Horizontal well fracturing crack width monitoring method

Abstract

The invention relates to the technical field of exploration and development of oil and gas resources, in particular to a horizontal well fracturing crack width monitoring method which comprises the following steps: step 1, assembling a test pipe string; 2, the test pipe string is put into a newly-drilled horizontal well, and the test pipe string is dragged at a first constant speed in a target interval; and thirdly, the test pipe string is pulled out, and segmented multi-cluster fracturing is conducted on the horizontal well. According to the horizontal well fracturing crack width monitoring method, the fracturing crack width is judged by monitoring the half amplitude point of change of a reservoir residual magnetic field before and after fracturing, in the process that a reservoir is fractured, the cooling effect of fracturing fluid on a stratum, a newly-made fracturing crack and the crack filled with an artificial proppant can change residual magnetism of rocks, and the fracturing crack width is judged. Through comparison of the residual magnetic curves before and after fracturing, the residual magnetic curves have change inflection points, and the distance between the two half-amplitude points is the width of the extended wave of the fracturing crack, so that the accuracy of monitoring the width of the fracturing crack is improved, and meanwhile, the method is low in monitoring process cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas resource exploration and development, and is a horizontal well fracture width monitoring method. BACKGROUND

[0002] In recent years, low-porosity and low-permeability oil and gas reservoirs have become the focus of exploration and development. In order to improve single-well productivity and reduce development costs, multi-stage segmented multi-cluster fracturing of horizontal wells has become a key technology for benefit development. In the horizontal well segmented fracturing technology, the segmented and clustered parameter design is a key factor affecting reservoir reconstruction. An excessively large cluster spacing will generate an un-reconstructed area between the fractures, affecting the reservoir producing degree, and an excessively small cluster spacing will cause the reconstructed area to overlap between the cluster fractures, reducing the reconstruction efficiency. In order to improve the fracturing reconstruction effect, it is necessary to monitor the fracturing width to provide a basis for optimizing the cluster spacing.

[0003] The acquisition of fracturing fracture parameters can be mainly divided into direct monitoring and indirect evaluation. The direct monitoring method includes microseismic monitoring, well temperature and casing outer optical fiber testing technologies; the indirect evaluation method is usually based on the construction of a percolation model or a numerical model for fitting.

[0004] The Chinese paper document entitled "Shale horizontal well hydraulic fracturing fracture morphology in Jimsar Sag of Junggar Basin" by Fang Zheng et al. records the establishment of a microseismic data inversion method, and the secondary reconstruction of the inversion results, giving the three-dimensional hydraulic fracturing fracture geometry of a shale horizontal well, and verifying the fracture morphology and the microseismic data inversion method through a true triaxial fracturing physical simulation experiment.

[0005] The Chinese patent document with publication number CN113392595A discloses a conglomerate reservoir horizontal well fracturing fracture network characterization method, which discloses a model of a fracturing fracture network formed by microseismic monitoring data points to determine the fracturing fracture network fractal dimension of each fracturing fracture section of the horizontal well; according to the fracturing fracture network fractal dimension and the reservoir rock physical parameters, a multi-element regression analysis method is used to determine the fracture expansion fractal factor of the reservoir; and the fracture expansion fractal factor is simulated for fracture initiation and expansion. The present application solves the problem of being unable to accurately simulate the fracture network morphology formed by the fracturing of a conglomerate reservoir horizontal well in the prior art.

[0006] At present, the construction cost of the direct monitoring method is generally high, and "one well one measurement" is difficult to achieve, while the indirect evaluation method needs to input a large number of geological and engineering parameters into the model, and some parameters are difficult to accurately obtain, the fitting result error is large, and at present, it is urgent to establish a horizontal well fracturing width monitoring method to reduce the monitoring cost and improve the monitoring precision. SUMMARY

[0007] The application provides a horizontal well fracture width monitoring method, which overcomes the defects of the prior art and effectively solves the problems of high monitoring cost and low monitoring precision of the horizontal well fracture width monitoring method.

