CN105044283A - Multi-zone polymer injection well injection capability evaluation method according to polymer viscoelasticity - Google Patents

Abstract

The invention relates to a multi-zone polymer injection well injection capability evaluation method according to polymer viscoelasticity. The method comprises 1, building an effective shear rate model of a polymer solution flowing in a rock porous medium, 2, building a polymer solution viscoelasticity apparent viscosity model, 3, constructing conditions of a polymer injection well polymer injection capability evaluation model, 4, building a multi-zone polymer injection well geologic model, and providing model parameters, 5, building a polymer injection well flowing control equation, a multi-zone seepage control equation and polymer injection well and multi-zone contact surface continuity equations, 6, listing polymer injection well and multi-zone boundary conditions, 7, constructing an equation set of the effective shear rate model, the viscoelasticity apparent viscosity model, the polymer injection well flowing control equation, the multi-zone seepage control equation and the polymer injection well and multi-zone contact surface continuity equations, and solving the equation set under different polymer injection well injection pressures, and 8, calculating an injection amount and injection intensity of the result and evaluating the polymer injection well injection capability according to the injection intensity.

Description

A kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic

Technical field

The present invention relates to a kind of injection well injectability evaluation method, particularly relate to and a kind ofly use polymer flooding to develop oil fields to consider the multiple zone injection well injectability evaluation method of polymer viscoelastic in process.

Background technology

At present, polymer flooding has become the major technique that land oilfields in high water cut period improves recovery ratio, also becomes the important means that offshore oilfield improves recovery ratio simultaneously.In polymer flooding heavy industrialization application process, expose some technical matterss gradually, a wherein outstanding problem is: injection well Severe blockage, injection pressure is caused sharply to rise unreasonably, cause injectability degradation, injection well cannot complete injection allocation by injection allocation ratio, even stops note.Therefore, how to assess injection well injection pressure and injectability exactly, be one of key issue affecting polymer flooding development effectiveness and whole economic efficiency, particularly important in the enforcement that guarantee testing in Bohai heavy oil fields premature polymerization thing drives.

The polymer solution being applied to polymer flooding belongs to non-Newtonian fluid, and oil reservoir belongs to rock porous medium, when studying the rheological behaviour of non-Newtonian fluid in porous medium, generally non-Newtonian fluid is assumed to power rate fluid.But research in recent years finds, polymer solution shows complicated rheological behaviour when flowing in subsurface rock porous medium, along with the increase of flow rate, carry out from Newtonian fluid to shear thinning again to the transformation of shear thickening rheological behaviour, namely not only show viscous effect, also show certain elastic effect.But not yet find the injection well injectability evaluation method considering polymer solution Viscoelastic effect in prior art, cause injection pressure and the injectability that can not assess injection well exactly.

In addition, oil reservoir may be stratified reservoir, multiple zone has nonuniformity feature, also not yet finds the injection well injectability evaluation method under consideration stratified reservoir conjunction injection-molded, cause injection pressure and the injectability that can not assess injection well exactly equally in prior art.

Summary of the invention

For the problems referred to above, the object of this invention is to provide a kind of injection well injectability evaluation method simultaneously considering polymer viscoelastic and multiple zone feature, can quick and precisely evaluate injection well injectability, instruct injection well Water injection rate, prevent reservoir choke and stop the problems such as note.

For achieving the above object, the present invention takes following technical scheme: a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic, and it comprises the following steps:

1) the effective shear rate model of polymer solution in rock porous medium during seepage flow is set up;

2) polymer solution viscoelasticity apparent viscosity model is set up;

3) set up the condition of injection well polymer flooding injectability evaluation model is provided;

4) according to step 3) the model set up the condition that provides, set up the stratified reservoir injection well geologic model closing injection well injectability under injection-molded for evaluating stratified reservoir, and provide its model parameter;

5) according to step 3) the model set up the condition that provides and step 4) the stratified reservoir injection well geologic model that provides, set up the Fluid Control Equation of injection well, the osmotic control equation of each oil reservoir and injection well and each oil reservoir surface of contact continuity equation;

6) according to step 3) the model set up the condition that provides and step 4) the stratified reservoir injection well geologic model that provides, list the boundary condition of injection well and multiple oil reservoir;

7) by step 4) model parameter that provides substitutes into step 1) and step 2) in effective shear rate model of obtaining and polymer solution viscoelasticity apparent viscosity model, by step 6) injection well and each oil reservoir boundary condition substitution step 5) in the injection well Fluid Control Equation set up, each oil reservoir osmotic control equation and injection well and each oil reservoir surface of contact continuity equation, be unified into vertical system of equations, under different injection well injection pressures, solve the flowing velocity u of injection well interpolymer solution _wellwith the percolation flow velocity u of each oil reservoir interpolymer solution _res;

8) according to step 7) solving result, calculating injection rate IR Q and inject intensity q, evaluating by injecting intensity q the injectability that stratified reservoir closes injection well under injection-molded; Inject intensity q larger, the injectability of injection well is stronger.

