阅读说明：本技术 一种凝灰岩测井识别方法 (Tuff logging identification method ) 是由 夏冬冬 于 2019-02-18 设计创作，主要内容包括：本发明公开了一种凝灰岩测井识别方法,包括以下步骤：(1)建立地层凝灰岩综合识别模型；(2)根据地层凝灰岩综合识别模型,获取地层各深度采样点的凝灰岩综合识别指数；(3)根据地层各深度采样点的凝灰岩综合识别指数的大小,确定地层中是否存在凝灰岩。本发明能够利用测井手段在宏观层面进行地层凝灰岩高精度识别,避免单一测井曲线在识别凝灰岩过程中存在的容易误判和识别准确率低的弊端,准确快速地识别地层中的凝灰岩层。(The invention discloses a tuff logging identification method, which comprises the following steps: (1) establishing a stratum tuff comprehensive identification model; (2) acquiring tuff comprehensive identification indexes of each depth sampling point of the stratum according to the stratum tuff comprehensive identification model; (3) and determining whether tuff exists in the stratum according to the magnitude of the tuff comprehensive identification indexes of each depth sampling point of the stratum. The invention can utilize the logging means to carry out high-precision identification on the tuff of the stratum on a macroscopic level, avoids the defects of easy misjudgment and low identification accuracy of a single logging curve in the process of identifying the tuff, and accurately and quickly identifies the tuff in the stratum.)

1. A tuff logging identification method is characterized by comprising the following steps:

(1) establishing a stratum tuff comprehensive identification model;

(2) acquiring tuff comprehensive identification indexes of each depth sampling point of the stratum according to the stratum tuff comprehensive identification model;

(3) and determining whether tuff exists in the stratum according to the magnitude of the tuff comprehensive identification indexes of each depth sampling point of the stratum.

2. The tuff logging identification method of claim 1, wherein the comprehensive identification index value of the formation tuff is between 0.01 and 0.5, and the presence of the tuff in the formation is determined.

3. The tuff logging identification method of claim 1, wherein the comprehensive identification model of the formation tuff comprises a comprehensive identification index of the formation tuff.

4. The tuff log identification method of claim 2, wherein the formula according to which the formation tuff comprehensive identification index is determined is:

in the formula, LITH is the comprehensive identification index of the formation tuff, Δ GR is the relative value of the natural gamma of the formation,is the apparent acoustic wave porosity value of the pure rock skeleton of the stratum,the apparent density porosity value of the pure rock skeleton of the stratum is shown.

5. The method for identifying tuff logging according to claim 4, wherein the natural gamma relative values of the formation are obtained by calculation according to a natural gamma curve of the formation, and the natural gamma relative values of the formation are determined according to the formula:

in the formula, GR_maxIs the maximum value of the natural gamma value of the formation, GR_minIs the minimum value of the natural gamma value of the stratum, and GR is the tuff corresponding to each depth sampling point of the stratumBut the gamma value.

6. The tuff logging identification method of claim 5, wherein the apparent acoustic porosity of the pure rock framework of the formation is obtained by calculation according to the acoustic curve of the formation, and the apparent acoustic porosity of the pure rock framework of the formation is determined according to the following formula:

in the formula, AC_{Sandstone ma}For the acoustic wave skeleton value, AC, of the formation pure sandstone_{Shale ma}Is the acoustic wave skeleton value of the pure shale of the stratum, AC_{Sandstone ma}And AC_{Shale ma}And the AC is the tuff sound wave time difference value corresponding to each depth sampling point of the stratum.

7. The method for identifying a tuff log according to claim 6, wherein the apparent density porosity of the pure rock skeleton of the stratum is obtained by calculation according to a stratum density curve, and the formula according to which the apparent density porosity of the pure rock skeleton of the stratum is determined is as follows:

in the formula, DEN_{Sandstone ma}Is the density skeleton value of the stratum pure sandstone, DEN_{Shale ma}Is the density skeleton value of the pure shale of the stratum, DEN_{Sandstone ma}And DEN_{Shale ma}The DEN is a constant, and the DEN is the tuff density value corresponding to each depth sampling point of the reservoir in the test area.

8. The tuff logging identification method of claim 7, wherein the natural gamma value of the formation tuff is greater than the natural gamma value of the pure sandstone of the formation and less than the natural gamma value of the pure shale of the formation.

9. The method for identifying a tuff log according to claim 7, wherein the difference in the acoustic wave time of the formation tuff is greater than the acoustic wave skeleton value of the pure sandstone of the formation and less than the acoustic wave skeleton value of the pure shale of the formation.

