CN104345346A - Method for obtaining crack widths - Google Patents

Abstract

The embodiment of the invention provides a method for obtaining crack widths. The method comprises the following steps: obtaining a full-diameter core of a target stratum fracture section, wherein a natural crack exists in the middle of the full-diameter core; dividing the full-diameter core into two parts by taking the natural crack as a boundary, fabricating a crack model with different crack widths; obtaining stoneley wave relative amplitudes of the crack model at different crack widths; calculating the parameters of an equivalent crack width model according to the stoneley wave relative amplitudes; obtaining acoustic well logging data of the target stratum fracture section and determining the stoneley wave relative amplitude; calculating the crack width of the target stratum fracture section according to the stoneley wave relative amplitude of the target stratum fracture section and the equivalent crack width model. According to the crack width model built by the method disclosed by the embodiment of the invention, the real condition of a target stratum crack is reflected; the calculation method is relatively convenient and concise, and is convenient to rapid treatment of actual data.

Description

A kind of method obtaining fracture width

Technical field

The invention belongs to petroleum exploration domain, be specifically related to a kind of method obtaining fracture width.

Background technology

In carbonatite, volcanics and compact clastic rock reservoir, matrix permeability is often very low, and active to oil gas flowing is various cracks, and therefore, accurate identification and the evaluation in crack are significant to complicated reservoirs oil-gas exploration.

The parameter of fracture evaluation mainly comprises the density in crack, inclination angle and width, imaging logging new technology ratio is utilized to be easier to calculate fracture density, inclination angle, and the Obtaining Accurate of fracture width is comparatively difficult, it is also one of significant challenge faced in current logging evaluation.

At present, the detection method of fracture width mainly contains three major types: quantitatively detect according to the fracture width of al-lateral resistivity difference, detect according to the fracture width of high-resolution imaging well-log information and detect according to the fracture width of Stoneley wave attenuation amplitude.

When there is crack, in drilling process, slurry compounding is remarkable, due to depth bilateral to investigation depth different, therefore, slurry compounding is also different on the impact of resistivity, thus causes depth side direction resistivity there are differences.On numerical simulation study basis, a lot of scholar establishes the quantitative relationship between fracture width and al-lateral resistivity difference, but, fracture width is one of influence factor of deep and shallow resistivity difference, except fracture width, the size of the inclination angle in crack, the permeability on stratum itself, basement rock resistivity and reservoir water salinity etc. all have a significant impact to amplitude difference tool bilateral.Therefore, although according to bilateral to amplitude difference can carry out qualitative recognition by fracture, with regard to quantitative evaluation, its precision comparison is low.

Along with the development of surveying instrument and treatment technology, the effect of imaging logging new technology in fracture evaluation is increasing.But common fracture width is in micron number magnitude, the crack that can reach millimeter is fewer, and the highest resolution of imaging logging is 0.5cm, therefore, for fracture width, the resolution of imaging logging is still lower, and its accuracy of calculatingcrackswidth based on imaging logging is poor.

Because the size fracture width of Stoneley wave reflection coefficient is quick on the draw, therefore fracture width can be estimated with Stoneley wave.The now widely used Stoneley wave fracture width evaluation method being the people such as Hornby and proposing, roughly step is: first extract through Stoneley wave and reflected Stoneley-wave, utilizes deconvolution computing to obtain the reflection coefficient of Stoneley wave; And then the relation between the fracture width utilizing the people such as Hornby to propose and reflection coefficient calculates fracture width.It is to be noted, relation between the fracture width that the people such as Hornby propose and reflection coefficient proposes based on the tabular fractured model simplified, in actual formation, crack can not be flat, but has the Irregular Boundary Surface of certain concavo-convex change.Secondly, the inclination angle in the Analysis of Crack Width that the people such as Hornby propose and crack has much relations, and fracture dip is different, and the funtcional relationship between reflection coefficient and fracture width is different.Moreover the method needs calculating 0 rank and 1 rank Hankel function, and actual computation and program realize all more complicated.Therefore, set up a kind of easy, practical Stoneley wave equivalent crack opening computing method, have very important significance to containing fracture formation logging evaluation.

Summary of the invention

For the deficiency obtaining fracture width method in prior art, the object of the invention is to set up a kind of equivalent crack opening acquisition methods based on Stoneley wave, this invention proposes the new approaches accurately being determined undetermined parameter in fracture width and Stoneley wave relative amplitude explicit function relational expression by true stratum containing crack rock core shock tube experiment.

