CN104990854A - Method and device for determining irreducible water saturation - Google Patents

Abstract

The invention provides a method and device for determining irreducible water saturation. The method comprises the steps of measuring and inventing nuclear magnetic relaxation echo data of a core, and obtaining nuclear magnetic resonance transverse relaxation time T2 spectrum; measuring irreducible water saturation data of the core; according to the T2 spectrum, selecting transverse relaxation time T2 of different inversion distribution points as T2ct, and calculating optimized spectrum coefficients under the different T2ct; according to the optimized spectrum coefficients under the different T2ct, calculating nuclear magnetism irreducible water saturation of the core under the different T2ct; calculating errors between the irreducible water saturation of the core and the nuclear magnetism irreducible water saturation of the core under the different T2ct respectively, and when the minimum value is acquired for the errors, treating the corresponding optimized spectrum coefficient as the optimum spectrum coefficient and the corresponding nuclear magnetism irreducible water saturation as the optimum nuclear magnetism irreducible water saturation. According to the method and device for determining the irreducible water saturation, the optimum spectrum coefficient is obtained through the nuclear magnetic resonance method, according to the optimum spectrum coefficient, the irreducible water saturation is calculated, and the irreducible water saturation calculating precision is remarkably improved.

Description

Determine method and the device of irreducible water saturation

Technical field

The present invention relates to rock seepage flow characteristics studying technological domain, particularly a kind of method and device determining irreducible water saturation.

Background technology

Irreducible water saturation characterizes one of most important parameter of reservoir properties, in sand mud reservoir evaluation, play key effect.Along with reservoir shale index is higher, permeability variation is larger, and pore texture is more complicated, and its effect is more aobvious important, determines that difficulty is larger.Spectral coefficient method is a kind of method calculating rock irreducible water saturation, for the seepage flow characteristics of study of rocks.Existing spectral coefficient method, just simply utilizes the method for data fitting, obtains spectral coefficient, then, calculates the irreducible water saturation of rock according to spectral coefficient.The problem of this method is the spectral coefficient that can not obtain having better precision, namely cannot ensure to obtain optimum spectral coefficient to improve the computational accuracy of irreducible water saturation.

Summary of the invention

Embodiments provide a kind of method determining irreducible water saturation, obtain optimum spectral coefficient by optimization method, thus obtain optimum nuclear-magnetism irreducible water saturation, improve the computational accuracy of nuclear-magnetism irreducible water saturation.The method comprises:

The nuclear magnetic relaxation echo data of inverting rock core, obtains nuclear magnetic resonance T2 T ₂spectrum;

Obtain the Pore structure degrees of data of rock core;

According to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as T2 T ₂cutoff T _2ct, calculate different cutoff T _2ctunder optimization spectral coefficient;

According to different cutoff T _2ctunder optimization spectral coefficient, calculate different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core;

Calculate the irreducible water saturation of rock core and different cutoff T respectively _2ctunder the error of nuclear-magnetism irreducible water saturation of rock core, optimization spectral coefficient corresponding for the least error calculated is defined as optimum spectral coefficient, and the corresponding nuclear-magnetism irreducible water saturation of optimum spectral coefficient is defined as optimum nuclear-magnetism irreducible water saturation.

In one embodiment, described according to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as T2 T ₂cutoff T _2ct, calculate different cutoff T _2ctunder optimization spectral coefficient, calculate according to following formula:

$C_{bvi-nj}=\left\{\begin{array}{cc}1,& T_{2j}\≤T_{2ct}\\ \frac{1}{a\×T_{2j}+b},& T_{2j}>T_{2ct}\end{array}\right.;$

Wherein, C _bvi-njthe optimization spectral coefficient that the T2 of layouting for a jth inverting is corresponding, dimensionless;

T _2jfor the T2 that a jth inverting is layouted, ms;

T _2ctfor T2 T ₂cutoff, ms;

A, b are fitting coefficients.

