Method, processor and device for evaluating reservoir modification re-use flowback fluid scaling

Abstract

The application provides a method, a processor and a device for evaluating the scaling condition of reservoir reconstruction recycling flowback fluid. The method comprises the following steps: detecting the ion species and content in the to-be-recycled fracturing flowback fluid of the target fracturing reservoir; predicting the scaling tendency of the to-be-recycled fracturing flowback fluid; performing a simulated scaling experiment on the to-be-recycled fracturing flowback fluid to determine the scaling type of the to-be-recycled fracturing flowback fluid; performing a morphology analysis and a full-element analysis on the scale sample generated by the simulated scaling experiment to determine the scale sample type and composition, and comparing the scale sample type and composition with the scaling tendency prediction result and the simulated scaling experiment result to comprehensively evaluate the scaling condition of the to-be-recycled fracturing flowback fluid in the reconstruction process of the target fracturing reservoir. The processor is configured to perform the method. The device comprises the processor. The application has the advantages of being capable of evaluating the scaling condition of the fracturing flowback fluid in the fracturing reconstruction process of a shale gas reservoir, avoiding the harm and loss caused by scale body generation, and the like.

Description

Technical Field

[0001] This invention relates to the field of drilling equipment (shale gas reservoir stimulation) technology, specifically to a method, processor, and apparatus for evaluating scaling of flowback fluid in reservoir stimulation. Background Technology

[0002] With the ongoing development and stimulation of shale gas reservoirs in Sichuan and Chongqing, the amount of slickwater used in volumetric fracturing is increasing, leading to a continuous rise in the volume of fracturing flowback fluid. Currently, to mitigate environmental risks, the reuse of flowback fluid is being increased during construction. This is primarily achieved by treating the flowback fluid without desalination and then using anti-salt drag-reducing agents to prepare slickwater for repeated use. It is well known that the ionic composition of flowback fluid is complex. After repeated reuse, the content of ions such as calcium, magnesium, carbonate, and sulfate increases, resulting in higher salinity of the fracturing flowback fluid. When this high-salinity flowback fluid is injected into the shale gas well reservoir, questions arise regarding whether scaling will occur between the various ions, what type of scale will be formed, and whether chemical incompatibility will disrupt the stability of the formation water, leading to scaling within the formation water itself. Furthermore, the compatibility of the injected flowback fluid with the formation water under reservoir conditions, whether scaling will occur, and what type of scale will be formed are all issues that need to be addressed. The aforementioned issues regarding scaling during shale reservoir stimulation and whether scale negatively impacts the process are extremely challenging. This is because scale, once formed, is often composed of calcium carbonate, calcium sulfate, magnesium carbonate, and magnesium sulfate, exhibiting a dense structure and high hardness, making it difficult to remove. Such scale poses significant risks and causes unnecessary losses to shale gas extraction. Currently, the oil and gas development technology field only has evaluation methods for scaling during water injection in conventional oil and gas field development. Specific evaluation methods for scaling during shale gas reservoir stimulation under high-salinity flowback fluid reuse are not yet documented. Summary of the Invention

[0003] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of this invention is to provide a method for evaluating the scaling of recycled fracturing flowback fluid during shale gas reservoir fracturing stimulation. Another objective of this invention is to provide a processor for performing a method for evaluating the scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation.

[0004] To achieve the above objectives, one aspect of the present invention provides a method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation processes, the method comprising the steps of:

[0005] Detect the types and contents of ions in the fracturing flowback fluid to be reused in the target fracturing-treated reservoir;

[0006] Predict the scaling trend of the fracturing flowback fluid to be reused;

[0007] Simulated scaling experiments were conducted on the fracturing flowback fluid to be reused using both static and dynamic methods to determine the scaling type of the fracturing flowback fluid to be reused.

[0008] Morphological and elemental analyses were performed on the scale samples generated by the simulated scaling experiments to determine the scale type and composition. The results were then compared with the scaling trend prediction results and the simulated scaling experiment results to comprehensively evaluate the scaling situation of the recycled fracturing flowback fluid during the target fracturing reservoir stimulation process.

[0009] In one exemplary embodiment of one aspect of the present invention, the high-mineralization fracturing flowback fluid may have a mineralization of ≥10000 mg / L, a suspended solids content of ≤30 mg / L, an oil content of ≤50 mg / L, and a total iron content of ≤20 mg / L.

[0010] In one exemplary embodiment of one aspect of the present invention, the ion species may include K. + Na + Ca 2+ Mg 2+ Ba 2+ 、Sr 2+ Fe 3+ Cl - HCO3 - CO3 2- SO4 2- One or more of the following.

