CN1040412A - Image method for well log - Google Patents

Abstract

The present invention is that a kind of logging method, this method that is used for geophysical log comprises the setting of well as logging tool; The means of interpretation of well picture well logging: draw well logging well image pattern.The setting of the electrode system position, down-hole of this method is that measurement electrode is that the center is symmetrical arranged with the current electrode, thereby obtain out a kind of original well image well detecting curve, draw out well logging well image pattern according to well as log interpretation method, accurately and simply divide depth of stratum and formation thickness thereby reach, explain fuel-displaced, gas, water layer.

Description

Image method for well log

The present invention is a kind of logging method that is used for geophysical log, more specifically say so a kind of new method on the theoretical foundation of electrical log, the original log of measuring in this way, can draw out well logging well image pattern, to reach image true, that visual pattern ground reflects down-hole geological section variation.

Conventional electrical log mainly contains normal log and gradient electrode well logging etc., this class logging method is that down-hole logging equipment-electrode system is put into well, the curve that formation resistivity changes in the measuring well is in order to oil, gas, water layer and the lithological profile of the research geological section that well passed.Electrode system in the prior art is to constitute (seeing accompanying drawing 1) by emission electrode and collecting electrode, and in emission electrode, an electrode B is arranged on ground, and another electrode A is put into well, and the emission electrode A that puts into well also is referred to as current electrode.It is by the ground installation emission current, in the rock stratum, cause artificial electric field, one group of received electrode M, N also are referred to as measurement electrode, this measurement electrode M, N are arranged on a side (seeing accompanying drawing 2) of electrodes of A usually, sometimes can be arranged on the top of current electrode, can be arranged on the bottom of current electrode sometimes, measurement electrode and current electrode can exchange simultaneously, as the gradient array among Fig. 2, M, N; B, A location swap, but be provided with in any case, the paired electrode group all is arranged on a unipolar side.The setting of this measurement electrode position is in order to receive and to measure the potential difference of rock stratum M, N in artificial electric field at 2, the down-hole log that obtains therefrom, calculate the resistivity of rock stratum, the physical quantity that this measuring method is directly measured is an apparent resistivity on the stratigraphic section, the log of measuring all is presented at the curve right side at zero point, be that apparent resistivity does not have zero point, its boundary of log does not have obvious characteristic, can not show positive and negative extreme value, so this class curve can not pointwise reflects the actual value of down-hole apparent resistivity.

The present invention provides a kind of image method for well log on the basis of electrical survey.This method comprises 1, well is as the setting of logging tool, 2, well is as log interpretation method, 3, draw well logging well image pattern.The setting of the electrode system position, down-hole of this method is different with prior art, its current electrode is positioned at the centre of measurement electrode, be that measurement electrode is that the center is symmetrical arranged with the current electrode, two measurement electrode equate with distance between the current electrode, thereby obtain out a kind of original well image well detecting curve.According to well as log interpretation method with the original well image well detecting curve well image pattern that is interpreted as logging well.This well logging well image pattern is the relative value according to the variation of down-hole apparent resistivity, bed boundary position and two kinds of physical quantitys of resistivity value are unified in the tracing pattern, this well logging well image pattern can reflect on the geological section arbitrarily the actual value that group of rate changes of looking electric of any intuitively, accurately and simply divide depth of stratum and formation thickness thereby reach, thereby explain fuel-displaced, gas, water layer.This well all has good effect as log for research thin layer, heterogeneous body alternating layers group, clip layer, the cycle of sedimentation and quantitative solving formation parameter.

Accompanying drawing 1 is that the down-hole electrode of electrical log in the prior art is provided with schematic diagram.

Accompanying drawing 2 is that gradient array and potentiometric electrode system current electrode and measurement electrode position are provided with schematic diagram in the prior art.

Accompanying drawing 3 is that well is provided with schematic diagram as logging tool current electrode and measurement electrode position.

Accompanying drawing 4 is that well is symmetrical arranged position view as the many groups of logging tool.

Accompanying drawing 5 is one of image method for well log interpretation chart collection.

Accompanying drawing 6-a is original well image well detecting curve figure.

Accompanying drawing 6-b is the well logging well image pattern of making as log interpretation method according to well.

