A shale gas well fracturing effect evaluation method based on proppant detection experiment

Abstract

The application discloses a shale gas well fracturing effect evaluation method based on proppant detection experiment, and relates to the shale gas development field. The shale gas well fracturing effect evaluation method based on proppant detection experiment is to select a data well, select a data point in the data well, and sample drilling rock sample according to sampling design and selected well depth; the sampled rock sample is screened to obtain rock samples with different particle sizes; the rock sample with the same particle size as the proppant is selected and dispersed under a polarized fluorescence microscope for observation, and similar particles to the proppant are selected; the similar particles to the proppant are dried and placed under a scanning electron microscope for energy spectrum analysis to determine whether they are the proppant; and the fracturing scale is evaluated according to the experimental detection result and the interwell space relationship. The shale gas well fracturing effect evaluation method based on proppant detection experiment can accurately evaluate the fracture network distribution and the fracturing reconstruction scale after the shale gas volume fracturing.

Description

Technical Field

[0001] This application relates to the field of shale gas development, and more specifically, to a method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments. Background Technology

[0002] my country possesses abundant shale gas resources with enormous development potential. The efficient development of shale gas can significantly alleviate domestic energy shortages, promote reforms in the national energy production and consumption structure, and improve national energy security. Due to its self-generated and self-storing characteristics, shale gas exhibits extremely low porosity, extremely low permeability, and the coexistence of adsorbed and free gas. Lacking natural production capacity, it requires a "horizontal well + large-scale volumetric fracturing" production method, developed on a large scale using a "cluster horizontal well" operation mode. During hydraulic fracturing, after the fracturing fluid opens the formation, fracturing proppant needs to be injected into the formation. The length and scale of the fracture network are determined by detecting the proppant in the drilling cuttings. However, currently, there is no accurate method to evaluate the fracture network distribution and fracturing scale after shale gas volumetric fracturing, thus lacking a basis for production. Summary of the Invention

[0003] The purpose of this application is to provide a method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments. This method can accurately evaluate the fracture network distribution and fracturing scale after volumetric fracturing of shale gas wells, providing reliable experimental basis for shale gas well productivity evaluation and fracturing process optimization.

[0004] The embodiments of this application are implemented as follows:

[0005] This application provides a method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments, which includes the following steps:

[0006] S1. Select wells that are adjacent to the fracturing and testing wells in the shale gas production area as data collection wells;

[0007] S2. Calculate the spatial relationship between the fracturing test well and the data collection well using drilling inclination data, and select the well depth with the closest depth in the data collection well as the data collection point.

[0008] S3. Before drilling a data well or drilling into the target formation, conduct sampling design;

[0009] S4. After drilling into the target formation in the data acquisition well, take drilling cuttings samples according to the sampling design and selected well depth;

[0010] S5. The collected rock cuttings samples are sieved to obtain rock cuttings samples of different particle sizes;

[0011] S6. Select rock cutting samples with the same particle size as the proppant, disperse them under a polarized fluorescence microscope for observation, and select particles similar to the proppant.

[0012] S7. Fix particles similar to the proppant onto the sample drying stage, dry them, and then perform energy dispersive spectroscopy analysis under a scanning electron microscope to determine whether they are proppant.

[0013] S8. Evaluate the scale of fracturing based on experimental test results and the spatial relationship between wells.

[0014] In some alternative implementations, the distance between the well being drilled or not yet drilled and the well that has been fractured and tested is within 300m.

[0015] In some alternative implementations, the sampling design includes sampling well depth, sample weight, and sample handling requirements.

[0016] In some alternative implementations, when taking drilling cuttings samples, the sampling density is such that the interval between two samplings is at least 10 meters at a depth, and the weight of each sample is more than 250g.

[0017] In some alternative implementations, when rock cuttings samples with the same particle size as the proppant are dispersed and observed under a polarized fluorescence microscope, they are observed under single polarized light, reflected light, and fluorescence, respectively.

[0018] In some alternative implementations, when the sampled rock cuttings are contaminated with oil-based mud, the rock cuttings are washed with oil, dried, and then sieved.

[0019] The beneficial effects of this application are as follows: The method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments provided in this application includes the following steps: selecting adjacent wells in operation or not yet drilled within the shale gas production area that have completed fracturing testing as data collection wells; calculating the spatial relationship between the completed fracturing testing wells and data collection wells using drilling inclination data, and selecting the well depth closest to the data collection well as the data collection point; designing a sampling method before drilling the data collection well or before drilling into the target formation; after drilling the data collection well into the target formation, sampling drilling cuttings according to the sampling method and selected well depth; sieving the sampled cuttings to obtain cuttings samples of different particle sizes; selecting cuttings samples with the same particle size as the proppant and dispersing them under a polarized fluorescence microscope for observation, and selecting particles similar to the proppant; fixing particles similar to the proppant on a sample drying stage, drying them, and then conducting energy dispersive spectroscopy analysis under a scanning electron microscope to determine whether they are proppant; and evaluating the fracturing scale based on the experimental test results and the spatial relationship between wells. The shale gas well fracturing effect evaluation method based on proppant testing provided in this application can intuitively and effectively analyze the fracture range of underground shale through laboratory proppant testing and analysis experiments. This provides a basis for evaluating the fracturing effect of shale gas wells, establishing geological models, and evaluating production capacity. At the same time, this method uses drilling cuttings samples for testing, which has low sampling cost, simple method, low toxicity of indoor operation, and the testing instruments used are widely used in major laboratories in China. The testing process is fast and the results are intuitive. It is a method worth promoting for evaluating the fracturing effect of shale gas wells. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The spatial relationship diagram between the fracturing test wells and the data collection wells in the shale gas well fracturing effect evaluation method based on proppant testing provided in the embodiments of this application is calculated.

