CN101135732A - Formation fluid saturation degree evaluating method - Google Patents

Abstract

The method uses the relational model between the rock and the electricity to evaluate the saturation of the stratum fluid. In the method, I is a resistivity augmenting factor; R0 is a resistivity when the stratum contents 100% water, it unit is ohm.m; Rt is a stratum resistivity, its unit is ohm.m; SW is a water saturation of stratum; Phi is porosity; Vsh is shale content; U is wettability index; Y is parameter; C is constant.

Description

Formation fluid saturation degree evaluating method

Technical field

The present invention relates to the exploration engineering of logging well, particularly relate to a kind of formation fluid saturation degree evaluating method, is a kind of method of utilizing well-log information to come the oil-containing tolerance of quantitative evaluation reservoir concretely.

Background technology

Oil is a kind of important strategic resource.Angle from economy and technology, no matter be external cooperation, buy external oil field by international the bid, still explore at home and seek new HYDROCARBON-BEARING REGION and maturing field is reappraised, the reservoir Reserves Evaluation all is an important gordian technique, improve no matter the Reserves Evaluation technology is to development and national economy, still the oil reserve amount determines that rationally crucial meaning is all arranged.

The Reserves Evaluation of reservoir mainly refers to the quantitative evaluation of reservoir oil-gas possibility, and wherein utilizing the oil-gas possibility of the quantitative evaluation reservoir of well-log information is a kind of important method.At present, in the well-log information comprehensive and quantitative that the reservoir oil-gas possibility is estimated was explained, traditional Archie equation had critical role as the most basic explanation relational expression, and it is the basis of present well logging interpretation quantitative Analysis oil saturation (So).

Traditional Archie equation can be expressed as form:

$I=\frac{R_t}{R_o}=\frac{b}{S_w^n}$

In the formula, I-be resistivity enhancement coefficient (real number),

R _o-be the resistivity (resistivity unit be Ω m) of stratum when very moisture,

R _t-be formation resistivity (resistivity unit is Ω m),

S _w-be stratum water saturation (decimal),

N-be saturation exponent (real number),

B-be A Erqi parameter (real number).

But because above-mentioned traditional Archie equation is the half theoretical semiempirical formula that is based upon on the electrical experiment basis of clean sandstone rock (having greater porosity) physics, so there is certain limitation in it in practical application.In addition, in the experimental study of rock electricity relation (being the relation between water saturation and the resistivity enhancement coefficient), found a large amount of Fei Aerqi phenomenons, promptly the relation between resistivity enhancement coefficient and the water saturation (I-Sw) is not the described linear relationship of Archie equation under log-log coordinate, but buckling phenomenon occurs.The Fei Aerqi phenomenon comprises two kinds: a kind of I-Sw of being closes and ties up under the log-log coordinate, along with reducing of water saturation, is partial to saturation axis gradually; Another kind is that the I-Sw pass ties up under the log-log coordinate, along with reducing of water saturation, departs from saturation axis (as shown in Figure 1) gradually.The Fei Aerqi phenomenon is the very important phenomenon of a class, for the oil-gas possibility of quantitative evaluation reservoir fundamental influence is arranged, and the existence of Fei Aerqi phenomenon makes and is difficult to utilize Archie equation that reservoir oil-containing tolerance is accurately estimated.Such as, for the reservoir that has first kind of Fei Aerqi phenomenon, if utilize Archie equation to carry out the oil-gas possibility evaluation, the explanation results of its hydrocarbon saturation can be on the low side under the same conditions, this will cause many hydrocarbon zone to be missed for the reservoir that has second kind of Fei Aerqi phenomenon, if utilize Archie equation to carry out the oil-gas possibility evaluation, the explanation results of its hydrocarbon saturation can be higher under the same conditions, will think some low pay sands by mistake prolific reservoir like this, thereby cause the waste of production cost.Therefore, the origin cause of formation of research Fei Aerqi phenomenon, setting up corresponding rock electricity relational model is to improve reservoir oily quantitative evaluation accuracy, improves the key of calculation of reserves precision.

