CN104950327B - The method for determining the position of the wave detector of ground micro-seismic observation system - Google Patents

Abstract

The present invention provides a kind of method of the position of the wave detector for determining ground micro-seismic observation system, including：A () obtains the existing data in work area, set up geological model；B () carries out fracture simulation according to the geological model, purpose layer depth and pressing crack construction scale, obtain the lateral extent that reservoir fracturing crack is involved；C lateral extent, purpose layer depth and microseism signal wavelength that () is involved according to reservoir fracturing crack determine the laying scope of wave detector；D () determines spacing according to microseism signal wavelength；E () determines the laying coordinate of each wave detector according to mouth coordinate, the laying scope of wave detector and road spacing.According to an exemplary embodiment of the present, the related monitoring task information such as parameter, target zone geologic feature of pressing crack construction scale is combined to be designed ground micro-seismic observation system, the pressure break rupture microseism signal of high-quality can be cost-effectively obtained, it is economical and practical.

Description

Method for determining the position of the geophone of a ground microseismic observation system

Technical Field

The present invention relates generally to the field of seismic exploration and, more particularly, to a method for locating geophones of a ground microseismic observation system for a target interval.

Background

Reservoir fracturing is one of important means for realizing high yield of low-permeability reservoirs, and the microseism monitoring technology is the most accurate, most timely and most abundant monitoring means in the current reservoir fracturing process. The microseism monitoring technology according to the arrangement position of the geophone is divided into ground microseism monitoring, shallow well microseism monitoring and deep well microseism monitoring.

The micro-seismic monitoring of the deep well needs to install a geophone string in one monitoring well near a fracturing well, the distance of the monitoring well has great influence on the monitoring effect, and the number of wells in the initial stage of exploration and development is small, so the application is limited. The shallow well micro-seismic monitoring needs to drill 3-5 shallow wells around the fracturing well, the construction cost is high, and the early preparation time is long. The ground micro-seismic monitoring is a method for determining the hydraulic fracturing fracture morphology of an oil-gas well by arranging a detector on the ground to receive micro-seismic signals released by rock fracture in the fracturing process, and is increasingly applied to the production practice of oil-gas fields at home and abroad. The microseism monitoring result can determine the fracture distribution geometrical form and the spatial characteristics and is used for evaluating the reservoir fracturing modification effect.

The ground micro-seismic monitoring construction condition has low requirements, but the micro-seismic signal energy for hydraulic fracturing rock fracture is weak, and is easily influenced by stratum attenuation and various ground interferences, and higher requirements are provided for signal acquisition. Therefore, the optimal design of the observation system is directly related to the reliability of ground micro-seismic monitoring, the design of the current ground micro-seismic monitoring observation system has low pertinence, and the quality of the obtained ground micro-seismic data is low.

In recent years, with the continuous deepening of the exploration and development of the shale gas in Sichuan, the ground micro-seismic monitoring service market is increased, and in order to economically and effectively obtain the micro-seismic signals for hydraulic fracturing rock fracture, accurately describe the fracture artificial fracture form and evaluate the reservoir volume transformation effect, a micro-seismic observation system design method capable of obtaining high-quality ground micro-seismic data is urgently needed.

Disclosure of Invention

The embodiment of the invention aims to provide a method for determining the position of a geophone of a ground micro-seismic observation system of a target layer, which can solve the problem that the ground micro-seismic data obtained by an observation system designed by the existing method is not high in quality.

An exemplary embodiment of the present invention provides a method of determining a position of a geophone of a ground microseismic observation system for a target interval, including: (a) acquiring the existing data of a work area, and establishing a geological model; (b) performing fracturing simulation according to the geological model, the depth of the target layer and the fracturing construction scale to obtain the transverse range of the reservoir fracturing fracture spread; (c) determining the layout range of the geophone according to the transverse range of the reservoir fracturing fracture spread, the depth of a target layer and the wavelength of the microseism signal; (d) determining the trace spacing according to the micro seismic signal wavelength; (e) and determining the layout coordinates of the detectors according to the coordinates of the well mouth, the layout range of the detectors and the track spacing.