For achieving the above object, embodiments provide a kind of method obtaining fracture width, described method comprises:

Obtain object formation fracture interval full-hole core, in the middle of described full-hole core, there is a natural fracture;

With described natural fracture for described full-hole core is divided into two parts by boundary, make the fractured model with different fracture width;

Obtain the first Stoneley wave relative amplitude of described fractured model under different fracture width;

The parameter of equivalent crack opening model is calculated according to the first Stoneley wave relative amplitude of described fractured model under different fracture width;

Obtain described object formation fracture interval Sonic Logging Data and determine its second Stoneley wave relative amplitude;

According to the second Stoneley wave relative amplitude of described object formation fracture interval and the fracture width of described equivalent crack opening model calculating object formation fracture interval.

Preferably, in an embodiment of the present invention, described equivalent crack opening model is:

$R_{\mathrm{st}}=e^{-a({\mathrm{\β}}_f^{{\mathrm{\β}}_1}+{\mathrm{\ω}}_f^{{\mathrm{\β}}_2})}$

Wherein, R _stbe the first Stoneley wave relative amplitude, ω _ffor fracture width, α, β ₁, β ₂for model parameter.

Preferably, in an embodiment of the present invention, the described parameter according to the first Stoneley wave relative amplitude calculating equivalent crack opening model of described fractured model under different fracture width comprises:

Set up the R of the first Stoneley wave relative amplitude and fracture width _st-ω _fcoordinate system;

The experimental data point of the first Stoneley wave relative amplitude under described different fracture width is substituted into described R _st-ω _fin coordinate system;

Utilize experimental data point described in described equivalent crack opening models fitting, obtain α, β in described equivalent crack opening model ₁, β ₂parameter value.

Preferably, in an embodiment of the present invention, the first Stoneley wave relative amplitude of the described fractured model of described acquisition under different fracture width is obtained by shock tube experiment, comprising:

Obtain the first Stoneley wave amplitude that in shock tube, Stoneley wave records before crack;

Obtain the first Stoneley wave amplitude that described Stoneley wave records behind crack;

Calculate the ratio of the first Stoneley wave amplitude that described shock wave records behind crack and the first Stoneley wave amplitude that described Stoneley wave obtains before crack, obtain the relative amplitude of described first Stoneley wave, expression formula is:

$R_{\mathrm{st}}=\frac{A_{\mathrm{st}}({\mathrm{\ω}}_f=n)}{A_{\mathrm{st}}({\mathrm{\ω}}_f=0)}$

Wherein, R _stbe the first Stoneley wave relative amplitude, ω _ffor fracture width, A _st(ω _f=n) the first Stoneley wave amplitude of recording behind the crack that width is n for described Stoneley wave, A _st(ω _f=0) be the first Stoneley wave amplitude that described Stoneley wave records before crack.

Preferably, in an embodiment of the present invention, the rock core at described natural fracture two ends is without another cracks or microfracture.

Preferably, in an embodiment of the present invention, it is the fractured model that 1mm, 2mm, 4mm, 6mm etc. four kinds are different that the fractured model described in different fracture width comprises width.

Preferably, in an embodiment of the present invention, described acquisition described object formation fracture interval Sonic Logging Data also determines its second Stoneley wave relative amplitude, comprising: moved according to a fixed sample interval in the interval of described crack by acoustic logging instrument and obtain the Sonic Logging Data of described crack interval at different depth.

Preferably, in an embodiment of the present invention, acoustic logging instrument moved according to a fixed sample interval in the interval of described crack described and obtain described crack interval after the Sonic Logging Data of different depth, also comprising:

Extract the second Stoneley wave of described Sonic Logging Data, and calculate described crack interval at the second Stoneley wave amplitude of different depth and the second Stoneley wave relative amplitude.

The method of the acquisition fracture width that the embodiment of the present invention provides proposes the explicit function relational expression between fracture width and Stoneley wave relative amplitude first, this relational expression is simple and clear, direct, be convenient to model parameter determine and the process of real well data, this equivalent crack opening quantitative calculation method that the embodiment of the present invention is set up is easy, practical, significant to the quantitative evaluation of complicated reservoirs crack.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

Fig. 1 is the process flow diagram of the acquisition fracture width method that the embodiment of the present invention one proposes.

