CN103670358B - Hydraulically created fracture is sentenced knowledge method at thin sand-mud interbed geological interface propagation path - Google Patents

Abstract

The invention provides a kind of hydraulically created fracture and sentence knowledge method at thin sand-mud interbed geological interface propagation path, according to existing hydraulic fracture extended model has been carried out to correction, perfect, in the expanded configuration criterion of thin interbed geological interface place, can determine more accurately the deflection angle of hydraulic fracture at geological interface place by thin interbed hydraulic fracture. Make up and applied the defect that existing fracture propagation model prediction hydraulic fracture occurs in thin interbed expansion.

Description

Hydraulically created fracture is sentenced knowledge method at thin sand-mud interbed geological interface propagation path

Technical field

The invention belongs to hydraulically created fracture control technology field, be specifically related to a kind of hydraulically created fracture thin at sand shaleAlternating layers geological interface propagation path is sentenced knowledge method.

Background technology

Crack geometric shape definite is one of key issue of fracturing design, crack geometric shape and of the fracturing fluidFluid flow characteristics and seepage field and should in the mechanical property of character, formation fluid property, formation rock, scope of construction item, seamThe coupled relations in the field of force etc. are closely related. Take a broad view of the development of domestic and international fracturing technique, the research of fracture extension Mathematical Modeling is passed byOne from simple to complicated, from more and more comprehensively process of 2 d-to-3 d, Consideration.

Abroad, before the eighties, the research of most fracture propagation simulations is all the situation of extending based on monolete,Under normal circumstances because not obtaining the accurately extension of simulation fracture of stress distribution. Many different skills subsequently grow upArt is carried out the rule of predicted stresses along with change in depth, thereby also makes multilayered reservoir well fracturing renovation technique obtain very largeDevelopment. At present, external 3-dimensional multi-layered pressure break analog synthesis has been considered fracture height growth, fluid with time and temperature correlationThe pressure drop of rheological characteristic, various filtration mechanism, bridging plug and sand fallout, the nearly limited generation of pit shaft fracture extension, eyelet abrasion, two dimension supportThe factors such as agent migration and heat transmission.

But, for thin sand-mud interbed fracturing, rock composition structure difference between layers, lithology, powerLearn character not identical, in fracture process, deformation form is not identical yet. Existing model is not considered the poor of rock deformation formThe impact of geological interface fracture expanded configuration between different and rock stratum, is not suitable for and describes the expansion of thin sand-mud interbed reservoir fracturesForm. Thin sand-mud interbed oil reservoir is thin, poor properties, and anisotropism is serious, oiliness heterogeneity, hydraulic fracture is at sand shaleExpanded configuration complexity in thin interbed, between sand shale geological interface, expansion there will be deflection, slippage, the unlatching of secondary crack etc.Complicated phenomenon, effectively supports seam short, and primary fracture expansion theory and model are difficult to prediction.

For the deficiency existing in current hydraulically created fracture extended model, need to adopt a kind of improvement, perfect sand shaleThin interbed fracturing fracture expanded configuration Forecasting Methodology, to carrying out more accurately and reasonably the pre-of thin sand-mud interbed fracture patternSurvey.

Summary of the invention

Key problem in technology to be solved by this invention is to be to overcome existing model cannot describe crack at thin sand-mud interbedThe problem of geological interface place expanded configuration, provides a kind of hydraulically created fracture to expand in thin sand-mud interbed reservoir geology interfaceThe knowledge method of sentencing of spread state. The method is utilized the each formation properties of thin sand-mud interbed, determine reservoir geology interfacial stress intensity because ofSon, forms hydraulic fracture at thin sand-mud interbed geological interface expanded configuration decision criteria. Can be more accurate by described criterionIn reflection thin sand-mud interbed there is, expand overall process in hydraulic fracture. Thereby solve original two dimension, intended the complete three-dimensional mould of three peacekeepingsType is ignored geological interface impact and is made forecasting inaccuracy in the time of prediction hydraulic fracture expanded configuration, and large with reality cracking situation errorProblem.