Do to describe in detail below in conjunction with accompanying drawing: from accompanying drawing 3 as can be seen image method for well log be the centre that electrodes of A is placed one group of measurement electrode, promptly two measurement electrode are that the center is symmetrical arranged with the current electrode, and these two measurement electrode equate with distance between the current electrode.From accompanying drawing 4 as can be seen, according to the needs of image method for well log, can be that the center is symmetrical arranged many group measurement electrode with the current electrode.Obtain the relative value that formation downhole interface apparent resistivity changes by image method for well log.From the original well image well detecting curve of accompanying drawing 6-a as can be seen, this original log is maximum at the place, stratigraphic boundary, up and down electrically symmetric points null value appears, according to well as log interpretation method, can be unified in position, stratigraphic boundary and resistivity physical quantity in the tracing pattern, make well logging well image pattern 6-b.

Well is as log interpretation method:

1, the division of formation thickness: according to well picture well logging primitive curve Fig. 6-a, up-and-down boundary place in stratum is positive and negative maximum as can be seen, locates mark stratigraphic boundary by 1 of the maximum on Fig. 6-a and at 2.The well depth of 1 correspondence is 913 meters, and 2 well depths of curve are 915 meters, according to the well depth of 2 correspondences, just can calculate 2 meters of formation thicknesses simply.

2, the very big range value of curve is characterized by the difference △ Ri of adjacent two formation resistivities in the well logging well image pattern.

(1) adopt accompanying drawing 5 image method for well log interpretation charts, find out known formation thickness H=2 rice (establishing d=1), the value of reading that stratigraphic boundary maximum is 1 is-the a(constant), 2 the value of reading is+the b(constant), obtain △ R1 with plate, △ R2 value, △ R1=17, △ R2=38.

(2) ask well as the resistivity value Ri of log in the alternating layers group, image method for well log resistivity equation formula of random layer in the alternating layers group is:

Ri＝Ro±△R1±△R2±△R3±…±△Ri （1）

Or writing: $\mathrm{Ri\; =Ro\; \pm }\underset{\mathrm{i\; =\; 1}}{\overset{n}{\mathrm{\Σ}}}\mathrm{△Ri}$

Wherein Ri is the i formation apparent resistivity;

Ro is the o formation apparent resistivity;

△ R1 is the poor of o layer and first floor apparent resistivity, i.e. △ R1=R1-Ro;

△ R2 is the poor of first floor and second layer apparent resistivity, i.e. △ R2=R2-R1;

△ R3 is the poor of the second layer and the 3rd layer of apparent resistivity, i.e. △ R3=R3-R2;

△Ri＝Ri+1-Ri。

This method is when adopting recurrence method (diminishing method or incremental method) to ask target zone resistivity Ri in advance, at first should know the resistivity of the initiating terminal Ro of alternating layers group, obtains various adjacent layer resistivity differences again, and according to instance graph 6-a, the resistivity value of target zone is pressed

$\mathrm{Ri\; =Ro\; \pm }\underset{\mathrm{i\; =\; 1}}{\overset{n}{\mathrm{\Σ}}}\mathrm{△Ri}$ Formula is obtained.

R1＝10

R2＝7

R3＝17

Claims (5)

1, a kind of image method for well log, this method comprises:

It is that the center is symmetrical arranged that the position of a, down-hole electrode system is set to two measurement electrode, and two measurement electrode equate with distance between the current electrode;

B, with well as the log well explanation of figure of well image pattern of log interpretation method;

Position, stratigraphic boundary and resistivity physical quantity in c, the well logging well image pattern are unified in the tracing pattern, make well logging well image pattern.

2, image method for well log according to claim 1 is characterized in that with the current electrode being the center, and equidistant up and down being symmetrical arranged organized measurement electrode more.

3,, it is characterized in that original well image curve figure is positive and negative very big value at the place, stratigraphic boundary according to the described image method for well log of claim.

4, image method for well log according to claim 1, it is characterized in that original well image pattern up and down electrically symmetric points null value appears.

5, image method for well log according to claim 1 also should comprise:

A, be positive and negative very big value at stratigraphic boundary place, mark off the stratum up-and-down boundary according to this and obtain formation thickness and depth of stratum according to original well image curve;

B, according to known formation thickness, utilize the interpretation chart of image method for well log, obtain adjacent resistivity reservoir difference;

C, adopt recurrence method, obtain the apparent resistance resistance rate of well picture well logging random layer in the alternating layers group.

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