CN100588990C - Formation Fluid Saturation Evaluation Method - Google Patents

Abstract

The invention provides a method for evaluating formation fluid saturation, which utilizes the following rock-electricity relationship model to evaluate formation fluid saturation: (see the right formula), wherein, I is the resistivity increase coefficient; R _O is when the formation is 100% water-bearing Resistivity, unit is Ω m; R _t is formation resistivity, unit is Ω m; S _W is formation water saturation; φ is porosity; Vsh is mud content; U is wettability index; parameter; C is a constant. The invention reflects the influence of the distribution form of the saturation itself, wettability, shale content and porosity on the rock-electricity relationship, can effectively improve the accuracy of reservoir oil and gas evaluation, and reduce oil and gas exploration risks.

Description

Formation Fluid Saturation Evaluation Method

technical field

The invention relates to well logging exploration technology, in particular to a method for evaluating formation fluid saturation, specifically a method for quantitatively evaluating the oil and gas content of reservoirs by using well logging data.

Background technique

Oil is an important strategic resource. From an economic and technical point of view, whether it is foreign cooperation, purchasing foreign oil fields through international bidding, or conducting domestic exploration to find new oil and gas areas and re-evaluating old oil fields, reservoir reserve evaluation is an important key technology to improve Reserve evaluation technology is of great significance not only for the development of national economy, but also for the reasonable determination of oil reserves.

The reserve evaluation of the reservoir mainly refers to the quantitative evaluation of the oil-gas content of the reservoir, and it is an important method to use the logging data to quantitatively evaluate the oil-gas content of the reservoir. At present, in the comprehensive quantitative interpretation of well logging data for reservoir oil and gas evaluation, the traditional Archie's formula plays a pivotal role as the most basic interpretation relation. Foundation.

The traditional Archie's formula can be expressed as follows:

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, I- is the resistivity increase coefficient (real number),

R ₀ - is the resistivity when the formation contains 100% water (resistivity unit is Ω·m),

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

S _W - is the formation water saturation (decimal),

n- is the saturation index (real number),

b- is the Archie parameter (real number).

However, since the above-mentioned traditional Archie formula is a semi-theoretical and semi-empirical formula based on physical and electrical experiments of pure sandstone rock (with high porosity), it has certain limitations in practical application. In addition, a large number of non-Archiian phenomena have been found in the experimental study of the lithoelectric relationship (that is, the relationship between water saturation and resistivity increase coefficient), that is, the relationship between resistivity increase coefficient and water saturation in log-logarithmic coordinates. The relationship between degrees (I-Sw) is not the linear relationship described by Archie's formula, but a bending phenomenon. There are two types of non-Archie phenomena: one is that the I-Sw relationship in the log-log coordinates gradually shifts to the saturation axis as the water saturation decreases; the other is the I-Sw relationship in the log-log coordinates In the lower case, as the water saturation decreases, it gradually deviates from the saturation axis (as shown in Figure 1). The non-Archie phenomenon is a very important phenomenon, which has a crucial impact on the quantitative evaluation of the oil and gas content of the reservoir. The existence of the non-Archie phenomenon makes it difficult to use the Archie formula to accurately evaluate the oil and gas content of the reservoir. . For example, for reservoirs with the first type of non-Archie phenomenon, if the Archie formula is used to evaluate the oil and gas content, the interpretation result of the oil and gas saturation under the same conditions will be low, which will cause many oil and gas layers to be For the reservoirs with the second non-Archie phenomenon, if the Archie formula is used to evaluate the oil and gas content, the interpretation result of the oil and gas saturation under the same conditions will be relatively high, which will make some low-production oil layers Mistaking it as a high-yield oil layer, resulting in a waste of production costs. Therefore, studying the causes of non-Archie phenomena and establishing corresponding rock-electricity relationship models are the key to improving the accuracy of quantitative evaluation of oil and gas in reservoirs and the accuracy of reserve calculation.

Contents of the invention

In view of this, the purpose of the present invention is to provide a formation fluid saturation evaluation method, through a new rock-electricity relationship model to more accurately evaluate the reservoir.