The present invention provides a kind of hydraulically created fracture disconnected at thin sand-mud interbed geological interface for solveing the technical problemSplit expansion and sentence knowledge method, adopt following steps:

(1) a selected thin sand-mud interbed is treated fractured well, determines in pressing crack construction process net pressure p crack in, and MPa is trueDetermine in pressing crack construction process effective shear stress τ in crack_ef, MPa; Well test analysis is measured thin sand-mud interbed fractured interval sand layersWith the individual layer height h of shale layer, m; Horizontal maximum principal stress σ_H, MPa; Horizontal minimum principal stress σ_h，MPa；

(2) measure respectively the Young's modulus of lasticity E of the individual layer of thin sand-mud interbed fractured interval sand layers and shale layer,MPa; Poisson's ratio v, the internal friction angle of rock stratum° (degree); The cohesive force C of rock stratum, MPa;

(3) measure respectively the critical rupture strength factor K of I type of thin sand-mud interbed fractured interval sand layers and shale layer_IC，MPa·m^0.5; The critical rupture strength factor K of II type_IIC，MPa·m^0.5；

(4) determine the compound Young's modulus of lasticity E at thin sand-mud interbed reservoir geology interface^*, MPa, wherein,

$E^{*}=\frac{2E_1{E}_2}{E_1(1+v_2^2)+E_2(1+v_1^2)}$

In formula, E^*For the compound Young's modulus of elasticity of geological interface, MPa; E is the Young elasticity of sand layers and shale layer individual layerModulus, MPa; V is the Poisson's ratio of sand layers and shale layer individual layer, and subscript 2 represents crack tip place layer, and treat in 1 expression crackExtension layer;

Note: for the mutual thin interbed of absolute sand shale, thin sand-mud interbed oil reservoir is vertical upper from ground to groundUnder distribution of strata distribute in strict accordance with this distribution form of sand layers, shale layer, sand layers, shale layer, sand layers. If splitStitching most advanced and sophisticated place layer is sand layers, v₂、E₂For the Young's modulus of elasticity of sand layers individual layer, v₁、E₁For the poplar of shale layer individual layerFamily name's elastic modelling quantity; Otherwise, if crack tip place layer is shale layer, v₂、E₂For the Young springform of shale layer individual layerAmount, v₁、E₁For the Young's modulus of elasticity of sand layers individual layer;

(5) determine the different material parameter beta in interface at thin sand-mud interbed reservoir geology interface, wherein,

$\mathrm{\β}=\frac{E_1(1-2v_2)(1+v_2)-E_2(1-2v_1)(1+v_1)}{E_1(2-2v_2)(1+v_2)+E_2(2-2v_1)(1+v_1)}$

In formula, E is the Young's modulus of elasticity of sand layers and shale layer individual layer, MPa; V is sand layers and shale layer individual layerPoisson's ratio, subscript 2 represents crack tip place layer, extension layer is treated in 1 expression crack;

(6) determine the critical rupture strength factor in interface at thin sand-mud interbed reservoir geology interfaceWithUnit isMPa·m^0.5, wherein,

$K_{\mathrm{IC}}^{*}=\frac{K_{\mathrm{IC}1}\·h_1+K_{\mathrm{IC}2}\·{\left(h_2\right)}^{3/4}}{h_1+h_2}$ $K_{\mathrm{IIC}}^{*}=\frac{K_{\mathrm{IIC}1}\·h_1+K_{\mathrm{IIC}2}\·{\left(h_2\right)}^{3/4}}{h_1+h_2}$

In formula: K_IC、K_IICBe respectively I type, the critical rupture strength factor of II type of sand layers and shale layer individual layer, MPam^0.5; H sand layers and shale layer individual layer floor height, m, subscript 2 represents crack tip place layer, extension layer is treated in 1 expression crack.

