CN104864994A - Geostress measurement method and system - Google Patents

Abstract

The invention discloses a geostress measurement method. Positive strain on three planes and strain in direction of the angular bisector of every two intersected planes are acquired so that stress components describing the rock core sample strain state are confirmed according to the shear strain reciprocal theorem. The invention also provides a geostress measurement system. Positive strain on the planes is obtained by measurement through a displacement sensor contacted with the plane of a rock core sample, strain on the two intersected planes sharing the edges is obtained by measurement through a displacement sensor contacted with the edges of the rock core sample, and shear strain on the intersected planes is obtained by decomposing the strain so that six strain components describing the strain state of the rock core sample are conveniently obtained. Besides, angular deviation probably caused by pasting strain sheets and bubbles between the strain sheets and the rock core sample can be avoided so that measurement precision is greatly enhanced.

Description

A kind of method and system measuring terrestrial stress

Technical field

The invention belongs to oilfield prospecting developing technical field, particularly relating to a kind of method and system of the measurement terrestrial stress for evaluating stress state residing for core.

Background technology

Terrestrial stress controls one of key factors such as Accumulation zone distribution, hydraulically created fracture expansion, Reservoirs distribution, oil well casing destruction, is that formulation and the oil well engineering design of Oil and gas field development scheme must obligato basic data.Therefore Study on Rock Stress has very important meaning in oil-gas exploration and development.

Evaluating the most direct method reliably of core stress state is geostress survey.Differential strain analysis method is common indoor core measuring method, and achieving good effect in the numerous geostress survey application at home and abroad of this method, is a kind of up-and-coming earth stress measuring method.

The ultimate principle of differential strain analysis method is: core is in compressive state in depths, stratum due to the existence of terrestrial stress, and its natural fracture contained also is in closure state.When core is taken out to ground, core departs from terrestrial stress environment and produces elastic stress release.Due to three-dimensional stress numerical value not etc., the release of stress concomitantly, creates the strain proportional with unloading degree, and described strain is relevant with the stress field residing for core, is the reflection of underground stress field.Under the stress condition of three-dimensional confined pressure, carry out restorative loading to the core drilling through out, the recovery strain of different directions is also different, and the direction strain value maximum at virgin stress is maximum, and the direction strain value minimum at virgin stress is minimum.By measuring the strain obtaining core all directions under simulation stratum condition, the stress state suffered by core in the earth formation just can be known.

Refer to Fig. 1.For conventional differential strain analysis method, required experiment core at least will have 3 planes intersected each other, each plane at least will paste 3 foil gauges, wherein 2 foil gauges are parallel with the seamed edge of experiment core, 3rd foil gauge is positioned on the angular bisector of front 2 foil gauges, is 45 ° with the angle of front 2 foil gauges.

Experiment core, after sealing, is put into pressure chamber and is applied confined pressure and test, can be obtained the strain value ε of 9 foil gauges by strain measurement _i(i=1,2 ... 9), according to the strain value ε obtained _i(i=1,2 ... 9), utilize formula (1) to calculate, obtain six components of strain that may be used for the strain regime describing core:

$\left\{\begin{array}{ccc}{\mathrm{\ϵ}}_x=\frac{1}{2}({\mathrm{\ϵ}}_1+{\mathrm{\ϵ}}_9)& {\mathrm{\ϵ}}_y=\frac{1}{2}({\mathrm{\ϵ}}_3+{\mathrm{\ϵ}}_4)& {\mathrm{\ϵ}}_z=\frac{1}{2}({\mathrm{\ϵ}}_6+{\mathrm{\ϵ}}_7)\\ {\mathrm{\ϵ}}_{\mathrm{xy}}={2\mathrm{\ϵ}}_8-{\mathrm{\ϵ}}_7-{\mathrm{\ϵ}}_9& {\mathrm{\ϵ}}_{\mathrm{yz}}=2{\mathrm{\ϵ}}_5-{\mathrm{\ϵ}}_4-{\mathrm{\ϵ}}_6& {\mathrm{\ϵ}}_{\mathrm{zx}}={2\mathrm{\ϵ}}_2-{\mathrm{\ϵ}}_1-{\mathrm{\ϵ}}_3\end{array}\right.---\left(1\right)$

Six components of strain are once determine, then the strain regime of testing core is just determined completely.

Experiment core strain regime determine after, utilize the constitutive relation between stress and strain, can calculate experiment core stress state, then can judge crustal stress states residing for it.

From the principle of above-mentioned poor strain measurement terrestrial stress, wish to get six components of strain of the strain regime describing experiment core, must paste in experiment core 3 planes intersected each other and amount to 9 foil gauges.Therefore, paste foil gauge before not only measuring to waste time and energy; And measure obtain 9 strain datas after, utilize formula (1) calculate the components of strain still very loaded down with trivial details.