Fig. 2 is Stoneley wave experimental result when fracture width is 2mm in the embodiment of the present invention two, and wherein, ordinate is the pressure that sensor records, and the range value of its numerical values recited reflection Stoneley wave, horizontal ordinate is the distance of measurement point from shock tube transmitting site.

Fig. 3 is experimental data point and the matched curve of the Stoneley wave relative amplitude of full-hole core under different fracture width that in the embodiment of the present invention two, somewhere formation fracture interval is chosen, and wherein, horizontal ordinate is fracture width (ω _f), ordinate is Stoneley wave relative amplitude (R _st).

Fig. 4 is Sonic Logging Data and Stoneley wave relative amplitude after treatment and fracture width.

Embodiment

For making the object of the embodiment of the present invention, technical scheme and advantage clearly, below in conjunction with the accompanying drawing in the embodiment of the present invention, technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

Embodiment one

The embodiment of the present invention provides a kind of method obtaining fracture width, and Fig. 1 is the process flow diagram of the acquisition fracture width method of the present embodiment, and this flow process comprises the steps:

S101, obtains object formation fracture interval full-hole core, there is a natural fracture in the middle of this full-hole core.

In this step, full-hole core chosen two principle:

(1) there is an obvious natural fracture in rock core, be easy in laboratory conditions with this crack for rock core is divided into two parts by boundary, and do not damage the natural form in crack; (2) rock core at two ends, crack is without another cracks or microfracture.

Select above-mentioned rock core to make fractured model to have the following advantages: first, adopt fissureless true core as the base portion of fractured model, can not contain pore structure characteristic and the physical parameter such as factor of porosity, permeability such as type, distribution of rift portion hole in Reality simulation stratum completely; Secondly, select the rock core with obvious natural fracture, be easy in laboratory make real fracture plane.

S102, with described natural fracture for full-hole core is divided into two parts by boundary, makes the fractured model with different fracture width.

S103, obtains the Stoneley wave relative amplitude of fractured model under different fracture width.

Stoneley wave relative amplitude can by carrying out shock tube experiment realization to selected full-hole core.Shock tube is the direct measurement mechanism of a kind of novel Stoneley wave, by shock tube experiment, directly can not only measure Stoneley wave, and can study the rule that fracture width, inclination angle and distribution etc. affect Stoneley wave.Utilize the fractured model with different fracture width made in step S102, accurately can be obtained the Changing Pattern of full-hole core Stoneley wave relative amplitude under different fracture width by shock tube experiment.

S104, calculates the parameter of equivalent crack opening model according to the Stoneley wave relative amplitude of fractured model under different fracture width.

In order to form the Analysis of Crack Width based on Stoneley wave, on, experimental study theoretical in early stage is basic, the present invention proposes a kind of new formula calculating equivalent crack opening according to Stoneley wave relative amplitude first:

$R_{\mathrm{st}}=e^{-a({\mathrm{\ω}}_f^{{\mathrm{\β}}_1}+{\mathrm{\ω}}_f^{{\mathrm{\β}}_2})}---\left(1\right)$

In formula, ω _ffor fracture width (mm), α, β ₁, β ₂for model parameter, model parameter can be determined by shock tube experiment.

R _stfor the relative amplitude of the Stoneley wave that Stoneley wave in shock tube records before and after crack area, be defined as:

$R_{\mathrm{st}}=\frac{A_{\mathrm{st}}({\mathrm{\ω}}_f=n)}{A_{\mathrm{st}}({\mathrm{\ω}}_f=0)}---\left(2\right)$

In formula, A _st(ω _f=n) the Stoneley wave amplitude that records behind the crack that width is n (mm) for Stoneley wave in shock tube, A _st(ω _f=0) be Stoneley wave amplitude that Stoneley wave records before crack in fractured model.

The equivalent crack opening computing formula (1) that the present invention proposes gives the relation of the explicit function between fracture width and Stoneley wave relative amplitude, treat rational method as long as be determined through experimentation in actual applications in formula (1), just can calculate equivalent crack opening easily according to Stoneley wave relative amplitude.For former Analysis of Crack Width, this formula is more convenient, direct, is convenient to real data process.

S105, obtains described crack interval Sonic Logging Data and determines its Stoneley wave relative amplitude.