(7) determine the most advanced and sophisticated composite elastic energy release rate G of thin sand-mud interbed reservoir geology interface fracturing fracture^*, singlePosition is N/m,

$G^{*}=\frac{1-{\mathrm{\β}}^2}{E^{*}}[{\left(K_I^{*}\right)}^2+{\left(K_{\mathrm{II}}^{*}\right)}^2]$

Wherein: $K_I^{*}=\sqrt{2\mathrm{\πx}}[{\mathrm{\τ}}_{\mathrm{ef}}\sin \left(\mathrm{\ϵ}\ln x\right)+p\cos \left(\mathrm{\ϵ}\ln x\right)],$

$K_{\mathrm{II}}^{*}=\sqrt{2\mathrm{\πx}}[{\mathrm{\τ}}_{\mathrm{ef}}\cos \left(\mathrm{\ϵ}\ln x\right)+p\sin \left(\mathrm{\ϵ}\ln x\right)],$ $\mathrm{\ϵ}=\frac{1}{2\mathrm{\π}}\ln \frac{1-\mathrm{\β}}{1+\mathrm{\β}},$

In formula, β is the different material parameter in interface; E^*For compound Young's modulus of elasticity, MPa;WithBe respectively I type, II type groundMatter interface mixed-mode stress-intensity factor, MPam^0.5; P is net pressure in crack in pressing crack construction process, MPa; τ_efFor pressure break is executedEffective shear stress in crack in work process, MPa; X is the distance of crack tip apart from geological interface, m; σ_H、σ_hBe respectively rock stratum waterFlat maximum, minimum principal stress, MPa;For rock stratum internal friction angle, °; θ is the final cracking azimuth in crack, °; ε is two materialsMedium interface index of oscillation; C is rock stratum cohesive force, MPa;

(8) according to the most advanced and sophisticated composite elastic energy release rate G of thin sand-mud interbed reservoir geology interface fracturing fracture^*LargeLittle, determine the form in crack.

Wherein, according to the most advanced and sophisticated composite elastic energy release rate G of thin sand-mud interbed reservoir geology interface fracturing fracture^*'sSize, determine and be specially the breaking morphology in crack:

1)G^*While meeting following formula:

$\underset{x\→0}{\lim }{G}^{*}=0$

Determine that crack is in the time of the crack arrest of geological interface place, and the final cracking azimuth angle theta in definite crack, θ=0 °;

2)G^*While meeting following formula:

$\underset{x\→0}{\lim }{G}^{*}=\∞$

Determine that crack directly breaks through geological interface, determine the final cracking azimuth angle theta in crack, θ=0 °;

3)G^*While meeting following formula:

$\underset{x\→0}{\lim }{G}^{*\≠}0,\∞$

Determine that crack is in the slippage of geological interface place; And wherein,

In the time that final cracking azimuth angle theta meets following formula,

$\frac{\&PartialD;K_I^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;\mathrm{\&theta;}}=0,$ $\frac{{\&PartialD;}^2{K}_I^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;{\mathrm{\&theta;}}^2}<0,$ $\frac{\left|K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)\right|}{\left|K_I^{*}\left(\mathrm{\&theta;}\right)\right|}\&le;\frac{\left|K_{\mathrm{IIC}}^{*}\right|}{\left|K_{\mathrm{IC}}^{*}\right|},$ And $\frac{\left|K_{I\max }^{*}\left(\mathrm{\&theta;}\right)\right|}{\left|K_{\mathrm{IC}}^{*}\right|}\&GreaterEqual;1$

Or the azimuth angle theta that finally ftractures meets following formula:

$\frac{\&PartialD;K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;\mathrm{\&theta;}}=0,$ $\frac{{\&PartialD;}^2{K}_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;{\mathrm{\&theta;}}^2}<0,$ $\frac{\left|K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)\right|}{\left|K_I^{*}\left(\mathrm{\&theta;}\right)\right|}\&le;\frac{\left|K_{\mathrm{IIC}}^{*}\right|}{\left|K_{\mathrm{IC}}^{*}\right|},$ And $\frac{\left|K_{I\max }^{*}\left(\mathrm{\&theta;}\right)\right|}{\left|K_{\mathrm{IC}}^{*}\right|}\&GreaterEqual;1$

Wherein:

$K_{I\max }^{*}\left(\mathrm{\&theta;}\right)=\max \left\{K_I^{*}\left(\mathrm{\&theta;}\right)\right\},$ $K_{\mathrm{II}\max }^{*}\left(\mathrm{\&theta;}\right)=\max \left\{K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)\right\},$ $K_I^{*}\left(\mathrm{\&theta;}\right)=K_I^{*}{\cos }^3\left(\frac{\mathrm{\&theta;}}{2}\right)+K_{\mathrm{II}}^{*}[-\sin \frac{\mathrm{\&theta;}}{2}{\cos }^2\left(\frac{\mathrm{\&theta;}}{2}\right)],$