Summary of the invention

When adopting stickup foil gauge method to measure crustal stress states residing for core for prior art, waste time and energy because pasting foil gauge, and the deficiency that post-processed data are loaded down with trivial details, the invention provides the method and system measuring a kind of terrestrial stress.Its technical scheme is as follows:

Measure a method for terrestrial stress, comprise the steps:

Prepare core sample to be measured, described core sample has at least three planes intersecting each other;

Confined pressure is applied to described core sample, makes it deform;

Gather the strain value of core sample, the strain value of collection comprises the normal strain in three planes, and the strain in angular bisector direction along two intersecting planes;

Utilize the strain value gathered, calculate the terrestrial stress of core sample.

The method of measurement terrestrial stress as above, utilizes the strain value gathered, and the step obtaining the components of strain describing core sample strain regime is:

Decompose the strain along the angular bisector direction of intersecting plane between two, the direction of decomposition is the tangential direction of two intersecting planes;

The strain in the angular bisector direction of at least three planes intersecting each other is decomposed, obtains the shear strain of three planes intersecting each other;

Utilize the normal strain of these at least three planes intersecting each other collected, obtain the components of strain describing core sample strain regime.

The method of measurement terrestrial stress as above, the strain in the angular bisector direction along two intersecting planes of collection comprises: along the either direction strain in the angular range of two intersecting planes.

Measure a system for terrestrial stress, comprising:

Hold original mold block, described original mold block of holding comprises base for placing core sample to be measured, described core sample has at least three the first planes intersecting each other, second plane and the 3rd plane, the seamed edge that first plane and the second plane, the 3rd plane have is respectively the first seamed edge and the second seamed edge, and the seamed edge that the second plane and the 3rd plane have is the 3rd seamed edge;

Confined pressure module, described confined pressure module can apply confined pressure to described core sample;

Strain acquirement module, described strain acquirement module comprises:

First displacement transducer, second displacement sensor and triple motion sensor, the contact jaw of described first displacement transducer, second displacement sensor and triple motion sensor can respectively with described first plane, the second plane and the 3rd plane contact;

4th displacement transducer, the 5th displacement transducer and the 6th displacement transducer, described 4th displacement transducer, the 5th displacement transducer can contact with the 3rd seamed edge with described first seamed edge, the second seamed edge respectively with the contact jaw of the 6th displacement transducer;

Strained handling module, described strained handling module can process the strain gathered.

Geostress survey system as above, comprises stuck-module, and described stuck-module comprises:

Be fixedly arranged on the first fixed arm on described base, described first displacement transducer, second displacement sensor and the 4th displacement transducer are installed on described first fixed arm;

Be fixedly arranged on the second fixed arm on described base, described triple motion sensor is installed on described second fixed arm;

Be fixedly arranged on the 3rd fixed arm on described base, described 5th displacement transducer and the 6th displacement transducer are installed on described 3rd fixed arm.

Geostress survey system as above, described base has orthogonal first direction and second direction, and and the third direction at angle all at 45 ° between described first direction and second direction, and these three directions are on the same base plane of described base;

Described first fixed arm is fixedly arranged on described base plane along first direction, and the second described fixed arm is fixedly arranged on described base plane along second direction, and the 3rd described fixed arm is fixedly arranged on described base plane along third direction.

Geostress survey system as above, comprise: be fixedly arranged on the 4th fixed arm on described base plane along first direction, described 4th fixed arm can set firmly three displacement transducers, the contact jaw of wherein two displacement transducers of three displacement transducers that described 4th fixed arm sets firmly can respectively with two plane contact of described core sample, and these two planes are relative with the second plane with described first plane respectively, seamed edge total between another contact jaw and this two planes of three described displacement transducers contacts, this total seamed edge is relative with described first seamed edge.

Geostress survey system as above, comprise: be fixedly arranged on the 5th fixed arm on described base plane along second direction, described 5th fixed arm can set firmly a displacement transducer, the contact jaw of the displacement transducer that described 5th fixed arm sets firmly can with a plane contact of described core sample, this plane is relative with described 3rd plane.

Geostress survey system as above, comprise: be fixedly arranged on the 6th fixed arm on described base plane along third direction, described 6th fixed arm can set firmly two displacement transducers, the contact jaw of these two displacement transducers that described 6th fixed arm sets firmly can be crossing with two articles of described core sample respectively seamed edge contact, described two articles crossing determined planes of seamed edge are relative with described 3rd plane.

Geostress survey system as above, described in hold original mold block and comprise brace table, described brace table is fixedly arranged on described base plane, and described brace table is used for placing and supporting described core sample.