In order to achieve the above object, the technical solution of the present invention is:

A method for evaluating formation fluid saturation, using the following rock-electricity relationship model to evaluate formation fluid saturation:

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}^{{{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; US</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}}^{\frac{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vsh</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}^{\mathrm{<span\; class="notranslate">\; c</span>}}}}}<span\; class="notranslate">\; ,</span>$

Among them, I is the resistivity increase coefficient; _R0 is the resistivity when the formation is 100% water-bearing, and the unit is Ω m;

R _t is formation resistivity, unit is Ω m; SW is formation water saturation; φ is porosity; Vsh is shale content; U is wettability index; Y is parameter; C is constant.

For the above rock-electricity relationship model, the relationship model between formation factors (F) and formation porosity (φ) is combined, that is, F=R _o /R _w =a/φ ^m (for this relationship model, please refer to the relevant method), and get:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&phi;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}^{\mathrm{<span\; class="notranslate">\; c</span>}}}{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vsh</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ,</span>$

W(·)为lambertW函数；a、m为参数(实数)；in,

W( ) is lambertW function; a, m are parameters (real numbers);

RX is the resistivity of formation water, in Ω m;

Formation oil and gas saturation So=1-Sw.

When the change of shale content is not considered, the rock-electricity relationship is equivalent to

其中d为实数；When the change of shale content and porosity is not considered, the rock-electricity relationship is equivalent to

where d is a real number;

When the influence of porosity is not considered, the rock-electricity relationship is equivalent to

即When the influence of wettability is not considered, the above rock-electric relations are equivalent to

Right now

When the influence of wettability is not considered, the lithoelectric relationship is equivalent to

When the influence of shale content and wettability is not considered, the rock-electricity relationship is equivalent to

When the effects of shale content, porosity and wettability are not considered, the rock-electricity relationship is equivalent to $I=\frac{R_t}{R_o}={-S}_W^{{-S}_W^d};$

When the effects of porosity and wettability are not considered, the rock-electricity relationship is equivalent to

Generally, the value of the constant C is between -20 and 20.

Preferably, the constant C is 1/2.

The formation fluid saturation evaluation method of the present invention provides a rock-electricity relationship model suitable for non-Archie phenomena and Archie phenomena, reflecting the distribution of saturation itself, wettability, shale content, and porosity. The impact of the relationship can effectively improve the accuracy of reservoir oil and gas evaluation and reduce the risk of oil and gas exploration.

Description of drawings

Fig. 1 is a curve diagram of Archie phenomenon and non-Archie phenomenon found in existing rock-electricity relationship experiments;

Fig. 2 is a graph showing the variation of resistivity increase coefficient caused by shale content in rock physics experiments;

Fig. 3 is a graph showing the variation of resistivity increase coefficient caused by porosity in rock physics experiments;

Fig. 4 is a change diagram of resistivity increase coefficient caused by wettability in rock physics experiments;

Fig. 5 a is the relationship figure of the rock-electricity relation curve of the present invention and experimental data when C gets-20;

Fig. 5 b is the relationship diagram of the rock-electricity relationship curve of the present invention and the experimental data when C gets -2;

Fig. 5c is the relationship diagram of the rock-electricity relationship curve and experimental data of the present invention when C is 1/10;

Fig. 5 d is the relationship diagram between the rock-electricity relationship curve and the experimental data of the present invention when C is 1/3;

Fig. 5 e is the relationship diagram of the rock-electricity relationship curve and experimental data of the present invention when C gets 1/2;

Fig. 5 f is the relationship diagram of the rock-electricity relationship curve and experimental data of the present invention when C is 3/2;

Fig. 5 g is the relationship diagram of the rock-electricity relationship curve and experimental data of the present invention when C is 9;

Fig. 5h is the relationship diagram of the rock-electricity relationship curve and experimental data of the present invention when C is 20;

Fig. 6 is the matching figure of experimental data and Archie's formula in the embodiment of the present invention 1;

Fig. 7 is the matching figure of experimental data and new rock-electricity relationship model in the embodiment of the present invention 1;

FIG. 8 is a graph showing the relationship between the formation resistivity Rt and the depth of the measurement point relative to the surface obtained by logging technology in Example 1 of the present invention.

