Fracturing cluster opening monitoring method

Abstract

The invention relates to the technical field of oil and gas resource exploration and development, in particular to a fracturing cluster opening monitoring method which comprises the steps that the reservoir residual magnetism intensity before and after fracturing of a target interval of a newly-drilled horizontal well of a development horizon target is monitored, and the change amplitude of the residual magnetism of the target interval is determined; determining the opening condition of the fracturing cluster after the target interval is fractured; according to the change amplitude of the residual magnetism of the target interval and the opening condition of the fracturing cluster, determining a residual magnetism change critical value for judging the opening state of the fracturing cluster; the fracturing clusters with the residual magnetism change amplitude higher than the residual magnetism change critical value are judged to be opened, or else, the fracturing clusters are not opened. The method is not influenced by wellbore liquid, is wide in application range and low in cost, can visually judge whether the perforation cluster is opened or not through comparison before fracturing and after fracturing, is high in accuracy, and has important significance for optimizing a segmented clustering scheme and fracturing design and improving the cluster opening rate and the reservoir transformation effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas resource exploration and development, and is a fracturing cluster opening monitoring method. BACKGROUND

[0002] In recent years, more than 70% of the newly added proven oil reserves and more than 90% of the newly added proven natural gas reserves in China every year are low-porosity and low-permeability oil and gas reservoirs, and the proportion is still increasing year by year. Low-permeability oil and gas resources have become the main exploration and development object in China. For low-porosity and low-permeability reservoirs, large-scale volume modification is generally required to obtain commercial oil and gas flow, and large-scale segmented multi-cluster fracturing modification has become the main technology for increasing production.

[0003] The core of segmented multi-cluster fracturing is to form a complex fracture network system with a large swept volume in a low-permeability reservoir, to fully modify the reservoir, and to enable the oil and gas in the formation to flow into the wellbore. However, in the actual fracturing process, due to the influence of factors such as wellbore friction and reservoir heterogeneity, the perforation clusters in the fracturing section are selectively opened, some formations are over-modified, and some perforation clusters are not opened, so the reservoir is not modified. Therefore, monitoring the opening of the fracturing cluster and analyzing the factors affecting the opening of the cluster are of great significance for optimizing the segmented and clustered scheme and fracturing design, improving the cluster opening rate, and improving the reservoir modification effect and productivity.

[0004] Fracturing cluster opening monitoring technology can be divided into indirect monitoring technology and direct monitoring technology. Indirect monitoring technology includes net pressure analysis and pump-off pressure drop data analysis technology, and direct monitoring technology includes multi-arm caliper logging, imaging monitoring and microseismic monitoring technology.

[0005] A method for determining the opening sequence and opening efficiency of perforation clusters in a fracturing interval is disclosed in Chinese patent document CN111734375A. It is proposed that under the actual discharge condition in the field, the water dynamic pressure distribution along the wellbore to the fracture is obtained by applying the cluster friction calculation method, and according to the total discharge conservation, the mutual coupling effect of cluster flow and pressure is considered, and the effective opening and opening sequence of each perforation cluster are judged by the system friction and fracture pressure balance relationship. When judging, a system water dynamic balance mathematical model needs to be applied, and the calculation parameters involved are difficult to accurately obtain, and the prediction accuracy is biased.

[0006] Chen Jian in the paper "Multi-arm caliper instrument measurement accuracy influence factor analysis" (Petroleum Geology and Engineering, 2014 (03)) mentioned that the multi-arm caliper instrument is an instrument that mainly relies on mechanical methods to measure the inner diameter of the casing, and its biggest advantage is high measurement accuracy and intuitive measurement results. Through a large number of field application analysis, it is found that the main factors affecting the measurement accuracy of the multi-arm caliper instrument are whether the measurement is completely centered in the casing, whether the measurement arm body is deformed during measurement, the cleanliness of the well wall, and the influence of factors such as speed measurement. For segmented multi-cluster fractured horizontal wells, the multi-arm caliper instrument is usually connected by coiled tubing for monitoring, and the centering problem of the instrument in the horizontal section, the cleaning of the sand and scale at the bottom of the casing in the horizontal section, etc. It is difficult to solve, often leading to poor measurement accuracy.