Summary of the invention

In view of this, the object of the present invention is to provide a kind of formation fluid saturation degree evaluating method, come to carry out more exactly evaluating reservoir by a kind of new rock electricity relational model.

To achieve these goals, technical scheme of the present invention is:

A kind of formation fluid saturation degree evaluating method, utilize following rock electricity relational model to estimate formation fluid saturation degree:

$I=\frac{R_t}{R_o}={S_W^{{-\mathrm{US}}_W}}^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}},$

Wherein, I is the resistivity enhancement coefficient; R _oBe the resistivity of stratum when very moisture, unit is Ω m; R _tBe formation resistivity, unit is Ω m; S _WBe the stratum water saturation; φ is a factor of porosity; Vsh is a shale index; U is a wettability index; Y is a parameter; C is a constant.

To above-mentioned rock electricity relational model, the relational model between associating formation factor (F) and the formation porosity (φ), i.e. F=R _o/ R _w=α/φ ^m(this relational model can referring to the interpretation of logging data correlation technique), find the solution and obtain:

$S_W=e^{W\left(f\left(\mathrm{\φ}\right)\right)}\frac{{\mathrm{\φ}}^c}{Y(1-\mathrm{Vsh})},$

Wherein, $f\left(\mathrm{\φ}\right)=\frac{Y(1-\mathrm{Vsh})}{U{\mathrm{\φ}}^c}\·\ln \frac{\mathrm{\α}{R}_W}{R_t{\mathrm{\φ}}^m},$ W () is the lambertW function; α, m are parameter (real number);

R _WBe the stratum resistivity of water, unit is Ω m;

Stratum hydrocarbon saturation So=1-Sw.

When not considering that shale index changes, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-\mathrm{US}}_W^{\frac{Y}{{\mathrm{\φ}}^C}}};$

When not considering the variation of shale index and factor of porosity, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-\mathrm{US}}_W^d},$ Wherein d is a real number;

When not considering the influencing of factor of porosity, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-\mathrm{US}}_W^Y(1-\mathrm{Vsh})};$

When not considering the influencing of wetting state, above-mentioned each rock electricity concerns that equivalence respectively is $I=\frac{R_t}{R_o}={S_W^{{-S}_W}}^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}}$ 、

$I=\frac{R_t}{R_o}=S_W^{{-S}_W^{\frac{Y}{{\mathrm{\φ}}^c}}}$ 、 $I=\frac{R_t}{R_o}=S_W^{{-S}_W^d}$ 、 $I=\frac{R_t}{R_o}=S_W^{{-S}_W^{Y(1-\mathrm{Vsh})}},$ Promptly

When not considering the influencing of wetting state, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}={S_W^{{-S}_W}}^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}};$

When not considering the influencing of shale index and wetting state, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-S}_W^{{\mathrm{\φ}}^{\frac{Y}{c}}}};$

When not considering the influencing of shale index, factor of porosity and wetting state, described rock electricity concerns that equivalence is

$I=\frac{R_t}{R_o}{=S}_W^{{-S}_W^d};$

When not considering the influencing of factor of porosity and wetting state, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-S}_W^{Y(1-\mathrm{Vsh})}}.$

The value of general described constant C is between-20 to 20.

Preferably described constant C is 1/2.

Formation fluid saturation degree evaluating method of the present invention provides the rock electricity relational model of a kind of Fei Aerqi of being applicable to phenomenon and A Erqi phenomenon, reflected the influence that the distribution form of saturation degree own, wetting state, shale index, factor of porosity concern the rock electricity, can effectively improve the accuracy that the reservoir oily is estimated, reduce the exploration risk of oil gas.