Fig. 9 is a graph of oil saturation results obtained by using the new rock-electricity relationship in Example 1 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

The present invention proposes a formation fluid saturation evaluation method applicable to non-Archie phenomena, which can reflect the influence of non-Archie phenomena, and can accurately evaluate formation oil and gas content through a new rock-electricity relationship model, That is, it can effectively improve the accuracy of reservoir oil and gas evaluation, thereby reducing the risk of oil and gas exploration.

Through a large number of petrophysical experiments, the inventor found that the relationship between the resistivity increase coefficient (I) and the formation water saturation (Sw) is not the linear relationship in the logarithmic coordinates described by Archie, and the fluid saturation , porosity, wettability, shale content and other factors can cause non-Archie phenomenon, that is, the resistivity increase coefficient is not only related to fluid saturation, but also to porosity, wettability, shale content, etc. factors. Figures 2 to 4 are the relationship diagrams of the influence of shale content, porosity and wettability on the resistivity increase coefficient in rock physics experiments. As shown in Figure 2, when the shale content is low, the Archie's formula can be better met, and the lower the shale content, the more it deviates from the Archie's phenomenon. As shown in Fig. 3, when the rock porosity is high, the relationship between the resistivity increase coefficient (I) and the formation water saturation (Sw) can be well consistent with the Archie phenomenon, and as the rock porosity decreases, gradually exhibits a non-Archie phenomenon. Similarly, as shown in Figure 4, as the wettability changes, the resistivity increase coefficient (I) also changes, and different wettability can produce different non-Archie phenomena.

从而确定本发明的岩电关系模型，即On the basis of the above-mentioned large amount of petrophysical experiments, the present invention has carried out single-factor experimental analysis to the above factors through numerical simulation experiments, and determined that the saturation index n in the Archie's formula is not a constant, but a function of the above factors . Through the statistical analysis of the measurement results of each single factor analysis, it is determined that the function form is

Thereby determine the rock-electricity relationship model of the present invention, i.e.

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}^{{{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; US</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}}^{\frac{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vsh</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}^{\mathrm{<span\; class="notranslate">\; C</span>}}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

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

R ₀ - is the resistivity when the formation is 100% water-containing (resistivity unit is Ω·m);

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

Sw- is formation water saturation (decimal, or percentage, percentage=decimal×100%);

So- is the oil and gas saturation of the formation (decimal, or percentage, percentage=decimal×100%);

φ- is the porosity (decimal);

Vsh- is mud content (decimal);

U- is the wettability index (real number);

Y- is a parameter (real number);

C- is a constant (real number).

The _formula ⁽ ₂ ) to solve, we can get:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&phi;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}^{\mathrm{<span\; class="notranslate">\; c</span>}}}{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vsh</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

W(·)为lambertW函数。Rw为地层水的电阻率(单位为Ω·m)；a、m-为参数。In the formula,

W(·) is the lambertW function. Rw is the resistivity of formation water (unit: Ω·m); a, m- are parameters.

Based on actual physical tests and numerical simulations, the value of constant C in the new rock-electricity relationship model of the present invention can take any value in theory and can make this rock point relationship and the non-Archie phenomenon in the experiment have better However, for different regions, the characteristics of formation rocks and pore structure characteristics are different, and the calculation accuracy of the computer is limited, and considering the complexity of the calculation, the value of C should be adjusted in the establishment of the actual rock-electricity relationship model. preferred. The following factors can be mainly considered when optimizing: (1) the selection of C can fully show the influence of porosity φ; (2) the selection of C should make φ ^C within the appropriate calculable accuracy range; (3) the selection of C should make Y is within the appropriate calculable accuracy range; (4) The choice of C should make φ ^C easy to calculate.