[0011] In one exemplary embodiment of one aspect of the present invention, the fouling trend prediction may include:

[0012] Based on the actual temperature and pressure of the target fracturing reservoir, the scaling trends of calcium carbonate, calcium sulfate, magnesium carbonate, and magnesium sulfate generated during the reuse of the fracturing flowback fluid are predicted.

[0013] In one exemplary embodiment of one aspect of the present invention, the static method may include the steps of:

[0014] The fracturing flowback fluid to be reused was placed in a sealed, constant-temperature water bath at the actual temperature of the target fracturing reservoir. After 48–72 hours, the sample was removed and the Fe content was tested. 3+ Ca 2+ Mg 2+ CO3 2- and SO4 2- The concentration.

[0015] In one exemplary embodiment of one aspect of the present invention, the dynamic method may include the following steps:

[0016] A shale core flow experiment was conducted, using fracturing flowback fluid to be reused to displace shale cores. The experimental temperature was set to the actual temperature of the target fracturing reservoir. Continuous water injection was used to maintain a constant water production rate. Fe content in water samples before and after displacement was measured. 3+ Ca 2+ Mg 2+ CO3 2- and SO4 2- The concentration.

[0017] In one exemplary embodiment of one aspect of the present invention, the morphology analysis may include:

[0018] The distribution and accumulation characteristics of scale on the fracture walls inside the experimental core were studied by scanning electron microscopy.

[0019] In one exemplary embodiment of one aspect of the present invention, the full element analysis may include:

[0020] X-ray fluorescence spectrometry was used to perform full elemental analysis on the scale sample, and then the type and specific content of scale were determined.

[0021] In another aspect, the present invention provides a processor configured to perform the method described in any of the preceding claims for evaluating scaling of the recycled fracturing flowback fluid during shale gas fracturing stimulation.

[0022] In another aspect, the present invention provides an apparatus for evaluating the scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation, the apparatus comprising the processor described above.

[0023] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0024] (1) This invention provides a method for evaluating the scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation, which can be used to evaluate the scaling during the reservoir stimulation process in future shale gas development.

[0025] (2) The method of evaluating the scaling of the recycled fracturing flowback fluid in the shale gas fracturing process of the present invention can predict the scaling of the flowback fluid in advance, making it convenient for operators to take corresponding measures to avoid the generation of scale and reduce the huge harm and unnecessary losses caused to shale gas extraction by the generation of scale.

[0026] (3) The method of evaluating the scaling of the recycled fracturing flowback fluid in the shale gas fracturing process of the present invention is scientific and reasonable, has a high prediction accuracy, can be mastered by operators after simple training, has a wide range of applications, and has high economic benefits. Attached Figure Description

[0027] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0028] Figure 1 A flowchart illustrating an exemplary embodiment of the present invention is shown, illustrating a method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation.

[0029] Figure 2a The overall morphology of the scale sample obtained according to a specific embodiment is shown;

[0030] Figure 2b A partial scanning electron microscope image of the scale sample obtained according to a specific embodiment is shown. Detailed Implementation

[0031] In the following sections, the method, processor, and apparatus for evaluating scaling of reservoir modification and reuse flowback fluid according to the present invention will be described in detail with reference to exemplary embodiments.

[0032] Figure 1 The diagram illustrates a process flow chart of an exemplary embodiment of the present invention for evaluating scaling of the recycled fracturing flowback fluid during shale gas fracturing stimulation.

[0033] In a first exemplary embodiment of the present invention, as Figure 1 The method for evaluating scaling of the recycled fracturing flowback fluid during shale gas fracturing stimulation, as shown in the figure, includes the following steps:

[0034] S1: Detect the types and contents of ions in the flowback fluid to be reused in the target fracturing reservoir.

[0035] S2: Predict the scaling trend of the fracturing flowback fluid to be reused.

[0036] S3: Simulate scaling experiments are conducted on the fracturing flowback fluid to be reused using both static and dynamic methods to determine the scaling type of the fracturing flowback fluid to be reused.

[0037] S4: Perform morphological and elemental analysis on the scale samples generated by the simulated scaling experiment to determine the scale type and composition. Compare the results with the scaling trend prediction results and the simulated scaling experiment results to comprehensively evaluate the scaling situation of the recycled fracturing flowback fluid during the target fracturing reservoir stimulation process.

[0038] In this exemplary embodiment, the fracturing flowback fluid is a high-mineralization fracturing flowback fluid, wherein the mineralization of the high-mineralization fracturing flowback fluid can be ≥10000 mg / L, the suspended solids content can be ≤30 mg / L, the oil content can be ≤50 mg / L, and the total iron content can be ≤20 mg / L. In this exemplary embodiment, the ion species can include K+. + Na +Ca 2+ Mg 2+ Ba 2+ 、Sr 2+ Fe 3 + Cl - HCO3 - CO3 2- SO4 2- One or more of the following ions may be present. The detection method for the ion species can be performed according to "SY / T 5523 Oilfield Water Analysis Method".