[0007] Zang Chuanzhen et al. in the paper "Multi-cluster fracture uniform initiation degree analysis based on perforation imaging monitoring—take the dense conglomerate in Mahu Sag of Junggar Basin as an example" (Petroleum Exploration and Development, 2022 (02)) mentioned that downhole imaging monitoring technology can directly obtain a large number of high-definition perforation images, and by calculating the erosion area of the perforation (the area change before and after the perforation) can reflect the erosion degree of the perforation and determine whether the cluster is opened. The transparency of the liquid in the wellbore is high when downhole imaging monitoring is performed, otherwise the monitoring video will be unclear. For oil production wells, a large amount of liquid needs to be used to wash the well before monitoring, and the core technologies such as storage and transmission of video monitoring are monopolized by foreign countries, so the monitoring cost is high.

[0008] The current monitoring method for the opening of the fracturing cluster has certain limitations in applicability, evaluation accuracy and monitoring cost, and it is urgent to establish a monitoring method for the opening of the fracturing cluster to improve the monitoring accuracy and reduce the monitoring cost. SUMMARY

[0009] The present application provides a monitoring method for the opening of the fracturing cluster, which overcomes the shortcomings of the prior art and effectively solves the problems of poor applicability, low evaluation accuracy and high monitoring cost of the existing monitoring method for the opening of the fracturing cluster.

[0010] The technical scheme of the present application is realized by the following measures: a monitoring method for the opening of the fracturing cluster, comprising the following steps:

[0011] Monitoring the residual magnetic intensity of the reservoir before and after fracturing in the target new drilled horizontal well of the development layer, and determining the change amplitude of the residual magnetism of the target layer;

[0012] Determine the opening condition of the fracturing cluster after fracturing in the target layer;

[0013] Determine the residual magnetic change critical value for judging the opening state of the fracturing cluster according to the change amplitude of the residual magnetism of the target layer and the opening condition of the fracturing cluster; if the change amplitude of the residual magnetism is higher than the residual magnetic change critical value, the fracturing cluster is judged to be opened, otherwise it is not opened.

[0014] The following is a further optimization or / and improvement of the above technical solutions:

[0015] The above-mentioned monitoring of the residual magnetic intensity of the target interval of the newly completed horizontal well before and after fracturing of the target interval includes:

[0016] Step one, monitoring the residual magnetism of the target newly completed horizontal well to obtain the residual magnetic intensity of the reservoir before fracturing;

[0017] Step two, segmenting and multi-cluster fracturing the target newly completed horizontal well;

[0018] Step three, monitoring the residual magnetism of the target newly completed horizontal well after fracturing to obtain the residual magnetic intensity of the reservoir after fracturing.

[0019] In the above-mentioned step one and step three, the residual magnetism monitoring is in the form of connecting a coiled tubing to a residual magnetism monitor, and the monitoring is uniform speed dragging monitoring.

[0020] In the above-mentioned step one and step three, the speed of the uniform speed dragging monitoring is the same.

[0021] The speed of the uniform speed dragging monitoring is 4-12 m / min.

[0022] The above-mentioned determination of the change range of the residual magnetism of the target interval includes calculating the change range of the residual magnetism according to the following formula

[0023]

[0024] In the formula, F is the change range of the residual magnetism, B 压前 is the residual magnetic intensity of the reservoir before fracturing, and B 压后 is the residual magnetic intensity of the reservoir after fracturing.

[0025] The above-mentioned residual magnetism change critical value for judging the opening state of the fracturing cluster is the maximum change range of the residual magnetism of the fracturing cluster that is not opened in the target newly completed horizontal well.

[0026] The above-mentioned determination of the opening state of the fracturing cluster after fracturing of the target interval according to the downhole imaging monitoring result.

[0027] The present application provides a monitoring method for the opening of a fracturing cluster, which judges whether the fracturing cluster is opened by monitoring the change of the residual magnetic field of the reservoir before and after fracturing. The method is not affected by the wellbore liquid, has a wide range of applications, is low in cost, can intuitively judge whether the perforation cluster is opened through pre-fracturing and post-fracturing comparison, has high accuracy, and has important significance for optimizing the segmentation and clustering scheme, improving the fracturing design, improving the cluster opening rate, and improving the reservoir reconstruction effect. DETAILED DESCRIPTION

[0028] The present application is not limited by the following examples, and the specific implementation can be determined according to the technical solutions of the present application and the actual situation.

[0029] The present application is further described below in conjunction with examples:

[0030] Example 1: The monitoring method of the fracturing cluster opening includes the following steps:

[0031] Monitoring the residual magnetism of the reservoir before and after the fracturing of the target new drilled horizontal well in the development layer, determining the change range of the residual magnetism of the target layer;

[0032] Determining the opening situation of the fracturing cluster after the fracturing of the target layer;

[0033] According to the change range of the residual magnetism of the target layer and the opening situation of the fracturing cluster, determining the residual magnetism change critical value for judging the opening state of the fracturing cluster; if the change range of the residual magnetism is higher than the residual magnetism change critical value, the fracturing cluster is determined to be opened, otherwise it is determined to be not opened.

