CN103628868B - A kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology - Google Patents

Abstract

The present invention relates to a kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology, the method comprises the following steps: 1) judge that note is adopted situation and whether reached balance: 1. oil reservoir has static pressure test, and whether current strata pressure maintains original level; 2. oil reservoir is without static pressure test, the numerical value of oil reservoir accumulation injection-production ratio VRR whether close to or be greater than 1.If then judge to reach equilibrium state.2) analyze gas injection development mechanism, judge that target reservoir is that the miscible displacement of reservoir is hidden, or non-phase-mixing driving oil reservoir.3) to the semilog fit correlation formula lnG of oil reservoir cumulative gas injected-oil reservoir cumulative oil production _i=h+mN _pcarry out parameter identification; According to development process oil reservoir cumulative gas injected G _iwith oil reservoir cumulative oil production N _phistorical data, pick out fitting coefficient h and m.4) use semilog fitting formula according to the rational cumulative gas injected G of predicted time section oil reservoir _ito oil reservoir cumulative oil production N _ppredict.It is high volatile volatile crude oil that the present invention is applicable to reservoir fluid, and adopts the oil reservoir of natural gas injection pressurize exploitation.

Description

A kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology

Technical field

The present invention relates to field of oil development, particularly relate to a kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology.

Background technology

High volatile volatile crude oil is a kind of natural formation, hydrocarbon mixture based on intermediate species, and its character, between dirty oil and condensate gas, exists under reservoir conditions in liquid form.A key character of high volatile oil has obvious composition gradient, and namely fluid components changes with change in depth (molar content of light component reduces with the increase of reservoir buried depth, and the molar content of heavy constituent increases with the increase of reservoir buried depth); Another key character of high volatile volatile crude oil has highly shrinkable exactly, when strata pressure is lower than saturation pressure, crude oil is because of degassed and volume shrinks rapidly, because of gas phase, comparatively oil phase seepage velocity is high and cause oil well production gas-oil ratio to rise fast, oil phase is stranded in oil reservoir, recovery ratio is reduced greatly, is approximately 8%-25%.Therefore pressurize exploitation will obtain higher recovery ratio.

It is that conventional mining type hidden by waving property of height hair oil that oil reservoir crestal gas injection edge is recovered the oil.When the high pressure gas injected contacts with volatile oil, easily form miscible bank, material is thus formed the miscible displacement of reservoir.Due to the double action that composition gradient and gas injection are driven, production gas-oil ratio is made constantly to increase in recovery process, in development process, gas injection driving mechanism is from the non-phase-mixing driving after the mixed phase expulsion gradual transition to breakthrough of gas before breakthrough of gas, oil reservoir internal flow phase-state change and percolation law complexity, increase the difficulty of oil production prediction.At present, for the prediction of oil production in high volatile volatile reservoir gas injection development process, great majority research all carries out production forecast by means of method for numerical simulation, but reservoir understanding unclear meeting logarithm value simulation and forecast result bring very big error; And from Geologic modeling to numerical reservoir model, process is complicated, the cycle is long, personal expenditures is high, be unfavorable for carrying out gas injection recruitment evaluation and oil production prediction fast.Therefore, in the urgent need to set up a set of simply, easily and fast, the oil production Forecasting Methodology of high volatile volatile reservoir gas injection exploitation accurately.

Summary of the invention

For the problems referred to above, the object of this invention is to provide one for high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology, it is high volatile volatile crude oil that the method is applicable to reservoir fluid, and adopts the oil reservoir of natural gas injection pressurize exploitation.