Described step 1) in effective shear rate model be:

In formula, for the effective shear rate of polymer solution in rock porous medium during seepage flow; C is the effective shear rate constant of polymer solution, and relevant with factor of porosity to the permeability of rock porous medium, the present embodiment gets 1; n ₁for polymer solution shear Thinning Index; u _resfor the percolation flow velocity of polymer solution in rock porous medium; K is rock porous medium permeability; k _rwfor polymer solution relative permeability; S _wfor polymer solution saturation degree; for rock porous medium factor of porosity.

Described step 2) in polymer solution viscoelasticity apparent viscosity model comprise shear thinning apparent viscosity μ when polymer solution flows in injection well _{app, well}with polymer flow through rock porous medium time viscoelasticity apparent viscosity μ _{app, res}, wherein:

${\mathrm{\μ}}_{app,well}={\mathrm{\μ}}_{\mathrm{\∞}}+({\mathrm{\μ}}_0-{\mathrm{\μ}}_{\mathrm{\∞}}){\left(1+{\left({\mathrm{\λ}}_1\stackrel{\·}{\mathrm{\γ}}\right)}^{\mathrm{\α}}\right)}^{(n_1-1)/\mathrm{\α}}$

${\mathrm{\μ}}_{app,res}={\mathrm{\μ}}_{\mathrm{\∞}}+({\mathrm{\μ}}_0-{\mathrm{\μ}}_{\mathrm{\∞}}){(1+{\left({\mathrm{\λ}}_1{\stackrel{\·}{\mathrm{\γ}}}_{eff}\right)}^{\mathrm{\α}})}^{(n_1-1)/\mathrm{\α}}+{\mathrm{\μ}}_{max}\left(1-e^{\left\{-{\left({\mathrm{\τ}}_r{\mathrm{\λ}}_2{\stackrel{\·}{\mathrm{\γ}}}_{eff}\right)}^{n_2-1}\right\}}\right)$

In formula, μ _∞for polymer solution high shear viscosity; μ ₀for polymer solution zero-shear viscosity; λ ₁, λ ₂be respectively polymer solution shear desaturation constant and shear thickening constant; for polymer solution shear speed; α is empirical constant, generally gets 2; n ₂for polymer solution shear thickening index; μ _maxfor the mxm. of shear degradation generation prepolymer solution viscosity; τ _rfor injecting the slack time of fluid; E is natural logarithm.

Described step 3) in model set up the condition specifically comprise:

1. the viscoelastic effect of polymer solution is considered;

2. being coupled of flowing and seepage flow in oil reservoir in injection well pit shaft is considered;

3. single oil reservoir homogeneous, uniform thickness, isotropy is supposed;

4. open hole completion, injection well is hydrodynamic force completely penetrating well, ignores skin effect;

5. injection well bottom end closure, ignores the centripetal stream of sphere of injection well bottom;

6. suppose that in each oil reservoir, seepage flow is planar radial steady flow, flow process ignores the impact of gravity and capillary force;

7. suppose that in flowing and oil reservoir, seepage flow is single-phase flow in pit shaft, the moisture and polymkeric substance two kinds of components of polymer solution fluid, and water and polymkeric substance complete miscibility;

8. suppose that the polymer solution injected is micro-compressible fluid;

9. the reservoir permeability ignored caused by the Adsorption And Retention of polymkeric substance on porous medium surface declines;

10. the degraded of polymkeric substance in rock porous medium during seepage flow is ignored;

assuming that pit shaft in flowing and oil reservoir in flow event be isothermal process;

do not consider the interaquifer flow between each oil reservoir.