[0034] Example 2: As an optimization of the above-mentioned example, monitoring the residual magnetism of the reservoir before and after the fracturing of the target new drilled horizontal well in the development layer includes:

[0035] Step one, monitoring the residual magnetism of the target new drilled horizontal well to obtain the residual magnetism of the reservoir before the fracturing;

[0036] Step two, segmenting and multi-cluster fracturing the target new drilled horizontal well;

[0037] Step three, monitoring the residual magnetism of the target new drilled horizontal well after the fracturing to obtain the residual magnetism of the reservoir after the fracturing.

[0038] Example 3: As an optimization of the above-mentioned example, in step one and step three, the residual magnetism monitoring adopts the way of connecting the residual magnetism monitor with the coiled tubing, and the monitoring is uniform speed dragging monitoring.

[0039] Example 4: As an optimization of the above-mentioned example, in step one and step three, the residual magnetism monitoring, the speed of the uniform speed dragging monitoring is the same.

[0040] Example 5: As an optimization of the above-mentioned example, the speed of the uniform speed dragging monitoring is 4-12m / min.

[0041] Example 6: As an optimization of the above-mentioned example, determining the change range of the residual magnetism of the target layer includes calculating the change range of the residual magnetism according to the following formula

[0042]

[0043] Wherein, F is the change amplitude of the residual magnetism, B before pressure is the residual magnetism intensity of the reservoir before fracturing, and B after pressure is the residual magnetism intensity of the reservoir after fracturing.

[0044] Embodiment 7: As an optimization of the above-mentioned embodiments, the change critical value of the residual magnetism for judging the opening state of the fracturing cluster is the maximum change amplitude of the residual magnetism of the fracturing cluster that is not opened in the target newly drilled horizontal well.

[0045] Embodiment 8: As an optimization of the above-mentioned embodiments, the opening state of the fracturing cluster after the fracturing of the target layer is determined according to the downhole imaging monitoring result.

[0046] The present application solves the limitations of the current monitoring methods of the opening of the fracturing cluster, such as the downhole television and the pump pressure drop data analysis, by judging whether each perforation fracturing cluster is fractured or not according to the change of the residual magnetism of the rock in the target layer before the perforation fracturing and the residual magnetism of the rock in each layer after the segmented multi-cluster fracturing. The rock in the reservoir is magnetized by the earth magnetic field during the formation process, and the original natural residual magnetism is still retained in the rock. During the fracturing of the reservoir, the cooling effect of the fracturing fluid on the formation, the newly created fracturing cracks and the artificial proppant filled in the cracks all change the residual magnetism of the rock. By comparing before and after the fracturing, the opening of the perforation cluster can be judged according to the change amplitude of the residual magnetism of the rock at the position of the cluster. The advantage of the present application is that the residual magnetism monitoring instrument has a small outer diameter, does not need to be centered during the monitoring, is not affected by the liquid in the wellbore, has a wide range of applications and low cost. Meanwhile, by comparing before and after the fracturing, it can be directly judged whether the fracturing cluster is opened or not, and the accuracy is high.

[0047] Embodiment 9: The specific application of the monitoring method of the opening of the fracturing cluster in the shale oil reservoir of the Mahu Fengcheng group in Xinjiang oilfield is as follows:

[0048] For the shale oil reservoir of the Mahu Fengcheng group in Xinjiang oilfield, the newly drilled horizontal well MaHW002 is selected, the coiled tubing is connected with the storage type high-sensitivity residual magnetism monitoring instrument, the monitoring is carried out at a uniform speed of 10 meters per minute in the target layer (4900 meters to 5700 meters) of the well, the residual magnetism data of the reservoir before the fracturing are obtained, and the coiled tubing and the instrument are removed after the monitoring is completed.

[0049] The MaHW002 horizontal well is subjected to segmented multi-cluster fracturing, a total of 10 segments, 3 clusters of fracturing in each segment, the coiled tubing is used to drill the bridge plug after the fracturing, and the well is cleaned.

[0050] After the fracturing, the coiled tubing is connected with the storage type high-sensitivity residual magnetism monitoring instrument, the monitoring is carried out at a uniform speed of 10 meters per minute in the target layer, the monitoring speed is the same as that before the fracturing, the residual magnetism data of the reservoir after the fracturing are obtained, and the change amplitude of the residual magnetism of each fracturing cluster is calculated. In addition, the depth is positioned by comparing the data measured by the magnetic positioning instrument with the casing coupling data.