[0008] The technical scheme of the application is achieved by the following measures: a horizontal well fracture width monitoring method, comprising the following steps: Step one, assembling a test pipe string; Step two, lowering the test pipe string into a newly drilled horizontal well, and uniformly dragging the test pipe string at a first speed in a target layer section; Step three, lifting the test pipe string, and performing segmented multi-cluster fracturing on the horizontal well; Step four, lowering the test pipe string again, uniformly dragging the test pipe string at a second speed in the target layer section, and obtaining reservoir residual magnetic data before and after fracturing; Step five, respectively drawing a reservoir residual magnetic curve before fracturing and a reservoir residual magnetic curve after fracturing according to the reservoir residual magnetic data before fracturing and the reservoir residual magnetic data after fracturing, and drawing the two curves in the same graph; Step six, comparing the reservoir residual magnetic curve after fracturing with the reservoir residual magnetic curve before fracturing, taking points, at which the reservoir residual magnetic curve after fracturing and the reservoir residual magnetic curve before fracturing are separated from each other and coincide with each other, corresponding to each perforation cluster as two reservoir residual magnetic anomaly inflection points of the perforation cluster, and sequentially determining the two reservoir residual magnetic anomaly inflection points of each perforation cluster; Step seven, determining half-amplitude points of an abnormal curve on the reservoir residual magnetic curve after fracturing between the two reservoir residual magnetic anomaly inflection points of the first perforation cluster, and the distance between the two half-amplitude points being a fracture width; Step eight, repeating step seven to determine the fracture width corresponding to the remaining perforation cluster.

[0009] The following is a further optimization or / and improvement of the above technical scheme of the application: The test pipe string in step one can comprise, from top to bottom, a coiled tubing, a residual magnetic monitor and a magnetic positioning instrument connected together in sequence.

[0010] In step four, the reservoir residual magnetic data before and after fracturing can be obtained by comparing data measured by the magnetic positioning instrument with casing collar data, positioning the depth, and extracting the reservoir residual magnetic data before and after fracturing.

[0011] The second speed in step four can be the same as the first speed in step two.

[0012] In step three, a coiled tubing can be used to drill a bridge plug after fracturing and clean the well.

[0013] This invention provides a method for monitoring fracture width in horizontal wells. The fracture width is determined by monitoring the half-amplitude point of the change in the reservoir's residual magnetic field before and after fracturing. During formation, reservoir rocks are magnetized by the Earth's magnetic field, and they still retain their original natural residual magnetism. During fracturing, the cooling effect of the fracturing fluid, the creation of new fractures, and the filling of artificial proppant within the fractures all alter the residual magnetic field. By comparing the residual magnetic field curves before and after fracturing, the distance between the two half-amplitude points at the inflection point of the curve represents the width extended by the fracturing fracture, thus improving the accuracy of fracture width monitoring. Furthermore, this method has low monitoring costs and minimal requirements for wellbore conditions. Testing can be performed immediately after coiled tubing drilling, sand flushing, and other operations are completed, by simply running the test string. The application of this technology promotes segmented cluster optimization and refined fracturing design. Attached Figure Description

[0014] Appendix Figure 1 These are the residual magnetic curves of the reservoir before and after fracturing for the two perforation clusters in Embodiment 1 of the present invention. Detailed Implementation

