RU2730105C1 - Method of vertical seismic profiling - Google Patents

Abstract

FIELD: geophysics.SUBSTANCE: invention relates to geophysics and can be used to detect seismic vibrations in cased wells. Method of vertical seismic profiling (VSP) is designed to perform work in drill pipes, immersed in wells without subsequent cementing of annular space. In order to ensure reliable contact of drill pipe with well wall to outer surface of pipe with pitch commensurate with pitch of observations inside well, clamping devices are attached. Reliable contact of the pipe with the well wall, and borehole instruments equipped with clamping devices, with the drill pipe allows achieving reliable contact of each seismic receiver of the VSP probe with rocks in the analyzed well.EFFECT: possibility of recording seismic vibrations of different types and classes in drill pipes and casing pipes without cement in their annular space.1 cl

Description

The invention relates to geophysical methods for studying the geological environment and is intended for recording seismic vibrations in cased wells.

A prerequisite for obtaining high-quality seismic records inside the environment is reliable contact of downhole tools with the borehole wall. It was with the provision of such a contact that the transition from P-wave seismic logging began, in which only the time of arrival of the direct P-wave was determined, to vertical seismic profiling (VSP), the object of which is the entire wave field formed inside the medium. The design of borehole seismic instruments, equipped with various clamping devices, began much earlier. With their introduction, it became possible to register undistorted pulses of direct waves and reflected waves inside the medium.

Known methods for recording seismic vibrations in wells, in which contact with the borehole wall is carried out by means of pressure devices rigidly attached to the downhole tools (Voronin Yu.A., Zhadin V.V. Geophysics, 1964, No. 3, pp. 154-156; Shekhtman GA, Kaplunov AI On the influence of downhole tool clamping force on the nature of recorded signals during vertical seismic profiling (VSP) // Applied Geophysics, 1974. Vol. 73, pp. 95-101; Shekhtman G.A., Kasimov A.N.Borehole seismic instrument: RF Patent No. 2503978 dated 16.08.2012; Shekhtman G.A., Korobov V.I., Kurasov M.I. seismic device: USSR AS No. 1073725, class G01V 1/40, 1984; Gaiser J.Е, Fulp TJ, Petermann SG, Karner GM Vertical seismic profile sonde coupling // Geophysics, 1988. Vol. 53. No. 2, P. 206-214).

A common disadvantage of all known clamping devices attached to downhole tools is their inability to prevent vibrations of the casing in which the research is carried out. If the casing does not contain cement in its annulus, then no pressure devices attached directly to the downhole tools will prevent tubing and vibration tubing waves from occurring directly in the casing. In such cases, the low quality of seismic records practically excludes the possibility of extracting any useful information from them.

The closest technical solution to the proposed one is "A method for determining the boundaries of VCHR by the method of direct MSC in combination with the method of refracted waves" (RF patent No. 2690068 dated 05.14.2018, authors: Siraev I.A. and Gafarov R.M.). In this method, the registration of seismic vibrations is carried out in the drill pipes included in the set of the drilling tool. These pipes play the role of casing in which seismic vibrations are usually recorded in the VSP method. However, unlike casing pipes, drill pipes are removed from the borehole after seismic vibrations are recorded in them by a probe consisting of downhole seismic instruments containing hold-down devices.

The main disadvantage of the prototype is the registration of seismic vibrations in drill pipes that do not reliably contact with the environment. That is why, in this method, only the first arrivals of refracted (head) waves are recorded, removing for this the source of oscillations at a sufficiently large distance from the investigated well. If, on the other hand, vibrations are excited near the borehole, then tube waves will be recorded along the drill string in the first arrivals, and not waves along the rocks surrounding the borehole. Moreover, the recording of converted and shear waves arriving at the probe in subsequent arrivals is excluded due to the unreliable contact of the drill pipe with rocks.

The purpose of the present invention is to expand the functionality of the method by ensuring reliable contact of the drill pipe with the surrounding rocks.

This goal is achieved by the fact that in the method of vertical seismic profiling, including three-component registration with the adopted step of observations of seismic vibrations by a downhole probe equipped with clamping devices, clamping devices are attached to the drill pipe from the outside with the possibility of ensuring reliable contact of the pipe with the borehole wall, while the step between clamping devices are taken commensurate with the step of seismic observations along the wellbore.

Compared with analogues and the prototype, the proposed method of vertical seismic profiling is characterized by the following significant differences:

• In addition to contact with the drill pipe, into which geophones with pressure devices are immersed, the pipe itself is pressed against the borehole wall by means of pressure devices attached to it.

• Reliability of contact of the drill (or casing) pipe with the surrounding rocks is increased due to the fact that the clamping devices are attached to the outside of the pipe with a step commensurate with the observation step.

• Compared with the known methods of ensuring the contact of the casing with the borehole wall by injecting cement into the annulus of the casing, the proposed method allows you to extract the drill pipe from the borehole after seismic observations in it.

Let us consider in more detail the essence of the proposed method.