In one embodiment, described fitting coefficient a, b obtains in the following manner:

The nuclear magnetic relaxation echo data of inverting polylith rock core, obtains the nuclear magnetic resonance T2 T of polylith rock core ₂spectrum;

According to T ₂spectrum, calculates the T2 T of polylith rock core ₂geometrical mean;

Obtain the Pore structure degrees of data of polylith rock core;

By the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching, obtain fitting coefficient a, b.

In one embodiment, described by the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching, calculate according to following formula:

$\frac{1}{S_{bvi}}=a\×T_{2lm}+b;$

Wherein, S _bviit is the irreducible water saturation of rock core;

T _2lmthe T2 T of rock core ₂geometrical mean, ms.

In one embodiment, described according to different cutoff T _2ctunder optimization spectral coefficient, calculate different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core, according to following formulae discovery;

${\mathrm{NS}}_{bvi}=\frac{\underset{j=1}{\overset{128}{\Σ}}{C}_{bvi-nj}{A}_j}{\underset{j=1}{\overset{128}{\Σ}}{A}_j};$

Wherein, NS _bvifor nuclear-magnetism irreducible water saturation;

A _jfor a jth inverting is layouted the range value of corresponding factor of porosity.

The embodiment of the present invention additionally provides a kind of device determining irreducible water saturation, obtains optimum spectral coefficient by optimization method, thus obtains optimum nuclear-magnetism irreducible water saturation, improves the computational accuracy of nuclear-magnetism irreducible water saturation.This device comprises:

T ₂spectrum acquiring unit, for the nuclear magnetic relaxation echo data of inverting rock core, obtains nuclear magnetic resonance T2 T ₂spectrum;

Irreducible water saturation acquiring unit, for obtaining the Pore structure degrees of data of rock core;

Optimize spectral coefficient acquiring unit, for according to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as T2 T ₂cutoff T _2ct, calculate different cutoff T _2ctunder optimization spectral coefficient;

Nuclear-magnetism irreducible water saturation acquiring unit, for according to different cutoff T _2ctunder optimization spectral coefficient, calculate different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core;

Optimum nuclear-magnetism irreducible water saturation determining unit, for calculating the irreducible water saturation of rock core and different cutoff T respectively _2ctunder the error of nuclear-magnetism irreducible water saturation of rock core, optimization spectral coefficient corresponding for the least error calculated is defined as optimum spectral coefficient, nuclear-magnetism irreducible water saturation corresponding for optimum spectral coefficient is defined as optimum nuclear-magnetism irreducible water saturation.

In one embodiment, described optimization spectral coefficient acquiring unit is specifically for being calculated as follows different cutoff T _2ctunder optimization spectral coefficient:

$C_{bvi-nj}=\left\{\begin{array}{cc}1,& T_{2j}\≤T_{2ct}\\ \frac{1}{a\×T_{2j}+b},& T_{2j}>T_{2ct}\end{array}\right.;$

Wherein, C _bvi-njthe optimization spectral coefficient that the T2 of layouting for a jth inverting is corresponding, dimensionless;

T _2jfor the T2 that a jth inverting is layouted, ms;

T _2ctfor T2 T ₂cutoff, ms;

A, b are fitting coefficients.

In one embodiment, described optimization spectral coefficient acquiring unit is specifically for obtaining described fitting coefficient a, b as follows:

The nuclear magnetic relaxation echo data of inverting polylith rock core, obtains the nuclear magnetic resonance T2 T of polylith rock core ₂spectrum;

According to T ₂spectrum, calculates the T2 T of polylith rock core ₂geometrical mean;

Obtain the Pore structure degrees of data of polylith rock core;

By the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching, obtain fitting coefficient a, b.

In one embodiment, described optimization spectral coefficient acquiring unit is specifically for pressing following formula by the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching:

$\frac{1}{S_{bvi}}=a\×T_{2lm}+b;$

Wherein, S _bviit is the irreducible water saturation of rock core;

T _2lmthe T2 T of rock core ₂geometrical mean, ms.