By above technical scheme, beneficial effect of the present invention is: to the core sample collection strain applying confined pressure, the strain gathered comprises the normal strain in three planes intersecting each other, with the strain along the angular bisector direction of intersecting plane between two, this strain is the synthesis of the shear strain of two intersecting planes, according to shear strain reciprocal theorem, decompose the shear strain obtained on two intersecting planes, thus obtain the components of strain describing core sample strain regime easily and quickly;

The beneficial effect of geostress survey system provided by the invention is: measure by the displacement transducer of the plane contact with core sample the normal strain obtained in this plane; The shear strain obtained in two planes of this seamed edge total measured by the displacement transducer contacted with the seamed edge of core sample, according to shear strain reciprocal theorem, decompose the shear strain obtained on each intersecting plane, thus obtain the components of strain of the strain regime describing core sample easily;

In addition, strained by displacement sensor, the angular deviation that the method monitor strain avoiding prior art to paste foil gauge on core sample may cause, also solve prior art when pasting foil gauge simultaneously, bubble may be produced between foil gauge and core sample, cause the problem of measuring error, thus improve the precision of measurement greatly;

The core sample prepared, when measuring, is directly placed on brace table, then can applies confined pressure and directly measure by the present invention, easy and simple to handle, thus improves measurement efficiency.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme in the embodiment of the present invention, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

Fig. 1 is the experiment core schematic diagram being pasted with foil gauge in prior art difference strain experiment;

Fig. 2 is the process flow diagram of the measurement terrestrial stress method of embodiment of the present invention;

The components of strain schematic diagram of Fig. 3 strain regime residing for the strain unit under complex stress condition;

Fig. 4 is core sample schematic diagram in the measurement terrestrial stress method of embodiment of the present invention;

Fig. 5 is close-up schematic view in Fig. 4;

Fig. 6 gathers the schematic illustration of strain intersecting unspecified angle direction within the scope of plane included angle along two;

Fig. 7 is the structural representation holding original mold block and strain acquirement module in the measurement terrestrial stress system of embodiment of the present invention;

Fig. 8 is the schematic diagram of core sample in the measurement terrestrial stress system of embodiment of the present invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

Refer to Fig. 2.A kind of earth stress measuring method that the application's embodiment provides, comprise the steps: to prepare core sample to be measured, described core sample has at least three planes intersecting each other; Confined pressure is applied to described core sample, makes it deform; Gather the strain value of core sample, the strain value of collection comprises the normal strain in three planes, and along the strain in the angular bisector direction of intersecting plane between two; Utilize the strain value gathered, calculate the terrestrial stress of core sample.

Present embodiment is to the core sample collection strain applying confined pressure, the strain gathered comprises the normal strain in three planes intersecting each other, with the strain along the angular bisector direction of intersecting plane between two, this strain is the synthesis of the shear strain of two crossing planes, according to shear strain reciprocal theorem, decompose the shear strain obtained on two intersecting planes, thus obtain the components of strain describing core sample strain regime easily and quickly.

The committed step measuring terrestrial stress is six components of strain obtaining describing stress state residing for strain unit.The principle that the earth stress measuring method of embodiment of the present invention obtains these six components of strain is: according to shear strain reciprocal theorem, and the shearing stress numerical value in strain unit on two intersecting planes is equal, and direction is pointed to simultaneously or deviated from the total seamed edge of this two intersecting plane.Refer to Fig. 3 particularly, face a and face b is two intersecting planes, then both pointing to, the shear strain of total seamed edge AB is numerically equal, i.e. ε _xy=ε _yx.

Embodiment of the present invention utilizes shear strain reciprocal theorem, and the step obtaining the components of strain describing core sample strain regime is:

Core sample as shown in Figure 4 has three plane intersecting each other-face c, face d and face e, and the total seamed edge of three planes intersecting each other is respectively seamed edge FC, seamed edge FD, seamed edge FE.After applying confined pressure, core sample deforms.Gather the strain along the angular bisector direction of intersecting plane between two, be respectively ε _fC, ε _fDand ε _fE.

For clear display decomposing schematic representation, face c and face d is stripped out, refers to Fig. 5.ε _fEbe the synthesis of the shear strain of face c and face d, decompose it, the direction of decomposition is the tangential direction of face c and face d, and the seamed edge FE that tangential direction and face c and face d have is perpendicular.Obtain after decomposition strain stress ' be the shear strain of face c and face d, due to ε _fEbe the angular bisector direction along face c and face d, therefore the shear strain of the shear strain of face c and face d is equal, and this meets shear strain reciprocal theorem.So, a shear strain of face c and face d is determined.

In like manner, to ε _fCdecompose, determine a shear strain of face c and face e; To ε _fDdecompose, determine a shear strain of face d and face e.

