CN106226217A - A kind of descend the method for fracture opening, device and application thereof definitely - Google Patents

Abstract

The invention provides a kind of method descending fracture opening definitely, particularly as follows: determine Crack Detection region, fathom the quiet rock confined pressure in region residing for the subterranean fracture of x, according to formula e_i=a^f(x)+ b calculates subterranean fracture opening width e_i；Wherein, f (x) represents the quiet rock confined pressure in residing region when the penetration of fracture is x；A, b are the fitting coefficient of Mathematical Fitting.The technical scheme that the present invention provides, for determining that fracture opening under the conditions of the confined pressure of stratum, porosity and permeability provide feasible way, intrinsic fracture opening width, intrinsic fracture porosity and the intrinsic fracture permeability true distribution situation under the conditions of Different Strata confined pressure can be recovered quantitatively, provide effective means for objective intrinsic fracture preserving in fine and close low permeability reservoir, seepage effect and the contribution reasonably evaluated.

Description

A kind of descend the method for fracture opening, device and application thereof definitely

Technical field

The present invention relates to petroleum exploration field, be specifically related to a kind of descend definitely the method for fracture opening, device and Application.

Background technology

Intrinsic fracture underground aperture, the quantitative assessment of porosity and permeability are reflection intrinsic fracture role and tribute thereof Offer 3 core parameters of size, be also the key parameter needed for fractured hydrocarbon reservoir exploitation.Rock core information is to characterize intrinsic fracture to determine Amount parameter the most reliably, the most direct and the most frequently used approach.But it is later due to the release of stratum confined pressure that rock core gets earth's surface, exists The process that one rock core expands, can cause the opening width of intrinsic fracture on the rock core of earth's surface to be far longer than its truly opening in underground Degree, the fracture porosity obtained thereby through earth's surface core description and permeability can be far longer than the actual value of underground, such gesture Must cause the error evaluation of intrinsic fracture effect, the intrinsic fracture parameter obtained can not reflect that they are in stratum confined pressure objectively Under the conditions of truth.

Therefore, when carrying out the quantitatively characterizing of intrinsic fracture parameter, it is necessary to recover the crack to the confined pressure of stratum 3 parameters of the permeability in the opening width of actual parameter, mainly crack, the porosity in crack and crack, the most just can be objective Ground quantitative assessment intrinsic fracture, to the effect of fine and close low-permeability oil gas reservoir and contribution, correctly instructs Fractured densification low The exploration of infiltration oil-gas reservoir and reasonable development.

Summary of the invention

It is an object of the invention to provide a kind of method descending fracture opening definitely, and crack exists to apply the method to determine A porosity and permeability of underground, to instruct production application.

In several important parameters in crack, owing on rock core, the occurrence of intrinsic fracture and scale be in earth's surface and underground almost Do not change, but after the opening width of intrinsic fracture obtains earth's surface due to drill cores, confined pressure discharges the expansion generation occurred A lot of change.Therefore, present invention firstly provides a kind of method descending fracture opening definitely, described in include following step Rapid: to determine Crack Detection region, fathom the quiet rock confined pressure in region residing for the subterranean fracture of x, calculates underground according to formula I Fracture opening e_i:

e_i=a^f(x)+b I；

In described formula I, f (x) represents the quiet rock confined pressure in residing region when the penetration of fracture is x；A, b are fitting coefficient. Use above-mentioned formula, it becomes possible to obtain underground, the crack opening width under the conditions of Different Strata confined pressure.