10. The method of claim 7, wherein the value of the stratigraphic tuff density is less than the value of the stratigraphic pure sandstone density skeleton and greater than the value of the stratigraphic pure shale density skeleton.

Technical Field

The invention relates to a tuff logging identification method, and belongs to the field of logging.

Background

Under the condition that the lithological characteristics of the stratum are simple, lithological identification by utilizing natural gamma rays, resistivity and three-pore curves is a main method for dividing the lithological characteristics by using a logging technology. However, in the case of a formation having a complicated mineral composition and a special lithology, if lithology recognition is performed using only the curve, erroneous judgment is liable to occur and the recognition accuracy is low.

Tuff belongs to volcaniclastic rock, is rich in radioactive uranium, mainly contains quartz, feldspar, clay and pyrite, has the characteristics of igneous rock and sedimentary rock, has good oil-gas content, and is one of the targets of dense-shale oil exploration and development. However, as the logging response characteristics of tuff are complex and variable, the tuff shows high gamma characteristics similar to shale on a natural gamma curve; on the resistivity curve, tuff appears as a relatively high resistance, similar to shale, oil-bearing sandstone; on the three-porosity curve, the tuff is relatively low in sound wave, low in neutron and high in density, and is similar to tight sandstone, so that the tuff is difficult to distinguish from shale and sandstone by using a single logging curve, the recognition accuracy cannot achieve a satisfactory effect, and great difficulty is brought to the oil exploration and development of the tight-shale taking the tuff as a target.

The pyro-lithology is mentioned in the 'three-pond lake basin sedimentary tuff compact reservoir well logging evaluation technology and application' (lithologic oil and gas reservoir, 2015 4 months) that the two-section sedimentary tuff of the three-pond lake basin strip lake group shows the characteristics of 'three high and one low' on a well logging curve, namely high natural gamma, high acoustic wave time difference, high compensation neutrons and low density. The response characteristics of the tuff and mudstone on the log are similar, with the difference that the tuff has medium resistivity, while the mudstone is low resistivity; the tuff shows a higher potassium content than mudstone in the natural gamma spectrum. The method comprises the steps of establishing a two-section lithology identification chart of a lake bank group by utilizing 3 logging information of natural gamma, resistivity and acoustic wave time difference which are sensitive to lithology change response through core homing, and determining an identification standard of typical lithology, wherein the acoustic wave time difference of the cemented limestone is usually between 230 and 310 mu s/m (microseconds per meter), the natural gamma is more than 40API (1/200 of reading difference of a high-radioactivity stratum and a low-radioactivity stratum measured in a natural gamma logging graduated well), and the resistivity is between 10 and 100 omega m (omega). Although the standard can approximately separate the two-section tuff of the lake streak group from the mudstone and the basalt area, the logging identification standard established by the graphic method is a qualitative identification standard, has limited precision, is only suitable for identifying the two-section tuff of the lake streak group of the three ponds and has strong regional characteristics, so that the tuff identification standard is difficult to popularize in other regions.

Chinese patent application No. CN201610256740.0 relates to a method for identifying black oil-containing tuff based on a light reflection system of a polarization microscope. The method discloses a method for identifying tuff by using a light reflection system of a polarization microscope, which comprises the following steps: grinding an electronic probe sheet or a common rock sheet without a cover plate; and secondly, placing the electronic probe sheet or the common rock sheet without the cover plate under a polarization microscope, and observing and identifying under transmitted light and reflected light respectively. However, this method belongs to the microscopic lithology recognition category under the mirror, has a narrow viewing field, and has a limited effect on macroscopic tuff recognition.

The Chinese patent document with the application number of CN201310389139.5 relates to an identification method of particle-grade volcanic ash tuff. The method discloses a method for identifying particle-level volcanic ash tuff by using an orthogonal polarization microscope, however, the method belongs to the field of microscopic lithology identification under a mirror, so that the effect of the method on macroscopic tuff identification is still limited.

The traditional logging chart method for identifying tuff has the defects of low precision and poor popularization. Although the method for identifying tuff through the microscope has the advantage of high precision, microscopic identification under the microscope still has the defects of narrow visual field, difficulty in popularization on a macroscopic level and limited effect on macroscopic identification of the tuff.

Disclosure of Invention

In view of the above problems, the present invention aims to provide a tuff logging identification method, which can perform high-precision identification of formation tuff on a macroscopic level by using a logging means, avoid the disadvantages of easy misjudgment and low identification accuracy existing in the process of identifying tuff by using a single logging curve, and accurately and quickly identify the tuff in the formation.