[0039] In this exemplary embodiment, the fouling trend prediction may include:

[0040] Based on the actual temperature and pressure of the target fracturing reservoir, the scaling trends of calcium carbonate, calcium sulfate, magnesium carbonate, and magnesium sulfate generated during the reuse of the fracturing flowback fluid are predicted. Here, the scaling trend prediction method follows the "SY / T0600-2009 Oilfield Water Scaling Trend Prediction" standard.

[0041] In this exemplary embodiment, the static method may include the following steps:

[0042] The fracturing flowback fluid to be reused was placed in a sealed, constant-temperature water bath at the actual temperature of the target fracturing reservoir. After 48–72 hours, the sample was removed and the Fe content was tested. 3+ Ca 2+ Mg 2+ CO3 2- and SO4 2- The concentration.

[0043] In this exemplary embodiment, the dynamic method may include the following steps:

[0044] A shale core flow experiment was conducted using fracturing flowback fluid intended for reuse. The cores used were approximately 25 mm in diameter with a fracture width of 0.2 mm. The experimental temperature was set to the actual temperature of the target fracturing reservoir. A horizontal flow pump with a displacement of 2 mL / min was used, and continuous injection was employed to maintain a constant flow rate. The Fe content in the water samples before and after displacement was measured. 3+ Ca 2+ Mg 2+ CO3 2- and SO4 2- The concentration.

[0045] In this exemplary embodiment, the morphology analysis may include:

[0046] The distribution and accumulation characteristics of scale on the fracture walls inside the experimental core were studied by scanning electron microscopy.

[0047] In this exemplary embodiment, the full element analysis may include:

[0048] X-ray fluorescence spectrometry (XRF) was used to perform full elemental analysis on the scale samples to determine the types and specific contents of the scale.

[0049] Figure 2a The overall morphology of the scale sample obtained according to a specific embodiment is shown; Figure 2b A partial scanning electron microscope (SEM) image of a scale sample obtained according to a specific embodiment is shown. To better understand the present invention, specific examples are provided below to further illustrate its content; however, the scope of the present invention is not limited to the examples described below.

[0050] Step 1: Conduct ionic composition analysis on the fracturing flowback fluid to be reused in a shale gas platform well (Shaanxi W well) reservoir stimulation project, and detect the pH and K content in the flowback fluid. + Na + Ca 2+ Mg 2+ Ba 2+ 、Sr 2+ Fe 3+ Cl - HCO3 - CO3 2- and SO4 2- The concentrations of ions and the detection results are shown in Table 1.

[0051] Table 1. Ionic composition of fracturing flowback fluid to be reused

[0052]

[0053] Step 2: Based on the ionic composition of the fracturing flowback fluid to be reused measured above, the scaling trend of the YeW well reservoir stimulation is predicted. The predicted temperature is 90℃, which is the simulated actual average temperature of the YeW well reservoir stimulation.

[0054] The scaling trends of calcium carbonate were predicted using the Davis-Stiff saturation index method and the Ryznar stability index method, respectively. The scaling trends of calcium sulfate were predicted using the Skillman thermodynamic dissolution method. The scaling trends of magnesium carbonate and magnesium sulfate were predicted according to the method in "SY / T 0600-2009 Oilfield Water Scaling Trend Prediction". The prediction results are shown in Table 2.

[0055] Table 2. Results of Scaling Trend Prediction

[0056]

[0057] Step 3: Conduct static and dynamic simulated scaling experiments on the fracturing flowback fluid to be reused in the reservoir of Well W.

[0058] Static scaling experiment: 500 mL of the backflow solution was placed in a sealed container in a water bath at 90°C for 72 hours. The appearance of the backflow solution was observed, and the Ca content in the backflow solution was tested. 2+ Mg 2+ CO3 2- and SO4 2- The concentrations of these ions were compared with those of the reflux solution before and after placement. The test results are shown in Table 3.

[0059] Dynamic scaling experiment: Displacement experiments were conducted on core samples from the reservoir of well W to be treated, using fracturing flowback fluid to be reused. The core diameter was 25.06 mm, the fracture width was 0.21 mm, the experimental temperature was 90℃, and the flow rate of the horizontal flow pump was 2 mL / min. Water was continuously injected during the experiment to maintain a constant flow rate. After displacement, the Ca content in the water samples before and after displacement was measured. 2+ Mg 2+ CO3 2- and SO4 2- The concentrations and test results are shown in Table 3.