For achieving the above object, the present invention is by the following technical solutions: a kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology, comprises the following steps:

1) judge that note is adopted situation and whether reached balance, criterion is: if 1. oil reservoir has static pressure test, checks whether current strata pressure maintains original level, if it is judges that note is adopted and reaches equilibrium state, carry out step 2); If 2. oil reservoir is without static pressure test, whether the numerical value of oil reservoir cumulative voidage replacement ratio VRR, close to 1 or be greater than 1, if it is judges that the note situation of adopting reaches equilibrium state, and carry out step 2):

VRR=Q _ingc/Q _oc

In formula: Q _ingcbe that fluidly lower volume is injected in oil reservoir accumulation, unit is m ³; Q _ocbe oil reservoir accumulation produced fluid subsurface volume, unit is m ³;

2) analyze gas injection development mechanism, judge that target reservoir is that the miscible displacement of reservoir is hidden, or non-phase-mixing driving oil reservoir;

3) to the semilog fit correlation formula lnG of oil reservoir cumulative gas injected-oil reservoir cumulative oil production _i=h+mN _pcarry out parameter identification;

In formula: G _ibe oil reservoir cumulative gas injected, unit is m ³; N _pbe oil reservoir cumulative oil production, unit is m ³; H and m is fitting coefficient;

Hide for the miscible displacement of reservoir, recovery percent of reserves reaches R _f1after, and for non-phase-mixing driving oil reservoir, recovery percent of reserves need reach R _f2after, above-mentioned semilog fitting formula is suitable for; According to oil reservoir cumulative gas injected G in development process _iwith oil reservoir cumulative oil production N _phistorical data, pick out fitting coefficient h and m;

In formula: R _f1semilog relational expression for miscible displacement of reservoir Tibetan cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable; R _f2semilog relational expression for non-phase-mixing driving oil reservoir cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable;

4), after picking out fitting coefficient h and m, semilog fit correlation formula lnG can be used _i=h+mN _paccording to the rational cumulative gas injected G of predicted time section oil reservoir _ito the oil reservoir cumulative oil production N of this time period _ppredict.

The subsurface volume Q of fluid is injected in oil reservoir accumulation in described step 1) _ingcfor:

$Q_{\mathrm{ingc}}=\underset{i=1}{\overset{r}{\mathrm{\Σ}}}\left(\underset{t=1}{\overset{t_g^i}{\mathrm{\Σ}}}{\left[q_{\mathrm{ing}}^i{B}_{\mathrm{ing}}^i\right]}_t\right)$

In formula: be i-th mouthful gas injection well day gas injection rate, unit is m ³/ sky; I is natural number; it is the volume factor of i-th mouthful of gas injection well injected gas; be i-th mouthful of gas injection well injection length, unit is sky; R is oil reservoir injection gas well quantity, and unit is mouth;

The subsurface volume Q of oil reservoir accumulation produced fluid _ocfor:

$Q_{\mathrm{oc}}=\underset{i=1}{\overset{s}{\mathrm{\Σ}}}\left[q_{\mathrm{oc}}^i\right]$

In formula: be the subsurface volume of i-th mouthful of oil well accumulation produced fluid, unit is m ³; S is oil reservoir oil well quantity, and unit is mouth.

The subsurface volume of described i-th mouthful of oil well accumulation produced fluid following formulae discovery is adopted before gas injection breaks through:

$q_{\mathrm{oc}}^i=\underset{t=1}{\overset{t_o^i}{\mathrm{\Σ}}}{(q_o^i{B}_o^i+q_w^i{B}_w^i)}_t$

In formula: be i-th mouthful of oil well daily oil production, unit is m ³/ sky; be i-th mouthful of oil well water yield per day, unit is m ³/ sky; be i-th mouthful of sewage from oil-well volume factor, unit is m ³/ m ³; be i-th mouthful of oil well crude oil volume factor, unit is m ³/ m ³; be i-th mouthful of oil well production time, unit is sky.

The subsurface volume of described i-th mouthful of well accumulation produced fluid following formulae discovery is adopted after gas injection breaks through:

$q_{\mathrm{oc}}^i=\underset{t=1}{\overset{t_b^i-1}{\mathrm{\Σ}}}{(q_o^i{B}_o^i+q_w^i{B}_w^i)}_t+\underset{t=t_b^i}{\overset{t_o^i}{\mathrm{\Σ}}}{(q_o^i{B}_o^{\mathrm{mean}}+q_w^i{B}_w^i+({\mathrm{GOR}}^i-{\mathrm{GOR}}^{\mathrm{mean}})q_o^i{B}_{\mathrm{pg}})}_t$

In formula: be Reservoir Crude Oil average external volume coefficient, unit is m ³/ m ³; GOR ⁱbe i-th mouthful of oil well production gas-oil ratio, unit is m ³/ m ³; GOR ^meanbe Reservoir Crude Oil average dissolution gas-oil ratio, unit is m ³/ m ³; B _pgbe the volume factor of output gas, unit is m ³/ m ³; be i-th mouthful of oil well gas injection break through, unit is sky; i-th mouthful of oil well production time, unit is sky.

