CN-116449102-B - Function description method of rock resistivity

CN116449102BCN 116449102 BCN116449102 BCN 116449102BCN-116449102-B

Abstract

The application provides a function description method of rock resistivity, which comprises the steps of selecting at least two rock samples of the same type, carrying out a saturated water experiment and a centrifugal experiment on the rock samples, measuring the pore water resistivity of the rock samples, the rock resistivity corresponding to the saturated water saturation and the rock resistivity under different partial water saturation, respectively obtaining a first function coefficient and a second function coefficient of a saturated water rock resistivity description function equation according to the rock porosity, the pore water resistivity, the rock resistivity corresponding to the saturated water saturation and the rock resistivity under different water saturation, and obtaining a third function coefficient and a fifth function coefficient of a relation equation of the partial saturated water rock resistivity and the bound water saturation corresponding to different effective water saturation, finally obtaining the function description of the rock resistivity, and improving the accuracy of the rock resistivity description.

Inventors

XIE WEIBIAO
YIN QIULI
WANG GUIWEN
XIE QINGBIN
LAI JIN
FENG CHENG
ZHANG PAN

Assignees

中国石油大学(北京)

Dates

Publication Date: 20260512
Application Date: 20230314

Claims (9)

1. A method of describing a function of rock resistivity, comprising: Selecting at least two rock samples of the same type of rock, carrying out saturated water experiments and centrifugal experiments on the rock samples, and measuring the pore water resistivity of the rock samples, the rock resistivity corresponding to the saturated water saturation and the rock resistivity under different partial water saturation, wherein the different partial water saturation comprises the partial saturated water saturation and the irreducible water saturation; According to the rock porosity, the pore water resistivity and the rock resistivity corresponding to the saturated water saturation, calculating a first function coefficient and a second function coefficient in a saturated water rock resistivity description function equation by adopting a least square method; Determining the rock resistivity of each rock sample under the same effective water saturation by adopting an interpolation method according to the different partial water saturation and the rock resistivity under the different partial water saturation; According to the irreducible water saturation and the rock resistivity of each rock sample under the same effective water saturation, calculating a third function coefficient of a relation equation of the rock resistivity of partial saturated water and the irreducible water saturation corresponding to different effective water saturation by adopting a least square method; calculating a fourth function coefficient and a fifth function coefficient of a partially saturated water rock resistivity description function by adopting a least square method according to different effective water saturation and the third function coefficient corresponding to different effective water saturation; determining a rock resistivity description function of the rock type according to the first function coefficient, the second function coefficient, the fourth function coefficient and the fifth function coefficient; the rock resistivity description function of the rock type is: In the formula, To a water saturation of Rock resistivity per unit ; Is the pore water resistivity, unit ; Is the partial water saturation in v/v; Units v/v for effective water saturation; In v/v for irreducible water saturation; c. m is a first function coefficient and a second function coefficient in a saturated water rock resistivity description function equation respectively, and is dimensionless; d. η is a fourth function coefficient and a fifth function coefficient of the partial saturated water rock resistivity description function, and is dimensionless; Is rock porosity, dimensionless.
2. The method of claim 1, wherein performing a saturated water test and a centrifugal test on the rock sample and measuring pore water resistivity, rock resistivity corresponding to saturated water saturation, and rock resistivity at different partial water saturation of the rock sample comprises: selecting at least two rock samples of the same type of rock, carrying out a saturated water experiment on the rock samples and measuring the pore water resistivity of the rock samples and the rock resistivity corresponding to the saturated water saturation; and then performing a centrifugation experiment on the rock sample, and measuring rock resistivity of the rock sample under different partial water saturation in the centrifugation experiment process.
3. The method of claim 2, wherein after performing a saturated water test on the rock sample, further comprising: The porosity of the rock sample is measured and recorded.
4. The method of claim 1, wherein determining the rock resistivity of each rock sample at the same effective water saturation using interpolation based on the different partial water saturation and the rock resistivity at the different partial water saturation comprises: determining effective water saturation corresponding to different partial water saturation according to the irreducible water saturation; And determining the rock resistivity of each rock sample under the same effective water saturation by adopting an interpolation method according to the effective water saturation and the rock resistivity corresponding to the effective water saturation.
5. The method of claim 4, wherein the calculating formula for determining the effective water saturation corresponding to the different partial water saturation according to the irreducible water saturation is: In the formula, Units v/v for effective water saturation; Is the partial water saturation in v/v; to tie water saturation, v/v.
6. The method of claim 1, wherein the saturated water rock resistivity describes a functional equation as follows: In the formula, Is the pore water resistivity, unit ; Rock resistivity in units of saturated water saturation ; Is rock porosity, dimensionless; c. m is a first function coefficient and a second function coefficient in a saturated water rock resistivity description function equation respectively, and the saturated water rock resistivity description function equation is dimensionless.
7. The method of claim 1, wherein the partially saturated water rock resistivity versus irreducible water saturation equation is: In the formula, To a water saturation of Rock resistivity per unit ; Rock resistivity in units of saturated water saturation ; Is the partial water saturation in v/v; In v/v for irreducible water saturation; And the third function coefficient is a relation equation of the resistivity of the partially saturated water rock and the saturation of the irreducible water, and is dimensionless.
8. The method of claim 1, wherein the equation for the partially saturated water rock resistivity function is: In the formula, The third function coefficient of the relation equation of the resistivity of the rock of the partially saturated water and the saturation of the irreducible water is dimensionless; Units v/v for effective water saturation; d. η is a fourth function coefficient and a fifth function coefficient of the partial saturated water rock resistivity description function, and is dimensionless.
9. The method according to any one of claims 1 to 8, wherein the rock of the same type is one or more of the same rock properties: Mineral composition type, rock pore type.