When conducting seismic observations in boreholes, the main type of interference is technical interference caused by the existence of the well and its structure (Shekhtman G A. Vertical seismic profiling. - M: OOO EAGE Geomodel, 2017, - 284 s).

In the absence of contact of the drill pipe with the surrounding rocks, weakly damped standing waves appear in it, preventing the registration of useful longitudinal, converted and transverse waves. And in the first arrivals, a tube wave is recorded, the speed of which can be an order of magnitude higher than the speed in rocks located in the upper part of the geological section. In this case, the presence of reliable hold-down devices in seismic instruments located inside the pipe ceases to be essential, since the drill pipe itself does not reliably contact the borehole wall. Attaching the hold-down devices to the drill pipe before lowering it into the well, carried out in accordance with the invention, allows the pipe to be pressed against the borehole wall and thereby achieve the required reliable contact of the geophones located in the pipe, pressed against it from the inside, with the surrounding rocks. The reliability of such contact is increased due to the fact that the step between the clamping devices attached to the outside of the drill pipe is taken commensurate with the step between adjacent downhole geophones located in the pipe in a fixed position or moved inside it during well development.

The sequence of procedures in accordance with the proposed invention is as follows:

1. Clamping devices are attached from the outside to the drill pipe or to the lengths of drill pipes, butted together during their lowering into the borehole, which create a friction force at the contact of the pipe with the borehole wall, which is quite acceptable for the power of the drilling rig pressing the pipe into the well. In this case, the step between the clamping devices attached to the outside of the pipe is taken commensurate with the step between the seismic receivers, which is determined by the method of work.

2. The drill pipe, equipped with clamping devices, is pressed into the drilled hole to the desired depth.

3. A probe with clamping devices is lowered into the drill pipe to each tool.

4. After observation in the borehole, the probe is removed from the drill pipe and the drill pipe from the borehole.

As clamping devices attached to the drill pipes, one can use non-separable spring centralizers of the TsPN type, which are well known to drillers. They are designed to center the casing string during running and cementing them in the well, uniform formation of cement stone in the annular space in order to eliminate gas and fluid flows. The centralizer is fixed to the pipe using a special wrench included in the delivery set. In the proposed invention, centralizers of this type are expediently changed so that the springs contained therein are attached asymmetrically. Thus, the drill pipe will better adhere to the borehole wall, and its position in the center of the borehole is not required.

The technology, which includes the proposed invention, allows:

1. To register vibrations inside drill pipes or casing pipes, immersed in the investigated well without subsequent cementing of the annular space.

2. Conduct micro-VSP directly in the process of drilling shallow wells drilled in order to study the upper part of the section (VCR).

3. Carry out observations on different types of waves at different distances from the excitation point from the investigated well.

SOURCES OF INFORMATION:

1. Voronin Yu.A., Zhadin V.V. On the frequency distortions of the seismic signal when registering with a three-component borehole seismic receiver. - "Geology and Geophysics", 1964, No. 3, p. 154-156.

2. Kupovykh PN, Gogonenkov GN, Ryabkov VV, Blagov VV. Downhole seismic instrument. USSR author's certificate No. 254803, class. G01V 1/16, 1967 (prototype).

3. Shekhtman G.A., Kaplunov A.I. On the influence of the downhole tool clamping force on the nature of the recorded signals during vertical seismic profiling (VSP). - Sat "Applied Geophysics", vol. 73, 1974.

4. Shekhtman G.A., Korobov V.I., Kurasov M.I. Downhole seismic instrument. USSR author's certificate No. 1073725, class. G01V 1/40, 1984.

5. Shekhtman G.A., Kasimov AN. Downhole seismic instrument. RF patent No. 2503978 dated 16.08.2012.

6. Shekhtman G.A. Vertical seismic profiling. - M: OOO EAGE Geomodel, 2017, - 284 p.

7. Gaiser J.E., Fulp T.J., Petermann S.G., and Karner G.M., 1988, Vertical seismic profile sonde coupling. - Geophysics, vol. 53, NO. 2, P. 206-214.

, M.N., and Stewart, R.R., Eds., Vertical seismic profiling, Part B: Advanced concepts: Geophysical Press, 177-188.8. Beydoun WB, 1984, Seismic tool-formation coupling in boreholes, in

, MN, and Stewart, RR, Eds., Vertical seismic profiling, Part B: Advanced concepts: Geophysical Press, 177-188.

9. Siraev I.A., Gafarov P.M. A method for determining the boundaries of the near-surface region by the direct MSC method in combination with the refracted wave method // RF Patent No. 2690068 dated 05/14/2018, published 05/30/2019, Bul. No. 16.

Claims (1)

The method of vertical seismic profiling, including three-component recording in the borehole inside the drill pipe with the adopted step of observations of seismic vibrations by a downhole probe equipped with clamping devices, characterized in that, in order to expand functionality, clamping devices are attached to the outer surface of the drill pipe before it is immersed in the borehole with a step commensurate with the step of observations.