Description of drawings

A Erqi phenomenon and the Fei Aerqi phenomenon curve map of Fig. 1 for finding in the experiment of existing rock electricity relation;

The variation diagram of the resistivity enhancement coefficient that Fig. 2 causes for shale index in the rock physics experiment:

The variation diagram of the resistivity enhancement coefficient that Fig. 3 causes for rock physics experiment mesoporosity degree;

The variation diagram of the resistivity enhancement coefficient that Fig. 4 causes for wetting state in the rock physics experiment;

Fig. 5 a is the graph of a relation that C gets-20 o'clock rock of the present invention electricity relation curves and experimental data;

Fig. 5 b is the graph of a relation that C gets-2 o'clock rock of the present invention electricity relation curves and experimental data;

Fig. 5 c is the graph of a relation that C gets 1/10 o'clock rock of the present invention electricity relation curve and experimental data:

Fig. 5 d is the graph of a relation that C gets 1/3 o'clock rock of the present invention electricity relation curve and experimental data:

Fig. 5 e is the graph of a relation that C gets 1/2 o'clock rock of the present invention electricity relation curve and experimental data:

Fig. 5 f is the graph of a relation two that C gets 3/2 o'clock rock of the present invention electricity relation curve and experimental data

Fig. 5 g is the graph of a relation that C gets 9 o'clock rock of the present invention electricity relation curves and experimental data:

Fig. 5 h is the graph of a relation that C gets 20 o'clock rock of the present invention electricity relation curves and experimental data:

Fig. 6 is the identical figure of experimental data and Archie equation in the embodiment of the invention 1;

Fig. 7 is the identical figure of experimental data and new rock electricity relational model in the embodiment of the invention 1:

Fig. 8 is the graph of a relation of the relative ground with its measurement point of the formation resistivity Rt degree of depth of utilizing logging technology to obtain in the embodiment of the invention 1.

Fig. 9 is the oil saturation that utilizes new rock electricity relation in the embodiment of the invention 1 and obtain figure as a result.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, specific embodiments of the invention are elaborated below in conjunction with accompanying drawing.

The present invention proposes a kind of formation fluid saturation degree evaluating method of the Fei Aerqi of being applicable to phenomenon, this method can reflect the influence of Fei Aerqi phenomenon, can estimate the stratum hydrocarbon content exactly by a kind of new rock electricity relational model, promptly can effectively improve the accuracy that the reservoir oily is estimated, thereby reduce the exploration risk of oil gas.

By a large amount of rock physics experiments, the inventor finds that the relation between resistivity enhancement coefficient (I) and stratum water saturation (SW) is not the described linear relationship in log-log coordinate of A Erqi, and factor such as fluid saturation, factor of porosity, wetting state, shale index all can cause the generation of Fei Aerqi phenomenon, be that the resistivity enhancement coefficient is not only relevant with fluid saturation, but also relevant with factors such as factor of porosity, wetting state, shale indexs.Fig. 2 to Fig. 4 is respectively in the rock physics experiment shale index, factor of porosity and wetting state to the graph of a relation that influences of resistivity enhancement coefficient.As shown in Figure 2, shale index can meet Archie equation when low preferably, and shale index is low more, departs from the A Erqi phenomenon more.As shown in Figure 3, when rock porosity was higher, the A Erqi phenomenon of can also coincideing preferably between resistivity enhancement coefficient (I) and the stratum water saturation (SW) along with the reduction of rock porosity, presented the Fei Aerqi phenomenon gradually.Equally, as shown in Figure 4, along with the variation of wetting state, resistivity enhancement coefficient (I) is also along with change, and different wetting states can produce different Fei Aerqi phenomenons.

The present invention has carried out the experiment of single factor analysis by the numerical simulation experiment to each top factor on the basis of above-mentioned a large amount of rock physics experiments, determined that the saturation exponent n in the Archie equation is not constant, but the function of above each factor.By each single factor analysis measurement result is carried out statistical study, determine that its functional form is ${n={\mathrm{US}}_W}^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}},$ Thereby determine rock electricity relational model of the present invention, promptly

$I=\frac{R_t}{R_o}={S_W^{{-\mathrm{US}}_W}}^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}}---\left(2\right)$

In the formula (2), I-is resistivity enhancement coefficient (real number);

R _o-be the resistivity (resistivity unit be Ω m) of stratum when very moisture;

R _t-be formation resistivity (resistivity unit is Ω m);

SW-is stratum water saturation (decimal, or percentage, percentage=decimal * 100%):

So-is stratum hydrocarbon saturation (decimal, or percentage, percentage=decimal * 100%);

φ-be factor of porosity (decimal);

Vsh-is shale index (decimal):

U-is wettability index (real number);

Y-is parameter (real number);

C-is constant (real number).

