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Resistivity log correction method

A technology of resistivity logging and resistivity, which is applied in radio wave measurement systems, electrical/magnetic detection and measurement devices for logging records, etc. And other issues

Inactive Publication Date: 2003-12-10
SHELL INT RES MAATSCHAPPIJ BV
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  • Summary
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  • Claims
  • Application Information

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Problems solved by technology

[0004] The disadvantage of the above-mentioned known method is that the drilling fluid invasion into the formation is not taken into account, therefore, the obtained resistivity profile does not represent the resistivity of the formation

Method used

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Embodiment Construction

[0030] Now refer to figure 1 , figure 1 The inversion scheme of the iterated forward simulation of the resistivity profile of the formation 1 with a well (not shown) is schematically shown in which a resistivity logging electrode system 2 is placed.

[0031] When applying the method of the present invention, the resistivity logging electrode system 2 is made to work in a well, so as to provide resistivity logging records (FLG) at different radial distances around the well-drilled formation. 1 , FLG 2 ,...FLG n )3. The well is filled with drilling fluid, which penetrates into the surrounding formation for a certain radial distance. The radial distance interval starts from the drilling wall and extends to a radius that exceeds the desired penetration depth of the drilling fluid by a suitable distance. Thus, the logging electrode system provides multiple resistivity logging records (FLG 1 , FLG 2 ,...FLG n ) 3. Each resistivity logging record corresponds to each radial distance inter...

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Abstract

A method of determining electric resistivity of an earth formation (1) surrounding a wellbore filled with a wellbore fluid, is provided, which method comprises: operating a resistivity logging tool (2) in the wellbore so as to provide a plurality of resistivity logs (FLG1, ..., n) (3) of the earth formation (1) for different radial intervals (1, ..., n) relative to the wellbore; for each radial interval (k), selecting a modelled resistivity profile (Rmodk) (4); inputting the modelled resistivity profiles (Rmod1, ..., n) (4) to a logging tool simulator (6) so as to provide for each radial interval (k) a modelled resistivity log (MLGk) (7) having a depth of investigation corresponding to the radial interval (k); for each radial interval (k) updating the modelled resistivity profile (Rmodk) (7) in dependence of an observed deviation of the resistivity log (FLGk) (3) from the modelled resistivity log (MLGk) (7); and repeating steps c) -d) until for each radial interval (k) the difference between the resistivity log (FLGk) (3) and the corresponding modelled resistivity log (MLGk) (7) is below a selected threshold value (8).

Description

Technical field [0001] The invention relates to a method for logging the formation surrounding a well filled with drilling fluid. Background technique [0002] A common method of formation logging is resistivity logging. In this method, current flows or induces into the formation, and the resulting voltage is determined to provide resistivity logging records. The resistivity is measured as a function of depth. However, resistivity logging seldom measures the true formation resistivity, which is the resistivity of the untouched formation in the so-called virgin region far away from the well. Resistivity logging is affected by interference effects, such as the presence of drilling, the penetration of drilling fluid into the formation (invasion of mud filtrate), and the presence of some adjacent formations (so-called wall rock barriers). In the case where one of these effects is significantly stronger than the others, a so-called correction chart can be used to correct the log recor...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01V3/38G01V3/20
CPCG01V3/20
Inventor 理查德·G·哈克夫尔特约翰尼斯·M·V·A·科尔曼
Owner SHELL INT RES MAATSCHAPPIJ BV