$K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)=K_I^{*}\sin \frac{\mathrm{\&theta;}}{2}{\cos }^2\left(\frac{\mathrm{\&theta;}}{2}\right)+K_{\mathrm{II}}^{*}\cos \frac{\mathrm{\&theta;}}{2}[1-3{\sin }^2\left(\frac{\mathrm{\&theta;}}{2}\right)],$ $K_I^{*}=0.79[{\mathrm{\&tau;}}_{\mathrm{ef}}\sin (-2.3\mathrm{\&epsiv;})+p\cos (-2.3\mathrm{\&epsiv;})],$

$K_{\mathrm{II}}^{*}=0.79[{\mathrm{\&tau;}}_{\mathrm{ef}}\cos (-2.3\mathrm{\&epsiv;})-p\sin (-2.3\mathrm{\&epsiv;})],$ $\mathrm{\&epsiv;}=\frac{1}{2\mathrm{\&pi;}}\ln \frac{1-\mathrm{\&beta;}}{1+\mathrm{\&beta;}},$

Determine that crack penetrates geological interface after the slippage of geological interface place;

In the time that final cracking azimuth angle theta meets following formula

$\frac{\&PartialD;K_I^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;\mathrm{\&theta;}}=0,$ $\frac{{\&PartialD;}^2{K}_I^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;{\mathrm{\&theta;}}^2}<0,$ ${\left(\frac{K_{I\max }^{*}\left(\mathrm{\&theta;}\right)}{K_{\mathrm{IC}}^{*}}\right)}^2+{\left(\frac{K_{\mathrm{II}\max }^{*}\left(\mathrm{\&theta;}\right)}{K_{\mathrm{IIC}}^{*}}\right)}^2\&GreaterEqual;1$

Determine crack arrest after the geological interface place slippage of crack.

The present invention has carried out correction, perfect to existing hydraulic fracture extended model, splits by thin sand-mud interbed waterpowerBe sewn on the expanded configuration criterion of thin sand-mud interbed geological interface place, can determine the deflection angle of hydraulic fracture at geological interface placeDegree. Thereby set up thin sand-mud interbed on-plane surface hydraulic fracture extended model, can accurately reflect crack rising at geological interface placeSplit, expand overall process, made up and applied that existing fracture propagation model prediction hydraulic fracture occurs in thin sand-mud interbed expansionDefect.

Brief description of the drawings

Fig. 1 is fracturing fracture schematic diagram in thin sand-mud interbed oil reservoir.

Fig. 2 be in thin sand-mud interbed oil reservoir fracturing fracture at geological interface place crack arrest schematic diagram.

Fig. 3 is that in thin sand-mud interbed oil reservoir, fracturing fracture is vertically broken through geological interface schematic diagram.

Fig. 4 is that in thin sand-mud interbed oil reservoir, fracturing fracture penetrates interface schematic diagram after the slippage of geological interface place.

Fig. 5 is pressure break crack arrest schematic diagram after the slippage of geological interface place in crack in thin sand-mud interbed oil reservoir.

In figure:

1 treats extension layer for thin sand-mud interbed fracturing fracture; 2 is thin sand-mud interbed fracturing fracture place layer; 3 is adjacentThe geological interface of ground interlayer; 4 is hydraulically created fracture;

Specific implementation method

Below in conjunction with accompanying drawing, content of the present invention is elaborated:

For thin sand-mud interbed oil reservoir, due to its deposition be in the vertical reservoir (sandstone) and non-reservoir (mud stone,Shale) mutually alternately occur, reservoir rock composition difference, sand shale deformation form difference is large and thickness is all less, make itself and thickThe form in formation fracturing crack is obviously different. Particularly at geological interface place, due to nature of subterranean reservoirs difference on geological interface, groundThe ability that layer deforms is also different, geological interface different in kind, and this has just determined that hydraulically created fracture is at longitudinal geological interfaceThe expanded configuration at place is complicated and changeable, finds (see figure 1) in the time that hydraulically created fracture expands to geological interface, waterpower according to investigationCrack may occur directly to penetrate after interface (Fig. 3), crack arrest (Fig. 2), slippage after crack arrest (Fig. 5) or slippage at geological interface placePenetrate again interface (Fig. 4), therefore need to consider the form of geological interface place fracture propagation, and hydraulic fracture extended model in the pastThe needs of thin sand-mud interbed oil reservoir pressure break are can not meet. Consider thin sand-mud interbed oil reservoir on-plane surface character, set up waterpowerCrack is at the expanded configuration model of thin sand-mud interbed oil reservoir interface. Concrete steps are as follows:

(1) a selected thin sand-mud interbed is treated fractured well, determines in pressing crack construction process net pressure p crack in, and MPa is trueDetermine in pressing crack construction process effective shear stress τ in crack_ef, MPa; Well test analysis is measured thin sand-mud interbed fractured interval sand layersWith the individual layer height h of shale layer, m; Horizontal maximum principal stress σ_H, MPa; Horizontal minimum principal stress σ_h，MPa。

(2) measure respectively the Young's modulus of lasticity E of the individual layer of thin sand-mud interbed fractured interval sand layers and shale layer,MPa; Poisson's ratio v, the internal friction angle of rock stratum° (degree); The cohesive force C of rock stratum, MPa; Preferably can learn by rock core three-axis forceExperiment is measured, and can certainly measure by other known method of this area.

(3) measure respectively the critical fracture of I type (opening mode) of thin sand-mud interbed fractured interval sand layers and shale layer strongDegree factor K_IC，MPa·m^0.5; The critical rupture strength factor K of II type (shearing-type)_IIC，MPa·m^0.5; Preferably can try by fatigueThe machine Experiments of Machanics of testing are measured, and can certainly measure by other known method of this area.

(4) determine the compound Young's modulus of lasticity E at thin sand-mud interbed reservoir geology interface^*，MPa；

According to the upper and lower stratum of geological interface (being stratum to be expanded with crack, stratum, current place, crack) mechanics parameter, meterCalculate the compound Young's modulus of lasticity E at thin sand-mud interbed reservoir geology interface^*, the present invention calculates in accordance with the following methods,

$E^{*}=\frac{2E_1{E}_2}{E_1(1+v_2^2)+E_2(1+v_1^2)}$

In formula, E^*For the compound Young's modulus of elasticity of geological interface, MPa; E is the Young elasticity of sand layers and shale layer individual layerModulus, MPa; V is the Poisson's ratio of sand layers and shale layer individual layer, and subscript 2 represents crack tip place layer, and treat in 1 expression crackExtension layer.

(5) determine the different material parameter beta in interface at thin sand-mud interbed reservoir geology interface;

Calculate thin sand-mud interbed reservoir geology interface different material parameter beta, the present invention specifically in accordance with the following methods:

$\mathrm{\&beta;}=\frac{E_1(1-2v_2)(1+v_2)-E_2(1-2v_1)(1+v_1)}{E_1(2-2v_2)(1+v_2)+E_2(2-2v_1)(1+v_1)}$

In formula, E is the Young's modulus of elasticity of sand layers and shale layer individual layer, MPa; V is sand layers and shale layer individual layerPoisson's ratio, subscript 2 represents crack tip place layer, extension layer is treated in 1 expression crack.

(6) determine the critical rupture strength factor in interface at thin sand-mud interbed reservoir geology interfaceWithUnit isMPa·m^0.5, the present invention specifically in accordance with the following methods:

$K_{\mathrm{IC}}^{*}=\frac{K_{\mathrm{IC}1}\&CenterDot;h_1+K_{\mathrm{IC}2}\&CenterDot;h_2^{3/4}}{h_1+h_2},$ $K_{\mathrm{IIC}}^{*}=\frac{K_{\mathrm{IIC}1}\&CenterDot;h_1+K_{\mathrm{IIC}2}\&CenterDot;h_2^{3/4}}{h_1+h_2}$

In formula: K_IC、K_IICBe respectively I type, the critical rupture strength factor of II type of sand layers and shale layer individual layer, MPam^0.5; H sand layers and shale layer individual layer floor height, m, subscript 2 represents crack tip place layer, extension layer is treated in 1 expression crack.

