K. Vidma, P. Abivin, Derek Fox, M. Reid, F. Ajisafe, A. Marquez, W. Yip, J. Still
The increasing trend of drilling infill wells (more than 60% of new wells in 2017) comes with the significant risk of well interference, or "frac hits". Frac hits occur during hydraulic fracturing operations when there is direct pressure communication between the well being treated and adjacent, pre-exisiting wells. In extreme cases, the fracture may fill the adjacent wellbore with sand, which requires expensive cleanup intervention. Fracture geometry control technologies aim to reduce the likelihood of well interference by deploying far-field diversion techniques. This paper presents a unique field experiment that demonstrates the value and effectiveness of these technologies. In the Bakken, two child wells were drilled 1,300 and 800 ft, respectively, on each side of an existing, partially depleted parent well. Each child well treatment comprised 50 stages of slickwater, completed in zipper frac style. Treatments in the farther well did not utilize any fracture geometry control technology. In the nearer well, 20 of 50 stages (one every 5 stages) included far-field diversion material. All other parameters of the pumping schedules were the same between the two treated wells. Pressures were monitored in all three wells (parent and two child wells) at high frequency during all operations. The parent well was not damaged during the operation. However, during the first 35 stages of the child well treatments, the parent well's pressure increased in spurts, until it stabilized near expected reservoir pressure. In this paper, each instance of well interference is quantified and attributed to a treatment stage in one of the child wells. Interestingly, not all stages contributed to the pressure buildup. Significantly, various levels of frac hits were observed, as determined by the magnitude and steepness of the pressure increase. The correlation of frac hit with the absence of far-field diverter is striking. The results clearly demonstrate that fracture geometry control technologies reduce the occurrence of direct well interference by containing fracture growth. The operations in these wells created a unique opportunity to design a field experiment to assess the effect of fracture geometry control technology on well interference during infill well stimulation. The results demonstrate that such technologies reduce the occurrence of direct frac hits in depleted parent wells.
{"title":"Fracture Geometry Control Technology Prevents Well Interference in the Bakken","authors":"K. Vidma, P. Abivin, Derek Fox, M. Reid, F. Ajisafe, A. Marquez, W. Yip, J. Still","doi":"10.2118/194333-MS","DOIUrl":"https://doi.org/10.2118/194333-MS","url":null,"abstract":"\u0000 The increasing trend of drilling infill wells (more than 60% of new wells in 2017) comes with the significant risk of well interference, or \"frac hits\". Frac hits occur during hydraulic fracturing operations when there is direct pressure communication between the well being treated and adjacent, pre-exisiting wells. In extreme cases, the fracture may fill the adjacent wellbore with sand, which requires expensive cleanup intervention. Fracture geometry control technologies aim to reduce the likelihood of well interference by deploying far-field diversion techniques. This paper presents a unique field experiment that demonstrates the value and effectiveness of these technologies.\u0000 In the Bakken, two child wells were drilled 1,300 and 800 ft, respectively, on each side of an existing, partially depleted parent well. Each child well treatment comprised 50 stages of slickwater, completed in zipper frac style. Treatments in the farther well did not utilize any fracture geometry control technology. In the nearer well, 20 of 50 stages (one every 5 stages) included far-field diversion material. All other parameters of the pumping schedules were the same between the two treated wells. Pressures were monitored in all three wells (parent and two child wells) at high frequency during all operations.\u0000 The parent well was not damaged during the operation. However, during the first 35 stages of the child well treatments, the parent well's pressure increased in spurts, until it stabilized near expected reservoir pressure. In this paper, each instance of well interference is quantified and attributed to a treatment stage in one of the child wells. Interestingly, not all stages contributed to the pressure buildup. Significantly, various levels of frac hits were observed, as determined by the magnitude and steepness of the pressure increase. The correlation of frac hit with the absence of far-field diverter is striking. The results clearly demonstrate that fracture geometry control technologies reduce the occurrence of direct well interference by containing fracture growth.