The another kind of embodiment of the acquisition pattern of the shear strain of intersecting plane gathers the either direction intersected within the scope of plane included angle along two to strain.Refer to Fig. 6.Suppose that face f and face g is two intersecting planes in core sample, direction two any one direction of intersecting within the scope of plane included angle, direction be the angular bisector direction of two intersecting planes, the resultant strain of the shear strain of two intersecting planes is maximum along angular bisector direction.Suppose measure time, collection be edge the strain stress in direction ", then the strain stress in this direction " be direction strain stress " ' one-component.Known direction with direction angle α ', solving a triangle OPQ, then ε " '=ε "/cos α '.Obtain along angular bisector direction strain stress " ' after, then its tangential direction along face f and face g to be decomposed, the shear strain on two intersecting planes can be obtained: ${\mathrm{\ϵ}}^{\′}={\mathrm{\ϵ}}^{\′\′\′}\·\cos \mathrm{\α}={\mathrm{\ϵ}}^{\′\′}\·\frac{\cos \mathrm{\α}}{{\cos \mathrm{\α}}^{\′}}.$

According to shear strain reciprocal theorem, utilize above-mentioned method, the shear strain of three planes intersecting each other can all be determined.

Normal strain on collection face c, face d and face e, is respectively ε _x, ε _yand ε _z.Six components of strain that amount to of three intersecting planes of core sample are determined.

The strain regime of six components of strain descriptions as shown in Figure 3.By above-mentioned six components of strain, the strain tensor ε of core sample can be obtained further _ij, shown in (2).

${\mathrm{\ϵ}}_{\mathrm{ij}}=\left[\begin{array}{ccc}{\mathrm{\ϵ}}_x& {\mathrm{\ϵ}}_{\mathrm{xy}}& {\mathrm{\ϵ}}_{\mathrm{xz}}\\ {\mathrm{\ϵ}}_{\mathrm{yx}}& {\mathrm{\ϵ}}_y& {\mathrm{\ϵ}}_{\mathrm{yz}}\\ {\mathrm{\ϵ}}_{\mathrm{zx}}& {\mathrm{\ϵ}}_{\mathrm{zy}}& {\mathrm{\ϵ}}_z\end{array}\right]---\left(2\right)$

From Elasticity knowledge, under any strain regime, at least can find three orthogonal directions, only there is normal strain in these three directions, and all shear strains be zero.The direction with this character is referred to as principal strain directions, and the strain of principal strain directions is principal strain.

If strain tensor ε _ijprincipal strain be ε _ii(i=1,2,3), corresponding principal strain directions is l, m, n, then the linear homogeneous equa tion set solving principal strain is:

$\left\{\begin{array}{c}({\mathrm{\ϵ}}_x-\mathrm{\ϵ})l+{\mathrm{\ϵ}}_{\mathrm{xy}}m+{\mathrm{\ϵ}}_{\mathrm{xz}}n=0\\ {\mathrm{\ϵ}}_{\mathrm{yx}}l+({\mathrm{\ϵ}}_y-\mathrm{\ϵ})m+{\mathrm{\ϵ}}_{\mathrm{yz}}n=0\\ {\mathrm{\ϵ}}_{\mathrm{zx}}l+{\mathrm{\ϵ}}_{\mathrm{zy}}m+({\mathrm{\ϵ}}_z-\mathrm{\ϵ})n=0\end{array}\right.---\left(3\right)$

Because of l ²+ m ²+ n ²=1, l, m, n can not be 0 simultaneously, and therefore system of equations (3) must have untrivialo solution, then its determinant of coefficient is zero, that is:

$\left|\begin{array}{ccc}{\mathrm{\ϵ}}_x-\mathrm{\ϵ}& {\mathrm{\ϵ}}_{\mathrm{xy}}& {\mathrm{\ϵ}}_{\mathrm{xz}}\\ {\mathrm{\ϵ}}_{\mathrm{yx}}& {\mathrm{\ϵ}}_y-\mathrm{\ϵ}& {\mathrm{\ϵ}}_{\mathrm{yz}}\\ {\mathrm{\ϵ}}_{\mathrm{zx}}& {\mathrm{\ϵ}}_{\mathrm{zy}}& {\mathrm{\ϵ}}_z-\mathrm{\ϵ}\end{array}\right|=0---\left(4\right)$

Formula (4) is launched, can obtain solving principal strain ε _iithe equation (5) of (i=1,2,3), this equation is referred to as strain characteristics equation:

ε ³-J ₁ε ²+J ₂ε-J ₃＝0 (5)

Wherein: J ₁=Σ ε _ii=ε _x+ ε _y+ ε _z;