Described oil well is after gas injection breaks through or pre-breakthrough criterion is: with the maximum dissolved gas oil ratio of crude oil under oil reservoir initial condition for boundary, as oil well production gas-oil ratio GOR ⁱbe before gas injection breaks through when being less than this value, as oil well production gas-oil ratio GOR ⁱbe after gas injection breaks through when being greater than this value.

In described step 3), recovery percent of reserves R hidden by the miscible displacement of reservoir _f1computational methods be:

$R_{f1}=\frac{0.2}{1-S_{\mathrm{wi}}}\×100$

In formula: R _f1semilog relational expression for miscible displacement of reservoir Tibetan cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable; S _wifor oil reservoir average tied water saturation.

Described non-phase-mixing driving oil reservoir recovery percent of reserves R _f2computational methods be:

$R_{f2}=\frac{S_{g1}}{1-S_{\mathrm{wi}}}\×100$

In formula: R _f2semilog relational expression for non-phase-mixing driving oil reservoir cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable; S _wifor oil reservoir average tied water saturation; S _g1for the logarithm of non-phase-mixing driving oil reservoir gas, oily two-phase relative permeability ratio and gas saturation relation curve start saturation ratio when there is linear relationship.

The present invention is owing to taking above technical scheme, and it has the following advantages: 1, provide a kind of Forecasting Methodology predicting high volatile volatile oil reservoir injection construction of natural gas fields output, filled up the blank of reservoir engineering technical field prediction aspect.2, avoid because reservoir understanding is unclear to the error brought of oil reservoir numerical Simulation Prediction result, and the problem such as method for numerical simulation process is complicated, cost is high, the cycle is long.3, simply, easily and fast, and can adjust fitting coefficient in real time according to production history Data Update, precision of prediction is high.

Detailed description of the invention

Below in conjunction with embodiment, the present invention is described in detail.

High volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology of the present invention, comprises the following steps:

1, judge that note is adopted situation and whether reached balance, concrete determination methods is as follows:

If oil reservoir has static pressure test, check whether current strata pressure maintains original level, if it is judge that note is adopted and reach equilibrium state, carry out step 2); If oil reservoir is without static pressure test, following step is adopted to judge:

1. oil volume factor is determined:

$B_o^i={\mathrm{aGOR}}^i+b$

$B_o^{\mathrm{mean}}={\mathrm{aGOR}}^{\mathrm{mean}}+b$

In formula: be i-th mouthful of oil well crude oil volume factor, unit is m ³/ m ³; be Reservoir Crude Oil average external volume coefficient, unit is m ³/ m ³; GOR ⁱbe i-th mouthful of oil well production gas-oil ratio, unit is m ³/ m ³; GOR ^meanbe Reservoir Crude Oil average dissolution gas-oil ratio, unit is m ³/ m ³; A, b are constant coefficient, and the volume factor obtained by the PVT analytical test of matching in-place oil and the linear relationship of gas-oil ratio are obtained.Wherein PVT analyzes as the usual analytical method of those skilled in the art, therefore repeats no more.

2. the subsurface volume of each gas injection well injected gas is sued for peace, obtains the subsurface volume that fluid is injected in oil reservoir accumulation:

$Q_{\mathrm{ingc}}=\underset{i=1}{\overset{r}{\mathrm{\Σ}}}\left(\underset{t=1}{\overset{t_g^i}{\mathrm{\Σ}}}{\left[q_{\mathrm{ing}}^i{B}_{\mathrm{ing}}^i\right]}_t\right)$

In formula: Q _ingcbe the subsurface volume that fluid is injected in oil reservoir accumulation, unit is m ³; I is natural number; be i-th mouthful gas injection well day gas injection rate, unit is m ³/ sky; be the volume factor of i-th mouthful of gas injection well injected gas, unit is m ³/ m ³; be i-th mouthful of gas injection well injection length, unit is sky; R is oil reservoir injection gas well quantity, and unit is mouth.