Optionally, the step (b) includes performing fracture simulation to obtain the length of the liquid fracture according to the geological model, the depth of the target layer and the fracture construction scale, and determining a region included by a circle which takes the wellhead as a center and takes a half of the length of the liquid fracture as a radius as a lateral range of the reservoir fracture spread.

Optionally, the step (c) includes determining an imaging aperture according to the depth of a target layer and the wavelength of the micro seismic signal, uniformly taking a plurality of points on the boundary of the transverse range of the reservoir fracture spread, drawing a circle by taking each point of the plurality of points as a center and the imaging aperture as a radius, and determining a region where a union of all drawn circles is located as the distribution range of the geophone.

Optionally, the imaging aperture is sized such that the difference in travel of the lowest frequency signal of a microseism from a source on the destination to the detector closest to the source and the detector furthest from the source is at least half the microseismic signal wavelength.

Optionally, in step (c), the imaging aperture is determined according to the following formula:

wherein,p denotes the imaging aperture, d denotes the depth of the layer of interest, λ_maxRepresenting the longest wavelength of the microseismic signal.

Optionally, the trace spacing is of a size such that the difference in travel of the highest frequency signal of a microseismic from a source on the destination to any two adjacent detectors is no more than half the microseismic signal wavelength.

Optionally, the trace pitch is half of the shortest wavelength of the micro seismic signals.

Optionally, in step (e), the deployment coordinates of any one of the detectors are determined according to the following formula:

wherein (x)_ij，y_ij) Denotes the coordinates of the jth detector on the ith line, i ∈ [1, m]，j∈[1,n_i]M represents the total number of detectors, n_iRepresenting the number of receivers on the ith line, g represents the track spacing, and (x, y) represents the coordinates of the wellhead.

In the method for determining the position of the geophone of the ground micro-seismic observation system aiming at the target stratum according to the exemplary embodiment of the invention, the ground micro-seismic observation system is designed by integrating the parameters of the fracturing construction scale, the geological characteristics of the target stratum and other related monitoring task information, so that high-quality fracturing fracture micro-seismic signals can be obtained economically and effectively, and a foundation is laid for determining the fracturing artificial fracture form and the reservoir volume transformation effect. In addition, only the transverse range of reservoir fracturing fracture spread is considered in the calculation process, and parameters such as the longitudinal range, the fracturing pressure and the like are not considered, so that the method is economical and practical.

Drawings

The above and other objects and features of exemplary embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings which illustrate exemplary embodiments, wherein:

FIG. 1 shows a flow diagram of a method of determining a position of a geophone of a ground microseismic observation system for a layer of interest in accordance with an exemplary embodiment of the present invention;

FIG. 2 shows a schematic diagram of the extent of reservoir fracture sweep generated by a fracture simulation according to an exemplary embodiment of the present invention;

FIG. 3 shows a schematic diagram of the spread range of a detector according to an exemplary embodiment of the present invention.

Detailed Description

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below in order to explain the present invention by referring to the figures.

FIG. 1 shows a flow diagram of a method of determining a position of a geophone of a ground microseismic observation system for a layer of interest, according to an illustrative embodiment of the invention.

Referring to fig. 1, in step S10, the existing data of the work area is obtained, and a geological model is built. Here, the existing data of the work area may include at least one of: including well drilling data, well logging data, geological data, etc. As can be understood by those skilled in the art, the geological model can be built by constructing a stratum framework and obtaining information such as stratum speed, density, rock elastic parameters and the like through the existing data of a work area.

And S20, performing fracturing simulation according to the geological model, the depth of the target layer and the fracturing construction scale, and obtaining the transverse range of reservoir fracturing fracture spread. The fracturing construction scale is preset data, and for example, the fracturing construction scale can comprise data such as a pumping program, discharge capacity, sand concentration, liquid volume, sand volume and the like. The reservoir fracture spread is generally an ellipsoid, and the transverse range of the reservoir fracture spread is a plane where the ellipsoid intersects the target layer. Here, the fracture simulation software may input parameters related to the geological model, the depth of the target layer, the scale of the fracture construction, and the like, and perform the fracture simulation.