In described formula I, f (x) represents the quiet rock confined pressure of a certain degree of depth, with crack bury infiltration, crack figure, crack In fluid pressure, stress direction relevant with factors such as sizes.Specifically, the computing formula of described f (x) is:

$f\left(x\right)=\frac{\mathrm{\μ}}{1-\mathrm{\μ}}Hf\left({\mathrm{\σ}}_v\right)\sin \mathrm{\θ}+{\mathrm{H\ρ}}_s\cos \mathrm{\θ}+Hf\left({\mathrm{\σ}}_H\right)\sin \mathrm{\θ}\cos \mathrm{\α}+Hf\left({\mathrm{\σ}}_h\right)\sin \mathrm{\θ}\cos \mathrm{\α}-{\mathrm{\γH\ρ}}_0$

Wherein, μ is Poisson's ratio；H is buried depth；F (σ H), f (σ v), f (σ h) respectively horizontal maximum principal stress, vertical should Power and horizontal minimum principal stress are with the gradient of change in depth；ρ₀For fluid unit weight；θ, α are respectively fracture dip and fracture strike Angle with horizontal biggest principal stress direction；γ is pore fluid pressure coefficient.The most each parameter all can use this area conventional Method is measured, is determined.

In described formula I, a, b are fitting coefficient, can the most artificially determine according to crack, area feature or use mathematics The method of matching obtains.

Invention also provides a kind of device descending fracture opening definitely, described device include loading system (1), Control pressurer system (2) and measurement processing system (3)；

The center of described loading system (1) is sample placement unit；The periphery of described sample placement unit is that confined pressure loads Unit；

Described control pressurer system (2) includes stratum confined pressure control unit and axial load control unit；

Described measurement processing system (3) processed for the later stage of the measurement of parameter, metering and experimental data.

Wherein, loading system (1) includes the confined pressure loading system two parts around the place system of core sample and sample, Under the conditions of ensure that different confined pressure, the dynamic of rock core fracture aperture changes；Control pressurer system (2) includes the ground that sample is subject to Layer confined pressure controls and control two parts of axial load, it is possible to ensure Different Strata confined pressure and the loading of crustal stress；Measured place Reason system (3) includes that the accurate measurement of parameters in series such as change of fluid in rock sample, deformation change and the later stage of experimental data process System, obtains the fracture aperture Changing Pattern under the conditions of Different Strata confined pressure.Utilize the physical modeling that the device of Fig. 1 is carried out, The Changing Pattern of natural fracture opening on rock core can be obtained under the conditions of different quiet rock confined pressures.

The present invention protects described method or apparatus descending the application in fracture porosity definitely simultaneously, specifically includes following Step:

(1) the opening width e of subterranean fracture is measured_iAnd the opening width e of surface cracks_0i, calculate underground according to formula II and split Joint opening and the proportionality coefficient A of surface cracks opening width_i；

$A_i=\frac{e_i}{e_{0i}}---II;$

(2) length L of each crack in earth's surface is measured_iAnd the gross area A shared by crack_s, calculate earth's surface according to formula III The porosity in rock core crack

${\mathrm{\φ}}_f=\left(\frac{1}{A_s}\right)\underset{i=1}{\overset{n}{\Σ}}{L}_i\·e_{0i}---III;$

In described formula III, the total number in crack in n representative sample；

(3) by described A_iWithSubstitute in formula IV, be calculated the porosity φ ' of subterranean fracture_f；

φ'_f=A_i×φ_f IV。

The present invention also protects described method or apparatus descending the application in fracture permeabgility definitely, comprises the following steps:

(1) the opening width e of subterranean fracture is measured_iAnd the opening width e of surface cracks_0i, calculate underground according to formula II and split Joint opening and the proportionality coefficient A of surface cracks opening width_i；

$A_i=\frac{e_i}{e_{0i}}---II;$

(2) length L of surface cracks is measured_iAnd occupied area A_s, the infiltration in rock core crack, earth's surface is calculated according to formula V Rate K_ff；

$K_f=C\·\frac{1}{A_s}\·\underset{i=1}{\overset{n}{\Σ}}{e}_{0i}^3\·L_i---V;$

In described formula III, the total number in crack in n representative sample；C represents fitting coefficient；

(3) by described A_iAnd K_fSubstitute in formula VI, be calculated permeability K' of subterranean fracture_f；

