the cable, making it possible to excite sufficiently intense light, then the use of a signal allowed from the winch collector is optional. The depth is determined by the timemeg propagation from the mouth of two signals — one to the well and back to the collector, and the other to the collector. In this case, from block 3 to block 6 a signal about time has appeared, a new one BCiibUifKii in the cable. For transmitting optic signals, one or several fibers can be used with aKTifflaiopaMiJ or without them, depending on the characteristics of the KOHCTpjivurai cable used, etc. The unit 6 itself with radiation emitting, forcing pulse, or the absence or absence of separate nodes n, d can be every time luibiM depending on the reasons listed above. The application of the proposed method for determining the depth in the well provides; PS: compared with existing methods, the following npeHMjmiecTBa. almost complete absence of inaccuracies of KSNsepeiisis depths during both geophysical surveys and proprietary work; no loss of time required for marking up the requirements for the stabilization of the cable in the factory (reduction of electrical heating and cable tension) with possible failure; in some cases, from stabilization | the absence of a reference to the depths of the reference points of radio logging and, consequently, a decrease in the volume of work at the opening of low-thickness formations; the possibility of simultaneous use of light guides for determining both the depth and the perpendicular distance of logs, for controllers for descending gnibs and for shooting-blasting operations, for possible initiation of explosives and so on, 77 reonorjiHecKOix) well cuts, will reduce the cost of performing a number of works and will allow you to reliably carry out keyhole blasting operations, which are often due to errors in the depth determination that lead to failure the results of testing oil and gas reservoirs. 1. Method for determining the depth in a well by measuring the distance in terms of the speed and time of propagation of a signal of a single wave and a shaft, so that, in order to increase the accuracy of depth measurement, in wells ; the fiber-optic communication line is delivered, the depths are determined by two signals, one of which is excited in the communication line. at the wellhead and the other direction from the end of the communication line on the surface of the earth. 2, the method according to claim 1, in that the depth is determined from two signals that excite in the communication line J the wellhead. Sources of information taken into account in the examination 1. SG Komarov Geophysical well survey methods. M., Nedra, 1973, p. 2. US patent number 3765768, class. 356/28, published, 1973.