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Fig. 4. (a) Comparisons of cutters by force and (b) Mechanical Specific Energy (MSE) vs area of cut. They show greater efficiency with the CAT configuration than the conventional or shaped cutter alone. In these graphs, PDC, TRI and CAT stand for conventional, shaped and conventional cutter after shaped cutter respectively. yield variations in section area, and force is a function of section area and rock hardness. The data compares a conventional PDC at 20° back rake vs the shaped cutter at 40°. With the shaped cutter, cutting force is not affected by back rake; this is not the case with a conventional cutter, which has a higher cutting force at 40° back rake than at 20°. A cutting force reduction is seen when the conventional cutter follows the rock-weakening action of the shaped cutter (CAT). The graphs shown in Figure 4(b) present the respective change in the MSE. Again, the CAT cutter configuration has a lower MSE, indicating a more efficient cutting process. v

Figure 4 (a) Comparisons of cutters by force and (b) Mechanical Specific Energy (MSE) vs area of cut. They show greater efficiency with the CAT configuration than the conventional or shaped cutter alone. In these graphs, PDC, TRI and CAT stand for conventional, shaped and conventional cutter after shaped cutter respectively. yield variations in section area, and force is a function of section area and rock hardness. The data compares a conventional PDC at 20° back rake vs the shaped cutter at 40°. With the shaped cutter, cutting force is not affected by back rake; this is not the case with a conventional cutter, which has a higher cutting force at 40° back rake than at 20°. A cutting force reduction is seen when the conventional cutter follows the rock-weakening action of the shaped cutter (CAT). The graphs shown in Figure 4(b) present the respective change in the MSE. Again, the CAT cutter configuration has a lower MSE, indicating a more efficient cutting process. v

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This template is provided to give authors a basic shell for preparing your manuscript for submittal to an SPE meeting or event. Styles have been included (Head1, Head2, Para, FigCaption, etc.) to give you an idea of how your finalized paper will look before it is published by SPE. All manuscripts submitted to SPE will be extracted from this template and tagged into an XML format; SPE’s standardized styles and fonts will be used when laying out the final manuscript. Links will be added to your manuscript for references, tables, and equations. Figures and tables should be placed directly after the first paragraph they are mentioned in. The technical content of your paper WILL NOT be changed. Please start your manuscript below.
This layered sandwich configuration of cutter rows and shock studs limits breakages in the primary row while protecting the secondary row. The novel configuration enables a PDC solution to be used in harsh heterogeneous environments by minimizing the risk of the total failure and having to pull out the drill- sting of the hole earlier than planned. In Figure 1(b) photographs are showing the drill-bits used for drilling through a hard and abrasive chert formation layer in West Africa compares a standard double- row design and the tailored protective cutting structure. Bits with the sandwich configuration are being used for drilling in a number of locations including Egypt, Europe, East Africa and Asia to achieve longer intervals and higher ROP than standard PDC bits. As a result, the bits have replaced several roller cone bits and achieved better performance than a conventional PDC cutting structure when encountering chert formations.
This layered sandwich configuration of cutter rows and shock studs limits breakages in the primary row while protecting the secondary row. The novel configuration enables a PDC solution to be used in harsh heterogeneous environments by minimizing the risk of the total failure and having to pull out the drill- sting of the hole earlier than planned. In Figure 1(b) photographs are showing the drill-bits used for drilling through a hard and abrasive chert formation layer in West Africa compares a standard double- row design and the tailored protective cutting structure. Bits with the sandwich configuration are being used for drilling in a number of locations including Egypt, Europe, East Africa and Asia to achieve longer intervals and higher ROP than standard PDC bits. As a result, the bits have replaced several roller cone bits and achieved better performance than a conventional PDC cutting structure when encountering chert formations.
With the help of 3D simulation software developed in house by Varel, described by Pelfrene et al., 2019 cutting structure optimization have been performed to fine tune the radius, exposure and back rake angle of each cutting element for a given application objective. This 3D bit simulator puts the full bit model into a virtual 3D block of rock to simulate the interactions between the whole bit body and the rock (see an example of the 3D output in Figure 2(a)). These interactions consist of cutting forces associated with each cutter and contact forces associated with the non-cutting parts of the drill bit, such as blade tops, backup elements or gages. These local forces can be summed over the whole bit body to predict global quantities, such as the WOB, the side force, the steerability or the walk angle. Fig. 2. Modelling of the wellbore creation and cuttings generation at the PDC/Rock interface; (a) example output from the 3D simulation software and (b) example of 3 different exposure settings of the shape cutter elements
With the help of 3D simulation software developed in house by Varel, described by Pelfrene et al., 2019 cutting structure optimization have been performed to fine tune the radius, exposure and back rake angle of each cutting element for a given application objective. This 3D bit simulator puts the full bit model into a virtual 3D block of rock to simulate the interactions between the whole bit body and the rock (see an example of the 3D output in Figure 2(a)). These interactions consist of cutting forces associated with each cutter and contact forces associated with the non-cutting parts of the drill bit, such as blade tops, backup elements or gages. These local forces can be summed over the whole bit body to predict global quantities, such as the WOB, the side force, the steerability or the walk angle. Fig. 2. Modelling of the wellbore creation and cuttings generation at the PDC/Rock interface; (a) example output from the 3D simulation software and (b) example of 3 different exposure settings of the shape cutter elements
Fig. 3. Experiments on the Linear Rig to gain insight into the cutting mechanics of the shape cutter. (a) Photograph of the shape cutter single cutter; (b) the shape cutter cutting a linear grove and its position on the new drill-bit; (c) a schematic of the Linear Rig with its main components and instrumentation.