J ₂＝ε _xε _y+ε _yε _z+ε _zε _x-(ε _xy ²+ε _yz ²+ε _zx ²)；

$J_3=\left|{\mathrm{\ϵ}}_{\mathrm{ij}}\right|=\left|\begin{array}{ccc}{\mathrm{\ϵ}}_x& {\mathrm{\ϵ}}_{\mathrm{xy}}& {\mathrm{\ϵ}}_{\mathrm{xz}}\\ {\mathrm{\ϵ}}_{\mathrm{yx}}& {\mathrm{\ϵ}}_y& {\mathrm{\ϵ}}_{\mathrm{yz}}\\ {\mathrm{\ϵ}}_{\mathrm{zx}}& {\mathrm{\ϵ}}_{\mathrm{zy}}& {\mathrm{\ϵ}}_z\end{array}\right|.$

J ₁, J ₂, J ₃for strain invariant, be called first, second, and third invariant.According to strain characteristics equation (5), three principal strains can be solved.Bringing system of equations (3) respectively into by solving three the principal strain values obtained, direction (l, the m, n) of corresponding principal strain can be obtained.

According to the three-dimensional principal strain ε obtained ₁₁, ε ₂₂, ε ₃₃, three-dimensional principle stress σ can be drawn by following formula _v, σ _h, σ _hmutual ratios:

σ _V:σ _H:σ _h＝[μ(ε ₂₂+ε ₃₃)+(1-μ)ε ₁₁]:[μ(ε ₂₂+ε ₁₁)+(1-μ)ε ₃₃]:[μ(ε ₁₁+ε ₃₃)+(1-μ)ε ₂₂] (6)

Wherein: μ-Poisson ratio.

Can law according to Generalized Hu, strain unit is under complex stress condition, and the constitutive relation between stress and strain is as follows:

$\left\{\begin{array}{c}{\mathrm{\σ}}_x=\frac{E}{(1+\mathrm{\μ})(1-2\mathrm{\μ})}[(1-\mathrm{\μ}){\mathrm{\ϵ}}_x+\mathrm{\μ}({\mathrm{\ϵ}}_y+{\mathrm{\ϵ}}_z)]\\ {\mathrm{\σ}}_y=\frac{E}{(1+\mathrm{\μ})(1-2\mathrm{\μ})}[(1-\mathrm{\μ}){\mathrm{\ϵ}}_y+\mathrm{\μ}({\mathrm{\ϵ}}_z+{\mathrm{\ϵ}}_x)]\\ {\mathrm{\σ}}_z=\frac{E}{(1+\mathrm{\μ})(1-2\mathrm{\μ})}[(1-\mathrm{\μ}){\mathrm{\ϵ}}_z+\mathrm{\μ}({\mathrm{\ϵ}}_x+{\mathrm{\ϵ}}_y)]\\ {\mathrm{\τ}}_{\mathrm{xy}}={\mathrm{G\ϵ}}_{\mathrm{xy}}\\ {\mathrm{\τ}}_{\mathrm{yz}}={\mathrm{G\ϵ}}_{\mathrm{yz}}\\ {\mathrm{\τ}}_{\mathrm{zx}}={\mathrm{G\ϵ}}_{\mathrm{zx}}\end{array}\right.---\left(7\right)$

Wherein: ε _x, ε _y, ε _zbe respectively strain unit normal strain in the x, y, z-directions; ε _xy, ε _yz, ε _zxbe respectively the shear strain on strain unit three face intersecting each other; E is the elastic modulus of material, and μ is Poisson ratio, and G is shear modulus, elastic modulus E, shear modulus G are properties of materials, do not change with environmental change.Utilize formula (7) that six components of stress and the stress tensor of stress state residing for description core sample can be calculated, thus determine the crustal stress states of core sample.

Embodiment of the present invention also provides a kind of and measures terrestrial stress system.Please also refer to Fig. 7 and Fig. 8.In order to the position relationship of the geostress survey system and core sample that can clearly illustrate embodiment of the present invention, in accompanying drawing, both are peeled away.

The one of embodiment of the present invention is measured terrestrial stress system and is comprised: hold original mold block, described original mold block of holding comprises base 25 for placing core sample 10 to be measured, described core sample 10 has at least three the first planes 31 intersecting each other, second plane 32 and the 3rd plane 33, the seamed edge that the seamed edge that first plane 31 and the second plane 32, the 3rd plane 33 have is respectively the first seamed edge 41 and the second seamed edge 42, second plane 32 and the 3rd plane 33 total is the 3rd seamed edge 43.Confined pressure module, described confined pressure module can apply confined pressure to described core sample 10.Strain acquirement module, described strain acquirement module comprises: the first displacement transducer 37, second displacement sensor 41 and triple motion sensor 35; First displacement transducer 37, second displacement sensor 41 contact with the 3rd plane 33 with described first plane 32, second plane 32 respectively with the contact jaw of triple motion sensor 35.4th displacement transducer 39, the 5th displacement transducer 12 and the 6th displacement transducer 14, described 4th displacement transducer 39, the 5th displacement transducer 12 contact with the 3rd seamed edge 43 with described first seamed edge 41, second seamed edge 42 with the contact jaw of the 6th displacement transducer 14.Strained handling module, described strained handling module can process the strain gathered.