Described step 4) in set up stratified reservoir injection well geologic model be arranged in order from top to bottom level, homogeneous, uniform thickness circle multiple oil reservoirs, each oil reservoir all belongs to rock porous medium, closes up and down, and outer boundary is constant-pressure boundary; Injection well passes the center of circle of multiple oil reservoir simultaneously, injection well bottom end closure, and polymer solution is injected by injection well inlet end level pressure; The model parameter of described stratified reservoir injection well geologic model is: injection well radius R _w, injection well degree of depth h, injection well injection pressure P _w, each Oil reservoir radius R _ei, core intersection h _i, oil reservoir terminal pressure P _ei, inject τ slack time of fluid _ri, reservoir permeability k _i, polymer solution relative permeability k _rwi, oil reservoir factor of porosity wherein, i=1,2 ..., represent the i-th oil reservoir respectively.

Described step 5) in set up injection well interpolymer solution Fluid Control Equation be:

$\mathrm{\ρ}({\stackrel{\→}{u}}_{well}\·\▿{\stackrel{\→}{u}}_{well})=\▿\·\{p_{well}+{\mathrm{\μ}}_{app,well}(\▿{\stackrel{\→}{u}}_{well}+{\left(\▿{\stackrel{\→}{u}}_{well}\right)}^T)\}$

Multiple oil reservoir interpolymer fluid flow governing equation is:

$\▿\·{\stackrel{\→}{u}}_{res,i}=0;{\stackrel{\→}{u}}_{res,i}=-\frac{k_i}{{\mathrm{\μ}}_{app,res,i}}\▿\·p_{res,i}(i=1,2,\mathrm{......})$

Injection well and the first oil reservoir surface of contact continuity equation are:

$\begin{array}{c}{p}_{well}=p_{res,1}\\ u_{well}=u_{res,1}\end{array}(r=R_w,0\≤z\≤h_1)$

Injection well and other each oil reservoir surface of contact continuity equation are:

$\begin{array}{c}{p}_{well}=p_{res,i}\\ u_{well}=u_{res,i}\end{array}\left(r=R_w,\underset{1}{\overset{i-1}{\Σ}}{h}_{i-1}\≤z\≤\underset{1}{\overset{i}{\Σ}}{h}_i,i=2,3,\mathrm{......}\right)$

Above-mentioned various in, ρ is the density of polymer solution, u _wellfor the flowing velocity of injection well 4 interpolymer solution, u _{res, i}be the percolation flow velocity of i-th oil reservoir interpolymer solution, p _wellfor the pressure of injection well 4 interpolymer solution, p _{res, i}be the pressure of i-th oil reservoir interpolymer solution, T is the temperature of polymer solution.

Described step 6) in the injection well boundary condition that obtains be:

p _well＝P _w(z＝h，0≤r≤R _w)

u _well＝0(z＝0，0≤r≤R _w)

The boundary condition of multiple oil reservoir is:

p _res，1＝P _e1(r＝R _e1，0≤z≤h ₁)

u _res，1＝0(z＝0，R _w≤r≤R _e1)

$u_{res,i}=0(z={\mathrm{\Σ}}_1^i{h}_i,R_w\≤r\≤R_{ei},i=1,2,\mathrm{......})$

$p_{res,i}=P_{ei}(r=R_{ei},{\mathrm{\Σ}}_1^{i-1}{h}_{i-1}\≤z\≤{\mathrm{\Σ}}_1^i{h}_i,i=1,2,\mathrm{......}).$

Described step 8) in the computing formula of injection rate IR Q be:

Q＝πR _w ²u _well(z＝h，0≤r≤R _w)

The computing formula injecting intensity q is:

$q=\frac{Q}{P_w}.$

Adopt analysis of finite element method solve described step 7) in system of equations.

The polymer solution injected is polyacrylamide solution.

The present invention is owing to taking above technical scheme, it has the following advantages: 1, the present invention proposes a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic, by introducing the computing formula of the viscoelastic polymer solution apparent viscosity of quantification characterize polymers, and flow in the injection well that is coupled and seepage flow condition in oil reservoir porous medium, consider Nonhomogeneous multiple oil-layer feature simultaneously, set up stratified reservoir and close injection well injectability evaluation model under injection-molded, realize the accurate quantitative analysis evaluation to injection well injectability, thus instruct the Water injection rate of injection well in oilfield development process, prevent reservoir choke and stop the problems such as note, 2, the present invention adopts analysis of finite element method to solve injection well injectability evaluation model, realizes quick and precisely evaluating injection well injectability, make the practicality of the technology of the present invention method and operability stronger.

Accompanying drawing explanation

Fig. 1 is the decomposition texture schematic diagram of stratified reservoir geologic model of the present invention;

Fig. 2 is the partial enlargement structural representation of stratified reservoir geologic model of the present invention.