3. with the maximum dissolved gas oil ratio of crude oil under oil reservoir initial condition for boundary, as oil well production gas-oil ratio GOR ⁱbe, before gas injection breaks through, before gas injection breaks through, adopt the subsurface volume of following formulae discovery individual well accumulation produced fluid when being less than this value

$q_{\mathrm{oc}}^i=\underset{t=1}{\overset{t_o^i}{\mathrm{\Σ}}}{(q_o^i{B}_o^i+q_w^i{B}_w^i)}_t$

In formula: be the subsurface volume of i-th mouthful of oil well accumulation produced fluid, unit is m ³; be i-th mouthful of oil well daily oil production, unit is m ³/ sky; be i-th mouthful of oil well water yield per day, unit is m ³/ sky; be i-th mouthful of sewage from oil-well volume factor, unit is m ³/ m ³; be i-th mouthful of oil well production time, unit is sky.

As oil well production gas-oil ratio GOR ⁱbe, after gas injection breaks through, after gas injection breaks through, then adopt the subsurface volume of following formulae discovery individual well accumulation produced fluid when being greater than this value:

$q_{\mathrm{oc}}^i=\underset{t=1}{\overset{t_b^i-1}{\mathrm{\Σ}}}{(q_o^i{B}_o^i+q_w^i{B}_w^i)}_t+\underset{t=t_b^i}{\overset{t_o^i}{\mathrm{\Σ}}}{(q_o^i{B}_o^{\mathrm{mean}}+q_w^i{B}_w^i+({\mathrm{GOR}}^i-{\mathrm{GOR}}^{\mathrm{mean}})q_o^i{B}_{\mathrm{pg}})}_t$

In formula: B _pgbe the volume factor of output gas, unit is m ³/ m ³; be i-th mouthful of oil well gas injection break through, unit is sky; i-th mouthful of oil well production time, unit is sky.

The defining method of oil volume factor is:

$B_o^i={\mathrm{aGOR}}^i+b$

$B_o^{\mathrm{mean}}={\mathrm{aGOR}}^{\mathrm{mean}}+b$

In formula: a, b are constant coefficient, the volume factor obtained by the PVT analytical test of matching in-place oil and the linear relationship of gas-oil ratio are obtained.Wherein PVT analyzes as the usual analytical method of those skilled in the art, therefore repeats no more.

4. the subsurface volume of each oil well produced fluid is sued for peace, obtains the subsurface volume of oil reservoir accumulation produced fluid:

$Q_{\mathrm{oc}}=\underset{i=1}{\overset{s}{\mathrm{\Σ}}}\left[q_{\mathrm{oc}}^i\right]$

In formula: Q _ocbe the subsurface volume of oil reservoir accumulation produced fluid, unit is m ³; S is oil reservoir oil well quantity, and unit is mouth.

5. oil reservoir cumulative voidage replacement ratio VRR is calculated:

VRR=Q _ingc/Q _oc

Wherein:

$Q_{\mathrm{ingc}}=\underset{i=1}{\overset{r}{\mathrm{\Σ}}}\left(\underset{t=1}{\overset{t_g^i}{\mathrm{\Σ}}}{\left[q_{\mathrm{ing}}^i{B}_{\mathrm{ing}}^i\right]}_t\right)$

In formula: Q _ingcbe the subsurface volume that fluid is injected in oil reservoir accumulation, unit is m ³; be i-th mouthful gas injection well day gas injection rate, unit is m ³/ sky; it is the volume factor of i-th mouthful of gas injection well injected gas; be i-th mouthful of gas injection well injection length, unit is sky; R is oil reservoir injection gas well quantity, and unit is mouth.

When the oil reservoir cumulative voidage replacement ratio VRR calculated is close to when being more than or equal to 1, namely show that the note situation of adopting reaches equilibrium state, meeting under oil well flowing bottomhole pressure (FBHP) is in process of production greater than the prerequisite of saturation pressure, subsequent step can be carried out oil reservoir cumulative oil production is predicted.