In one embodiment, described nuclear-magnetism irreducible water saturation acquiring unit is specifically for being calculated as follows different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core:

${\mathrm{NS}}_{bvi}=\frac{\underset{j=1}{\overset{128}{\Σ}}{C}_{bvi-nj}{A}_j}{\underset{j=1}{\overset{128}{\Σ}}{A}_j};$

Wherein, NS _bvifor nuclear-magnetism irreducible water saturation;

A _jfor a jth inverting is layouted the range value of corresponding factor of porosity.

In embodiments of the present invention, according to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as cutoff T _2ct, spectral coefficient is optimized, obtains different T _2ctunder optimization spectral coefficient, spectral coefficient according to optimizing calculates nuclear-magnetism irreducible water saturation, calculate the Pore structure degrees of data of rock core and the error of nuclear-magnetism irreducible water saturation, optimization spectral coefficient corresponding for the least error calculated is defined as optimum spectral coefficient, nuclear-magnetism irreducible water saturation corresponding for optimum spectral coefficient is defined as optimum nuclear-magnetism irreducible water saturation, spectral coefficient is obtained by simple data fitting with prior art, the method calculating the irreducible water saturation of rock again according to spectral coefficient is compared, adopt the inventive method can obtain the spectral coefficient with better precision, thus improve the computational accuracy of irreducible water saturation.

Accompanying drawing explanation

Accompanying drawing described herein is used to provide a further understanding of the present invention, forms a application's part, does not form limitation of the invention.In the accompanying drawings:

Fig. 1 is a kind of method flow diagram determining irreducible water saturation that the embodiment of the present invention provides;

Fig. 2 is a kind of nuclear magnetic resonance T2 T that the embodiment of the present invention provides ₂spectrum;

Fig. 3 is that the one that the embodiment of the present invention provides selects T _2ctthe method schematic diagram of transformation original spectrum coefficient;

Fig. 4 is a kind of structure drawing of device determining irreducible water saturation that the embodiment of the present invention provides;

Fig. 5 is the dependency diagram between a kind of irreducible water saturation using the irreducible water saturation of original spectrum coefficient calculations and experiment to record that the embodiment of the present invention provides;

Fig. 6 is that a kind of use that the embodiment of the present invention provides improves the irreducible water saturation that spectral coefficient calculates and the comparative result figure testing the irreducible water recorded;

Fig. 7 is that a kind of that the embodiment of the present invention provides improves the blind spot inspection X plot that spectral coefficient calculates irreducible water saturation.

Embodiment

For making the object, technical solutions and advantages of the present invention clearly understand, below in conjunction with embodiment and accompanying drawing, the present invention is described in further details.At this, exemplary embodiment of the present invention and illustrating for explaining the present invention, but not as a limitation of the invention.

Calculating in the algorithm of irreducible water saturation according to nuclear-magnetism experimental data, key to obtain rational spectral coefficient, and the existing method of data fitting that just simply utilizes obtains spectral coefficient, this method can not obtain the spectral coefficient of better precision, and the precision calculating the irreducible water saturation of gained equally according to spectral coefficient is also not high.If can propose a kind of method, obtain optimum spectral coefficient by being optimized spectral coefficient, the spectral coefficient according to optimum calculates nuclear-magnetism irreducible water saturation, just can improve the computational accuracy of irreducible water saturation.Based on this, the present invention proposes a kind of method determining irreducible water saturation.

Fig. 1 is a kind of method flow diagram determining irreducible water saturation that the embodiment of the present invention provides; As shown in Figure 1, the method comprises:

Step 101: experiment measuring the nuclear magnetic relaxation echo data of inverting rock core, obtains nuclear magnetic resonance T2 T ₂spectrum;

Step 102: the Pore structure degrees of data of experiment measuring rock core;

Step 103: according to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as cutoff T _2ct, calculate different T _2ctunder optimization spectral coefficient;

Step 104: according to different T _2ctunder optimization spectral coefficient, calculate different T _2ctunder the nuclear-magnetism irreducible water saturation of rock core;

Step 105: calculate the irreducible water saturation of rock core and different T respectively _2ctunder the error of nuclear-magnetism irreducible water saturation of rock core, when error obtains minimal value, corresponding optimization spectral coefficient is optimum spectral coefficient, and corresponding nuclear-magnetism irreducible water saturation is optimum nuclear-magnetism irreducible water saturation.