\u0000 The operations in these wells created a unique opportunity to design a field experiment to assess the effect of fracture geometry control technology on well interference during infill well stimulation. The results demonstrate that such technologies reduce the occurrence of direct frac hits in depleted parent wells.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79892322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Cooper Basin of Australia is challenged by strike-slip to reverse stress regimes, adversely affecting hydraulic fracturing treatments. In drilling, the high deviatory stress conditions increase borehole breakout, affect log acquisition and impact cementing job quality. The non-favourable stress conditions in conjunction with natural fracturing result in: complex fracturing (with shear and sub-vertical components); high near-wellbore pressure loss (NWBPL) values; and stimulation of lower permeability, low modulus intervals (e.g., carbonaceous shales, interbedded coals) in preference to the targeted and higher modulus, tight-gas sandstones. Typically, vertical wells have been employed in past completions of the Cooper Basin as well as in the offsetting areas to the case study in the Windorah Trough, Southwest Queensland. We will present the results from two case study wells offsetting a previous vertical well where well trajectory, completion and fracture design changes were employed in an ongoing experiment to improve job execution for Patchawarra tight gas reservoir treatments in the Cooper Basin. The two wells were directionally deviated at 31° and 25° final inclinations from vertical with azimuth <10 deg from the maximum horizontal stress direction, as determined from offsetting well data. To better define sections with limited, poor or missing log data (because of difficult hole conditions), drilling data, logging while drilling (LWD) gamma ray data, openhole conventional and dipole sonic logs, along with prior 1D stress data were used with a machine learning model to improve stress profiling and reservoir characterization. Next, perforations were shot 0 and 180° phased along the wellbore and initial fluid viscosity was increased to better align the hydraulic fracture and reduce NWBPL, respectively. Finally, diagnostic fracture injection tests (DFIT) were performed in sections of varying moduli below and in the zone of interest in order to verify the horizontal strains and calibrate the final 1D stress profile prior to stimulating both wells. The improved well and perforation alignment to the maximum horizontal stress direction has improved reservoir connection, lowered NWBPL in some cases, and in some cases improved fracture containment. Decreasing injection rates and minimizing perforated intervals has improved targeting of desired intervals; however, overall fracture widths remain low and continue to be sensitive to proppant sizing and concentrations with several screen outs experienced. This experimentation has resulted in short-term production improvements in the wells using 4- and 3-stage treatments relative to the offsetting vertical well where a 5-stage treatment was executed.
{"title":"Well Trajectory, Completion and Fracture Design Changes Improve Execution for Deep Unconventional Tight Gas Targets in the Cooper Basin, Australia","authors":"Raymond L. Johnson, Ruizhi Zhong, Lan Nguyen","doi":"10.2118/194366-MS","DOIUrl":"https://doi.org/10.2118/194366-MS","url":null,"abstract":"\u0000 The Cooper Basin of Australia is challenged by strike-slip to reverse stress regimes, adversely affecting hydraulic fracturing treatments. In drilling, the high deviatory stress conditions increase borehole breakout, affect log acquisition and impact cementing job quality. The non-favourable stress conditions in conjunction with natural fracturing result in: complex fracturing (with shear and sub-vertical components); high near-wellbore pressure loss (NWBPL) values; and stimulation of lower permeability, low modulus intervals (e.g., carbonaceous shales, interbedded coals) in preference to the targeted and higher modulus, tight-gas sandstones. Typically, vertical wells have been employed in past completions of the Cooper Basin as well as in the offsetting areas to the case study in the Windorah Trough, Southwest Queensland.