2, gas injection development mechanism is judged, reservoir fluid minimum miscibility pressure is determined by reservoir fluid infrastest, theoretical formula, empirical formula or Method for Numerical etc., also gas injection development mechanism can be proved by means such as triangle Phase Diagram Analysis, judge that this oil reservoir is that the miscible displacement of reservoir is hidden, or non-phase-mixing driving oil reservoir.The above-mentioned method proving gas injection development mechanism is the analytical method that those skilled in the art are usual, therefore repeats no more.

3, to the semilog fit correlation formula lnG of oil reservoir cumulative gas injected-oil reservoir cumulative oil production _i=h+mN _pcarry out parameter identification, in formula: G _ibe oil reservoir cumulative gas injected, unit is m ³; N _pbe oil reservoir cumulative oil production, unit is m ³; H and m is fitting coefficient.Hide for the miscible displacement of reservoir, recovery percent of reserves reaches R _f1after, and for non-phase-mixing driving oil reservoir, recovery percent of reserves need reach R _f2after, oil reservoir cumulative gas injected G _ilogarithm and oil reservoir cumulative oil production N _poccur linear relationship, above-mentioned semilog fitting formula is suitable for.

Recovery percent of reserves R hidden by the miscible displacement of reservoir _f1computational methods be:

$R_{f1}=\frac{S_{g1}}{1-S_{\mathrm{wi}}}\×100$

In formula: R _f1semilog relational expression for miscible displacement of reservoir Tibetan cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable, adopts percentage units; S _wifor oil reservoir average tied water saturation, adopt percentage units.

Described non-phase-mixing driving oil reservoir recovery percent of reserves R _f2computational methods be:

$R_{f2}=\frac{S_{g1}}{1-S_{\mathrm{wi}}}\×100$

In formula: R _f2semilog relational expression for non-phase-mixing driving oil reservoir cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable, adopts percentage units; S _wifor oil reservoir average tied water saturation, adopt decimal unit; S _g1for the logarithm of non-phase-mixing driving oil reservoir gas, oily two-phase relative permeability ratio and gas saturation relation curve start saturation ratio when there is linear relationship, adopt decimal unit.

According to development process oil reservoir cumulative gas injected G _iwith oil reservoir cumulative oil production N _phistorical data, adopt least squares identification go out fitting coefficient h and m.Adopt least square method to carry out identification to fitting coefficient, be mathematical basic parameter discrimination method, therefore repeat no more.

4, use semilog fitting formula according to the rational cumulative gas injected G of predicted time section (year, season, the moon, day) oil reservoir _ito the oil reservoir cumulative oil production N of this time period (year, season, the moon, day) _ppredict.

The various embodiments described above are only for illustration of the present invention, and wherein the implementation step etc. of method all can change to some extent, and 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 (6)

1. a high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology, comprises the following steps:

1) judge that note is adopted situation and whether reached balance, criterion is: if 1. oil reservoir has static pressure test, checks whether current strata pressure maintains original level, if it is judges that note is adopted and reaches equilibrium state, carry out step 2); If 2. oil reservoir is without static pressure test, whether the numerical value of oil reservoir cumulative voidage replacement ratio VRR, close to 1 or be greater than 1, if it is judges that the note situation of adopting reaches equilibrium state, and carry out step 2):

VRR＝Q _ingc/Q _oc

In formula: Q _ingcbe that fluidly lower volume is injected in oil reservoir accumulation, unit is m ³; Q _ocbe oil reservoir accumulation produced fluid subsurface volume, unit is m ³;

2) analyze gas injection development mechanism, judge that target reservoir is that the miscible displacement of reservoir is hidden, or non-phase-mixing driving oil reservoir;

3) to the semilog fit correlation formula lnG of oil reservoir cumulative gas injected-oil reservoir cumulative oil production _i=h+mN _pcarry out parameter identification;

In formula: G _ibe oil reservoir cumulative gas injected, unit is m ³; N _pbe oil reservoir cumulative oil production, unit is m ³; H and m is fitting coefficient;

Hide for the miscible displacement of reservoir, recovery percent of reserves reaches R _f1after, and for non-phase-mixing driving oil reservoir, recovery percent of reserves need reach R _f2after, above-mentioned semilog fitting formula is suitable for; According to oil reservoir cumulative gas injected G in development process _iwith oil reservoir cumulative oil production N _phistorical data, pick out fitting coefficient h and m;

In formula: R _f1semilog relational expression for miscible displacement of reservoir Tibetan cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable; R _f2semilog relational expression for non-phase-mixing driving oil reservoir cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable;

4), after picking out fitting coefficient h and m, semilog fit correlation formula lnG can be used _i=h+mN _paccording to the rational cumulative gas injected G of predicted time section oil reservoir _ito the oil reservoir cumulative oil production N of this time period _ppredict.

