Method for experimentally determining influence of acid liquor on Young's modulus of compact carbonate rock

Patent metadata

Field	Value
Publication number	US-11199483-B2
Application number	US-201816627037-A
Country	US
Kind code	B2
Filing date	Apr 3, 2018
Priority date	Dec 21, 2017
Publication date	Dec 14, 2021
Grant date	Dec 14, 2021

Abstract

The present invention discloses a method for experimentally determining the influence of acid liquor on the Young modulus of compact carbonate rock. The method comprises the following steps: (1), selecting a standard core of compact carbonate rock for use, carrying out a uniaxial compressive strength experiment to establish an empirical relationship between the uniaxial compressive strength and the Young modulus of the compact carbonate rock; (2), selecting a full-diameter core in a target work area for use, carrying out a rock scratching experiment by using a rock scoring instrument, testing the compressive strength of the core, and acquiring the Young modulus of the core before acid treatment; (3), soaking the acid liquor and the core in a high-temperature and high-pressure reactor for a soaking reaction; and (4), carrying out a scratching experiment again on the core soaked with the acid liquor in the original scratching experiment position, testing the compressive strength of the core, acquiring the Young modulus of the core after acid treatment, and determining the influence of the acid liquor on the Young modulus of the compact carbonate rock. The method disclosed by the present invention is reliable in principle, and simple and convenient in operation. The influence of the acid liquor on the Young modulus of the compact carbonate rock under reservoir conditions is authentically evaluated, and the acid fracturing transformation effect of the compact carbonate rock is further improved.

First claim

The invention claimed is:

1. A method for experimentally determining the influence of acid liquor on the Young's modulus of compact carbonate rock, which comprises the following steps:
(1) selecting a standard core of a compact carbonate rock in a target work area for use, and carrying out a uniaxial compressive strength experiment to establish an empirical relationship between the uniaxial compressive strength and the Young's modulus of the compact carbonate rock;
(2) selecting a full-diameter core of the target work area, carrying out a rock scratching experiment by using a rock scoring instrument to test the compressive strength of the core, and obtaining the Young's modulus of the sample rock before acid treatment according to the empirical relationship between the compressive strength and the Young's modulus in step (1);
(3) sealing a portion of the full-diameter core, which never contacts the acid liquor, with potting glue, determining experimental conditions according to a reservoir temperature in the acid fracturing process, a fluid pressure in a crack, and the acid injection time, selecting an acid liquor system for acid fracturing in the field for use, and placing the acid liquor and the core in a high temperature and high pressure reactor for a soaking reaction; and
(4) carrying out a scratching experiment again on the rock soaked with acid in the original scratching experiment position to test the compressive strength of the core, acquiring the young's module of the sample rock after acid treatment according to the empirical relationship between the compressive strength and the Young's modulus in the step (1), and comparing the Young's modulus of the sample core with the Young's modulus of the sample core before acid treatment to determine the influence of the acid liquor on the Young's modulus of the compact carbonate rock.

2. A method for experimentally determining the influence of the acid liquor on the Young's modulus of the compact carbonate rock according to claim 1 , wherein the step (1) comprises the following steps:
1) selecting the compact carbonate core in the target work area, and manufacturing the compact carbonate core into a standard cylindrical rock sample; placing the sample in an incubator for drying, and then carrying out a uniaxial experiment using a triaxial rock mechanics testing system to obtain the compressive strength and the Young's modulus of the core; and
2) testing the compressive strength and the Young's modulus of at least 10 core samples according to the method in 1), and establishing the following two empirical correlations between the compressive strength and the Young's modulus:
E=C 1 σ c C 2   (1)

E=C 1 σ c +C 2   (2)

determining C 1 and C 2 in the correlations and a correlation coefficient squared value R 2 according to the acquired compressive strength and Young's modulus of the samples and the empirical correlations between the compressive strength and the Young's modulus according to formula (1) or (2) by using a regression statistics method; comparing the R 2 values in the two regression formulas, selecting the empirical correlation corresponding to R 2 having the larger value as the empirical correlation between the compressive strength and Young's modulus of a research area, and requiring R 2 in the selected empirical correlation to be greater than 0.3; and in case of the corresponding R 2 ≤0.3 in the formula (1) and the formula (2), increasing the number of test samples until the requirement is satisfied.

3. A method for experimentally determining the influence of the acid liquor on the Young's modulus of the compact carbonate rock according to claim 1 , wherein the step (2) comprises the following steps:
1) taking a diameter of the end surface of the full-diameter core as a reference line and forming two cutting lines perpendicular to the reference line, the two cutting lines being symmetric about the center of the circle; calibrating the diameter that passes through the center of the circle and is perpendicular to the reference line as a scratch line, carrying out a rock scratching experiment by using a rock scoring instrument to obtain the compressive strength distribution of the end surface of the core; and
(2) acquiring the Young's modulus distribution of the tested core before acid treatment according to a compressive strength distribution profile, and the empirical relationship between the compressive strength and the Young's modulus determined in the step (1).

4. A method for experimentally determining the influence of the acid liquor on the Young's modulus of the compact carbonate rock according to claim 1 , wherein the step (3) comprises the following steps:
1) preparation of the core before acid treatment: performing a glue sealing treatment on the core subjected to the scratching experiment, that is, encapsulating an unscratched end surface with potting glue, and exposing a scratched end surface;
2) setting of acid treatment experiment conditions: selecting an experimental acid liquor system as an acid liquor system used in the acid fracturing construction, wherein an experimental temperature is a crack temperature in the acid fracturing construction; an experimental time is an acid injection time; an experimental pressure is a difference between a fluid pressure and a formation pressure in an acid-fractured crack:

Δ
⁢

⁢
p

=

1.502
×

10

-
6

⁡

[

E
3

⁢
μ
⁢

⁢
QL

(

1
-

υ
2

)

3

⁢

h
4

]

1
/
4

+

σ
min

-

p
e

where, p is the fluid pressure in the acid-fractured crack, Pa; σmin is a minimum horizontal principal stress of the

Assignees

• Univ Southwest Petroleum

Inventors

• Gou Bo
• Guo Jianchun
• Liu Zhuang
• Li Xiao
• Zeng Mingyong
• Zhan Li

Classifications

• G01N2203/0075

  Strain-stress relations or elastic constants · CPC title

• G01N3/46

  the indentors performing a scratching movement · CPC title

• G01N33/24 Primary

  Earth materials (G01N33/42 takes precedence) · CPC title

• G01N2203/0019

  Compressive · CPC title

• G01N2203/022

  Environment of the test · CPC title