By the relational model between associating formation factor (F) and the formation porosity (φ), i.e. F=R _o/ R _w=α/φ ^m(this relational model can referring to the interpretation of logging data correlation technique) be found the solution formula (2), can be obtained:

$S_W=e^{W\left(f\left(\mathrm{\φ}\right)\right)\·\frac{{\mathrm{\φ}}^C}{Y(1-\mathrm{Vsh})}},---\left(3\right)$

In the formula, $f\left(\mathrm{\φ}\right)=\frac{Y(1-\mathrm{Vsh})}{{\mathrm{U\φ}}^c}\·\ln \frac{\mathrm{\α}{R}_W}{R_t{\mathrm{\φ}}^m},$ W () is the lambertW function.Rw is stratum resistivity of water (unit is Ω m); α, m-be parameter.

Based on actual physical test and numerical simulation, the value of constant C can be got any value in theory and can both be made this rock point relation and Fei Aerqi phenomenon in the experiment have identical preferably in the new rock electricity relational model of the present invention, but for different regions, the characteristic of formation rock is different with pore structure characteristic, and but the computational accuracy of computing machine is limited, therefore consider the complexity of calculating again, in the foundation of the rock electricity relational model of reality, should carry out preferably the value of C.Can mainly consider following factor when preferred: the selection of (1) C can fully manifest the influence of factor of porosity φ; (2) selection of C should make φ ^CBut in suitable computational accuracy scope; (3) but the selection of C should make Y in suitable computational accuracy scope; (4) selection of C should make φ ^CBe convenient to calculate.

Selection to constant C is illustrated below.In general, therefore the formation porosity variation range is that example is analyzed with this interval between 0.4～0.01.Table 1 is the data analysis table in a certain area, in order to the preferred value of determining C (data of table 1 in order to explanation the present invention, but not be used to limit the present invention).From table 1, can analyze: 1. when the C value is too small when (as C=0.001), φ ^CVariation with factor of porosity φ changes hardly, is almost a constant (φ ^C0.99), this moment, the influence of factor of porosity was weakened, present embodiment needs take into full account under the situation of influence of factor of porosity can be with table in 0.1,0.01,0.001 these three C values eliminatings; 2. when the C value is excessive (as C=10), φ ^CVery little (as φ ^C=1E-20=1 * 10 ^-20), be almost 0, but exceeded the computational accuracy scope of computing machine, therefore consider the computational accuracy of computing machine and suitable φ ^CValue, present embodiment can be got rid of these two values of C=10 and C=2 in the table: 3. in addition, the selection of C also should make Y in suitable accuracy rating, in the table when C＜0.6, Y〉0.1, this moment, Y was in proper range, can guarantee the precision of COMPUTER CALCULATION, 1 in the table 1 and 0.7 these two C values can be got rid of thus; 4. in addition, consider φ ^CDifficulty in computation, in these 3 C values of (promptly 3/5), 0/5 (promptly 1/2) and 0.3 obviously 0.6 (promptly 3/10), the φ during C=1/2 ^C(promptly

) be easier to calculate, so can select in the present embodiment C be 3/5,1/2, and 3/10 in one, preferably, it is 1/2 that present embodiment is selected C.

Table 1.

As above the selection to the value of C only is used to illustrate the present invention, but not is used to limit the present invention.Usually, the value of constant C can be between-20 to 20.Experimental data for different regions and Different Strata characteristic, can be to span and the preferred C value that different C should be arranged, when the precision of computing machine or other corresponding computational tool changes, the span of C also may have difference (as the raising of computational accuracy, constant C is value in the larger context).