Embodiment

Below for three-layer reservoir as goal in research, in conjunction with the accompanying drawings and embodiments the present invention is described in detail.

Accompanying drawing 1, accompanying drawing 2 hollow core arrow and filled arrows are the flow direction of polymer solution.

A kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic of the present invention, comprises the following steps:

1) the effective shear rate model of polymer solution in rock porous medium during seepage flow is set up:

In formula, for the effective shear rate of polymer solution in rock porous medium during seepage flow; C is the effective shear rate constant of polymer solution, and relevant with factor of porosity to the permeability of rock porous medium, the present embodiment gets 1; n ₁for polymer solution shear Thinning Index; u _resfor the percolation flow velocity of polymer solution in rock porous medium; K is rock porous medium permeability; k _rwfor polymer solution relative permeability; S _wfor polymer solution saturation degree; for rock porous medium factor of porosity.

2) polymer solution viscoelasticity apparent viscosity model is set up:

Shear thinning apparent viscosity μ when polymer solution apparent viscosity can be divided into polymer solution to flow in injection well by situation _{app, well}with polymer flow through rock porous medium time viscoelasticity apparent viscosity μ _{app, res}, be characterized by respectively:

${\mathrm{\μ}}_{app,well}={\mathrm{\μ}}_{\mathrm{\∞}}+({\mathrm{\μ}}_0-{\mathrm{\μ}}_{\mathrm{\∞}}){(1+{\left({\mathrm{\λ}}_1\stackrel{\·}{\mathrm{\γ}}\right)}^{\mathrm{\α}})}^{(n_1-1)/\mathrm{\α}}---\left(2\right)$

${\mathrm{\μ}}_{app,res}={\mathrm{\μ}}_{\mathrm{\∞}}+({\mathrm{\μ}}_0-{\mathrm{\μ}}_{\mathrm{\∞}}){(1+{\left({\mathrm{\λ}}_1{\stackrel{\·}{\mathrm{\γ}}}_{eff}\right)}^{\mathrm{\α}})}^{(n_1-1)/\mathrm{\α}}+{\mathrm{\μ}}_{max}(1-e^{\left\{-{\left({\mathrm{\τ}}_r{\mathrm{\λ}}_2{\stackrel{\·}{\mathrm{\γ}}}_{eff}\right)}^{n_2-1}\right\}})---\left(3\right)$

In formula, μ _∞for polymer solution high shear viscosity; μ ₀for polymer solution zero-shear viscosity; λ ₁, λ ₂be respectively polymer solution shear desaturation constant and shear thickening constant; for polymer solution shear speed; α is empirical constant, generally gets 2; n ₂for polymer solution shear thickening index; μ _maxfor the mxm. of shear degradation generation prepolymer solution viscosity; τ _rfor injecting the slack time of fluid; E is natural logarithm.

From formula (3), viscoelasticity apparent viscosity μ _{app, res}closely related with reservoir geology parameter, the therefore viscoelasticity apparent viscosity μ of different oil reservoir interpolymer solution _{app, res}different.

3) provide the set up the condition of injection well polymer flooding injectability evaluation model, specifically comprise:

1. the viscoelastic effect of polymer solution is considered;

2. being coupled of flowing and seepage flow in oil reservoir in injection well pit shaft is considered;

3. single oil reservoir homogeneous, uniform thickness, isotropy is supposed;

4. open hole completion, injection well is hydrodynamic force completely penetrating well, ignores skin effect;

5. injection well bottom end closure, ignores the centripetal stream of sphere of injection well bottom;

6. suppose that in each oil reservoir, seepage flow is planar radial steady flow, flow process ignores the impact of gravity and capillary force;

7. suppose that in flowing and oil reservoir, seepage flow is single-phase flow in pit shaft, the moisture and polymkeric substance two kinds of components of polymer solution fluid, and water and polymkeric substance complete miscibility;

8. suppose that the polymer solution injected is micro-compressible fluid;

9. the reservoir permeability ignored caused by the Adsorption And Retention of polymkeric substance on porous medium surface declines;

10. the degraded of polymkeric substance in rock porous medium during seepage flow is ignored;

assuming that pit shaft in flowing and oil reservoir in flow event be isothermal process;

do not consider the interaquifer flow between each oil reservoir.

4) according to step 3) model set up the condition, set up the three-layer reservoir injection well geologic model closing injection well injectability under injection-molded for evaluating three-layer reservoir, and provide model parameter.