In order to achieve the purpose, the invention adopts the following technical scheme: a tuff logging identification method is characterized by comprising the following steps: (1) establishing a stratum tuff comprehensive identification model; (2) acquiring tuff comprehensive identification indexes of each depth sampling point of the stratum according to the stratum tuff comprehensive identification model; (3) and determining whether tuff exists in the stratum according to the magnitude of the tuff comprehensive identification indexes of each depth sampling point of the stratum.

In one specific embodiment, the comprehensive identification index value of the formation tuff is between 0.01 and 0.5, and the tuff is determined to exist in the formation.

In a particular embodiment, the formation tuff comprehensive identification model includes a formation tuff comprehensive identification index.

In one embodiment, the formula according to which the comprehensive identification index of the formation tuff is determined is as follows:

in the formula, LITH is the comprehensive identification index of the formation tuff, Δ GR is the relative value of the natural gamma of the formation,is the apparent acoustic wave porosity value of the pure rock skeleton of the stratum,the apparent density porosity value of the pure rock skeleton of the stratum is shown.

In one embodiment, the formation natural gamma relative value is obtained by calculation according to a formation natural gamma curve, and the formula according to which the formation natural gamma relative value is determined is as follows:

in the formula, GR_maxIs the maximum value of the natural gamma value of the formation, GR_minAnd GR is the natural gamma value of tuff corresponding to each depth sampling point of the stratum.

In one specific embodiment, the apparent acoustic porosity of the pure rock skeleton of the stratum is obtained by calculation according to the stratum acoustic curve, and the formula for determining the apparent acoustic porosity of the pure rock skeleton of the stratum is as follows:

in the formula, AC_{Sandstone ma}For the acoustic wave skeleton value, AC, of the formation pure sandstone_{Shale ma}Is the acoustic wave skeleton value of the pure shale of the stratum, AC_{Sandstone ma}And AC_{Shale ma}And the AC is the tuff sound wave time difference value corresponding to each depth sampling point of the stratum.

In a specific embodiment, the apparent density porosity of the pure rock skeleton of the stratum is obtained by calculation according to a stratum density curve, and the formula for determining the apparent density porosity of the pure rock skeleton of the stratum is as follows:

in the formula, DEN_{Sandstone ma}Is the density skeleton value of the stratum pure sandstone, DEN_{Shale ma}Is the density skeleton value of the pure shale of the stratum, DEN_{Sandstone ma}And DEN_{Shale ma}The DEN is a constant, and the DEN is the tuff density value corresponding to each depth sampling point of the reservoir in the test area.

In a particular embodiment, the natural gamma value of the formation tuff is greater than the natural gamma value of the pure sandstone of the formation and less than the natural gamma value of the pure shale of the formation.

In one embodiment, the difference in the formation tuff sonic waves is greater than the formation pure sandstone sonic skeleton value and less than the formation pure shale sonic skeleton value.

In a particular embodiment, the formation tuff density value is less than the formation pure sandstone density skeleton value and greater than the formation pure shale density skeleton value.

Due to the adoption of the technical scheme, the invention has the following advantages: 1. the method utilizes the natural gamma relative value, the visual acoustic wave porosity and the visual density porosity to construct the comprehensive identification index of the tuff of the stratum to judge whether the tuff exists in the stratum or not, is simple and efficient, can avoid the defects of easy misjudgment and low identification accuracy of a single logging curve in the process of identifying the tuff, and provides technical support for the exploration and development of the tuff oil-gas layer. 2. The invention establishes the tuff identification quantitative standard and can improve the accuracy of identifying the tuff.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

In order to more clearly illustrate the technical solution in the embodiments of the present invention, the following briefly introduces the drawings required in the description of the embodiments:

FIG. 1 is a schematic flow chart diagram of one embodiment of a tuff log identification method of the present invention;

FIG. 2 is a diagram showing the effect of identifying 7 tuff at Bin 1 well length in the field of Baldos basin jing in China.

Detailed Description

The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.

As shown in fig. 1, the tuff logging identification method provided by the invention comprises the following steps:

(1) establishing a comprehensive identification model of formation tuff

And establishing a comprehensive identification model of the formation tuff, wherein the comprehensive identification model comprises a comprehensive identification index of the formation tuff.

The formula for determining the comprehensive identification index of the formation tuff is as follows:

in the formula, LITH is the comprehensive identification index of the formation tuff, Δ GR is the relative value of the natural gamma of the formation,is the apparent acoustic wave porosity value of the pure rock skeleton of the stratum,the apparent density porosity value of the pure rock skeleton of the stratum is shown.