Fig. 5 a to Fig. 5 h (gets-20 ,-2,1/10 respectively as C when being respectively and getting different numerical value corresponding to C, 1/3,01/2,3/2,9,20 o'clock) according to resistivity enhancement coefficient (I) and the graph of relation of stratum water saturation (SW) and the identical situation of experimental data that formula (3) obtains, visible C is applicable to different numerical value, get-20 ,-2,1/10 at C, 1/3,1/2,3/2,9, and can coincide preferably with experimental data in 20 o'clock.

In new rock electricity relational model of the present invention, when C=1/2:

$I=\frac{R_t}{R_o}{=S_W^{{-\mathrm{US}}_W}}^{\frac{Y(1-\mathrm{Vsh})}{\sqrt{\mathrm{\φ}}}},$

$S_W=e^{W\left(f\left(\mathrm{\φ}\right)\right)\·\frac{\sqrt{\mathrm{\φ}}}{Y(1-\mathrm{Vsh})}},$

In the formula, $f\left(\mathrm{\φ}\right)=\frac{Y(1-\mathrm{Vsh})}{U\sqrt{\mathrm{\φ}}}\·\ln \frac{\mathrm{\α}{R}_W}{R_t{\mathrm{\φ}}^m},$ W () is the lambertW function.

The model of the new rock electricity relation that the present invention proposes has reflected the influence of factors such as fluid saturation, factor of porosity, wetting state, shale index to rock electricity relation.Resistivity enhancement coefficient (I) that this model provided and the relation between stratum water saturation (SW) are coincide finely with the Fei Aerqi phenomenon in the experiment of rock electricity, can estimate (hydrocarbon stratum content So=1-Sw) to the stratum hydrocarbon content exactly.

Illustrate below how rock electricity relational model according to the present invention carries out the evaluation of formation fluid saturation degree (as hydrocarbon saturation).

Embodiment 1

At first utilize rock electricity experiment measuring, obtain the resistivity data Ro of rock core when complete saturation water, obtain rock core then at different water cut saturation degree (Sw, and the resistivity data Rt in the time of Sw+So=1), utilize the radiometer of Rt and Ro to calculate resistivity enhancement coefficient I, in order to make suitable better effects if of the present invention, when measuring, the distribution range of saturation degree should obtain more extensive, can be about 0.1 should carry out corresponding measurement in water saturation.

For example: get a rock core, its shale index Vsh=0, factor of porosity φ=0.09.

Resistivity when recording its complete saturation water is:

Ro＝147.5Ω.m

According to the resistivity data Rt of rock core when different water cut saturation degree (Sw, and Sw+So=1), utilize the radiometer of Rt and Ro to calculate resistivity enhancement coefficient I then, table 2 is the rock electricity experimental measurements of present embodiment:

Table 2.

Saturation degree (Sw)	Resistivity enhancement coefficient (I)
		1.00 0.93 0.85 0.72 0.59 0.41 0.32 0.22 0.12	1.00 1.27 1.69 2.70 4.08 8.21 10.41 12.78 15.50

(get C=1/2 in the present embodiment, promptly the rock electricity closes and is to utilize Archie equation and rock of the present invention electricity relational model respectively $I=\frac{R_t}{R_o}={S_W^{{-\mathrm{US}}_W}}^{\frac{Y(1-\mathrm{Vsh})}{\sqrt{\mathrm{\φ}}}}$ ) data in the his-and-hers watches 2 analyze, its result is respectively as shown in Figure 6 and Figure 7.By Fig. 6 and Fig. 7 as seen, traditional Archie equation (Fig. 6 bend) exists than mistake with experimental data (Diamond spot among Fig. 6), and rock of the present invention electricity relational model (curve among Fig. 7) coincide fine with experimental data (Diamond spot among Fig. 7).

According to these data that obtain, and utilize new rock electricity relational model provided by the invention, can obtain the value of parameter Y and U.For example obtain: U=3.47, Y=0.14.To same rock core, because φ value determines, when C gets any value, can obtain the Y value of a correspondence, so the electric relational model of rock of C present embodiment when getting any value can both be well identical with experimental data.