Embodiment of the present invention measures by the displacement transducer of the plane contact with core sample 10 normal strain obtained in this plane; The strain that the displacement sensor contacted with the seamed edge of core sample 10 obtains is the resultant strain of the shear strain on two intersecting planes of this seamed edge total.Resultant strain is learnt in measurement, and angle and the direction of measurement of two intersecting planes are known, then the shear strain value in the plane intersected can calculate to be learnt, utilizes strained handling module, can obtain the crustal stress states of core sample 10 fast, easily.

Prior art adopts the method for pasting foil gauge monitor strain, and the stickup of foil gauge may angle of arrival deviation; And due to rock sample surface to be tested, because making, precision is bad may cause its air spots, may there is bubble between the foil gauge therefore pasted and rock sample to be tested.And the principle of work of foil gauge the dependent variable of test specimen is converted to resistance change, foil gauge stretches with test specimen, is realized the measurement of dependent variable by the change of resistance value; And once the foil gauge angle of arrival deviation of pasting, or between itself and rock sample, there is bubble, then the dependent variable that its measurement obtains truly cannot reflect actual strain amount, thus it is larger to cause finally measuring the terrestrial stress error obtained.Embodiment of the present invention is strained by displacement sensor, the angular deviation that the method monitor strain avoiding prior art to paste foil gauge on core sample 10 may cause, also solve prior art when pasting foil gauge simultaneously, bubble may be produced between foil gauge and core sample 10, cause the problem of measuring error, thus improve the precision of measurement greatly.

In order to stable displacement sensor, make its contact jaw can all the time well and the plane of core sample 10 and seamed edge keep in touch.Embodiment of the present invention arranges fixed arm on the relevant position of base 25, is fixedly arranged on described fixed arm by displacement transducer.Scheme on base 25, is installed with the first fixed arm 15, first displacement transducer 37, second displacement sensor 41 and the 4th displacement transducer 39 be installed on the first fixed arm 15 particularly.Due to the first fixed arm 15 having set firmly three displacement transducers, in order to make corresponding displacement transducer can contact with the corresponding site of core sample 10, the first fixed arm 15 is designed to the three folding shapes adapting to core sample 10 change of shape.Such as, when core examination 10 is regular hexahedron shapes, then the shape of the first fixed arm 15 can make the first displacement transducer 37 in 90 ° with second displacement sensor 41,4th displacement transducer 39 at the first displacement transducer 37 with on the folder bisector of angle direction of second displacement sensor 41, thus make the first displacement transducer 37 and second displacement sensor 41 can respectively with the first plane 31 and the second plane 32 perpendicular contact, 4th displacement transducer 39 contacts with the first seamed edge 41, its direction and the first plane 31 and the second plane 32 angle all at 45 °.

In order to fix triple motion sensor 35, base 25 is installed with the second fixed arm 11, triple motion sensor 35 is installed on described second fixed arm 11.Because a displacement transducer fixed by the second fixed arm 11 need, therefore its shape can be set to more simply, the overall strip extended along lengthwise.

Base 25 is installed with the 3rd fixed arm the 21, five displacement transducer 12 and the 6th displacement transducer 14 is installed on the 3rd fixed arm 21.Because the 5th displacement transducer 12 and the 6th displacement transducer 14 are all contact with the seamed edge of core sample 10, therefore be the three folding shapes being arranged to the 3rd fixed arm 21 adapt to core sample 10 change of shape equally, its shape is similar to the first fixed arm 15, repeats no more.

In addition, in order to ensure contacting well with seamed edge with the plane of core sample 10, the contact jaw of what displacement transducer adopted is interchangeable flat or point.Such as, due to less with the area of seamed edge, the contact jaw contacted with it can be set to forward type, or with other shapes of seamed edge adaptation, with enlarge active surface, that guarantees to contact is good.

In order to simplified operation, under normal circumstances strain unit style is made regular hexahedron.Therefore, in order to adapt to this shape straining unit, embodiment of the present invention has made adaptive design.Refer to Fig. 7.Base 25 has orthogonal first direction w and second direction l, and wherein first direction w is along the Width of base 25, and second direction l is along the length direction of base 25; And and first direction w and second direction l between the third direction d at angle all at 45 °.And these three directions define a plane, i.e. base plane 27.First fixed arm 15 is fixedly arranged on base plane 27 along first direction w, and the second fixed arm 11 is fixedly arranged on base plane 27 along second direction l, and the 3rd fixed arm 21 is fixedly arranged on base plane 27 along third direction d.