During concrete enforcement, before the nuclear magnetic relaxation echo data of inverting rock core, first will obtain the nuclear magnetic relaxation echo data that rock core is full of salt solution, and the method obtaining said data is specific as follows:

Step 1011: pre-service is carried out to experiment rock core, comprises washing oil, the desalinization of soil by flooding or leaching, dry, vacuumize.

Step 1012: configuration has the salt solution of certain salinity, the salinity of salt solution can be configured to 80000ppm (ppm is volumetric concentration, i.e. the volume number of contained pollutant in the air of 1,000,000 volumes).

Step 1013: use salt solution saturated core, measure the nuclear magnetic relaxation echo data that rock core is full of salt solution, and inverting nuclear magnetic relaxation echo data obtains T ₂spectrum.As shown in Figure 2, wherein T ₂the inverting range set of layouting of spectrum is between 0.01-10000ms, and choose 128 cloth point data, cloth point mode is logarithmic.

Concrete, obtain the MARAN Ultra nuclear-magnetism experiment instrument that rock core is full of the experimental apparatus employing Oxford Instruments of the nuclear magnetic relaxation echo data of salt solution.Simultaneously in order to ensure the precision of experimental data, in nuclear-magnetism experiment, the mode that suggestion adopts Multiple-Scan cumulative, improve the signal to noise ratio (S/N ratio) of data, the signal to noise ratio (S/N ratio) of experimental data is at least greater than 25.Because different inversion algorithms also can obtain the significant inverting T of comparison in difference ₂spectrum, this method suggestion adopts the algorithm based on svd (SVD).Unless expressly stated, following nuclear magnetic resonance measuring method and data inversion method similar.

In addition, the embodiment of the present invention also needs the Pore structure degrees of data obtaining rock core, and these data are by carrying out centrifugal to the above-mentioned rock core being full of salt solution, obtains the T of apocarpy as shown in Figure 2 ₂spectrum, then makes rock core be in Pore structure state, by measuring the Pore structure degrees of data obtaining rock core.

Because the existing precision according to original spectrum coefficient calculations irreducible water saturation is not high, therefore need to be optimized original spectrum coefficient, concrete optimization method is: at acquisition nuclear magnetic resonance T2 T ₂after spectrum, according to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as T2 T ₂cutoff T _2ct, calculate different cutoff T _2ctunder optimization spectral coefficient, specifically as shown in Figure 3.Wherein, SBVI model refers to the model calculating original spectrum coefficient; New model refers to the model of calculation optimization spectral coefficient; T2cutoff model refers to and calculates T2 T ₂the model of cutoff, C _bVIrepresent spectral coefficient.

According to the spectral coefficient that following formulae discovery is original:

$C_{bvi-oj}=\frac{1}{a\×T_{2j}+b}---\left(1\right)$

Wherein, C _bvi-ojthe original spectrum coefficient that the T2 of layouting for a jth inverting is corresponding, dimensionless;

T _2jfor the T2 that a jth inverting is layouted, ms;

A, b are fitting coefficients.

According to following formula, original spectrum coefficient is optimized:

$C_{bvi-nj}=\left\{\begin{array}{cc}1,& T_{2j}\≤T_{2ct}\\ \frac{1}{a\×T_{2j}+b},& T_{2j}>T_{2ct}\end{array}\right.---\left(2\right)$

Wherein, C _bvi-njthe optimization spectral coefficient that the T2 of layouting for a jth inverting is corresponding, dimensionless;

T _2ctfor T2 T ₂cutoff, ms.