In step S20, a fracture simulation may be performed to obtain the length of the liquid fracture, and a region encompassed by a circle centered on the wellhead and having a radius of half the length of the liquid fracture is determined as a lateral extent of the reservoir fracture sweep. The wellhead refers to a wellhead of a vertical well. After inputting relevant parameters such as the geological model, the depth of the target zone, and the fracturing construction scale (for example, the liquid volume is 1500 square, the sand volume is 70 square) in the fracturing simulation software, and performing fracturing simulation, a range 2 of a reservoir fracturing fracture wave generated by the fracturing simulation according to the exemplary embodiment of the present invention shown in fig. 2 is obtained, the length L of the liquid fracture is 380 meters, and the lateral range of the reservoir fracturing fracture wave is an area enclosed by a circle which takes the wellhead position 4 of the vertical well 1 in the target interval 3 as the center and takes half of the length L of the liquid fracture as the radius.

In step S30, the distribution range of the geophones is determined according to the transverse range of the reservoir fracture spread, the depth of the target layer and the wavelength of the micro seismic signal. Here, the deployment range of the geophone refers to the geographical range over which the geophone is deployed on the ground. The deployment range of the geophones can be determined from the lateral extent of the reservoir fracture sweep, the depth of the target zone, and the micro-seismic signal wavelength in various suitable ways. For example, as shown in fig. 3, the layout range of the geophone according to the exemplary embodiment of the present invention may be determined by determining an imaging aperture r according to the depth of a target layer and the wavelength of a microseismic signal, uniformly taking four points 5 on the boundary of the lateral range of the reservoir fracture spread, drawing four circles with each point 5 of the four points 5 as a center and the imaging aperture as a radius r, and determining the region where the union of the four circles is located as the layout range of the geophone. Those skilled in the art will appreciate that the number of points taken on the boundary of the lateral extent is not limited to four, but may be other numbers.

Here, the imaging aperture is sized such that the difference in travel of the lowest frequency microseismic signal from the source on the destination to the detector closest to the source and the detector furthest from the source is at least half the microseismic signal wavelength. The imaging aperture may be determined by the following equation (1).

Where p denotes the imaging aperture, d denotes the depth of the layer of interest, λ_maxRepresenting the longest wavelength of the microseismic signal. Those skilled in the art will appreciate that the manner in which the imaging aperture is calculated according to the exemplary embodiment of the present invention is not limited to the manner of equation (1), and the imaging aperture may be determined in other suitable manners.

In step S40, trace spacing is determined based on the microseismic signal wavelengths. Here, the track pitch refers to a distance between adjacent detectors on the same line. The trace spacing is required to be large enough to ensure that the difference of the travel of the maximum frequency signal of the micro earthquake from the earthquake source on the target layer to any two adjacent detectors is not more than half of the wavelength of the micro earthquake signal. To simplify the calculation, the trace spacing may be sized to be half the shortest wavelength of the microseismic signals.

Those skilled in the art will appreciate that the step numbers of step S30 and step S40 are not used to limit the execution order, and either step may be executed first.

In step S50, the layout coordinates of each geophone are determined according to the wellhead coordinates, the layout range of the geophone and the track pitch. The wellhead coordinates are those of the vertical well at the surface.

Alternatively, in S step 50, the layout coordinates of any one of the detectors may be determined according to equations (2) and (3):

wherein (x)_ij，y_ij) Denotes the distribution coordinates of the jth detector on the ith line, i ∈ [1, m]，j∈[1,n_i]M represents the total number of detectors, n_iRepresenting the number of receivers on the ith line, g represents the track spacing, and (x, y) represents the coordinates of the wellhead. Here, the number m of the detector bus lines is preset data. Number n of detectors on ith line_iThe length of the detectors in the ith line is obtained by dividing the length of the detectors in the ith line by the track pitch, and the length of the detectors in the ith line can be determined according to the azimuth angle of the ith lineAnd the layout range of the detector.

