CN-115828558-B - Rock elastic modulus measuring method and system based on cyclic loading and unloading

CN115828558BCN 115828558 BCN115828558 BCN 115828558BCN-115828558-B

Abstract

The specification relates to the technical field of petrophysics and provides a rock elastic modulus measuring method and system based on cyclic loading and unloading. The method comprises the steps of preparing a rock sample, determining a pressing-in lattice of the rock sample, circularly loading and unloading each pressing-in point in the pressing-in lattice to obtain the relation data of the load and the pressing-in depth of each pressing-in point, calculating the elastic modulus of each pressing-in point according to the relation data of the load and the pressing-in depth of each pressing-in point, and calculating the elastic modulus of the rock sample according to the elastic modulus of each pressing-in point. According to the embodiment of the invention, the efficiency, convenience and accuracy of rock elastic modulus measurement can be improved.

Inventors

SUN XUN
WANG YEHAN
Ding Jianghui
SHANG LITAO
YANG XIANGTONG
WANG YONGHONG
YE YU
ZHANG YANG
Hou tengfei
QIAO YAN
WU XI

Assignees

中国石油天然气集团有限公司
中国石油集团工程技术研究院有限公司

Dates

Publication Date: 20260508
Application Date: 20221123

Claims (10)

1. A method for measuring elastic modulus of rock based on cyclic loading and unloading, which is characterized by comprising the following steps: Preparing a rock sample; Performing dot matrix dotting on the rock sample at the pressed dot pitch by utilizing a spherical pressure head matched with the rock sample, so as to determine a pressed dot matrix of the rock sample; According to the maximum load and the minimum load of the rock sample, carrying out cyclic loading and unloading on each pressing-in point in the pressing-in lattice to obtain the relation data of a plurality of groups of loads and pressing-in depths of each pressing-in point; the method comprises the steps of loading and unloading each pressed point in the pressed dot matrix once, wherein the step of controlling the spherical pressure head to load the selected point at a constant speed until the maximum load is reached, and the step of controlling the spherical pressure head to unload the selected point at a constant speed until the minimum load is reached after the load is maintained, and recording the load and the pressed depth in the loading process; Calculating the elastic modulus of each press-in point according to the relation data of the load and the press-in depth of each press-in point; And calculating the elastic modulus of the rock sample according to the elastic modulus of each pressing-in point.
2. The method of claim 1, wherein preparing the rock sample comprises: acquiring rock to be tested; Cutting the rock to be tested to enable the rock to be tested to have a pair of planes which are parallel and have projections coincident; polishing the plane by using sand paper; And cleaning and drying the rock to be tested by using absolute alcohol to obtain the rock sample.
3. The method of claim 2, wherein the cutting the rock to be tested further comprises: When the size of the rock to be tested is smaller than a first threshold value, packaging the rock to be tested by using thermosetting plastic; cutting the packaged rock to be tested, so that the packaged rock to be tested is provided with a pair of planes which are parallel and have the projections overlapped.
4. The method of claim 1, wherein the ball indenter determination process for the indentation point spacing and the rock sample matching comprises: Determining the distance between the pressed points, wherein the distance between the pressed points is larger than a second threshold value; And matching the corresponding spherical pressure head from a preset spherical pressure head matching table according to the rock type of the rock sample.
5. The method of claim 1, wherein the determining of the maximum and minimum loads of the rock sample comprises matching corresponding maximum and minimum loads from a predetermined load matching table according to the rock type of the rock sample; The step of controlling the spherical pressure head to load the selected point at a constant speed until the maximum load is reached, which comprises traversing each pressed point as the selected point at a first displacement rate, and controlling the spherical pressure head to load the selected point at a constant speed until the load reaches the maximum load; controlling the spherical pressure head to uniformly unload the selected point until the minimum load is reached, wherein the controlling the spherical pressure head to uniformly unload the selected point by a first displacement rate until the load reaches the minimum load stops unloading; recording load and pressing depth in the loading process comprises the following steps: Recording corresponding time and load in a constant-speed loading process, a load holding process and a constant-speed unloading process; Calculating a corresponding indentation depth according to the first displacement rate and the time; And obtaining a set of data of the relation between the load and the indentation depth at the selected point according to the indentation depth and the load.
6. The method of claim 1, wherein calculating the modulus of elasticity of each indentation point based on the load versus indentation depth data for each indentation point comprises: Obtaining a relation fitting curve of the load and the indentation depth at each indentation point based on the relation data of the load and the indentation depth of each indentation point; And calculating the elastic contact stiffness of the corresponding press-in points and the contact area between the spherical press head and the press-in points by using the following formula through a relation fitting curve of the load at each press-in point and the press-in depth: , wherein, ; , wherein, , ; Wherein P is a relation fitting curve of load and pressing depth, The depth of the spherical pressure head to the pressed point is a fitting parameter, a and b, For the residual depth of the pressed-in point after unloading, S is the elastic contact stiffness of the pressed-in point, For the maximum depth of penetration of the spherical indenter into the point of penetration, In order for the depth of contact to be the same, The contact radius of the spherical pressure head and the pressing point is D is the diameter of the spherical pressure head, Is the contact area between the spherical pressure head and the pressing point, Is a spherical indenter geometry parameter; Based on the elastic contact stiffness and the contact area, the folding modulus corresponding to the press-in point and the elastic modulus corresponding to the press-in point are calculated by using the following formula: ; ; Wherein, the For the folding modulus of the press-in point, Is the elastic modulus of the spherical pressure head, Is the poisson ratio of a spherical indenter, Is the poisson's ratio of the rock sample, Is the modulus of elasticity of the pressed point.
7. A cyclic loading and unloading based rock elastic modulus measurement system, comprising: A rock sample preparation unit for preparing a rock sample; The pressed-in lattice determining unit is used for carrying out lattice tracing on the rock sample at the pressed-in point distance by utilizing the spherical pressure head matched with the rock sample so as to determine a pressed-in lattice of the rock sample; The data acquisition unit is used for circularly loading and unloading each press-in point in the press-in lattice according to the maximum load and the minimum load of the rock sample to obtain the relation data of a plurality of groups of loads and press-in depths of each press-in point; the method comprises the steps of loading and unloading each pressed point in the pressed dot matrix once, wherein the step of controlling the spherical pressure head to load the selected point at a constant speed until the maximum load is reached, and the step of controlling the spherical pressure head to unload the selected point at a constant speed until the minimum load is reached after the load is maintained, and recording the load and the pressed depth in the loading process; the indentation point elastic modulus calculation unit is used for calculating the elastic modulus of each indentation point according to the relation data of the load and the indentation depth of each indentation point; and the rock sample elastic modulus calculating unit is used for calculating the elastic modulus of the rock sample according to the elastic modulus of each pressing-in point.
8. A computer device comprising a memory, a processor, and a computer program stored on the memory, characterized in that the computer program, when being executed by the processor, performs the instructions of the method according to any of claims 1-6.
9. A computer storage medium having stored thereon a computer program, which, when executed by a processor of a computer device, performs the instructions of the method according to any of claims 1-6.
10. A computer program product, characterized in that the computer program product comprises a computer program which, when being executed by a processor, executes instructions of the method according to any of claims 1-6.