[0015] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0016] The present invention will be further described below with reference to embodiments and accompanying drawings: Example 1: As shown in the attached document Figure 1 As shown, the method for monitoring fracture width in horizontal wells includes the following steps: Step 1: Assemble the test tube string; Step 2: Run the test string into the newly drilled horizontal well and drag it at a constant speed in the target section. Step 3: Remove the test tubing string and perform segmented multi-cluster fracturing on the horizontal well; Step 4: Lower the test string again and drag it at a constant speed of the second speed in the target layer to obtain the reservoir residual magnetic data before and after fracturing. Step 5: Based on the reservoir residual magnetic data before fracturing and the reservoir residual magnetic data after fracturing, plot the reservoir residual magnetic curve before fracturing and the reservoir residual magnetic curve after fracturing respectively, and plot the reservoir residual magnetic curve before fracturing and the reservoir residual magnetic curve after fracturing in the same figure. Step 6: Compare the residual magnetic curve of the reservoir after fracturing with the residual magnetic curve of the reservoir before fracturing. Take the points where the residual magnetic curve of the reservoir after fracturing and the residual magnetic curve of the reservoir before fracturing are separated and coincident with each other for each perforation cluster as the two residual magnetic anomaly inflection points of the perforation cluster. Sequentially determine the two residual magnetic anomaly inflection points of each perforation cluster. Step seven, determining the half amplitude points of the abnormal curve on the reservoir residual magnetic curve after fracturing between the two remaining magnetic anomaly inflection points of the first perforation cluster, the distance between the two half amplitude points is the fracture width; Step eight, repeating step seven to determine the fracture width corresponding to the remaining perforation cluster.

[0017] The half amplitude point is the point on the reservoir residual magnetic curve after fracturing corresponding to half of the abnormal amplitude value. The present application provides a horizontal well fracture width monitoring method, which judges the fracture width by monitoring the half amplitude points of the changes of the reservoir residual magnetic field before and after fracturing. The reservoir rock is magnetized during the formation process, and the original natural residual magnetism is still retained in the rock. During the fracturing process of the reservoir, the cooling effect of the fracturing fluid on the formation, the newly created fracture and the artificial proppant filled in the fracture will all change the residual magnetism of the rock. By comparing the residual magnetic curves before and after fracturing, the change inflection point of the residual magnetic curve appears, and the distance between the two half amplitude points is the width of the fracture extended and affected, which improves the accuracy of the fracture width monitoring. At the same time, the monitoring process cost of the method is low, and the requirement for the wellbore condition is low. After the coiled tubing drilling plug, sand washing and other operations are completed, the test pipe string can be lowered for testing. The application of this technology promotes the optimization of staged and clustered fracturing and the fine design of fracturing.

[0018] The horizontal well fracture width monitoring method described above can be further optimized or / and improved according to actual needs: Example two: As an optimization of the above-mentioned examples, the test pipe string in step one includes a coiled tubing, a residual magnetic monitor and a magnetic positioning instrument connected together from top to bottom. According to the needs, the residual magnetic monitor is a known technology, such as a residual magnetic tester. The residual magnetic monitor has a small outer diameter, does not need to be centered for testing, is not affected by the liquid in the wellbore, has a wide range of applications, and is low in cost. It can accurately extract the reservoir residual magnetic data before and after fracturing.

[0019] Example three: As an optimization of the above-mentioned examples, in step four, the reservoir residual magnetic data before and after fracturing is obtained by comparing the data measured by the magnetic positioning instrument with the casing collar data to position the depth and extract the reservoir residual magnetic data before and after fracturing. In this way, the reservoir residual magnetic data before and after fracturing of each perforation cluster can be compared, avoiding the interference of the reservoir residual magnetic data before and after fracturing between the perforation clusters on the determination of the two residual magnetic anomaly inflection points.

[0020] Example four: As an optimization of the above-mentioned examples, the second speed in step four is the same as the first speed in step two. In this way, the measurement results of the reservoir residual magnetic data before and after fracturing are consistent, the reservoir residual magnetic curve before fracturing and the reservoir residual magnetic curve after fracturing are drawn in the same graph, and the determination of the two residual magnetic anomaly inflection points on the reservoir residual magnetic curve after fracturing is facilitated.

[0021] Example 5: As an optimization of the above examples, in step 3, after fracturing, a bridge plug is drilled using coiled tubing and the well is thoroughly flushed. This method of drilling the bridge plug using coiled tubing and flushing the well after fracturing avoids interference from residual fluid during the fracturing process on the reservoir's residual magnetism, thus improving the accuracy of residual magnetism data measurements after fracturing.