After the core sample of regular hexahedron to be measured is in place, due to the regular shape of core sample, and each fixed arm being arranged symmetrically with relative to core sample on base plane 27, the contact jaw of the displacement transducer therefore touched with the flat face of core sample will with this plane being perpendicular; And the contact jaw of the displacement transducer contacted with the seamed edge of core sample will divide the angle of two intersecting planes of this seamed edge total equally.Be orthogonal between two faces that the core sample 10 of regular hexahedron intersects, if it is ε that the displacement sensor that therefore contact jaw contacts with seamed edge obtains strain, then the shear strain having two intersecting planes of this seamed edge is

For isotropic material, the strain tensor that six components of strain in three orthogonal crossing planes are formed, has been enough to describe the strain regime of strain residing for unit, and then can have obtained the stress state suffered by it.And under normal circumstances, most of material is anisotropic, for anisotropic material, six components of strain on three that sample above-mentioned orthogonal crossing faces, to describe its strain regime, may cause error to stress state suffered by it.

Therefore, in order to eliminate the impact of anisotropy on measurement result of core sample, embodiment of the present invention, on the basis of existing three fixed arms, adopts symmetrically arranged mode to set up three fixed arms again, to realize the comprehensive description to the strain on six faces of regular hexahedron core sample.

Refer to Fig. 7.In order to the impact that the anisotropy eliminated along first direction w produces measurement result, the geostress survey system of present embodiment comprises: be fixedly arranged on the 4th fixed arm 17 on base plane 27 along first direction w, (in order to simplify accompanying drawing, only partial dislocation sensor shown in the drawings does schematic explanation 4th fixed arm 17 to set firmly three displacement transducers.For eliminating anisotropy and the displacement transducer that arranges is identical with the displacement sensor structure illustrated, and be symmetrical arranged, therefore by its economization and repeat no more), the contact jaw of wherein two displacement transducers of three displacement transducers that the 4th fixed arm 17 sets firmly can respectively with two plane contact of core sample 10, and these two planes are relative with the second plane 32 with the first plane 31 respectively, seamed edge total between another contact jaw and this two planes of three displacement transducers contacts, and this total seamed edge is relative with the first seamed edge 41.

In order to the impact that the anisotropy eliminated along second direction l produces measurement result, the geostress survey system of present embodiment comprises: be fixedly arranged on the 5th fixed arm 13 on base plane 27 along second direction l, 5th fixed arm 13 can set firmly a displacement transducer, the contact jaw of the displacement transducer that the 5th fixed arm 13 sets firmly can with of core sample 10 plane contact, this plane is relative with the 3rd plane 33.

In order to the impact that the anisotropy eliminated along third direction d produces measurement result, the geostress survey system of present embodiment comprises: be fixedly arranged on the 6th fixed arm 19 on base plane 27 along third direction d, 6th fixed arm 19 can set firmly two displacement transducers, the contact jaw of these two displacement transducers that the 6th fixed arm 19 sets firmly can be crossing with two articles of core sample 10 respectively seamed edge contact, two articles of crossing determined planes of seamed edge are relative with the 3rd plane 33.

The displacement transducer that three fixed arms that utilization is set up set firmly, in addition the level sensor on existing three fixed arms, the strain of measuring can cover six planes of regular hexahedron core sample completely, therefore make the description of core sample strain regime more perfect, eliminate anisotropy to the impact of measurement result.

The conveniently installation and removal of displacement transducer, the fixed arm of embodiment of the present invention offers fixed orifice 22 and pin-and-hole 24 setting firmly displacement transducer place, displacement transducer can be actively located in fixed orifice 22, can insert fixed pin 16 in pin-and-hole 24, with fixed displacement sensor.

In addition, base plane 27 is fixedly installed brace table 29, brace table is used for placing and supporting core sample 10.When measuring, the core sample 10 prepared directly being placed on brace table 29, then can applying confined pressure and directly measure, easy and simple to handle, thus improve measurement efficiency.

Confined pressure module core sample 10 being applied to confined pressure can adopt pressure chamber; Computing machine etc. can be used with the instrument of corresponding calculation procedure to the strained handling module that processes of strain gathered.These are all prior art means, do not limit at this to it, can select accordingly according to actual needs, not in pairs the restriction of embodiment of the present invention.

The foregoing is only several embodiments of the present invention, those skilled in the art can carry out various change or modification to the embodiment of the present invention according to content disclosed in application documents and not depart from the spirit and scope of the present invention.