)更易于计算，因此本实施例中可选择C为3/5，1/2、及3/10中的一个，优选地，本实施例选择C为1/2。The selection of the constant C is illustrated below with an example. Generally speaking, the variation range of formation porosity is between 0.4 and 0.01, so this range is taken as an example for analysis. Table 1 is a data analysis table for a certain region, which is used to determine the preferred value of C (the data in Table 1 is used to illustrate the present invention, but not to limit the present invention). Can analyze from table 1: 1. when C value is too small (as C=0.001), φ ^C hardly changes with the change of porosity φ, is almost a constant (φ ^C 0.99), the influence of porosity this moment Weakened, this embodiment can exclude these three C values of 0.1, 0.01, and 0.001 in the table under the situation that the influence of porosity needs to be fully considered; 2. When the C value is too large (such as C=10), φ ^C is very small (such as φ ^C ＝1E-20＝1×10 ^-20 ), almost 0, which has exceeded the calculation accuracy range of the computer. Therefore, considering the calculation accuracy of the computer and the appropriate value of φ ^C , this implementation For example, the two values C=10 and C=2 in the table can be excluded; 3. In addition, the choice of C should also make Y within the appropriate range of precision. When C<0.6 in the table, Y>0.1, at this time Y is within an appropriate range, which can ensure the accuracy of computer calculations, so the two C values of 1 and 0.7 in Table 1 can be excluded; 4. In addition, considering the difficulty of calculating φ ^C , it is obvious that 0.6 (that is, 3/ 5), 0.5 (i.e. 1/2) and 0.3 (i.e. 3/10), the φ ^C when C=1/2 (i.e.

) is easier to calculate, so in this embodiment, C can be selected as one of 3/5, 1/2, and 3/10. Preferably, in this embodiment, C is selected as 1/2.

Table 1.

The above selection of the value of C is only used to illustrate the present invention, but not to limit the present invention. Generally, the value of the constant C may be between -20 and 20. For the experimental data of different regions and different formation characteristics, there may be different C value ranges and preferred C values. When the accuracy of the computer or other corresponding calculation tools changes, the C value range may also be different (such as With the improvement of calculation accuracy, the constant C can take values in a larger range).

Fig. 5a to Fig. 5h respectively are corresponding to when C takes different numerical values (as C take respectively -20, -2, 1/10, 1/3, 1/2, 3/2, 9, 20) according to the formula (3 ) obtained by the resistivity increase coefficient (I) and formation water saturation (Sw) relationship curve and the experimental data, it can be seen that C can be applied to different values, and C takes -20, -2, 1/ 10, 1/3, 1/2, 3/2, 9, and 20 o'clock can all agree well with the experimental data.

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

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}^{{{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; US</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}}^{\frac{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vsh</span>}<span\; class="notranslate">\; )</span>}{\sqrt{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&phi;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}}{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vsh</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ,</span>$

In the formula, W(·) is the lambertW function.

The new rock-electricity relationship model proposed by the invention reflects the influence of fluid saturation, porosity, wettability, shale content and other factors on the rock-electricity relationship. The relationship between the resistivity increase coefficient (I) and formation water saturation (Sw) provided by the model is in good agreement with the non-Archie phenomenon in rock-electric experiments, and can accurately evaluate formation oil and gas content ( Formation oil and gas content So=1-Sw).

The following example illustrates how to evaluate formation fluid saturation (such as oil-gas saturation) according to the rock-electricity relationship model of the present invention.

Example 1

Firstly, the resistivity data Ro of the core is obtained when the core is completely saturated with water by rock electric experiment measurement, and then the resistivity data Rt of the core at different water saturations (Sw, and Sw+So=1) is obtained, and the value of Rt and Ro is used Ratio calculates the resistivity increase coefficient I, in order to make the applicable effect of the present invention better, when measuring, the distribution range of saturation should obtain wider, can be about 0.1 and should carry out corresponding measurement when water saturation.

For example: take a piece of core, its shale content Vsh=0, porosity φ=0.09.