[0060] Table 3. Results of Scaling Experiment

[0061]

[0062] Step 4: Elemental analysis and electron microscopy were performed on the scale samples generated in Step 3 and the core samples after displacement. The experimental results are shown in Table 4. Figure 2a and Figure 2b As shown.

[0063] Table 4 Elemental Analysis Results

[0064]

[0065] In summary, it can be seen that scale formation occurs when fracturing flowback fluid is used during the reservoir stimulation process of Well W. The scale sample consists of CaCO3 and MgCO3, with CaCO3 being the majority.

[0066] A second exemplary embodiment of the present invention provides a processor configured to perform the method described in the first exemplary embodiment for evaluating scaling of the recycled fracturing flowback fluid in a shale gas fracturing process.

[0067] In a third exemplary embodiment of the present invention, an apparatus is provided for evaluating the scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation processes, the apparatus comprising the processor described in the second exemplary embodiment above.

[0068] In summary, the beneficial effects of the present invention include at least one of the following:

[0069] (1) This invention provides a method for evaluating the scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation, which can be used to evaluate the scaling during the reservoir stimulation process in future shale gas development.

[0070] (2) The method of evaluating the scaling of the recycled fracturing flowback fluid in the shale gas fracturing process of the present invention can predict the scaling of the flowback fluid in advance, making it convenient for operators to take corresponding measures to avoid the generation of scale and reduce the huge harm and unnecessary losses caused to shale gas extraction by the generation of scale.

[0071] (3) The method of evaluating the scaling of the recycled fracturing flowback fluid in the shale gas fracturing process of the present invention is scientific and reasonable, has a high prediction accuracy, can be mastered by operators after simple training, has a wide range of applications, and has high economic benefits.

[0072] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation, characterized in that, The method includes the following steps: Detect the types and contents of ions in the fracturing flowback fluid to be reused in the target fracturing-treated reservoir; Predict the scaling trend of the fracturing flowback fluid to be reused; Simulated scaling experiments were conducted on the fracturing flowback fluid to be reused using both static and dynamic methods to determine the scaling type of the fracturing flowback fluid to be reused. Morphological and elemental analyses were performed on the scale samples generated by the simulated scaling experiment to determine the scale type and composition. The results were then compared with the scaling trend prediction results and the simulated scaling experiment results to comprehensively evaluate the scaling situation of the recycled fracturing flowback fluid during the target fracturing reservoir stimulation process. The fracturing flowback fluid is a high-mineralization fracturing flowback fluid, with a mineralization ≥10000 mg / L, suspended solids content ≤30 mg / L, oil content ≤50 mg / L, and total iron content ≤20 mg / L.

2. The method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation according to claim 1, characterized in that, The ion types include K. + Na + Ca 2+ Mg 2+ Ba 2+ 、Sr 2+ Fe 3+ Cl - HCO3 - CO3 2- SO4 2- One or more of the following.

3. The method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation according to claim 1, characterized in that, The scaling trend prediction includes: Based on the actual temperature and pressure of the target fracturing reservoir, the scaling trends of calcium carbonate, calcium sulfate, magnesium carbonate, and magnesium sulfate generated during the reuse of the fracturing flowback fluid are predicted.

4. The method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation according to claim 1, characterized in that, The static method includes the following steps: The fracturing flowback fluid to be reused was placed in a sealed, constant-temperature water bath at the actual temperature of the target fracturing reservoir. After 48–72 hours, the sample was removed and the Fe content in the water sample was tested. 3+ Ca 2+ Mg 2+ CO3 2- and SO4 2- The concentration.

5. The method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation according to claim 1, characterized in that, The dynamic method includes the following steps: A shale core flow experiment was conducted, using fracturing flowback fluid to be reused to displace shale cores. The experimental temperature was set to the actual temperature of the target fracturing reservoir. Continuous water injection was used to maintain a constant water production rate. Fe content in water samples before and after displacement was measured. 3+ Ca 2+ Mg 2+ CO3 2- and SO4 2- The concentration.

6. The method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation according to claim 5, characterized in that, The morphology analysis includes: The distribution and accumulation characteristics of scale on the fracture walls inside the experimental core were studied by scanning electron microscopy.

7. The method for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation according to claim 1, characterized in that, The full element analysis includes: X-ray fluorescence spectrometry was used to perform full elemental analysis on the scale sample, and then the type and specific content of scale were determined.

8. A processor, characterized in that, The method is configured to perform the method for evaluating scaling of the recycled fracturing flowback fluid during shale gas fracturing stimulation according to any one of claims 1 to 7.

9. A device for evaluating scaling of recycled fracturing flowback fluid during shale gas fracturing stimulation, characterized in that, The device includes the processor according to claim 8.

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