Fig. 3. Experiments on the Linear Rig to gain insight into the cutting mechanics of the shape cutter. (a) Photograph of the shape cutter single cutter; (b) the shape cutter cutting a linear grove and its position on the new drill-bit; (c) a schematic of the Linear Rig with its main components and instrumentation.
Fig. 5. Vertical Rig and its instrumentation. The Vertical Rig used for this study is the CADR Vertical RED rig modified to accommodate changes needed for this work. Specifically the RED actuator was replaced with a drilling pipe to undertake >onventional rotary drilling. The left panel details the main parts of the rig where the right one shows the drill-bit and the sample. Through this extensive laboratory testing program, it has been demonstrated that the use of a particular shaped cutter with the aim to weaken the rock and pre-fracture it for more efficient shearing action was indeed beneficial. The testing helped to further develop and fine-tune the positioning of shaped cutters by demonstrating that optimum point loading and mechanical effect was achieved with no offset of the cutting structure profile and a high back-rake angle.
Fig. 5. Vertical Rig and its instrumentation. The Vertical Rig used for this study is the CADR Vertical RED rig modified to accommodate changes needed for this work. Specifically the RED actuator was replaced with a drilling pipe to undertake >onventional rotary drilling. The left panel details the main parts of the rig where the right one shows the drill-bit and the sample. Through this extensive laboratory testing program, it has been demonstrated that the use of a particular shaped cutter with the aim to weaken the rock and pre-fracture it for more efficient shearing action was indeed beneficial. The testing helped to further develop and fine-tune the positioning of shaped cutters by demonstrating that optimum point loading and mechanical effect was achieved with no offset of the cutting structure profile and a high back-rake angle.
Fig. 6. From left to right, photographs of conventional PDC bit with empty cutter pockets to mount shaped cutters, and two new bits, Hybrid X1 and Hybrid X2 used in the experimental studies on the Vertical Rig.
Fig. 6. From left to right, photographs of conventional PDC bit with empty cutter pockets to mount shaped cutters, and two new bits, Hybrid X1 and Hybrid X2 used in the experimental studies on the Vertical Rig.
Fig. 7. Comparisons of ROP (top left panel) and MSE (three remaining ones) as the function of WOB, TOB and DOC for conventiona PDC and new hybrid drill-bits (TRI2 = X2). It is clearly visible that ROP increased for the experiments with the hybrid drill-bits. With respect to MSE the picture is more complex however it can be stated that that the pre-cracking by hybrid drill-bits helps to reduce it
Fig. 7. Comparisons of ROP (top left panel) and MSE (three remaining ones) as the function of WOB, TOB and DOC for conventiona PDC and new hybrid drill-bits (TRI2 = X2). It is clearly visible that ROP increased for the experiments with the hybrid drill-bits. With respect to MSE the picture is more complex however it can be stated that that the pre-cracking by hybrid drill-bits helps to reduce it
Figure 8. Final design of the 16-in. PDC with shaped cutter configuration to effectively tackle cherts and conglomerates Table 1. Lithology sequence of 16-in UAE offshore well showing eight different types of formations.
Figure 8. Final design of the 16-in. PDC with shaped cutter configuration to effectively tackle cherts and conglomerates Table 1. Lithology sequence of 16-in UAE offshore well showing eight different types of formations.
Figures 9. New 16-in PDC drill-bit performance summary and comparison showing the drilled depth with the new hybrid design and typical PDC drill-bits.
Figures 9. New 16-in PDC drill-bit performance summary and comparison showing the drilled depth with the new hybrid design and typical PDC drill-bits.
Figure 10. Typical dullness observed during the field trials with the new 16-in PDC drill-bit is marked with red circles. Typical dullness was observed on these runs show primary row with usual breakage due to chert and heavy minerals encountered but with a much lower severity and mainly confined to light chipped teeth while the row of shaped cutters remains in relatively good shape, see Figure 10. However, the field trial results demonstrate the efficiency of this combination of pre-fracturing the heterogeneous rock to weaken it and minimize the stress and load for the shearing process. With a better preserved and more efficient cutting structure, the bit finishes the more difficult bottom of the section with a much greater ROP.
Figure 10. Typical dullness observed during the field trials with the new 16-in PDC drill-bit is marked with red circles. Typical dullness was observed on these runs show primary row with usual breakage due to chert and heavy minerals encountered but with a much lower severity and mainly confined to light chipped teeth while the row of shaped cutters remains in relatively good shape, see Figure 10. However, the field trial results demonstrate the efficiency of this combination of pre-fracturing the heterogeneous rock to weaken it and minimize the stress and load for the shearing process. With a better preserved and more efficient cutting structure, the bit finishes the more difficult bottom of the section with a much greater ROP.
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