\u0000 We will present the results from two case study wells offsetting a previous vertical well where well trajectory, completion and fracture design changes were employed in an ongoing experiment to improve job execution for Patchawarra tight gas reservoir treatments in the Cooper Basin. The two wells were directionally deviated at 31° and 25° final inclinations from vertical with azimuth <10 deg from the maximum horizontal stress direction, as determined from offsetting well data. To better define sections with limited, poor or missing log data (because of difficult hole conditions), drilling data, logging while drilling (LWD) gamma ray data, openhole conventional and dipole sonic logs, along with prior 1D stress data were used with a machine learning model to improve stress profiling and reservoir characterization. Next, perforations were shot 0 and 180° phased along the wellbore and initial fluid viscosity was increased to better align the hydraulic fracture and reduce NWBPL, respectively. Finally, diagnostic fracture injection tests (DFIT) were performed in sections of varying moduli below and in the zone of interest in order to verify the horizontal strains and calibrate the final 1D stress profile prior to stimulating both wells.\u0000 The improved well and perforation alignment to the maximum horizontal stress direction has improved reservoir connection, lowered NWBPL in some cases, and in some cases improved fracture containment. Decreasing injection rates and minimizing perforated intervals has improved targeting of desired intervals; however, overall fracture widths remain low and continue to be sensitive to proppant sizing and concentrations with several screen outs experienced. This experimentation has resulted in short-term production improvements in the wells using 4- and 3-stage treatments relative to the offsetting vertical well where a 5-stage treatment was executed.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83165443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Kopp, Charles Kahn, C. Allen, Jake Huchton, Clark Robinson, E. Coenen
This paper discusses a STACK (Sooner Trend Anadarko Basin Canadian and Kingfisher Counties) case study that determined the effectiveness of different diversion techniques, including pods, sand ramps with sand slugs, rate cycling, and utilization of the completions order to control fracture growth. A secondary goal of this study was to evaluate the suitability of pressure-based fracture maps and oil and water phase tracers in monitoring diverter effectiveness. Effectiveness of a given diverter technique and diverter drop was evaluated using the two techniques on a 3-well pad. The three wells were completed using a combination of: 4 pods per treatment interval6 pods per treatment interval8 pods per treatment intervalhigh-volume proppant loading per treatment interval The effectiveness of the diverter drop was evaluated using each of the diagnostic techniques listed above. The pressure-based fracture analysis uses the pressure response recorded in an isolated stage in the monitor well to compute fracture geometry and the rate of growth of the fracture dimensions. The effectiveness of a given diverter drop is classified into one of four possible categories: stop dominant fracture growth, impede dominant fracture growth, no impact on growth of dominant fracture and accelerate the growth of dominant farcture. These results were then compared with the analysis from oil and water phase tracers and treatment pressure analysis. Successful (effective) diversion was observed on 82 % of the stages with pods compared to 64% successful diversion where sand ramps were used. In addition, stages using 8 pods for diversion had a 15% reduction in average fracture half-length compared to stages using 4 pods. Fracture height was better controlled through the order of completions of the stages between 3 wells. Completing the middle well in the upper part of the zone ahead of the two outer wells in the lower part of the zone, controlled the vertical height growth of the two outer wells. The offset pressure-based analysis proved to be as effective in accurately diagnosing the diverter effectiveness and provided a significant cost and timing advantage compared to other diagnostic techniques.
{"title":"Determining the Most Effective Diversion Strategy Using Pressure Based Fracture Maps : A Meramec STACK Case Study","authors":"J. Kopp, Charles Kahn, C. Allen, Jake Huchton, Clark Robinson, E. Coenen","doi":"10.2118/194330-MS","DOIUrl":"https://doi.org/10.2118/194330-MS","url":null,"abstract":"\u0000 This paper discusses a STACK (Sooner Trend Anadarko Basin Canadian and Kingfisher Counties) case study that determined the effectiveness of different diversion techniques, including pods, sand ramps with sand slugs, rate cycling, and utilization of the completions order to control fracture growth. A secondary goal of this study was to evaluate the suitability of pressure-based fracture maps and oil and water phase tracers in monitoring diverter effectiveness.