$K_f^{\′}=A_i^3\×K_f---VI.$

The method and device that the present invention provides, for determining fracture opening, porosity and permeability under the conditions of the confined pressure of stratum Provide feasible way, it is possible to recover intrinsic fracture opening width, intrinsic fracture porosity and intrinsic fracture permeability quantitatively and exist True distribution situation under the conditions of Different Strata confined pressure, for objective intrinsic fracture of reasonably evaluating in fine and close low permeability reservoir Preserve, seepage effect and contribution provide effective means.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of device described in embodiment 1；

Fig. 2 is the fracture aperture distribution relation figure under the different quiet rock confined pressure of embodiment 2 gained；

Fig. 3 is the distribution frequency figure of embodiment 2 gained earth's surface rock core fracture opening；

Fig. 4 is the distribution frequency figure that embodiment 2 gained rock core fracture opening recovers to the confined pressure of stratum；

Fig. 5 is the distribution frequency figure of embodiment 2 gained earth's surface rock core fracture porosity；

Fig. 6 is the distribution frequency figure that embodiment 2 gained rock core fracture porosity recovers to the confined pressure of stratum；

Fig. 7 is embodiment 2 gained earth's surface rock core fracture permeabgility distribution frequency figure；

Fig. 8 is the distribution frequency figure that embodiment 2 gained rock core fracture permeabgility recovers to the confined pressure of stratum.

Detailed description of the invention

Following example are used for illustrating the present invention, but are not limited to the scope of the present invention.

Embodiment 1

Present embodiments provide a kind of device descending fracture opening definitely, as it is shown in figure 1, described device includes loading System (1), control pressurer system (2) and measurement processing system (3)；

The center of described loading system (1) is sample placement unit；The periphery of described sample placement unit is that confined pressure loads Unit；

Described control pressurer system (2) includes stratum confined pressure control unit and axial load control unit；

Described measurement processing system (3) processed for the later stage of the measurement of parameter, metering and experimental data.

Embodiment 2

Fracture aperture distribution relation figure under the difference quiet rock confined pressure that the device that the present embodiment utilizes embodiment 1 to provide obtains (Fig. 2), reflecting and increase with landing surface confined pressure (degree of depth), the opening width in crack is the Changing Pattern that negative exponential function successively decreases.

Particularly as follows:

Determining Crack Detection region, fathom the quiet rock confined pressure in region residing for the subterranean fracture of x, counts according to formula I Calculate subterranean fracture opening width e_i:

e_i=a^f(x)+b I；

In described formula I, f (x) represents the quiet rock confined pressure in residing region when the penetration of fracture is x；The calculating of described f (x) is public Formula is:

$f\left(x\right)=\frac{\mathrm{\μ}}{1-\mathrm{\μ}}Hf\left({\mathrm{\σ}}_v\right)sin\mathrm{\θ}+{\mathrm{H\ρ}}_{s}cos\mathrm{\θ}+Hf\left({\mathrm{\σ}}_H\right)sin\mathrm{\θ}cos\mathrm{\α}+Hf\left({\mathrm{\σ}}_h\right)sin\mathrm{\θ}cos\mathrm{\α}-{\mathrm{\γH\ρ}}_0$

Wherein, μ is Poisson's ratio；H is buried depth；F (σ H), f (σ v), f (σ h) respectively horizontal maximum principal stress, vertical should Power and horizontal minimum principal stress are with the gradient of change in depth；ρ₀For fluid unit weight；θ, α are respectively fracture dip and fracture strike Angle with horizontal biggest principal stress direction；γ is pore fluid pressure coefficient；The most each parameter all uses this area routine side Method measurement determines；

Described a, b use the method for Mathematical Fitting to obtain；

Measuring through conventional method, the crack opening width on earth's surface is mainly 150-400 micron, average out to 307.0 microns；Should The distribution frequency of area surface cracks opening width is as shown in Figure 3；

