SU1677664A1 - Method of determination of conductivity of drilling fluid in boreholes - Google Patents

Abstract

This invention relates to a well logging survey and can be used to determine the electrical conductivity of a drilling fluid. The aim of the invention is to improve the reliability of the probe. The method consists in that, in order to determine the specific electrical conductivity of the drilling fluid in the well, an induction method is used to measure measurements based on the excitation of an electromagnetic field and to measure the signal from currents excited in a space bounded by a multi-coil probe with vertical magnetic dipoles relative moments and coordinates of which are determined from the condition of equality to zero of the geometric factor of the reservoir, defined by a mathematical expression, are given m in the claims. 2 ill., 1 tab. SO with

Description

This invention relates to a well logging survey and can be used to determine the electrical conductivity of a drilling fluid.

The purpose of the invention is to increase reliability.

Figure 1 shows a diagram of a device that implements a method for determining the specific electrical conductivity of a drilling fluid in a well; figure 2 - integral radial characteristics

ideal (a) and real (b) resistivity meter.

The essence of the method is that to determine the conductivity of the washing liquid using an induction method, measurements are made based on the excitation of an electromagnetic field and measuring the signal of outflows excited in a space bounded by a well, a multi-coil probe with vertical magnetic dipoles, relative moments and coordinates which are determined from the condition

about VJ about o.

equality of the geometrical formation factor to zero, which ensures that the indications to the formation characteristics are insensitive. When simulating a medium with one cylindrical interface (well-reservoir), the value of the U signal measured by the probe is related to the coefficient of the probe Cs, the conductivity of the flushing fluid and the reservoir

(UssS + Upsp), (1)

Gche

where) -Q (ro) is the geometrical factor of the well;

(rc) - geometric factor of the reservoir;

r0 is the probe radius;

rc is the well radius;

Q (r) is the integral radial characteristic of the probe, determined by the position X | and the moment Mi of the generator circuit and the position YJ and the moment Mj of the measuring circuit, defined by the relation

(2)

51 $ M | N i 1 j i L | J

where Li I Xi-Yi I

Q0 (L / r) is the integral radial characteristic of a two-core probe with a length L, defined by the relation

{(

2G2

(3)

where K and E are the elliptic intervals of the first and second kind.

To eliminate the effect of the reservoir, taking into account relations (1) and (2), the condition can be written as a condition on the choice of the design parameters of the probe

$. () o.

I i i 1 LIJ J

(4) 55

When condition (4) is fulfilled, the probe reading ceases to depend on the electrical properties of the formation and the conductivity of the drilling fluid is determined by the magnitude of the measured signal U

v Kz | .

(five)

0

five

0

five

0

five

0

45

50

55

The device (induction resistive meter), which implements the method, consists of a radiotransparent case 1, inside of which is placed a four-cage probe with two generator 2 and two measuring coils 3, which are wound on a non-conductive rod 4, a power source 5 and a detector 6. With a rod length 4, equal to 200 mm, and the diameter of the radio transparent body 1, equal to 70 mm to fulfill the conditions (4) of the method, the necessary coordinates and moments are given in the table.

For an ideal resistivity meter with an integral radial characteristic shown in Fig. 2, the error in determining the specific electrical conductivity of the drilling fluid will be minimal, since the geometrical factor of the formation is zero.

For a specific resistivity meter

the efficiency of the equipment & - - & - can

Cs

be measured independently under laboratory conditions.

The resistivity meter is lowered into a container filled with a solution of known conductivity. The measurement results determine the sensitivity of the probe.

Under downhole conditions, the method is as follows.

When the device is moved in a well in a space bounded by a well, an electromagnetic field is created using the above mentioned induction probe, the signal of the measuring circuit is measured and the specific electrical conductivity of the mud is determined by the formula based on the sensitivity of the probe found in advance.

Using the proposed method for determining the electrical conductivity of the drilling fluid in a well provides an increase in the reliability of measurements, an improvement in the quality of interpretation of the results of electrical and electromagnetic well logging.

Claims (1)

Invention Formula The method of determining the electrical conductivity of the drilling fluid in a well, based on the excitation of an electromagnetic field using an induction probe and measuring signals from currents excited in space, characterized in that In order to increase reliability, the signal from the excitation currents in the space bounded by a multi-coil probe with vertical magnetic dipoles is measured, the relative moments and coordinates of which are determined from the condition of the equality of the geometrical factor of the formation to zero: 2 ()  1 j 1 h J -ABOUT fel , ,, U, L - U where Mi, NJ are the moments of the coils of the generator and measuring circuits, respectively; LIJ — spacing between a pair of coils; rc is the well radius; Qo is the integral radial characteristic of a double-core probe. Фа2.1 2 1 1L 0.1 go g, cm