Description

Function description method of rock resistivity Technical Field The application relates to the technical field of petrophysical, in particular to a function description method of rock resistivity. Background The function description of rock resistivity under different water-containing states is one of core contents of rock carbide physical and reservoir evaluation under the rock water-containing states, and the function description precision determines the accuracy of rock conductivity description and the accuracy of reservoir oil saturation estimation value, so that the function description method has great significance in reservoir evaluation research. In the prior art, an Alqi formula is generally adopted to describe functions of rock resistivity under different water conditions based on a correction model proposed by the Alqi formula. However, the inventor found that there is at least a technical problem in the prior art that, since the rock resistivity is not Abbe Ji Xianxiang, when the rock resistivity in a different water-containing state is described using the Abbe's formula in a state other than the Abbe's phenomenon, there is a case where accuracy is low. Disclosure of Invention The application provides a function description method of rock resistivity, which aims to solve the problem that the accuracy of rock resistivity in different water-containing states is low when an Alqi formula is used for describing the rock resistivity in a state other than the Alqi phenomenon. In a first aspect, the application provides a method for describing functions of rock resistivity, comprising: Selecting at least two rock samples of the same type of rock, carrying out saturated water experiments and centrifugal experiments on the rock samples, and measuring the pore water resistivity of the rock samples, the rock resistivity corresponding to the saturated water saturation and the rock resistivity under different partial water saturation, wherein the different partial water saturation comprises the partial saturated water saturation and the irreducible water saturation; According to rock porosity, pore water resistivity and rock resistivity corresponding to saturated water saturation, calculating a first function coefficient and a second function coefficient in a saturated water rock resistivity description function equation by adopting a least square method; according to the different partial water saturation and the rock resistivity under the different partial water saturation, determining the rock resistivity of each rock sample under the same effective water saturation by adopting an interpolation method; According to the irreducible water saturation and rock resistivity of each rock sample under the same effective water saturation, calculating a third function coefficient of a relation equation of the rock resistivity of partial saturated water and the irreducible water saturation corresponding to different effective water saturation by adopting a least square method; According to the effective water saturation and the third function coefficient corresponding to the effective water saturation, calculating a fourth function coefficient and a fifth function coefficient of the partial saturated water rock resistivity description function by adopting a least square method; and determining a rock resistivity descriptive function of the rock type according to the first function coefficient, the second function coefficient, the fourth function coefficient and the fifth function coefficient. In one possible design, a saturated water experiment and a centrifugal experiment are performed on a rock sample, and pore water resistivity of the rock sample, rock resistivity corresponding to saturated water saturation, and rock resistivity at different partial water saturation are measured, including: selecting at least two rock samples of the same type of rock, carrying out a saturated water experiment on the rock samples, and measuring the pore water resistivity of the rock samples and the rock resistivity corresponding to the saturated water saturation; A centrifugation experiment is then performed on the rock sample, during which the rock resistivity of the rock sample at different partial water saturation is measured. In one possible design, after performing the saturated water test on the rock sample, the method further comprises: the porosity of the rock sample was measured and recorded. In one possible design, interpolating rock resistivity for each rock sample at the same effective water saturation based on different partial water saturation and rock resistivity at different partial water saturation, comprising: determining effective water saturation corresponding to different partial water saturation according to the irreducible water saturation; And determining the rock resistivity of each rock sample under the same effective water saturation by adopting an interpolation method according to the effective water sat