[0051] The downhole imaging device is connected by coiled tubing to monitor the erosion of the perforation hole and determine the opening state of each fracturing cluster.

[0052] As shown in Table 1, the maximum F value in the unopened fracturing cluster is 20%, and the critical value of the residual magnetic change for determining the opening state of the fracturing cluster in the Mahu Fengcheng shale oil reservoir is 20%.

[0053] For other new drilled horizontal wells in the Mahu Fengcheng shale oil reservoir, residual magnetic monitoring is performed before and after fracturing, and when the residual magnetic change amplitude F of the fracturing cluster is greater than 20%, the cluster is evaluated as opened; when the residual magnetic change amplitude F of the fracturing cluster is less than or equal to 20%, the cluster is evaluated as unopened.

[0054] The present application has been applied and verified in Xinjiang Oilfield, Tuha shale oil and other blocks, and has important significance for optimizing the segmented cluster scheme and fracturing design, improving the cluster opening rate and reservoir reconstruction effect.

[0055] In summary, the monitoring method of the fracturing cluster opening of the present application determines the critical value of the residual magnetic change for determining the opening state of the fracturing cluster by monitoring the change of the residual magnetic field of the formation before and after fracturing, combined with the downhole imaging monitoring result, improves the accuracy of the evaluation of the fracturing cluster opening, solves the problems of low accuracy of the current reliance on fracturing software and mathematical model simulation, high cost of downhole imaging monitoring and poor accuracy of multi-arm well diameter, the method is not affected by wellbore liquid, has wide application range and low cost, and has important significance for optimizing the segmented cluster scheme and fracturing design, improving the cluster opening rate and reservoir reconstruction effect.

[0056] The above technical features constitute an embodiment of the present application, which has strong adaptability and implementation effect, and unnecessary technical features can be added or reduced according to actual needs to meet the needs of different situations.

[0057] Table 1

[0058]

Claims

1. A method of monitoring the opening of a frac cluster, characterized by The method comprises the following steps: monitoring the residual magnetism of the reservoir before and after fracturing of the target new drilled horizontal well in the target interval of the development interval, determining the variation range of the residual magnetism of the target interval; determining the opening condition of the fracturing cluster after fracturing of the target interval; determining the residual magnetism variation critical value for judging the opening state of the fracturing cluster according to the variation range of the residual magnetism of the target interval and the opening condition of the fracturing cluster; if the variation range of the residual magnetism is higher than the residual magnetism variation critical value, the fracturing cluster is determined to be opened, otherwise, the fracturing cluster is determined to be not opened.

2. The method of monitoring the opening of a frac cluster of claim 1, wherein The monitoring of the residual magnetism of the reservoir before and after fracturing of the target new drilled horizontal well in the target interval of the development interval comprises: Step one, monitoring the residual magnetism of the target new drilled horizontal well to obtain the residual magnetism of the reservoir before fracturing; Step two, performing staged multi-cluster fracturing on the target new drilled horizontal well; Step three, monitoring the residual magnetism of the target new drilled horizontal well after fracturing to obtain the residual magnetism of the reservoir after fracturing.

3. The method of monitoring the opening of a frac cluster of claim 2, wherein In step one and step three, the residual magnetism monitoring is performed by connecting the coiled tubing with the residual magnetism monitor, and the monitoring is uniform speed dragging monitoring.

4. The method of monitoring the opening of a frac cluster of claim 3, wherein In step one and step three, the speed of the uniform speed dragging monitoring is the same.

5. The method of monitoring the opening of a frac cluster of claim 4, wherein The speed of the uniform speed dragging monitoring is 4-12 m / min.

6. The method of monitoring the opening of a frac cluster of any of claims 1-5, wherein The determination of the variation range of the residual magnetism of the target interval comprises calculating the variation range of the residual magnetism according to the following formula, where F is the amplitude of the change in remanence, B 压前 B0is the remanent intensity of the reservoir before fracturing, 压后 B1is the remanent intensity of the reservoir after fracturing.

7. The method of monitoring the opening of a frac cluster of any of claims 1-6, wherein The residual magnetism variation critical value for judging the opening state of the fracturing cluster is the maximum variation range of the residual magnetism of the fracturing cluster that is not opened in the target new drilled horizontal well.

8. The method of monitoring the opening of a frac cluster of any of claims 1-7, wherein The opening condition of the fracturing cluster after fracturing of the target interval is determined according to the downhole imaging monitoring result.

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