Wherein, the fitting coefficient a in the fitting coefficient a in formula (1), b and formula (2), b is identical.Fitting coefficient a, b are unknown, need to obtain by the following method:

The first step: experiment measuring the nuclear magnetic relaxation echo data of inverting polylith (the present invention adopts 15 pieces) rock core (salt solution saturated core), obtains the nuclear magnetic resonance T2 T of polylith rock core ₂spectrum;

Second step: according to T ₂spectrum, calculates the T2 T of polylith rock core ₂geometrical mean;

3rd step: the Pore structure degrees of data of polylith rock core is measured in experiment (employing centrifugal method);

4th step: by the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out data fitting, obtain fitting coefficient a, b.

Data fitting formula is as follows:

$\frac{1}{S_{bvi}}=a\×T_{2lm}+b---\left(3\right)$

Wherein, S _bviit is the irreducible water saturation of rock core;

T _2lmthe T2 T of rock core ₂geometrical mean, ms.

Concrete experimental data (Pore structure degrees of data and T ₂geometrical mean) as shown in table 1.

Table 1

During concrete enforcement, after spectral coefficient that the optimization of original spectrum coefficient is optimized, calculate irreducible water saturation, namely according to different cutoff T according to optimization spectral coefficient _2ctunder optimization spectral coefficient, calculate different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core.Specifically according to following formulae discovery:

${\mathrm{NS}}_{bvi}=\frac{\underset{j=1}{\overset{128}{\Σ}}{C}_{bvi-nj}{A}_j}{\underset{j=1}{\overset{128}{\Σ}}{A}_j}---\left(4\right)$

Wherein, NS _bvifor nuclear-magnetism irreducible water saturation;

A _jfor a jth inverting is layouted the range value of corresponding factor of porosity.

During concrete enforcement, after the nuclear-magnetism irreducible water saturation obtaining multiple rock core, need the nuclear-magnetism irreducible water saturation determining that precision is the highest, concrete defining method is: calculate the irreducible water saturation of rock core and different cutoff T respectively _2ctunder the error of nuclear-magnetism irreducible water saturation of rock core, when will to calculate error be least error, its corresponding optimization spectral coefficient is defined as optimum spectral coefficient, and the corresponding nuclear-magnetism irreducible water saturation of optimum spectral coefficient is defined as optimum nuclear-magnetism irreducible water saturation.

Based on same inventive concept, additionally provide a kind of device determining irreducible water saturation in the embodiment of the present invention, as described in the following examples.Similar to determining the method for irreducible water saturation owing to determining the principle that the device of irreducible water saturation is dealt with problems, therefore determine that the enforcement of the device of irreducible water saturation see the enforcement of method determining irreducible water saturation, can repeat part and repeat no more.Following used, term " unit " or " module " can realize the software of predetermined function and/or the combination of hardware.Although the device described by following examples preferably realizes with software, hardware, or the realization of the combination of software and hardware also may and conceived.

Fig. 4 is a kind of apparatus structure block diagram determining irreducible water saturation of the embodiment of the present invention, and as shown in Figure 4, this device comprises:

T ₂spectrum acquiring unit 401, for the nuclear magnetic relaxation echo data of inverting rock core, obtains nuclear magnetic resonance T2 T ₂spectrum;

Irreducible water saturation acquiring unit 402, for obtaining the Pore structure degrees of data of rock core;

Optimize spectral coefficient acquiring unit 403, for according to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as T2 T ₂cutoff T _2ct, calculate different cutoff T _2ctunder optimization spectral coefficient;

Nuclear-magnetism irreducible water saturation acquiring unit 404, for according to different cutoff T _2ctunder optimization spectral coefficient, calculate different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core;

Optimum nuclear-magnetism irreducible water saturation determining unit 405, for calculating the irreducible water saturation of rock core and different cutoff T respectively _2ctunder the error of nuclear-magnetism irreducible water saturation of rock core, optimization spectral coefficient corresponding for the least error calculated is defined as optimum spectral coefficient, nuclear-magnetism irreducible water saturation corresponding for optimum spectral coefficient is defined as optimum nuclear-magnetism irreducible water saturation.