(7) determine the most advanced and sophisticated composite elastic energy release rate G of thin sand-mud interbed reservoir geology interface fracturing fracture^*, singlePosition be N/m, the present invention specifically in accordance with the following methods:

$G^{*}=\frac{1-{\mathrm{\&beta;}}^2}{E^{*}}[{\left(K_I^{*}\right)}^2+{\left(K_{\mathrm{II}}^{*}\right)}^2]$

Wherein: $K_I^{*}=\sqrt{2\mathrm{\&pi;x}}[{\mathrm{\&tau;}}_{\mathrm{ef}}\sin \left(\mathrm{\&epsiv;}\ln x\right)+p\cos \left(\mathrm{\&epsiv;}\ln x\right)],$

$K_{\mathrm{II}}^{*}=\sqrt{2\mathrm{\&pi;x}}[{\mathrm{\&tau;}}_{\mathrm{ef}}\cos \left(\mathrm{\&epsiv;}\ln x\right)+p\sin \left(\mathrm{\&epsiv;}\ln x\right)],$ $\mathrm{\&epsiv;}=\frac{1}{2\mathrm{\&pi;}}\ln \frac{1-\mathrm{\&beta;}}{1+\mathrm{\&beta;}},$

In formula, β is the different material parameter in interface; E^*For compound Young's modulus of elasticity, MPa;WithBe respectively I type, II type groundMatter interface mixed-mode stress-intensity factor, MPam^0.5; P is net pressure in crack in pressing crack construction process, MPa; τ_efFor pressure break is executedEffective shear stress in crack in work process, MPa; X is the distance of crack tip apart from geological interface, m; σ_H、σ_hBe respectively rock stratum waterFlat maximum, minimum principal stress, MPa;For rock stratum internal friction angle, °; θ is the final cracking azimuth in crack, °; ε is two materialsMedium interface index of oscillation; C is rock stratum cohesive force, MPa.

(8) according to the most advanced and sophisticated composite elastic energy release rate G of thin sand-mud interbed reservoir geology interface fracturing fracture^*LargeLittle, determine the breaking morphology in crack.

1) the most advanced and sophisticated composite elastic energy release rate G of described sand mud ground matter interface fracturing fracture^*Meet hydraulic fracture on ground(see figure 2) when matter interface crack arrest, G^*Meet following formula:

$\underset{x\&RightArrow;0}{\lim }{G}^{*}=0$

Determine the final cracking azimuth angle theta in crack, θ=0 °.

2) the most advanced and sophisticated composite elastic energy release rate G of described sand mud ground matter interface fracturing fracture^*Meet hydraulic fracture direct(see figure 3) while breaking through geological interface, G^*Meet following formula:

$\underset{x\&RightArrow;0}{\lim }{G}^{*}=\&infin;$

Determine the final cracking azimuth angle theta in crack, θ=0 °.

3) the most advanced and sophisticated composite elastic energy release rate G of described sand mud ground matter interface fracturing fracture^*, meet hydraulic fracture on groundWhen matter interface slippage, G^*Meet following formula:

$\underset{x\&RightArrow;0}{\lim }{G}^{*\&NotEqual;}0,\&infin;$

1. determine that final cracking azimuth angle theta meets hydraulic fracture in geological interface place cunning to hydraulic fracture at geological interface place(see figure 4) while penetrating geological interface after moving, θ meets following formula:

$\frac{\&PartialD;K_I^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;\mathrm{\&theta;}}=0,$ $\frac{{\&PartialD;}^2{K}_I^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;{\mathrm{\&theta;}}^2}<0,$ $\frac{\left|K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)\right|}{\left|K_I^{*}\left(\mathrm{\&theta;}\right)\right|}\&le;\frac{\left|K_{\mathrm{IIC}}^{*}\right|}{\left|K_{\mathrm{IC}}^{*}\right|},$ And $\frac{\left|K_{I\max }^{*}\left(\mathrm{\&theta;}\right)\right|}{\left|K_{\mathrm{IC}}^{*}\right|}\&GreaterEqual;1$

Or θ meets following formula:

$\frac{\&PartialD;K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;\mathrm{\&theta;}}=0,$ $\frac{{\&PartialD;}^2{K}_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;{\mathrm{\&theta;}}^2}<0,$ $\frac{\left|K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)\right|}{\left|K_I^{*}\left(\mathrm{\&theta;}\right)\right|}\&le;\frac{\left|K_{\mathrm{IIC}}^{*}\right|}{\left|K_{\mathrm{IC}}^{*}\right|},$ And $\frac{\left|K_{I\max }^{*}\left(\mathrm{\&theta;}\right)\right|}{\left|K_{\mathrm{IC}}^{*}\right|}\&GreaterEqual;1$

Wherein:

$K_{I\max }^{*}\left(\mathrm{\&theta;}\right)=\max \left\{K_I^{*}\left(\mathrm{\&theta;}\right)\right\},$ $K_{\mathrm{II}\max }^{*}\left(\mathrm{\&theta;}\right)=\max \left\{K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)\right\},$ $K_I^{*}\left(\mathrm{\&theta;}\right)=K_I^{*}{\cos }^3\left(\frac{\mathrm{\&theta;}}{2}\right)+K_{\mathrm{II}}^{*}[-\sin \frac{\mathrm{\&theta;}}{2}{\cos }^2\left(\frac{\mathrm{\&theta;}}{2}\right)],$

$K_{\mathrm{II}}^{*}\left(\mathrm{\&theta;}\right)=K_I^{*}\sin \frac{\mathrm{\&theta;}}{2}{\cos }^2\left(\frac{\mathrm{\&theta;}}{2}\right)+K_{\mathrm{II}}^{*}\cos \frac{\mathrm{\&theta;}}{2}[1-3{\sin }^2\left(\frac{\mathrm{\&theta;}}{2}\right)],$ $K_I^{*}=0.79[{\mathrm{\&tau;}}_{\mathrm{ef}}\sin (-2.3\mathrm{\&epsiv;})+p\cos (-2.3\mathrm{\&epsiv;})],$

$K_{\mathrm{II}}^{*}=0.79[{\mathrm{\&tau;}}_{\mathrm{ef}}\cos (-2.3\mathrm{\&epsiv;})-p\sin (-2.3\mathrm{\&epsiv;})],$ $\mathrm{\&epsiv;}=\frac{1}{2\mathrm{\&pi;}}\ln \frac{1-\mathrm{\&beta;}}{1+\mathrm{\&beta;}},$

2. determine that final cracking azimuth angle theta meets hydraulic fracture in geological interface place cunning to hydraulic fracture at geological interface place(see figure 5) while moving rear crack arrest, θ meets following formula:

$\frac{\&PartialD;K_I^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;\mathrm{\&theta;}}=0,$ $\frac{{\&PartialD;}^2{K}_I^{*}\left(\mathrm{\&theta;}\right)}{\&PartialD;{\mathrm{\&theta;}}^2}<0,$ ${\left(\frac{K_{I\max }^{*}\left(\mathrm{\&theta;}\right)}{K_{\mathrm{IC}}^{*}}\right)}^2+{\left(\frac{K_{\mathrm{II}\max }^{*}\left(\mathrm{\&theta;}\right)}{K_{\mathrm{IIC}}^{*}}\right)}^2\&GreaterEqual;1$

Just can judge the expanded configuration of crack at thin sand-mud interbed geological interface place by above-mentioned analysis.

The greatest differences of not considering ground interlayer mechanics parameter, deformability with respect to existing hydraulic fracture extended model withAnd the analog case of the factor such as the stress state of geological interface, the present invention to its revise, perfect, pass through thin sand-mud interbedHydraulic fracture is in the expanded configuration criterion of thin sand-mud interbed geological interface place, can determine that hydraulic fracture is at geological interface placeDeflection angle, more accurately reflects crack initiation, the expansion overall process of crack at geological interface place, has made up the existing fracture propagation mould of applicationThe defect that type prediction hydraulic fracture occurs in thin sand-mud interbed expansion.