The defining method of Stoneley wave relative amplitude is described for Array Sonic Logging Waveforms.First according to the conventional method process Array Sonic Logging Waveforms of acoustic logging data process, extract Stoneley wave and calculate the amplitude of Stoneley wave at different depth, then calculating the relative amplitude of Stoneley wave.

Array acoustic well logger utensil has multiple receiving transducer, be generally 8, during well logging, logging instrumentation moves gradually according to sampling interval from the bottom up in object formation fracture section, when running into crack area, first the probe (as the 8th receiving transducer) on instrument top runs into crack, runs into crack after the probe (as the 1st receiving transducer) of instrument bottom.In sampling interval, by there is instrument bottom probe (as the 1st receiving transducer) below crack (without crack, do not affect by crack), the probe (as the 8th receiving transducer) on instrument top on crack (through crack, affect by crack) such situation, now Stoneley wave relative amplitude (ratio as the 8th receiving transducer Stoneley wave amplitude and the 1st receiving transducer Stoneley wave amplitude) is minimum near this employing interval.Because the spacing between instrument top receiving transducer and bottom receiving transducer is less, the impact that distance is propagated Stoneley wave is less, can ignore, and therefore above-mentioned relative amplitude mainly reflects the decay of crack to Stoneley wave.

S106, calculates the equivalent width in crack according to described crack interval Stoneley wave relative amplitude and described equivalent crack opening model.

The model parameter determined in the equivalent fissure computing formula (1) utilizing the present invention to propose and step S104, can calculate the equivalent width that object formation fracture grows interval crack easily.

Embodiment two

The present invention also provides a specific embodiment by experiment, and concrete implementation step is as follows:

1, choose somewhere formation fracture interval full-hole core by above-mentioned rock core selection principle, core diameter is 67mm, length is 45cm.An obvious natural fracture is there is in rock core, with this crack for boundary is easy to rock core to be divided into two sections in laboratory conditions, and the other parts except crack, lithology is dense, significantly do not stitch hole, be convenient to make and there is different fracture width and the fractured model with natural fracture region feature.

2, shock tube experiment is carried out to selected full-hole core.Under obtaining different fracture width, the quantitative rule that Stoneley wave is decayed through crack, to utilize in step 1 the full-hole core selected made width and be respectively 1mm, 2mm, 4mm, the fractured model that 6mm etc. four kinds are different, shock tube is utilized to carry out Stoneley wave measurement to each fractured model, obtain the amplitude of Stoneley wave under each fracture width, Fig. 2 above-mentionedly chooses Stoneley wave experimental result when rock core fracture width is 2mm, Stoneley wave is through rock core compression experiment gas, in figure, horizontal ordinate is the distance of measurement point from shock wave transmitting site, the pressure of ordinate measured by sensor, this force value is directly proportional to Stoneley wave range value.

3, the parameter in equivalent crack opening computation model is determined.By processing the experimental data in step 2, the change of Stoneley wave through the amplitude of different cracks decay can be obtained, first, setting up the rectangular coordinate system of Stoneley wave relative amplitude and fracture width, i.e. R _st-ω _fcoordinate system, as shown in Figure 3, substitutes into R by the data point of the Stoneley wave relative amplitude under different fracture width _st-ω _fin coordinate system, utilize the above-mentioned data point of formula (1) matching, α, β in formula (1) can be obtained ₁, β ₂model parameter value.Obtain through optimal fitting that this area formation fracture interval α is 0.157, β ₁be 0.275, β ₂be 0.643, the explicit function namely between Stoneley wave relative amplitude and equivalent crack opening is closed and is:

$R_{\mathrm{st}}=e^{-0.157({\mathrm{\ω}}_f^{0.275}+{\mathrm{\ω}}_f^{0.643})}---\left(3\right)$

4, crack interval Stoneley wave relative amplitude is determined according to Sonic Logging Data.First according to the Sonic Logging Data of this well of conventional method process of acoustic logging data process, extract Stoneley wave and calculate the relative amplitude of Stoneley wave at different depth, result is as shown in the 3rd road in Fig. 4.

5, equivalent crack opening calculates.According to the relative amplitude R of Stoneley wave before and after slit band calculated in step 4 _st, utilize the equivalent crack opening computing formula (3) obtained in step 3, the equivalent width that object formation fracture grows interval crack can be calculated easily, as shown in the 4th road in Fig. 4.