2. a kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology as claimed in claim 1, is characterized in that: described step 1) in oil reservoir accumulation inject the subsurface volume Q of fluid _ingcfor:

In formula: be i-th mouthful gas injection well day gas injection rate, unit is m ³/ sky; I is natural number; B _i ⁱ _ngit is the volume factor of i-th mouthful of gas injection well injected gas; be i-th mouthful of gas injection well injection length, unit is sky; R is oil reservoir injection gas well quantity, and unit is mouth;

The subsurface volume Q of oil reservoir accumulation produced fluid _ocfor:

In formula: be the subsurface volume of i-th mouthful of oil well accumulation produced fluid, unit is m ³; S is oil reservoir oil well quantity, and unit is mouth.

3. a kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology as claimed in claim 2, is characterized in that: the subsurface volume of described i-th mouthful of oil well accumulation produced fluid following formulae discovery is adopted before gas injection breaks through:

In formula: be i-th mouthful of oil well daily oil production, unit is m ³/ sky; be i-th mouthful of oil well water yield per day, unit is m ³/ sky; be i-th mouthful of sewage from oil-well volume factor, unit is m ³/ m ³; be i-th mouthful of oil well crude oil volume factor, unit is m ³/ m ³; be i-th mouthful of oil well production time, unit is sky.

4. a kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology as claimed in claim 2, is characterized in that: the subsurface volume of described i-th mouthful of well accumulation produced fluid following formulae discovery is adopted after gas injection breaks through:

In formula: be Reservoir Crude Oil average external volume coefficient, unit is m ³/ m ³; GOR ⁱbe i-th mouthful of oil well production gas-oil ratio, unit is m ³/ m ³; GOR ^meanbe Reservoir Crude Oil average dissolution gas-oil ratio, unit is m ³/ m ³; B _pgbe the volume factor of output gas, unit is m ³/ m ³; be i-th mouthful of oil well gas injection break through, unit is sky; i-th mouthful of oil well production time, unit is sky; be i-th mouthful of oil well daily oil production, unit is m ³/ sky; be i-th mouthful of oil well water yield per day, unit is m ³/ sky; be i-th mouthful of oil well crude oil volume factor, unit is m ³/ m ³; be i-th mouthful of sewage from oil-well volume factor, unit is m ³/ m ³.

5. a kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology as described in claim 3 or 4, it is characterized in that: described oil well is after gas injection breaks through or pre-breakthrough criterion is: with the maximum dissolved gas oil ratio of crude oil under oil reservoir initial condition for boundary, as oil well production gas-oil ratio GOR ⁱbe before gas injection breaks through when being less than this value, as oil well production gas-oil ratio GOR ⁱbe after gas injection breaks through when being greater than this value.

6. a kind of high volatile volatile oil reservoir injection construction of natural gas fields oil production Forecasting Methodology as claimed in claim 1, is characterized in that: described step 3) in the miscible displacement of reservoir hide recovery percent of reserves R _f1computational methods be:

In formula: R _f1semilog relational expression for miscible displacement of reservoir Tibetan cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable; S _wifor oil reservoir average tied water saturation;

Non-phase-mixing driving oil reservoir recovery percent of reserves R _f2computational methods be:

In formula: R _f2semilog relational expression for non-phase-mixing driving oil reservoir cumulative gas injected-oil reservoir cumulative oil production starts the recovery percent of reserves of where applicable; S _g1for the logarithm of non-phase-mixing driving oil reservoir gas, oily two-phase relative permeability ratio and gas saturation relation curve start saturation ratio when there is linear relationship.