The resistivity when it is fully saturated with water is measured as:

Ro＝147.5Ω·m

Then according to the resistivity data Rt of the rock core at different water saturations (Sw, and Sw+So=1), the ratio of Rt and Ro is used to calculate the resistivity increase coefficient I, and table 2 is the rock electric experiment of the present embodiment Measurement result:

Table 2.

Utilize Archie's formula and rock-electricity relationship model of the present invention respectively (in this embodiment, get C=1/2, promptly rock-electricity relationship is ) to analyze the data in Table 2, and the results are shown in Figure 6 and Figure 7 respectively. As can be seen from Fig. 6 and Fig. 7, there is a large error between the traditional Archie's formula (oblique line in Fig. 6) and the experimental data (rhombic point in Fig. 6), while the rock-electricity relationship model of the present invention (the curve in Fig. (Rhombic point in Figure 7) fit very well.

According to these obtained data, and utilizing the new rock-electricity relationship model provided by the present invention, the values of parameters Y and U can be obtained. For example, it is obtained: U=3.47, Y=0.14. For the same core, since the value of φ is determined, when C takes any value, a corresponding Y value can be obtained, so when C takes any value, the rock-electricity relationship model of this embodiment can be well matched with the experimental data.

After determining Y and U, using the underground reservoir Rt data obtained by logging technology (as shown in Fig. 8),

And through the analysis of a large amount of logging data in the area where the core is located, the applicable formation water resistivity Rw in this area can be obtained (for example, Rw = 0.12Ωm, the specific analysis method can refer to the related technology of logging data processing), so as to obtain where a and m are the parameters to determine the relationship between the formation factor F and the porosity φ (ie F=a/φm), and the determination method of its value can refer to the related technologies of well logging data processing.

等)，来定量计算地下储层中的流体饱和度情况，从而对储层的含油气量进行定量的评价。对含油气量的计算结果如图9所示。Then the water saturation calculation formula and related parameters (U, Y,

etc.), to quantitatively calculate the fluid saturation in the underground reservoir, so as to quantitatively evaluate the oil and gas content of the reservoir. The calculation results of oil and gas content are shown in Fig. 9.

Utilizing the new rock-electricity relationship model of the present invention to evaluate formation fluid saturation can accurately evaluate formation oil and gas content, can effectively improve the accuracy of reservoir oil and gas evaluation, thereby reducing oil and gas exploration risks.

It should be noted that the rock-electricity relationship model of the present invention is not limited to the form of formula (2), but may have different equivalent forms. For example:

优选地，C＝1/2时，

I. When shale content changes are not considered, the rock-electricity relationship is equivalent to

Preferably, when C=1/2,

以参数d的形式表示时，所述岩电关系等效为

(不考虑泥质含量和孔隙度的变化时，d为实数)；II. When changes in shale content and porosity are not considered, or when

When expressed in the form of parameter d, the rock-electricity relationship is equivalent to

(d is a real number when changes in shale content and porosity are not considered);

III. When the influence of porosity is not considered, the rock-electric relationship is equivalent to

IV. The above formulas (including formula (2)), without considering the influence of wettability (that is, not including U), are equivalent to

In the above formulas, the equivalent forms formed when the symbols used are changed are also applicable to the present invention.

In the traditional Archie's formula, the saturation index n is a constant, but in the rock-electricity relationship model of the present invention, the saturation index n is a function of factors such as fluid saturation, porosity, wettability, shale content, etc., its It reflects the influence of one or more factors in the distribution form of saturation itself, wettability, shale content, and porosity on the rock-electricity relationship. Depending on the factors considered, the saturation index can have different forms. For example:

优选地，C＝1/2时，

I. Considering the effects of fluid saturation, porosity, wettability, mud content and other factors comprehensively,

Preferably, when C=1/2,

优选地，C＝1/2时，

II. When shale content changes are not considered,

Preferably, when C=1/2,

III. When the effect of porosity is not considered,

(不考虑泥质含量和孔隙度的变化时，d为实数)；IV. When changes in shale content and porosity are not considered, or when When expressed in the form of parameter d,

(d is a real number when changes in shale content and porosity are not considered);

V. In the above formulas, the form when the influence of wettability (that is, U is not included) is not considered.

In the above formulas, the equivalent form of the saturation index formed when the sign used changes is also applicable to the present invention.