The method using the present embodiment to provide calculates, and the opening width of this area's subterranean fracture is mainly 120-320 micron, flat Being 241.2 microns, compared with surface cracks opening width, the opening width of subterranean fracture averagely declines 21.5%；Stratum, this area The opening width distribution frequency of the subterranean fracture under the conditions of confined pressure is as shown in Figure 4；

By the opening width e of described subterranean fracture_iAnd the opening width e of surface cracks_0iSubstitute into formula II, calculate subterranean fracture Opening width and the proportionality coefficient A of surface cracks opening width_i；

$A_i=\frac{e_i}{e_{0i}}---II;$

Measure length L of each crack in earth's surface_iAnd the gross area A shared by crack_s, calculate earth's surface rock core according to formula III The porosity in crack

${\mathrm{\φ}}_f=\left(\frac{1}{A_s}\right)\underset{i=1}{\overset{n}{\Σ}}{L}_i\·e_{0i}---III;$

In described formula III, the total number in crack in n representative sample；

By described A_iWithSubstitute in formula IV, be calculated the porosity φ ' of subterranean fracture_f；

φ'_f=A_i×φ_fIV；

Measuring through conventional method, this area's surface cracks porosity is mainly 0.6%-1.4%, average out to 1.02%；Should The distribution frequency of area surface cracks porosity is as shown in Figure 5；

The method using the present embodiment to provide calculates, and the porosity of this area's subterranean fracture is mainly 0.4%-1.2%, flat Being 0.81%, compared with surface cracks porosity, subterranean fracture porosity averagely declines 20.6%；Subterranean fracture hole, this area Porosity distribution frequency under the conditions of the confined pressure of stratum is as shown in Figure 6；

Conventionally measure length L of surface cracks_iAnd occupied area A_s, calculate earth's surface rock core according to formula V and split Permeability K of seam_f；

$K_f=C\·\frac{1}{A_s}\·\underset{i=1}{\overset{n}{\Σ}}{e}_{0i}^3\·L_i---V;$

In described formula V, the total number in crack in n representative sample；C represents fitting coefficient；

By described A_iAnd K_fSubstitute in formula VI, be calculated permeability K' of subterranean fracture_f；

$K_f^{\′}=A_i^3\×K_f---VI;$

Measuring through conventional method, the permeability of this area's surface cracks is mainly 40-100 person of outstanding talent's darcy, average out to 87.07 person of outstanding talent Darcy；This area's surface cracks Permeability Distribution frequency is as shown in Figure 7；

The method using the present embodiment to provide calculates, and the permeability of this area's subterranean fracture is mainly 10-25 person of outstanding talent's darcy, flat Being 19.4 person of outstanding talent's darcies, compared with surface cracks permeability, the permeability of subterranean fracture averagely declines 77.8%；Underground, this area Fracture permeabgility distribution frequency under the conditions of the confined pressure of stratum is as shown in Figure 8.

The above results reflects that the crack opening width in underground, porosity and permeability all ratio earth's surfaces decline many, the most extensive Arrive the fracture parameters of underground again, can reflect and evaluate crack objectively big to effect and the contribution of fine and close low permeability reservoir Little.

The present invention can detect the accuracy of parameter by imaging logging survey material, sealing core data.Gained underground is split Opening width, the porosity in crack and the permeability in crack of seam, can objectively quantitative assessment intrinsic fracture to fine and close hyposmosis The effect of oil and gas reservoir and contribution, correctly instruct exploration and the reasonable development of Fractured densification Low permeable oil and gas reservoirs.

Although, used general explanation, detailed description of the invention and test, the present invention made detailed retouching Stating, but on the basis of the present invention, can make some modifications or improvements it, this is apparent to those skilled in the art 's.Therefore, these modifications or improvements without departing from theon the basis of the spirit of the present invention, belong to claimed Scope.