Claims (10)

1. measure a method for terrestrial stress, it is characterized in that, comprise the steps:

Prepare core sample to be measured, described core sample has at least three planes intersecting each other;

Confined pressure is applied to described core sample, makes it deform;

Gather the strain value of core sample, the strain value of collection comprises the normal strain in three planes, and along the strain in the angular bisector direction of intersecting plane between two;

Utilize the strain value gathered, calculate the terrestrial stress of core sample.

2. the method measuring terrestrial stress as claimed in claim 1, is characterized in that: utilize the strain value gathered, and the step obtaining the components of strain describing core sample strain regime is:

Decompose the strain along the angular bisector direction of two intersecting planes, the direction of decomposition is the tangential direction of two intersecting planes;

The strain in the angular bisector direction of at least three planes intersecting each other is decomposed, obtains the shear strain of three planes intersecting each other;

Utilize the normal strain of these at least three planes intersecting each other collected, obtain the components of strain describing core sample strain regime.

3. the method measuring terrestrial stress as claimed in claim 1, is characterized in that: the strain in the angular bisector direction along two intersecting planes of collection comprises: along the either direction strain in the angular range of two intersecting planes.

4. measure a system for terrestrial stress, it is characterized in that, comprising:

Hold original mold block, described original mold block of holding comprises base for placing core sample to be measured, described core sample has at least three the first planes intersecting each other, second plane and the 3rd plane, the seamed edge that first plane and the second plane, the 3rd plane have is respectively the first seamed edge and the second seamed edge, and the seamed edge that the second plane and the 3rd plane have is the 3rd seamed edge;

Confined pressure module, described confined pressure module can apply confined pressure to described core sample;

Strain acquirement module, described strain acquirement module comprises:

First displacement transducer, second displacement sensor and triple motion sensor, the contact jaw of described first displacement transducer, second displacement sensor and triple motion sensor can respectively with described first plane, the second plane and the 3rd plane contact;

4th displacement transducer, the 5th displacement transducer and the 6th displacement transducer, described 4th displacement transducer, the 5th displacement transducer can contact with the 3rd seamed edge with described first seamed edge, the second seamed edge respectively with the contact jaw of the 6th displacement transducer;

Strained handling module, described strained handling module can process the strain gathered.

5. geostress survey system as claimed in claim 4, it is characterized in that comprising stuck-module, described stuck-module comprises:

Be fixedly arranged on the first fixed arm on described base, described first displacement transducer, second displacement sensor and the 4th displacement transducer are installed on described first fixed arm;

Be fixedly arranged on the second fixed arm on described base, described triple motion sensor is installed on described second fixed arm;

Be fixedly arranged on the 3rd fixed arm on described base, described 5th displacement transducer and the 6th displacement transducer are installed on described 3rd fixed arm.

6. geostress survey system as claimed in claim 5, it is characterized in that: described base has orthogonal first direction and second direction, and and the third direction at angle all at 45 ° between described first direction and second direction, and these three directions are on the same base plane of described base;

Described first fixed arm is fixedly arranged on described base plane along first direction, and the second described fixed arm is fixedly arranged on described base plane along second direction, and the 3rd described fixed arm is fixedly arranged on described base plane along third direction.

7. geostress survey system as claimed in claim 6, it is characterized in that comprising: be fixedly arranged on the 4th fixed arm on described base plane along first direction, described 4th fixed arm can set firmly three displacement transducers, the contact jaw of wherein two displacement transducers of three displacement transducers that described 4th fixed arm sets firmly can respectively with two plane contact of described core sample, and these two planes are relative with the second plane with described first plane respectively, seamed edge total between another contact jaw and this two planes of three described displacement transducers contacts, this total seamed edge is relative with described first seamed edge.

8. geostress survey system as claimed in claim 7, it is characterized in that comprising: be fixedly arranged on the 5th fixed arm on described base plane along second direction, described 5th fixed arm can set firmly a displacement transducer, the contact jaw of the displacement transducer that described 5th fixed arm sets firmly can with a plane contact of described core sample, this plane is relative with described 3rd plane.

9. geostress survey system as claimed in claim 7 or 8, it is characterized in that comprising: be fixedly arranged on the 6th fixed arm on described base plane along third direction, described 6th fixed arm can set firmly two displacement transducers, the contact jaw of these two displacement transducers that described 6th fixed arm sets firmly can be crossing with two articles of described core sample respectively seamed edge contact, described two articles crossing determined planes of seamed edge are relative with described 3rd plane.

10. geostress survey system as claimed in claim 9, is characterized in that: described in hold original mold block and comprise brace table, described brace table is fixedly arranged on described base plane, and described brace table is used for placing and supporting described core sample.