As shown in Figure 1 and Figure 2, by assumed condition 1. ~ three-layer reservoir injection well geologic model comprises the level, homogeneous, the first oil reservoir 1, second oil reservoir 2 of uniform thickness circle and the 3rd oil reservoir 3 that are arranged in order from top to bottom, and each oil reservoir all belongs to rock porous medium, closes up and down, and outer boundary is constant-pressure boundary; Injection well 4 passes the center of circle of three oil reservoirs simultaneously, injection well 4 bottom end closure, and polymer solution is injected by injection well 4 inlet end level pressure; Be true origin with injection well 4 wellbore bottom center (being also the first oil reservoir 1 bottom centre), radial distance r points to outer, height z by initial point and point to injection well 4 entrance by initial point and set up cylindrical-coordinate system (due to the equal isotropy of each oil reservoir, user's parallactic angle is not needed in modeling, therefore omit), then each oil reservoir of three-layer reservoir injection well geologic model is with r=0 is the circular reservoir model of radial symmetry axis, setting model parameter: injection well 4 radius R _w, injection well 4 degree of depth h, injection well 4 injection pressure P _w, each Oil reservoir radius R _ei, core intersection h _i, oil reservoir terminal pressure P _ei, inject τ slack time of fluid _ri, reservoir permeability k _i, polymer solution relative permeability k _rwi, oil reservoir factor of porosity wherein, i=1,2,3, represent the first oil reservoir 1, second oil reservoir 2 and the 3rd oil reservoir 3 respectively.

5) Fluid Control Equation of injection well 4, the osmotic control equation of three oil reservoirs and injection well 4 and three oil reservoir surface of contact continuity equations are set up.

According to step 3) the model set up the condition that provides 1. ~ and step 4) the three-layer reservoir injection well geologic model that provides is known, the flowing of injection well 4 interpolymer solution is controlled by Navier-Stokes (Neville-Stokes) equation, the only generation shear thinning behavior and polymer solution flows in injection well 4, its apparent viscosity is determined by shear thinning model, and namely the apparent viscosity of injection well 4 interpolymer solution is shear thinning apparent viscosity μ _{app, well}; Three oil reservoirs are rock porous medium, the seepage flow of rock porous medium interpolymer solution is controlled by Darcy's law, and the apparent viscosity of polymer solution in rock porous medium during seepage flow is determined by viscoelasticity apparent viscosity model, namely the apparent viscosity of three oil reservoir interpolymer solution is viscoelasticity apparent viscosity μ _{app, res, i}; Meanwhile, the sidewall of injection well 4 and the surface of contact of three oil reservoirs all should meet the condition of continuity.Can draw according to above-mentioned conclusion:

Injection well 4 interpolymer solution Fluid Control Equation:

$\mathrm{\ρ}({\stackrel{\→}{u}}_{well}\·\▿{\stackrel{\→}{u}}_{well})=\▿\·\{p_{well}+{\mathrm{\μ}}_{app,well}(\▿{\stackrel{\→}{u}}_{well}+{\left(\▿{\stackrel{\→}{u}}_{well}\right)}^T)\}---\left(4\right)$

Three oil reservoir interpolymer fluid flow governing equations:

$\▿\·{\stackrel{\→}{u}}_{res,i}=0;{\stackrel{\→}{u}}_{res,i}=-\frac{k_i}{{\mathrm{\μ}}_{app,res,i}}\▿\·p_{res,i}(i=1,2,3)---\left(5\right)$

Injection well 4 and the first oil reservoir 1 surface of contact continuity equation:

$\begin{array}{c}{p}_{well}=p_{res,1}\\ u_{well}=u_{res,1}\end{array}(r=R_w,0\≤z\≤h_1)---\left(6\right)$

Injection well 4 and the second oil reservoir 2, the 3rd oil reservoir 3 surface of contact continuity equation:

$\begin{array}{c}{p}_{well}=p_{res,i}\\ u_{well}=u_{res,i}\end{array}(r=R_w,{\Σ}_1^{i-1}{h}_{i-1}\≤z\≤{\Σ}_1^i{h}_i,i=2,3)---\left(7\right)$

Above-mentioned various in, ρ is the density of polymer solution, u _wellfor the flowing velocity of injection well 4 interpolymer solution, u _{res, i}be the percolation flow velocity of i-th oil reservoir interpolymer solution, p _wellfor the pressure of injection well 4 interpolymer solution, p _{res, i}be the pressure of i-th oil reservoir interpolymer solution, T is the temperature of polymer solution.

6) according to step 3) the model set up the condition that provides and step 4) the three-layer reservoir injection well geologic model that provides, list the boundary condition of injection well 4 boundary condition and three oil reservoirs.