After having determined Y and U, the subsurface reservoir Rt data (as shown in Figure 8) that utilization is obtained by logging technology, and can obtain the formation water resistivity Rw that this area is suitable for (Rw=0.12 Ω m for example by analysis to these a large amount of well-log informations in rock core location, specific analytical method is consulted well-log information and is handled correlation technique), thus can obtain

Value, wherein α, m (are F=a/ φ for the parameter of relation between determining in stratum factor F and the factor of porosity ^m), definite method of its value is consulted well-log information and is handled correlation technique.

Can utilize then water saturation calculating formula that rock electric model provided by the invention solves and correlation parameter thereof (U, Y,

Deng), come the fluid saturation situation in the quantitative Analysis subsurface reservoir, thereby the oil-containing tolerance of reservoir is carried out quantitative evaluation.To the result of calculation of oil-containing tolerance as shown in Figure 9.

Utilize new rock electricity relational model of the present invention to estimate formation fluid saturation degree, can estimate the stratum hydrocarbon content exactly, can effectively improve the accuracy that the reservoir oily is estimated, thereby reduce the exploration risk of oil gas.

Need to prove that rock electricity relational model of the present invention is not limited to the form of formula (2), but different equivalents can be arranged.For example:

I. when not considering that shale index changes, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-\mathrm{US}}_W^{{\mathrm{\φ}}^{\frac{Y}{c}}}},$ Preferably, during C=1/2, $I=\frac{R_t}{R_o}=S_W^{{-\mathrm{US}}_W^{\frac{Y}{\sqrt{\mathrm{\φ}}}}};$

II. when not considering the variation of shale index and factor of porosity, perhaps work as

When representing with the form of parameter d, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-\mathrm{US}}_W^d}$ (when not considering the variation of shale index and factor of porosity, d is a real number):

III. when not considering the influencing of factor of porosity, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-\mathrm{US}}_W^{Y(1-\mathrm{Vsh})}};$

IV. above various (comprising formula (2)), the influence of not considering wetting state is not when (promptly comprising U), and equivalence is respectively $I=\frac{R_t}{R_o}={S_W^{{-S}_W}}^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}}$ 、 $I=\frac{R_t}{R_o}=S_W^{{-S}_W^{{\mathrm{\φ}}^{\frac{Y}{c}}}}$ 、 $I=\frac{R_t}{R_o}=S_W^{{-S}_W^d}$ 、 $I=\frac{R_t}{R_o}=S_W^{{-S}_W^{Y(1-\mathrm{Vsh})}}\·$

More than various in, when the symbol of employing changes and the equivalents that forms is equally applicable to the present invention.

In traditional Archie equation, saturation exponent n is a constant, and in the rock electricity relational model of the present invention, saturation exponent n is the function of factors such as fluid saturation, factor of porosity, wetting state, shale index, and it has reflected that one or more factors are to the influence of rock electricity relation in the distribution form of saturation degree own, wetting state, shale index, the factor of porosity.The factor of considering not simultaneously, saturation exponent can have different forms.

For example:

When I. taking all factors into consideration factor affecting such as fluid saturation, factor of porosity, wetting state, shale index,

$n=f(\mathrm{Sw},\mathrm{Vsh},\mathrm{\φ},U,Y)={{\mathrm{US}}_W}^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}},$ Preferably, during C=1/2, $n=f(\mathrm{Sw},\mathrm{Vsh},\mathrm{\φ},U,Y)={{\mathrm{US}}_W}^{\frac{Y(1-\mathrm{Vsh})}{\sqrt{\mathrm{\φ}}}};$

II. when not considering that shale index changes, $n=f(\mathrm{Sw},\mathrm{Vsh},\mathrm{\φ},U,Y)={\mathrm{US}}_W^{\[\frac{Y}{{\mathrm{\φ}}^c}\]},$ Preferably, during C=1/2, $n=f(\mathrm{Sw},\mathrm{Vsh},\mathrm{\φ},U,Y)={\mathrm{US}}_W^{\frac{Y}{\sqrt{\mathrm{\φ}}}};$