During concrete enforcement, optimize spectral coefficient acquiring unit 403 specifically for calculating different cutoff T by above-mentioned formula (2) _2ctunder optimization spectral coefficient, that is:

$C_{bvi-nj}=\left\{\begin{array}{cc}1,& T_{2j}\≤T_{2ct}\\ \frac{1}{a\×T_{2j}+b},& T_{2j}>T_{2ct}\end{array}\right.;$

Wherein, C _bvi-njthe optimization spectral coefficient that the T2 of layouting for a jth inverting is corresponding, dimensionless;

T _2ctfor T2 T ₂cutoff, ms.

Wherein, the fitting coefficient a in formula, b is unknown, needs to be asked for by certain method, and this is also the work that optimization spectral coefficient acquiring unit 403 will do.Concrete, optimize spectral coefficient acquiring unit 403 concrete also for obtaining fitting coefficient a as follows, b:

The nuclear magnetic relaxation echo data of inverting polylith rock core, obtains the nuclear magnetic resonance T2 T of polylith rock core ₂spectrum;

According to T ₂spectrum, calculates the T2 T of polylith rock core ₂geometrical mean;

Obtain the Pore structure degrees of data of polylith rock core;

By the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching, obtain fitting coefficient a, b.

Fit correlation formula is above-mentioned formula (3), that is:

$\frac{1}{S_{bvi}}=a\×T_{2lm}+b;$

Wherein, S _bviit is the irreducible water saturation of rock core;

T _2lmthe T2 T of rock core ₂geometrical mean, ms.

By obtaining optimization spectral coefficient to after the optimization of original spectrum coefficient, then calculate nuclear-magnetism irreducible water saturation by optimizing spectral coefficient, this is the work that nuclear-magnetism irreducible water saturation acquiring unit will do.Concrete, nuclear-magnetism irreducible water saturation acquiring unit 404 calculates nuclear-magnetism irreducible water saturation according to above-mentioned formula (4), that is:

${\mathrm{NS}}_{bvi}=\frac{\underset{j=1}{\overset{128}{\Σ}}{C}_{bvi-nj}{A}_j}{\underset{j=1}{\overset{128}{\Σ}}{A}_j};$

Wherein, NS _bvifor nuclear-magnetism irreducible water saturation;

A _jfor a jth inverting is layouted the range value of corresponding factor of porosity.

That calculate according to formula (4) is different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core, i.e. multiple nuclear-magnetism irreducible water saturation, then needs optimum nuclear-magnetism irreducible water saturation determining unit 405 to determine optimum nuclear-magnetism irreducible water saturation, and this optimum nuclear-magnetism irreducible water saturation is namely final required.

Below by the superiority of comparative illustration the inventive method and device.Fig. 5 is that the irreducible water saturation using original spectrum coefficient calculations gained irreducible water saturation and experiment to record compares, and uses original spectrum coefficient calculations gained irreducible water saturation to be 0.661 (r represents correlativity) with testing the irreducible water saturation correlativity between the two recorded.Fig. 6 uses optimization spectral coefficient to calculate gained irreducible water saturation and the comparative result figure testing the irreducible water saturation recorded, and using optimization spectral coefficient to calculate gained irreducible water saturation with testing the irreducible water saturation correlativity between the two recorded is 0.912.It can thus be appreciated that relative to traditional spectral coefficient computing method, the computational accuracy using the inventive method to optimize spectral coefficient calculating irreducible water saturation improves about 25%.

Utilize 7 blocks of rock cores to verify the inventive method below, detect also referred to as blind spot.As shown in table 2, wherein, second is classified as the irreducible water saturation BVI-NMR that other nuclear-magnetism methods obtain, the 3rd Pore structure degrees of data BVI-Core (S being classified as experiment measuring rock core _bvi); 4th is classified as the nuclear-magnetism irreducible water saturation NS using the inventive method to obtain _bvi; The 5th Pore structure degrees of data BVI-Core (S being classified as experiment measuring rock core _bvi) with use the nuclear-magnetism irreducible water saturation NS that obtains of the inventive method _bvibetween error.Fig. 7 uses the present invention to optimize spectral coefficient calculating gained irreducible water saturation and test the irreducible water saturation recorded to compare, known, the related coefficient that nuclear-magnetism calculates between irreducible water saturation and experiment test irreducible water saturation is 0.895, and average relative error is 12.45%.Relative to the calculating of original spectrum coefficient, greatly improve the computational accuracy of nuclear-magnetism irreducible water saturation.