Claims (6)

1. the method descending fracture opening definitely, it is characterised in that comprise steps of determining that Crack Detection region, Fathom the quiet rock confined pressure in region residing for the subterranean fracture of x, calculates subterranean fracture opening width e according to formula I_i:

e_i=a^f(x)+b I；

In described formula I, f (x) represents the quiet rock confined pressure in residing region when the penetration of fracture is x；A, b are fitting coefficient.

Method the most according to claim 1, it is characterised in that the computing formula of described f (x) is:

$f\left(x\right)=\frac{\mathrm{\μ}}{1-\mathrm{\μ}}Hf\left({\mathrm{\σ}}_v\right)sin\mathrm{\θ}+{\mathrm{H\ρ}}_{s}cos\mathrm{\θ}+Hf\left({\mathrm{\σ}}_H\right)sin\mathrm{\θ}cos\mathrm{\α}+Hf\left({\mathrm{\σ}}_h\right)sin\mathrm{\θ}cos\mathrm{\α}-{\mathrm{\γH\ρ}}_0$

Wherein, μ is Poisson's ratio；H is buried depth；F (σ H), f (σ v), f (σ h) respectively horizontal maximum principal stress, vertical stress and Horizontal minimum principal stress gradient；ρ₀For fluid unit weight；θ, α are respectively fracture dip and fracture strike and horizontal maximum principal stress The angle in direction；γ is pore fluid pressure coefficient.

Method the most according to claim 1 and 2, it is characterised in that described coefficient a, b are according to crack, area feature empirically Artificially determine or use the method for Mathematical Fitting to obtain.

4. the device descending fracture opening definitely, it is characterised in that described device includes loading system (1), pressure control System processed (2) and measurement processing system (3)；

The center of described loading system (1) is sample placement unit；The periphery of described sample placement unit is confined pressure loading unit；

Described control pressurer system (2) includes stratum confined pressure control unit and axial load control unit；

Described measurement processing system (3) processed for the later stage of the measurement of parameter, metering and experimental data.

5. device described in method described in claims 1 to 3 any one or claim 4 is descending in fracture porosity definitely Application, it is characterised in that comprise the following steps:

(1) the opening width e of subterranean fracture is measured_i, and measure the opening width e of surface cracks_0i, calculate subterranean fracture according to formula II Opening width and the proportionality coefficient A of surface cracks opening width_i；

$A_i=\frac{e_i}{e_{0i}}---II;$

(2) length L of each crack in earth's surface is measured_iAnd the gross area A shared by crack_s, calculate earth's surface rock core according to formula III The porosity in crack

${\mathrm{\φ}}_f=\left(\frac{1}{A_s}\right)\underset{i=1}{\overset{n}{\Σ}}{L}_i\·e_{0i}---III;$

In described formula III, the total number in crack in n representative sample；

(3) by described A_iWithSubstitute in formula IV, be calculated the porosity φ ' of subterranean fracture_f；

φ'_f=A_i×φ_f IV。

6. device described in method described in claims 1 to 3 any one or claim 4 is descending in fracture permeabgility definitely Application, it is characterised in that comprise the following steps:

(1) the opening width e of subterranean fracture is measured_i, and measure the opening width e of surface cracks_0i, calculate subterranean fracture according to formula II Opening width and the proportionality coefficient A of surface cracks opening width_i；

$A_i=\frac{e_i}{e_{0i}}---II;$

(2) length L of surface cracks is measured_iAnd occupied area A_s, permeability K in rock core crack, earth's surface is calculated according to formula V_f；

$K_f=C\·\frac{1}{A_s}\·\underset{i=1}{\overset{n}{\Σ}}{e}_{0i}^3\·L_i---V;$

In described formula III, the total number in crack in n representative sample；C represents fitting coefficient；

(3) by described A_iAnd K_fSubstitute in formula VI, be calculated permeability K' of subterranean fracture_f；

$K_f^{\′}=A_i^3\×K_f---VI.$