Description

Rock elastic modulus measuring method and system based on cyclic loading and unloading Technical Field The specification relates to the technical field of petrophysics, in particular to a rock elastic modulus measuring method and system based on cyclic loading and unloading. Background Accurate acquisition of mechanical parameters of rock stratum is an important premise for efficient development of deep oil and gas resources, a conventional method adopts a method of taking out a rock core through drilling, and mechanical parameters such as elastic modulus of the rock are obtained in an indoor experimental mode, however, the construction difficulty of the conventional drilling and rock core taking under a deep complex rock stratum environment is increased, and the probability of crack development and even fracture of the obtained rock core due to high pressure, high temperature and the like is greatly increased, so that the result error of mechanical parameters such as the elastic modulus of the rock obtained through experiments is increased, and even the experiments cannot be carried out. Therefore, there is a need for a method for measuring the elastic modulus of rock in situ, which can measure the elastic modulus of rock in situ, and does not require the rock to be measured to remain intact, and at the same time, improves the efficiency, convenience and accuracy of the measurement of the elastic modulus of rock. Disclosure of Invention In view of the low efficiency, convenience and accuracy of current rock elastic modulus measurements, the present solution has been proposed to overcome or at least partially solve the above-mentioned problems. In one aspect, some embodiments of the present description aim to provide a method for measuring the elastic modulus of rock based on cyclic loading and unloading, the method comprising: Preparing a rock sample; Determining a pressed-in lattice of the rock sample; circularly loading and unloading each press-in point in the press-in lattice to obtain the relation data of the load and the press-in depth of each press-in point; Calculating the elastic modulus of each press-in point according to the relation data of the load and the press-in depth of each press-in point; And calculating the elastic modulus of the rock sample according to the elastic modulus of each pressing-in point. Further, the preparing of the rock sample includes: acquiring rock to be tested; Cutting the rock to be tested to enable the rock to be tested to have a pair of planes which are parallel and have projections coincident; polishing the plane by using sand paper; And cleaning and drying the rock to be tested by using absolute alcohol to obtain the rock sample. Further, the cutting the rock to be tested further includes: When the size of the rock to be tested is smaller than a first threshold value, packaging the rock to be tested by using thermosetting plastic; cutting the packaged rock to be tested, so that the packaged rock to be tested is provided with a pair of planes which are parallel and have the projections overlapped. Further, the determining the pressed-in lattice of the rock sample includes: Determining the distance between the pressed points, wherein the distance between the pressed points is larger than a second threshold value; according to the rock type of the rock sample, matching a corresponding spherical pressure head from a preset spherical pressure head matching table; And carrying out dot matrix dotting on the rock sample at the pressed-in point spacing by utilizing the spherical pressure head, so as to determine the pressed-in dot matrix of the rock sample. Further, the circularly loading and unloading each pressed point in the pressed lattice to obtain the relationship data of the load and the pressed depth of each pressed point, which includes: according to the rock type of the rock sample, matching corresponding maximum load and minimum load from a preset load matching table; traversing each pressed point as a selected point at a first displacement rate, and controlling the spherical pressure head to load the selected point at a constant speed; When the load reaches the maximum load, carrying out load maintenance; After the load is kept, controlling the spherical pressure head to uniformly unload the selected point at a first displacement rate until the load reaches the minimum load; Recording corresponding time and load in a constant-speed loading process, a load holding process and a constant-speed unloading process; Calculating a corresponding indentation depth according to the first displacement rate and the time; Obtaining a set of data of the relation between the load and the indentation depth at the selected point according to the indentation depth and the load; And repeating the constant-speed loading process, the load maintaining process and the constant-speed unloading process to obtain a plurality of groups of relation data of the load and the pressing depth