Claims (2)

1. hydraulically created fracture is sentenced knowledge method at thin sand-mud interbed geological interface propagation path, it is characterized in that adopting following stepRapid:

Step 1: a selected thin sand-mud interbed is treated fractured well, determines in pressing crack construction process net pressure p crack in, and MPa is definiteEffective shear stress in crack in pressing crack construction process, MPa; Well test analysis is measured thin sand-mud interbed fractured interval sand layersIndividual layer height with shale layer, m; The horizontal maximum principal stress of individual layer of thin sand-mud interbed fractured interval sand layers and shale layer, MPa; The horizontal minimum principal stress of individual layer of thin sand-mud interbed fractured interval sand layers and shale layer，MPa；

Step 2: the Young's modulus of elasticity of measuring respectively the individual layer of thin sand-mud interbed fractured interval sand layers and shale layer，MPa; Poisson's ratio, the internal friction angle of rock stratum, °; The cohesive force of rock stratum，MPa；

Step 3: the critical rupture strength factor of I type of measuring respectively thin sand-mud interbed fractured interval sand layers and shale layer，; The critical rupture strength factor of II type，；

Step 4: the compound Young's modulus of elasticity of determining thin sand-mud interbed reservoir geology interface by following formula (1), wherein,

（1）

In formula,For the compound Young's modulus of elasticity of geological interface, MPa; E is the Young springform of sand layers and shale layer individual layerAmount, MPa;For the Poisson's ratio of sand layers and shale layer individual layer, subscript 2 represents crack tip place layer, and 1 expression crack waits to expandExhibition layer;

Step (5): through type (2) is determined the different material parameter in the interface at thin sand-mud interbed reservoir geology interface, wherein,

（2）

In formula, E is the Young's modulus of elasticity of sand layers and shale layer individual layer, MPa;For the Poisson of sand layers and shale layer individual layerRatio, subscript 2 represents crack tip place layer, extension layer is treated in 1 expression crack;

Step (6): the critical rupture strength factor in interface at thin sand-mud interbed reservoir geology interface is determined in through type (3) and (4)With, unit is，

（3），

（4）

Wherein, in formula:、Be respectively I type, the critical rupture strength factor of II type of sand layers and shale layer individual layer,；Sand layers and shale layer individual layer floor height, m; Subscript 2 represents crack tip place layer, and 1 expression crack waits to expandLayer;

Step 7: determine that according to formula (5) fracturing fracture most advanced and sophisticated composite elastic energy in thin sand-mud interbed reservoir geology interface dischargesRate, unit is N/m,

（5）

Wherein:，

，，

In formula,For different material parameter;For compound Young's modulus of elasticity, MPa;WithBe respectively I type, II type geological interfaceMixed-mode stress-intensity factor,；For net pressure in crack in pressing crack construction process, MPa;For pressing crack construction mistakeEffective shear stress in crack in journey, MPa; X is the distance of crack tip apart from geological interface, m;、Be respectively rock stratum waterFlat maximum, minimum principal stress, MPa;For rock stratum internal friction angle, °;For the final cracking azimuth in crack, °;For two materialsMaterial medium interface index of oscillation;For rock stratum cohesive force, MPa;

Step 8: according to the most advanced and sophisticated composite elastic energy release rate of thin sand-mud interbed reservoir geology interface fracturing fractureLargeLittle, determine the expanded configuration of crack at geological interface place, comprise that crack directly breaks through geology circle in the crack arrest of geological interface place, crackFace, crack penetrate the crack arrest after the slippage of geological interface place of geological interface and crack after the slippage of geological interface place.

2. a kind of hydraulically created fracture according to claim 1 is sentenced knowledge side at thin sand-mud interbed geological interface propagation pathMethod, according to the most advanced and sophisticated composite elastic energy release rate of thin sand-mud interbed reservoir geology interface fracturing fractureSize, determineThe breaking morphology in crack, is specially:

1)While meeting following formula:

Determine that crack is in the time of the crack arrest of geological interface place, and the final cracking azimuth in definite crack，；

2)While meeting following formula:

Determine that crack directly breaks through geological interface, determine the final cracking azimuth in crack，；

3)While meeting following formula:

Determine that crack is in the slippage of geological interface place; And wherein,

When final cracking azimuthWhile meeting following formula,

，，, and

Wherein:

，，，

，，

，，

Determine that crack penetrates geological interface after the slippage of geological interface place;

When final cracking azimuthWhile meeting following formula

，，

Determine crack crack arrest after the slippage of geological interface place.