[0022] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0023] The usage process of the preferred embodiment of the present invention: The first step is to assemble a test tube string, which mainly consists of a storage-type high-sensitivity residual magnetic field monitor and a magnetic positioning instrument connected by continuous tubing. The second step is to select the newly completed horizontal well M7, run the test string, and drag it at a constant speed of 10 meters per minute in the target section (4700-5700 meters) of the well for monitoring. After the monitoring is completed, the test string is pulled out. The third step is to perform segmented multi-cluster fracturing on the M7 horizontal well, which is divided into 15 segments, with 3 clusters of fracturing in each segment. After fracturing, the bridge plug is drilled out through coiled tubing and the well is cleaned. The fourth step is to lower the test string again and drag it at a constant speed of 10 m / min in the target layer (4700-5700 m) for monitoring. The depth is determined by comparing the data measured by the magnetic positioning instrument with the casing coupling data, and the residual magnetic data of the reservoir before and after compression is extracted. The fifth step is to plot the residual magnetic curves before and after fracturing on the same graph; Step 6: The inflection points of the residual magnetic anomaly of perforation cluster S1 are points a and b, respectively; the inflection points of the residual magnetic anomaly of perforation cluster S2 are points e and f, respectively. Step 7: In the residual magnetic curves before and after fracturing, the half-amplitude points between the inflection points a and b of the residual magnetic anomaly of the perforation cluster S1 are points c and d, respectively, and the distance between c and d is the width of the fracturing fracture; the half-amplitude points between the inflection points e and f of the residual magnetic anomaly of the perforation cluster S2 are points g and h, respectively, and the distance between g and h is the width of the fracturing fracture. Step 8: Repeat step 7 to determine the width of the hydraulic fracture corresponding to the remaining perforation cluster.

Claims

1. A method of monitoring fracture width in a horizontal well, characterized by The method comprises the following steps: Step one, assembling a test pipe string; Step two, lowering the test pipe string into a newly drilled horizontal well, and dragging the test pipe string at a first speed in the target layer; Step three, pulling out the test pipe string, and performing segmented multi-cluster fracturing on the horizontal well; Step four, lowering the test pipe string again, dragging the test pipe string at a second speed in the target layer, and obtaining reservoir residual magnetic data before and after fracturing; Step five, drawing a reservoir residual magnetic curve before fracturing and a reservoir residual magnetic curve after fracturing according to the reservoir residual magnetic data before fracturing and the reservoir residual magnetic data after fracturing respectively, and drawing the two curves in the same graph; Step six, comparing the reservoir residual magnetic curve after fracturing with the reservoir residual magnetic curve before fracturing, taking points where the reservoir residual magnetic curve after fracturing and the reservoir residual magnetic curve before fracturing are separated from each other and coincide with each other as two residual magnetic anomaly inflection points of each perforation cluster, and sequentially determining the two residual magnetic anomaly inflection points of each perforation cluster; Step seven, determining half-amplitude points of the abnormal curve on the reservoir residual magnetic curve after fracturing between the two residual magnetic anomaly inflection points of the first perforation cluster, and the distance between the two half-amplitude points being a fracturing crack width; Step eight, repeating step seven to determine the fracturing crack width corresponding to the remaining perforation cluster.

2. The method of claim 1, wherein The test pipe string in step one comprises, from top to bottom, a coiled tubing, a residual magnetic monitoring instrument and a magnetic positioning instrument.

3. The method of claim 2, wherein In step four, the reservoir residual magnetic data before and after fracturing are obtained by comparing the data measured by the magnetic positioning instrument with the casing coupling data, positioning the depth, and extracting the reservoir residual magnetic data before and after fracturing.

4. The method of claim 1 or 2 or 3, wherein The second speed in step four is the same as the first speed in step two.

5. The method of claim 1 or 2 or 5, wherein In step three, the bridge plug is drilled by the coiled tubing after fracturing, and the well is cleaned.

6. The method of claim 4, wherein In step three, the bridge plug is drilled by the coiled tubing after fracturing, and the well is cleaned.

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