As shown in Figure 2, three-layer reservoir injection well geologic model take r=0 as axis of symmetry, injection well 4 inlet end level pressure injection of polymer solution, injection well 4 bottom end closure, then injection well 4 boundary condition is:

p _well＝P _w(z＝h，0≤r≤R _w)(8)

u _well＝0(z＝0，0≤r≤R _w)

Oil reservoir is lower is on the whole closed boundary, and do not consider the interaquifer flow between each oil reservoir, outer boundary is constant-pressure boundary, then the boundary condition of three oil reservoirs is:

p _res，1＝P _e1(r＝R _e1，0≤z≤h ₁)(9)

u _res，1＝0(z＝0，R _w≤r≤R _e1)

$\begin{array}{c}{u}_{res,i}=0(z={\Σ}_1^i{h}_i,R_w\≤r\≤R_{ei},i=1,2,3)\\ p_{res,i}=P_{ei}(r=R_{ei},{\Σ}_1^{i-1}{h}_{i-1}\≤z\≤{\Σ}_1^i{h}_i,i=1,2,3)\end{array}---\left(10\right)$

7) model parameter and boundary condition are substituted into step 2) formula that provides and step 5) in the equation set up, simultaneous solution system of equations.

The geologic parameter of Polymer Solution Property parameter and i-th oil reservoir is substituted in formula (1), (2), (3), obtains the effective shear rate of polymer solution of i-th oil reservoir shear thinning apparent viscosity μ _{app, well, i}with viscoelasticity apparent viscosity μ _{app, res, i}, wherein i=1,2,3; By step 6) boundary condition (8) ~ (10) and the geologic parameter of Polymer Solution Property parameter and three oil reservoirs substitute in equation (4) ~ (7), be unified into vertical system of equations; At different injection well 4 injection pressure P _wunder solve the flowing velocity u of any position polymer solution in injection well 4 _wellwith the percolation flow velocity u of any position polymer solution in three oil reservoirs _{res, i}.

8) according to step 7) solving result, calculating injection rate IR Q and inject intensity q, evaluating by injecting intensity q the injectability that three-layer reservoir closes injection well under injection-molded.

Be less than the condition of formation rock parting pressure in injection pressure under, namely injection well injectability can be injected intensity q to represent by the injection rate IR under unit pressure reduction, and injecting intensity q can by injection rate IR Q and injection pressure P _wrelation obtain.

Wherein, the computing formula of injection rate IR Q is:

Q＝πR _w ²u _well(z＝h，0≤r≤R _w)(11)

The computing formula injecting intensity q is:

$q=\frac{Q}{p_w}---\left(12\right)$

Inject intensity q larger, then represent that the injectability of injection well is stronger.

In above-described embodiment, step 7) in solving equation group analysis of finite element method can be adopted to solve.Because polymer solution is non-Newtonian fluid, polymer solution apparent viscosity is the nonlinear function of shear rate, considers the viscoelastic effect of polymer solution simultaneously, and the analytical expression solving injectability will be more difficult; And according to setting up the mathematical model of three-layer reservoir injection well geologic model, adopt analysis of finite element method to solve, the different injection pressure P of injection well 4 can be obtained fast _wthe flowing velocity u of lower injection well 4 interpolymer solution _wellwith the percolation flow velocity u of three oil reservoir interpolymer solution _{res, i}numerical solution, thus obtain injection rate IR Q and injection pressure P _wrelation, and then obtain inject intensity q.

In above-described embodiment, the polymer solution of injection is polyacrylamide (HydrolyzedPolyacryamide, abbreviation HPAM) solution.

The present invention not only can be widely used in oil-field development research field, can also to be widely used in other research field relevant with seepage flow or as a reference, such as Groundwater movement research etc.

The various embodiments described above are only for illustration of the present invention; wherein the structure of each parts, setting position and connected mode etc. thereof all can change to some extent; every equivalents of carrying out on the basis of technical solution of the present invention and improvement, all should not get rid of outside protection scope of the present invention.