III. when not considering the influencing of factor of porosity, $n=f(\mathrm{Sw},\mathrm{Vsh},\mathrm{\φ},U,Y)={\mathrm{US}}_W^{Y(1-\mathrm{Vsh})};$

IV. when not considering the variation of shale index and factor of porosity, perhaps work as

When representing with the form of parameter d, $n=f(\mathrm{Sw},\mathrm{Vsh},\mathrm{\φ},U,Y)={\mathrm{US}}_W^d$ (when not considering the variation of shale index and factor of porosity, d is a real number);

V. above various in, do not consider the form of influence when (promptly not comprising U) of wetting state.

More than various in, when the symbol of employing changes and the equivalents of the saturation exponent that forms is equally applicable to the present invention.

The new rock electricity relational model that the present invention proposes has reflected the influence of factors such as wetting state, shale index to rock electricity relation, can reflect the Fei Aerqi rule of rock electricity relation on the whole.Traditional Archie equation be under certain condition special case of rock of the present invention electricity relational model (as $I=\frac{R_t}{R_o}=S_W^{{-\mathrm{US}}_W^d}$ The time), i.e. the present invention is not only applicable to the A Erqi phenomenon, and under the situation that Archie equation can not be suitable for, the present invention still is suitable for simultaneously.

In sum, the rock electricity relational model of the reflection Fei Aerqi phenomenon that proposes by the present invention can be realized more exactly the evaluation of stratum hydrocarbon content has been reduced the exploration risk of oil gas effectively, thereby avoided the waste of production cost.

Above embodiment only is used to illustrate the present invention, but not is used to limit the present invention.Within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (5)

1. formation fluid saturation degree evaluating method is characterized in that:

Utilize following rock electricity relational model to estimate formation fluid saturation degree:

$I=\frac{R_t}{R_o}=S_W^{-U{S}_W^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}}},$

Wherein, I is the resistivity enhancement coefficient; R ₀Be the resistivity of stratum when very moisture, unit is Ω m; R _tBe formation resistivity, unit is Ω m; S _wBe the stratum water saturation; φ is a factor of porosity; Vsh is a shale index; U is a wettability index; Y is a parameter; C is a constant.

2. method according to claim 1 is characterized in that, to the relational model F=R between above-mentioned rock electricity relational model associating stratum factor F and the formation porosity φ _o/ R _w=a/ φ ^m, find the solution and obtain:

$S_W=e^{W\left(f\left(\mathrm{\φ}\right)\right)\·\frac{{\mathrm{\φ}}^c}{Y(1-\mathrm{Vsh})}},$

Wherein, $f\left(\mathrm{\φ}\right)=\frac{Y(1-\mathrm{Vsh})}{U{\mathrm{\φ}}^c}\·\mathrm{In}\frac{a{R}_W}{R_t{\mathrm{\φ}}^m},$ W () is the lambertW function; A, m are parameter;

R _WBe the stratum resistivity of water, unit is Ω m;

Stratum hydrocarbon saturation So=1-Sw.

3. method according to claim 1 is characterized in that:

When not considering the influencing of shale index, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{-{\mathrm{US}}_W^{\frac{Y}{{\mathrm{\φ}}^C}}};$

When not considering the influencing of shale index and factor of porosity, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{-U{S}_W^d},$

Wherein d is a real number;

When not considering the influencing of factor of porosity, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}{=S}_W^{-U{S}_W^{Y(1-\mathrm{Vsh})}}.$

4. method according to claim 1 is characterized in that:

When not considering the influencing of wetting state, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}{S_W^{-U{S}_W}}^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\φ}}^c}};$

When not considering the influencing of shale index and wetting state, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{-S_W^{\frac{Y}{{\mathrm{\φ}}^c}}};$

When not considering the influencing of shale index, factor of porosity and wetting state, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{-S_W^d};$

When not considering the influencing of factor of porosity and wetting state, described rock electricity concerns that equivalence is $I=\frac{R_t}{R_o}=S_W^{{-S}_W^{Y(1-\mathrm{Vsh})}}.$

5. according to any described method among the claim 1-4, it is characterized in that:

The value of described constant C is between-20 to 20.

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