Embodiment of the present invention said method technical scheme has following beneficial effect: first, the determination of fracture width model parameter contains crack rock core shock tube experiment based on true stratum, therefore, the response model that the embodiment of the present invention one is set up more can reflect the truth of object formation fracture, and result of calculation also more accurately and reliably; Secondly, the Analysis of Crack Width that the present invention proposes is more convenient, succinct, is convenient to the fast processing of real data.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (8)

1. obtain a method for fracture width, it is characterized in that, described method comprises:

Obtain object formation fracture interval full-hole core, in the middle of described full-hole core, there is a natural fracture;

With described natural fracture for described full-hole core is divided into two parts by boundary, make the fractured model with different fracture width;

Obtain the first Stoneley wave relative amplitude of described fractured model under different fracture width;

The parameter of equivalent crack opening model is calculated according to the first Stoneley wave relative amplitude of described fractured model under different fracture width;

Obtain described object formation fracture interval Sonic Logging Data and determine its second Stoneley wave relative amplitude;

According to the second Stoneley wave relative amplitude of described object formation fracture interval and the fracture width of described equivalent crack opening model calculating object formation fracture interval.

2. the method for acquisition fracture width according to claim 1, is characterized in that, described equivalent crack opening model is:

$R_{\mathrm{st}}=e^{-a({\mathrm{\ω}}_f^{{\mathrm{\β}}_1}+{\mathrm{\ω}}_f^{{\mathrm{\β}}_2})}$

Wherein, R _stbe the first Stoneley wave relative amplitude, ω _ffor fracture width, α, β ₁, β ₂for model parameter.

3. the method for acquisition fracture width according to claim 1, is characterized in that, the described parameter according to the first Stoneley wave relative amplitude calculating equivalent crack opening model of described fractured model under different fracture width comprises:

Set up the R of the first Stoneley wave relative amplitude and fracture width _st-ω _fcoordinate system;

The experimental data point of the first Stoneley wave relative amplitude under described different fracture width is substituted into described R _st-ω _fin coordinate system;

Utilize experimental data point described in described equivalent crack opening models fitting, obtain α, β in described equivalent crack opening model ₁, β ₂parameter value.

4. the method for acquisition fracture width according to claim 1, is characterized in that, the first Stoneley wave relative amplitude of the described fractured model of described acquisition under different fracture width is obtained by shock tube experiment, comprising:

Obtain the first Stoneley wave amplitude that in shock tube, Stoneley wave records before crack;

Obtain the first Stoneley wave amplitude that Stoneley wave records behind crack;

Calculate the ratio of the first Stoneley wave amplitude that described shock wave records behind crack and the first Stoneley wave amplitude that described Stoneley wave obtains before crack, obtain the relative amplitude of described first Stoneley wave, expression formula is:

$R_{\mathrm{st}}=\frac{A_{\mathrm{st}}({\mathrm{\ω}}_f=n)}{A_{\mathrm{st}}({\mathrm{\ω}}_f=0)}$

Wherein, R _stbe the first Stoneley wave relative amplitude, ω _ffor fracture width, A _st(ω _f=n) the first Stoneley wave amplitude of recording behind the crack that width is n for described Stoneley wave, A _st(ω _f=0) be the first Stoneley wave amplitude that described Stoneley wave records before crack.

5. the method for acquisition fracture width according to claim 1, is characterized in that, the rock core at described natural fracture two ends is without another cracks or microfracture.

6. the method for acquisition fracture width according to claim 1, is characterized in that, described in there is different fracture width fractured model to comprise width be the fractured model that 1mm, 2mm, 4mm, 6mm etc. four kinds are different.

7. the method for acquisition fracture width according to claim 1, it is characterized in that, described acquisition described object formation fracture interval Sonic Logging Data also determines its second Stoneley wave relative amplitude, comprising: moved according to a fixed sample interval in the interval of described crack by acoustic logging instrument and obtain the Sonic Logging Data of described crack interval at different depth.

8. the method for acquisition fracture width according to claim 7, it is characterized in that, acoustic logging instrument moved according to a fixed sample interval in the interval of described crack described and obtain described crack interval after the Sonic Logging Data of different depth, also comprising:

Extract the second Stoneley wave of described Sonic Logging Data, and calculate described crack interval at the second Stoneley wave amplitude of different depth and the second Stoneley wave relative amplitude.