Claims (10)

1. consider a multiple zone injection well injectability evaluation method for polymer viscoelastic, it comprises the following steps:

1) the effective shear rate model of polymer solution in rock porous medium during seepage flow is set up;

2) polymer solution viscoelasticity apparent viscosity model is set up;

3) set up the condition of injection well polymer flooding injectability evaluation model is provided;

4) according to step 3) the model set up the condition that provides, set up the stratified reservoir injection well geologic model closing injection well injectability under injection-molded for evaluating stratified reservoir, and provide its model parameter;

5) according to step 3) the model set up the condition that provides and step 4) the stratified reservoir injection well geologic model that provides, set up the Fluid Control Equation of injection well, the osmotic control equation of each oil reservoir and injection well and each oil reservoir surface of contact continuity equation;

6) according to step 3) the model set up the condition that provides and step 4) the stratified reservoir injection well geologic model that provides, list the boundary condition of injection well and multiple oil reservoir;

7) by step 4) model parameter that provides substitutes into step 1) and step 2) in effective shear rate model of obtaining and polymer solution viscoelasticity apparent viscosity model, by step 6) injection well and each oil reservoir boundary condition substitution step 5) in the injection well Fluid Control Equation set up, each oil reservoir osmotic control equation and injection well and each oil reservoir surface of contact continuity equation, be unified into vertical system of equations, under different injection well injection pressures, solve the flowing velocity u of injection well interpolymer solution _wellwith the percolation flow velocity u of each oil reservoir interpolymer solution _res;

8) according to step 7) solving result, calculating injection rate IR Q and inject intensity q, evaluating by injecting intensity q the injectability that stratified reservoir closes injection well under injection-molded; Inject intensity q larger, the injectability of injection well is stronger.

2. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 1, is characterized in that, described step 1) in effective shear rate model be:

In formula, for the effective shear rate of polymer solution in rock porous medium during seepage flow; C is the effective shear rate constant of polymer solution, and relevant with factor of porosity to the permeability of rock porous medium, the present embodiment gets 1; n ₁for polymer solution shear Thinning Index; u _resfor the percolation flow velocity of polymer solution in rock porous medium; K is rock porous medium permeability; k _rwfor polymer solution relative permeability; S _wfor polymer solution saturation degree; for rock porous medium factor of porosity.

3. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 2, it is characterized in that, described step 2) in polymer solution viscoelasticity apparent viscosity model comprise shear thinning apparent viscosity μ when polymer solution flows in injection well _{app, well}with polymer flow through rock porous medium time viscoelasticity apparent viscosity μ _{app, res}, wherein:

${\mathrm{\μ}}_{app,well}={\mathrm{\μ}}_{\mathrm{\∞}}+({\mathrm{\μ}}_0-{\mathrm{\μ}}_{\mathrm{\∞}}){(1+{\left({\mathrm{\λ}}_1\stackrel{\·}{\mathrm{\γ}}\right)}^{\mathrm{\α}})}^{(n_1-1)/\mathrm{\α}}$

${\mathrm{\μ}}_{app,res}={\mathrm{\μ}}_{\mathrm{\∞}}+({\mathrm{\μ}}_0-{\mathrm{\μ}}_{\mathrm{\∞}}){(1+{\left({\mathrm{\λ}}_1{\stackrel{\·}{\mathrm{\γ}}}_{eff}\right)}^{\mathrm{\α}})}^{(n_1-1)/\mathrm{\α}}+{\mathrm{\μ}}_{max}(1-e^{\{-{\left({\mathrm{\τ}}_r{\mathrm{\λ}}_2{\stackrel{\·}{\mathrm{\γ}}}_{eff}\right)}^{n_2-1}\}})$

In formula, μ _∞for polymer solution high shear viscosity; μ ₀for polymer solution zero-shear viscosity; λ ₁, λ ₂be respectively polymer solution shear desaturation constant and shear thickening constant; for polymer solution shear speed; α is empirical constant, generally gets 2; n ₂for polymer solution shear thickening index; μ _maxfor the mxm. of shear degradation generation prepolymer solution viscosity; τ _rfor injecting the slack time of fluid; E is natural logarithm.

4. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 1, is characterized in that, described step 3) in model set up the condition specifically comprise:

1. the viscoelastic effect of polymer solution is considered;

2. being coupled of flowing and seepage flow in oil reservoir in injection well pit shaft is considered;

3. single oil reservoir homogeneous, uniform thickness, isotropy is supposed;

4. open hole completion, injection well is hydrodynamic force completely penetrating well, ignores skin effect;

5. injection well bottom end closure, ignores the centripetal stream of sphere of injection well bottom;

6. suppose that in each oil reservoir, seepage flow is planar radial steady flow, flow process ignores the impact of gravity and capillary force;

7. suppose that in flowing and oil reservoir, seepage flow is single-phase flow in pit shaft, the moisture and polymkeric substance two kinds of components of polymer solution fluid, and water and polymkeric substance complete miscibility;

8. suppose that the polymer solution injected is micro-compressible fluid;

9. the reservoir permeability ignored caused by the Adsorption And Retention of polymkeric substance on porous medium surface declines;

10. the degraded of polymkeric substance in rock porous medium during seepage flow is ignored;

assuming that pit shaft in flowing and oil reservoir in flow event be isothermal process;

do not consider the interaquifer flow between each oil reservoir.

5. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 3, it is characterized in that, described step 4) in set up stratified reservoir injection well geologic model be arranged in order from top to bottom level, homogeneous, uniform thickness circle multiple oil reservoirs, each oil reservoir all belongs to rock porous medium, close up and down, outer boundary is constant-pressure boundary; Injection well passes the center of circle of multiple oil reservoir simultaneously, injection well bottom end closure, and polymer solution is injected by injection well inlet end level pressure; The model parameter of described stratified reservoir injection well geologic model is: injection well radius R _w, injection well degree of depth h, injection well injection pressure P _w, each Oil reservoir radius R _ei, core intersection h _i, oil reservoir terminal pressure P _ei, inject τ slack time of fluid _ri, reservoir permeability k _i, polymer solution relative permeability k _rwi, oil reservoir factor of porosity wherein, i=1,2 ..., represent the i-th oil reservoir respectively.

6. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 5, is characterized in that, described step 5) in set up injection well interpolymer solution Fluid Control Equation be:

$\mathrm{\ρ}({\stackrel{\→}{u}}_{well}\·\▿{\stackrel{\→}{u}}_{well})=\▿\·\{p_{well}+{\mathrm{\μ}}_{app,well}(\▿{\stackrel{\→}{u}}_{well}+{(\▿{\stackrel{\→}{u}}_{well})}^T)\}$

Multiple oil reservoir interpolymer fluid flow governing equation is:

$\▿\·{\stackrel{\→}{u}}_{res,i}=0;{\stackrel{\→}{u}}_{res,i}=-\frac{k_i}{{\mathrm{\μ}}_{app,res,i}}\▿\·p_{res,i},(i=1,2,\mathrm{......})$

Injection well and the first oil reservoir surface of contact continuity equation are:

$,_{u_{well}=u_{res,1}}^{p_{well}=p_{res,1}}(r=R_w,0\≤z\≤h_1)$

Injection well and other each oil reservoir surface of contact continuity equation are:

$,_{u_{well}=u_{res,i}}^{p_{well}=p_{res,i}}(r=R_w,\underset{1}{\overset{i-1}{\Σ}}{h}_{i-1}\≤z\≤\underset{1}{\overset{i}{\Σ}}{h}_i,i=2,3,\mathrm{......})$

Above-mentioned various in, ρ is the density of polymer solution, u _wellfor the flowing velocity of injection well 4 interpolymer solution, u _{res, i}be the percolation flow velocity of i-th oil reservoir interpolymer solution, p _wellfor the pressure of injection well 4 interpolymer solution, p _{res, i}be the pressure of i-th oil reservoir interpolymer solution, T is the temperature of polymer solution.

7. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 6, is characterized in that, described step 6) in the injection well boundary condition that obtains be:

p _well＝P _w(z＝h,0≤r≤R _w)

u _well＝0(z＝0,0≤r≤R _w)

The boundary condition of multiple oil reservoir is:

p _res,1＝P _e1(r＝R _e1,0≤z≤h ₁)

u _res,1＝0(z＝0,R _w≤r≤R _e1)

$u_{res,i}=0(z={\mathrm{\Σ}}_1^i{h}_i,R_w\≤r\≤R_{ei},i=1,2,\mathrm{......})$

$p_{\mathrm{res},i}=P_{\mathrm{ei}}(r=R_{\mathrm{ei}},{\mathrm{\Σ}}_1^{i-1}{h}_{i-1}\≤z\≤{\mathrm{\Σ}}_1^i{h}_i,i=\mathrm{1,2},......).$

8. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 7, is characterized in that, described step 8) in the computing formula of injection rate IR Q be:

Q＝πR _w ²u _well(z＝h,0≤r≤R _w)

The computing formula injecting intensity q is:

$q=\frac{Q}{P_w}.$

9. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 1, is characterized in that, adopt analysis of finite element method solve described step 7) in system of equations.

10. a kind of multiple zone injection well injectability evaluation method considering polymer viscoelastic as claimed in claim 1, it is characterized in that, the polymer solution of injection is polyacrylamide solution.