SU1208524A1 - Method of acoustic logging - Google Patents

Description

The invention relates to a field geophysical study of wells by acoustic methods, p, and can be used to determine the permeability and porosity of rocks.

The aim of the invention is to increase the information content and resolution of logging on normal waves.

FIG. I shows a diagram1 1a of a multi-source (receiver) for n 4; 2 shows the layout of the multipole source from monopoly sources (the + and - marks indicate the phase with which each individual source works in groups in FIG. 3 an example of recording wave patterns of logging according to the proposed method.

The method is carried out as follows.

With acoustic cartography, the kelle of the full emitter and receiver are placed on the axis of the well at a certain distance from each other so that their radiation patterns (4g, 1) are located in the horizontal plane of the well and are aligned. Rotation of the plane of polarization of the waves is not taken into account.

When excited, the emitter (Fig. 1) causes radial oscillations of the borehole wall as cos 4 (p (or sin 4cf). The complex oscillation packet propagates along the well and is recorded by the receiver, which also records only the nth angular harmonic. The measurement can be made with Mukhshti half of different orders when

Registration by the receiver of only normal waves occurs for the following reasons.

The radiation and reception of the acoustic field of a multipole source: it allows to suppress almost completely longitudinal and transverse waves, which attenuate by that time

More- over, the larger the order of the multipole p. Normal waves, if there is no strong absorption in the rock, are weakened slightly.

For each angular harmonic of the n-order multipole, there is a family of normal waves. Each individual wave has its own cutoff frequency, at which its velocity is equal to the velocity of the transverse wave in the rock. Below this frequency, the wave attenuates quickly. Using these properties of normal waves, it is possible to distinguish individual modes in one family with the help of time and frequency selection. In the first arrivals, a mode is detected at a given frequency that is closer to its cut-off frequency.

Example. B the well radiated and received the acoustic field in the form of cos Cf, n 4 (figure 1). For this purpose, 8 emitters and receivers were used, according to a sensor for each petal. The sensors were located around a circle of 60 mm (see figure 2). Every two adjacent sensors operated in the homotive phase. Measurements were carried out in a well with a diameter of 200 mm using a probe consisting of two multipole emitters and one multipole receiver.

 probe

Ug 1.06 - and, - 1.35 - P.

On fig.Z shows an example of registration of wave patterns.

The pictures were recorded in a skavzhin after 1 m. The recording delay is 400 μs, the speed of the longitudinal waves in this interval is 5500 m / s, and the transverse - 3000 m / s.

As can be seen in FIG. 3, neither on the first, on the second channel are there any registered longitudinal waves. Intense waves are recorded approximately at the arrival times of the transverse waves.

l 2

fie.Z

Claims (1)

ACOUSTIC LOGGING METHOD J comprising emitting an acoustic signal into a well, receiving waves in a developing fluid, characterized in that, in order to increase the information content and resolution of the logging, the acoustic field in the well is emitted and received by multipole sources and receivers of the same order and, where η > 2, the higher angular modes of normal The wave field of a point source of waves with η periods in angle. in the well. - In the book. Questions of the dynamic theory of seismic wave propagation. XVI, L., 1976, from. 41-53. UK patent No. 1534854, publ. 1975. USSR copyright certificate ”672599, cl. G 01 V 1/40, 1979. Isakov II, Shcherbakova T.V. Using the parameters of Lamb waves in the allocation of zones with increased permeability of rocks. - Exploration Geophysics, vol. 92 ra, 1981, p. 150-155. / h ± / Fig. 7 ϊ 208524