Further, the formation includes a shale reservoir interval to be identified for a single well tuff.

Establishing relevant characteristic parameters of comprehensive identification of the formation tuff, and the specific process is as follows:

the method comprises the following steps of obtaining a stratum natural gamma relative value by calculation according to a stratum natural gamma curve, and determining the stratum natural gamma relative value according to the formula:

in the formula, GR_maxIs the maximum value of the natural gamma value of the formation, GR_minAnd GR is the natural gamma value of tuff corresponding to each depth sampling point of the stratum.

Specifically, when tuff exists in the stratum, due to radioactive uranium elements contained in the tuff of volcanic origin, during the deposition process, uranium elements in the tuff partially migrate to the adjacent shale, so that the natural gamma value of the tuff is far greater than that of sandstone but less than that of shale. Correspondingly, the natural gamma relative value of tuff is much greater than that of sandstone and smaller than that of shale. Therefore, the development degree of tuff can be qualitatively judged according to the stratum natural gamma relative value.

The apparent sound wave porosity of the stratum pure rock skeleton is obtained according to the calculation of the stratum sound wave curve, and the formula for determining the apparent sound wave porosity of the stratum pure rock skeleton is as follows:

in the formula, AC_{Sandstone ma}For the acoustic wave skeleton value, AC, of the formation pure sandstone_{Shale ma}Is the acoustic wave skeleton value of the pure shale of the stratum, AC_{Sandstone ma}And AC_{Shale ma}And the AC is the tuff sound wave time difference value corresponding to each depth sampling point of the stratum.

Wherein, the sound wave skeleton value of the stratum pure sandstone is 181 Mus/ft (microseconds/inch). The acoustic wave skeleton value of the pure shale of the stratum is 400 mu s/ft.

Specifically, when tuff is present in the formation, the difference in acoustic wave time is greatest due to shale, and the second is tuff, with the lowest sandstone. The porosity of the shale calculated by the formula (3) is the largest, the tuff is the second, and the sandstone is the lowest. Therefore, the development degree of the tuff can be qualitatively judged according to the visual-acoustic wave porosity of the stratum pure rock framework.

Calculating according to the stratum density curve to obtain the apparent density porosity of the stratum pure rock framework, wherein the formula for determining the apparent density porosity of the stratum pure rock framework is as follows:

in the formula, DEN_{Sandstone ma}Is the density skeleton value of the stratum pure sandstone, DEN_{Shale ma}Is the density skeleton value of the pure shale of the stratum, DEN_{Sandstone ma}And DEN_{Shale ma}The DEN is a constant, and the DEN is the tuff density value corresponding to each depth sampling point of the reservoir in the test area.

Wherein the density skeleton value of the stratum pure sandstone is 2.65g/cm³(g/cc). The density skeleton value of the stratum pure shale is 1.8g/cm³。

Specifically, when tuff is present in the formation, the shale has the lowest density skeleton value, the tuff is the second highest, and the sandstone is the highest. The porosity of the shale calculated by the formula (4) is the largest, the tuff is the second, and the sandstone is the lowest. Therefore, the development degree of the tuff can be qualitatively judged according to the apparent density porosity of the stratum pure rock framework.

(2) Acquiring tuff comprehensive identification indexes of each depth sampling point of the stratum according to the stratum tuff comprehensive identification model

And (3) calculating to obtain the numerical value of the tuff comprehensive identification index of each depth sampling point of the stratum according to the formula (1).

(3) Determining whether tuff exists in the stratum according to the magnitude of the tuff comprehensive identification indexes of each depth sampling point of the stratum

Specifically, the determination of whether tuff is present in the formation is based on the following rules:

and if the comprehensive identification index value of the tuff in the stratum is between 0.01 and 0.5, determining that the tuff exists in the stratum.

And if the comprehensive identification index value of the tuff of the stratum is less than 0.01 or more than 0.5, determining that the tuff does not exist in the stratum.

The method disclosed by the invention utilizes a logging means to carry out high-precision identification on the tuff of the stratum on a macroscopic level, avoids the defects of easy misjudgment and low identification accuracy in the process of identifying the tuff by using a single logging curve, and accurately and quickly identifies the tuff in the stratum. The quantitative standard for identifying the tuff in the stratum is established, the accuracy of a well logging technology in identifying the tuff can be greatly improved, and technical support is provided for exploration and development of tuff oil and gas layers.