The blind spot testing result of this invention, this inventive method has good applicability and good computational accuracy for rock nmr analysis data.

Table 2

Sample	BVI-NMR	BVI-Core(S bvi)	NS bvi	Err
					B284-71	0.4076	0.4309	0.423	0.054073
B284-72	0.2856	0.3294	0.285	0.132969
					B284-73	0.7474	0.7776	0.639	0.038837
B284-74	0.3308	0.3782	0.335	0.125331
					B284-75	0.2606	0.3063	0.289	0.1492
B284-76	0.4073	0.4831	0.393	0.156903
					B284-77	0.3597	0.4578	0.545	0.214286

Obviously, those skilled in the art should be understood that, each module of the above-mentioned embodiment of the present invention or each step can realize with general calculation element, they can concentrate on single calculation element, or be distributed on network that multiple calculation element forms, alternatively, they can realize with the executable program code of calculation element, thus, they can be stored and be performed by calculation element in the storage device, and in some cases, step shown or described by can performing with the order be different from herein, or they are made into each integrated circuit modules respectively, or the multiple module in them or step are made into single integrated circuit module to realize.Like this, the embodiment of the present invention is not restricted to any specific hardware and software combination.

The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the embodiment of the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1. determine a method for irreducible water saturation, it is characterized in that, comprising:

The nuclear magnetic relaxation echo data of inverting rock core, obtains nuclear magnetic resonance T2 T ₂spectrum;

Obtain the Pore structure degrees of data of rock core;

According to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as T2 T ₂cutoff T _2ct, calculate different cutoff T _2ctunder optimization spectral coefficient;

According to different cutoff T _2ctunder optimization spectral coefficient, calculate different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core;

Calculate the irreducible water saturation of rock core and different cutoff T respectively _2ctunder the error of nuclear-magnetism irreducible water saturation of rock core, optimization spectral coefficient corresponding for the least error calculated is defined as optimum spectral coefficient, and the corresponding nuclear-magnetism irreducible water saturation of optimum spectral coefficient is defined as optimum nuclear-magnetism irreducible water saturation.

2. the method for claim 1, is characterized in that, described according to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as T2 T ₂cutoff T _2ct, calculate different cutoff T _2ctunder optimization spectral coefficient, calculate according to following formula:

$C_{bvi-nj}=\left\{\begin{array}{cc}1,& T_{2j}\≤T_{2ct}\\ \frac{1}{a\×T_{2j}+b},& T_{2j}>T_{2ct}\end{array}\right.;$

Wherein, C _bvi-njthe optimization spectral coefficient that the T2 of layouting for a jth inverting is corresponding, dimensionless;

T _2jfor the T2 that a jth inverting is layouted, ms;

T _2ctfor T2 T ₂cutoff, ms;

A, b are fitting coefficients.

3. method as claimed in claim 2, it is characterized in that, described fitting coefficient a, b obtains in the following manner:

The nuclear magnetic relaxation echo data of inverting polylith rock core, obtains the nuclear magnetic resonance T2 T of polylith rock core ₂spectrum;

According to T ₂spectrum, calculates the T2 T of polylith rock core ₂geometrical mean;

Obtain the Pore structure degrees of data of polylith rock core;

By the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching, obtain fitting coefficient a, b.

4. method as claimed in claim 3, is characterized in that, described by the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching, calculate according to following formula:

$\frac{1}{S_{bvi}}=a\×T_{2lm}+b;$

Wherein, S _bviit is the irreducible water saturation of rock core;

T _2lmthe T2 T of rock core ₂geometrical mean, ms.