Those skilled in the art will appreciate that the manner of calculating the layout coordinates of the detectors according to the exemplary embodiment of the present invention is not limited to the manner of equations (2) and (3), and may be determined in other suitable manners.

After the layout coordinates of the detectors on each line are determined, parameters related to the detectors in the ground micro-seismic observation system, such as arrangement length of the detectors, channel spacing, total number of the detectors, layout coordinates of the detectors and the like, can be output.

According to the method for determining the position of the geophone of the ground micro-seismic observation system aiming at the target stratum, related monitoring task information such as parameters of fracturing construction scale and geological features of the target stratum is integrated to design the ground micro-seismic observation system, high-quality fracturing fracture micro-seismic signals can be obtained economically and effectively, a foundation is laid for determining the fracturing artificial fracture form and the reservoir volume transformation effect, and the method is economical and practical.

The above-described method according to an exemplary embodiment of the present invention may be implemented by an apparatus for designing a ground micro-seismic observation system for a target zone, and may also be implemented as a computer program so that when the program is executed, the above-described method is implemented.

Although a few exemplary embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

Claims (7)

1. A method of determining a position of a geophone of a ground microseismic observation system for a layer of interest, comprising:

(a) acquiring the existing data of a work area, and establishing a geological model;

(b) performing fracturing simulation according to the geological model, the depth of the target layer and the fracturing construction scale to obtain the transverse range of the reservoir fracturing fracture spread;

(c) determining the layout range of the geophone according to the transverse range of the reservoir fracturing fracture spread, the depth of a target layer and the wavelength of the microseism signal;

(d) determining the trace spacing according to the micro seismic signal wavelength;

(e) determining the layout coordinates of all the detectors according to the coordinates of the well mouth, the layout range of the detectors and the track spacing;

and (b) performing fracturing simulation according to the geological model, the target layer depth and the fracturing construction scale to obtain the length of the liquid fracture, and determining a region included by a circle which takes a well head as a circle center and takes half of the length of the liquid fracture as a radius as a transverse range of the reservoir fracturing fracture wave.

2. The method of claim 1, wherein step (c) comprises determining an imaging aperture based on the depth of the target layer and the wavelength of the micro seismic signal, uniformly taking a plurality of points on the boundary of the lateral range of the reservoir fracture spread, drawing a circle with each point of the plurality of points as a center and the imaging aperture as a radius, and determining the region where the union of all the drawn circles is located as the distribution range of the geophones.

3. The method of claim 2, wherein the imaging aperture is sized such that the difference in travel of the lowest frequency signal of a microseism from a source on the destination to a detector closest to the source and a detector furthest from the source is at least half the microseismic signal wavelength.

4. The method of claim 3, wherein in step (c), the imaging aperture is determined according to the following formula:

$p=\sqrt{{(d+{\mathrm{\λ}}_{max}/2)}^2-d^2},$

where p denotes the imaging aperture, d denotes the depth of the layer of interest, λ_maxRepresenting the longest wavelength of the microseismic signal.

5. The method of claim 1, wherein the trace spacing is of a size such that the difference in travel of the highest frequency signal of a microseism from a source on the destination to any two adjacent detectors is no more than half a microseismic signal wavelength.

6. The method of claim 5, wherein the trace pitch is one-half of the shortest wavelength of the microseismic signals.

7. The method of claim 1, wherein in step (e), the deployment coordinates of any one of the detectors are determined according to the following formula:

$x_{ij}=g\×j\×cos\left(\right(90-\frac{360\×i}{m})\×\frac{\mathrm{\π}}{180})+x,$

$y_{ij}=g\×j\×sin\left(\right(90-\frac{360\×i}{m})\×\frac{\mathrm{\π}}{180})+y,$

wherein (x)_ij，y_ij) Denotes the coordinates of the jth detector on the ith line, i ∈ [1, m]，j∈[1,n_i]M represents the total number of detectors, n_iRepresenting the number of receivers on the ith line, g represents the track spacing, and (x, y) represents the coordinates of the wellhead.