The new rock-electricity relationship model proposed by the invention reflects the influence of factors such as wettability and shale content on the rock-electricity relationship, and can reflect the non-Archie law of the rock-electricity relationship as a whole. Traditional Archie's formula is a special case of the rock-electricity relationship model of the present invention under certain conditions (such as ), that is, the present invention is not only applicable to the Archie phenomenon, but also the present invention is still applicable when the Archie's formula cannot be applied.

In summary, through the rock-electricity relationship model reflecting the non-Archie phenomenon proposed by the present invention, more accurate evaluation of formation oil and gas content can be realized, effectively reducing oil and gas exploration risks, thereby avoiding waste of production costs.

The above specific embodiments are only used to illustrate the present invention, but not to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (4)

1. A formation fluid saturation evaluation method, characterized in that: The following rock-electricity relationship model is used to evaluate formation fluid saturation: $\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}^{<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; US</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}^{\frac{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vsh</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}^{\mathrm{<span\; class="notranslate">\; c</span>}}}}}<span\; class="notranslate">\; ,</span>$ Among them, I is the resistivity increase coefficient; _R0 is the resistivity when the formation is 100% water-bearing, the unit is Ω m; R _t is the formation resistivity, the unit is Ω m; S _W is the water saturation of the formation; φ is porosity; Vsh is shale content; U is wettability index; Y is parameter; C is constant; For the rock-electricity relationship model combined with the relationship model F=R _o /R _w =a/φ ^m between the formation factor F and the formation porosity φ, the solution is obtained: ${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&phi;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}^{\mathrm{<span\; class="notranslate">\; c</span>}}}{\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vsh</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ,</span>$ in, $f\left(\mathrm{\&phi;}\right)=\frac{Y(1-\mathrm{Vsh})}{u{\mathrm{\&phi;}}^c}\&Center\; Dot;\ln \frac{a{R}_W}{R_t{\mathrm{\&phi;}}^m},$ W(·) is lambertW function; a, m are parameters; R _W is the resistivity of formation water, in Ω m; Formation oil and gas saturation So=1-Sw. 2. The method according to claim 1, characterized in that: When the influence of shale content is not considered, the rock-electricity relationship is equivalent to $I=\frac{R_t}{R_o}=S_W^{-{\mathrm{US}}_W^{\frac{Y}{{\mathrm{\&phi;}}^c}}};$ When the effects of shale content and porosity are not considered, the rock-electricity relationship is equivalent to $I=\frac{R_t}{R_o}=S_W^{-{\mathrm{US}}_W^d},$ where d is a real number; When the influence of porosity is not considered, the rock-electricity relationship is equivalent to $I=\frac{R_t}{R_o}=S_W^{-u{S}_W^{Y(1-\mathrm{Vsh})}}.$ 3. The method according to claim 1, characterized in that: When the influence of wettability is not considered, the lithoelectric relationship is equivalent to $I=\frac{R_t}{R_o}=S_W^{-S_W^{\frac{Y(1-\mathrm{Vsh})}{{\mathrm{\&phi;}}^c}}};$ When the influence of shale content and wettability is not considered, the rock-electricity relationship is equivalent to $I=\frac{R_t}{R_o}=S_W^{-S_W^{\frac{Y}{{\mathrm{\&phi;}}^c}}};$ When the effects of shale content, porosity and wettability are not considered, the rock-electricity relationship is equivalent to $I=\frac{R_t}{R_o}=S_W^{-S_W^d};$ When the effects of porosity and wettability are not considered, the rock-electricity relationship is equivalent to $I=\frac{R_t}{R_o}=S_W^{-S_W^{Y(1-\mathrm{Vsh})}}.$ 4. The method according to any one of claims 1-3, characterized in that: The value of the constant C is between -20 and 20.

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