[0022] Figure 2 Photographs of fracturing proppant in rock cuttings samples observed under a polarizing microscope in the shale gas well fracturing effect evaluation method based on proppant detection experiments provided in the embodiments of this application;

[0023] Figure 3 The image shows a photograph of the fracturing proppant in a rock cuttings sample observed under a laboratory fluorescence microscope in the shale gas well fracturing effect evaluation method based on proppant detection experiments provided in the embodiments of this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] The following detailed description of the features and performance of the shale gas well fracturing effect evaluation method based on proppant testing experiments of this application is provided in conjunction with the embodiments.

[0026] This application provides a method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments, which includes the following steps:

[0027] S1. Select adjacent drilling wells or un-drilled wells within the shale gas production area that have completed fracturing and testing as data collection wells; the distance between the drilling well or un-drilled well and the drilling well should be within 300m.

[0028] S2. Calculate the spatial relationship between the fractured test wells and data collection wells using drilling inclination data, as follows: Figure 1 As shown, the well depth closest to the data collection point is selected as the data collection point.

[0029] S3. Before drilling a data well or drilling into the target formation, a sampling design should be carried out. The sampling design includes the sampling well depth, sample weight, and sample processing requirements.

[0030] S4. After drilling into the target formation, the drilling site personnel shall strictly follow the sampling design and select the well depth to collect drilling cuttings samples. After the samples are selected as required, they shall be placed in plastic self-sealing bags for preservation. Further processing shall be carried out in the laboratory. Screening, cleaning and other work shall not be carried out on site to avoid affecting the test results. When collecting drilling cuttings samples, the sampling density shall be such that the interval between two samplings is at least 10 meters at a depth, and the weight of each sample shall be more than 250g.

[0031] S5. The sampled rock cuttings are sieved to obtain rock cuttings samples of different particle sizes; when the sampled rock cuttings are contaminated by oil-based mud, the rock cuttings are washed with oil, dried and then sieved.

[0032] S6. Select rock fragment samples with the same particle size as the proppant and disperse them under a polarized fluorescence microscope for observation. Identify particles similar to the proppant. When observing rock fragment samples with the same particle size as the proppant under a polarized fluorescence microscope, observe them under single polarized light, reflected light, and fluorescence light respectively. Figure 2 and Figure 3 As shown.

[0033] S7. Fix particles similar to the proppant onto the sample drying stage, dry them, and then perform energy dispersive spectroscopy analysis under a scanning electron microscope to determine whether they are proppant.

[0034] S8. Evaluate the scale of fracturing based on experimental test results and the spatial relationship between wells.

[0035] The method for evaluating the fracturing effect of shale gas wells based on proppant testing provided in this application confirms the extension of artificial fractures and the coupling status of artificial-natural fractures, clarifies the reasonable well spacing for horizontal shale gas wells, guides the preparation of shale gas development plans and the deployment of development well locations, can make full use of the inter-well stimulation volume, avoid excessive overlap of gas supply ranges between wells, save drilling and fracturing investment, significantly improve the utilization of block reserves and the efficiency of gas field development, and provide a reference for determining the reasonable well spacing of shale blocks.

[0036] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments, characterized in that, It includes the following steps: S1. Select the wells that are being drilled adjacent to the fracturing and testing wells in the shale gas production area as data-gathering wells; S2. Calculate the spatial relationship between the fracturing and testing well and the data collection well using drilling inclination data. Select the well depth in the data collection well that is closest to the fracturing and testing well as the data collection point. S3. Before drilling a data well or drilling into the target formation, conduct sampling design; S4. After drilling into the target formation in the data acquisition well, take drilling cuttings samples according to the sampling design and selected well depth; S5. The collected rock cuttings samples are sieved to obtain rock cuttings samples of different particle sizes; S6. Select rock cutting samples with the same particle size as the proppant, disperse them under a polarized fluorescence microscope for observation, and select particles similar to the proppant. When rock cuttings with the same particle size as the proppant were dispersed and observed under a polarized fluorescence microscope, they were observed under single polarized light, reflected light, and fluorescence, respectively. S7. Fix particles similar to the proppant onto the sample drying stage, dry them, and then perform energy dispersive spectroscopy analysis under a scanning electron microscope to determine whether they are proppant. S8. Evaluate the scale of fracturing based on experimental test results and the spatial relationship between wells.

2. The method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments according to claim 1, characterized in that, The distance between a well that is being drilled or has not yet started drilling and a well that has completed fracturing and testing is within 300m.

3. The method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments according to claim 1, characterized in that, Sampling design includes sampling well depth, sample weight, and sample processing requirements.

4. The method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments according to claim 1, characterized in that, When taking samples of drilling cuttings, the sampling density should be such that the interval between two samplings is at least 10 meters at a depth, and the weight of each sample should be more than 250g.

5. The method for evaluating the fracturing effect of shale gas wells based on proppant testing experiments according to claim 1, characterized in that, When the rock cuttings samples are contaminated with oil-based mud, the rock cuttings samples are washed with oil, dried and then screened.

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