5. method as claimed in claim 2, is characterized in that, described according to different cutoff T _2ctunder optimization spectral coefficient, calculate different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core, according to following formulae discovery;

${\mathrm{NS}}_{bvi}=\frac{\underset{j=1}{\overset{128}{\Σ}}{C}_{bvi-nj}{A}_j}{\underset{j=1}{\overset{128}{\Σ}}{A}_j};$

Wherein, NS _bvifor nuclear-magnetism irreducible water saturation;

A _jfor a jth inverting is layouted the range value of corresponding factor of porosity.

6. determine a device for irreducible water saturation, it is characterized in that, comprising:

T ₂spectrum acquiring unit, for the nuclear magnetic relaxation echo data of inverting rock core, obtains nuclear magnetic resonance T2 T ₂spectrum;

Irreducible water saturation acquiring unit, for obtaining the Pore structure degrees of data of rock core;

Optimize spectral coefficient acquiring unit, for according to T ₂spectrum, selects the T2 T that different invertings is layouted ₂as T2 T ₂cutoff T _2ct, calculate different cutoff T _2ctunder optimization spectral coefficient;

Nuclear-magnetism irreducible water saturation acquiring unit, for according to different cutoff T _2ctunder optimization spectral coefficient, calculate different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core;

Optimum nuclear-magnetism irreducible water saturation determining unit, for calculating the irreducible water saturation of rock core and different cutoff T respectively _2ctunder the error of nuclear-magnetism irreducible water saturation of rock core, optimization spectral coefficient corresponding for the least error calculated is defined as optimum spectral coefficient, nuclear-magnetism irreducible water saturation corresponding for optimum spectral coefficient is defined as optimum nuclear-magnetism irreducible water saturation.

7. device as claimed in claim 6, it is characterized in that, described optimization spectral coefficient acquiring unit is specifically for being calculated as follows different cutoff T _2ctunder optimization spectral coefficient:

$C_{bvi-nj}=\left\{\begin{array}{cc}1,& T_{2j}\≤T_{2ct}\\ \frac{1}{a\×T_{2j}+b},& T_{2j}>T_{2ct}\end{array}\right.;$

Wherein, C _bvi-njthe optimization spectral coefficient that the T2 of layouting for a jth inverting is corresponding, dimensionless;

T _2jfor the T2 that a jth inverting is layouted, ms;

T _2ctfor T2 T ₂cutoff, ms;

A, b are fitting coefficients.

8. device as claimed in claim 7, it is characterized in that, described optimization spectral coefficient acquiring unit is specifically for obtaining described fitting coefficient a, b as follows:

The nuclear magnetic relaxation echo data of inverting polylith rock core, obtains the nuclear magnetic resonance T2 T of polylith rock core ₂spectrum;

According to T ₂spectrum, calculates the T2 T of polylith rock core ₂geometrical mean;

Obtain the Pore structure degrees of data of polylith rock core;

By the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching, obtain fitting coefficient a, b.

9. device as claimed in claim 8, is characterized in that, described optimization spectral coefficient acquiring unit is specifically for pressing following formula by the T2 T of the polylith rock core of gained ₂geometrical mean and the Pore structure degrees of data of polylith rock core carry out matching:

$\frac{1}{S_{bvi}}=a\×T_{2lm}+b;$

Wherein, S _bviit is the irreducible water saturation of rock core;

T _2lmthe T2 T of rock core ₂geometrical mean, ms.

10. device as claimed in claim 7, it is characterized in that, described nuclear-magnetism irreducible water saturation acquiring unit is specifically for being calculated as follows different cutoff T _2ctunder the nuclear-magnetism irreducible water saturation of rock core:

${\mathrm{NS}}_{bvi}=\frac{\underset{j=1}{\overset{128}{\Σ}}{C}_{bvi-nj}{A}_j}{\underset{j=1}{\overset{128}{\Σ}}{A}_j};$

Wherein, NS _bvifor nuclear-magnetism irreducible water saturation;

A _jfor a jth inverting is layouted the range value of corresponding factor of porosity.