\u0000 Effectiveness of a given diverter technique and diverter drop was evaluated using the two techniques on a 3-well pad. The three wells were completed using a combination of: 4 pods per treatment interval6 pods per treatment interval8 pods per treatment intervalhigh-volume proppant loading per treatment interval\u0000 The effectiveness of the diverter drop was evaluated using each of the diagnostic techniques listed above. The pressure-based fracture analysis uses the pressure response recorded in an isolated stage in the monitor well to compute fracture geometry and the rate of growth of the fracture dimensions. The effectiveness of a given diverter drop is classified into one of four possible categories: stop dominant fracture growth, impede dominant fracture growth, no impact on growth of dominant fracture and accelerate the growth of dominant farcture. These results were then compared with the analysis from oil and water phase tracers and treatment pressure analysis.\u0000 Successful (effective) diversion was observed on 82 % of the stages with pods compared to 64% successful diversion where sand ramps were used. In addition, stages using 8 pods for diversion had a 15% reduction in average fracture half-length compared to stages using 4 pods. Fracture height was better controlled through the order of completions of the stages between 3 wells. Completing the middle well in the upper part of the zone ahead of the two outer wells in the lower part of the zone, controlled the vertical height growth of the two outer wells.\u0000 The offset pressure-based analysis proved to be as effective in accurately diagnosing the diverter effectiveness and provided a significant cost and timing advantage compared to other diagnostic techniques.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86091813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Garza, J. Baumbach, James Prosser, S. Pettigrew, Kirsten Elvig
This case study reviews Noble Energy's completion design, execution, and results of an Eagle Ford infill well B3 and the refracturing (refrac) treatments pumped on the direct offsets referred to in this paper as wells A1 and A2. The refrac stimulations were planned to serve the joint purpose of frac hit protection of the existing parent wells' reserves and re-pressurization of depleted zones to improve the performance of the infill child well. Both chemical diversion and mechanical diversion pods were utilized on the bullhead style refrac to optimize lateral placement of fracturing fluid and proppant. The A1 refrac was pumped first with a larger job size of proppant, water, and diversion material. The A2 refrac, pumped second, was half the size of the A1. Instantaneous shut-in pressure (ISIP) and diversion pressure response data was captured at each stage for both wells. Infill well B3 was completed last with normal plug-and-perf operations and the optimum job size of the time. The child well B3 production will be compared to offset wells with no depletion risk as well as to a 2014 vintage infill (Y3) well that was completed with no refrac on the direct offsets (X1 and X2). The A1 refrac data showed a gradual trend of increasing ISIP and treating pressure throughout the job indicating a more uniform stimulation of the lateral. There is a sustained production uplift resulting in a 36% improvement in estimated ultimate recovery (EUR). The A2 refrac data showed anomalous ISIP and pressure spikes mid-way through the job indicating the stimulation was not accessing the entire lateral. This blockage downhole was caused by being too aggressive with the concentration of pods pumped per stage. Since the A2 was not effectively re-pressurized, there was negligible change to EUR when the well was returned to production. In comparing the two refracs, we concluded that a larger job (increased proppant, fluid, and diversion) with less concentrated but more frequent diversion drops will increase lateral coverage and more effectively protect the parent well reserves. The surface treating pressures of the infill B3 indicate new rock was stimulated and initial production results trend with offset well production of the area showing no impact from depletion. Contrasting this with the prior infill Y3 completed with no refracs on parent wells, the Y3 has lower initial production (IP) rates and EUR when compared to its offset wells showing an obvious impact from depletion. Additionally, the refrac'd parent well A1 saw an improvement in EUR while the non-refrac'd parent X1 saw EUR degradation. In conclusion, pumping optimized refracs on the offset parent wells will both protect parent well reserves and improve the performance of the child well.
本案例研究回顾了Noble Energy在Eagle Ford B3井的完井设计、执行和结果，以及在本文中提到的A1和A2井的直接邻井进行的重复压裂(frac)处理。重复压裂措施的目的是为了保护现有母井的储量，并对枯竭区进行再加压，以提高填充子井的产量。为了优化压裂液和支撑剂的横向位置，在bullhead式压裂中使用了化学导流和机械导流吊舱。首先泵送的是A1压裂段，支撑剂、水和导流材料的用量较大。第二次泵入的A2折光管尺寸只有A1折光管的一半。在两口井的每个阶段捕获了瞬时关井压力(ISIP)和导流压力响应数据。B3井最后完成，采用了正常的桥塞射孔作业和最佳作业规模。B3子井的产量将与没有枯竭风险的邻井进行比较，并与2014年的一口旧井(Y3)进行比较，该井在直接邻井(X1和X2)上没有发生折光。A1裂缝数据显示，在整个作业过程中，ISIP和处理压力逐渐增加，这表明对分支层的增产更加均匀。由于产量持续上升，估计最终采收率(EUR)提高了36%。A2压裂数据显示了异常的ISIP和压力峰值，表明增产措施没有进入整个分支。这种井下堵塞是由于每级泵入的吊舱浓度太大造成的。由于A2没有进行有效的再加压，因此当井恢复生产时，EUR的变化可以忽略不计。通过对两种压裂方法的比较，我们得出结论，如果作业规模更大(增加支撑剂、流体和导流剂)，且导流剂投放浓度更低，但频率更高，则可以增加横向覆盖范围，更有效地保护母井储量。B3区块的地表处理压力表明，该区块已增产新岩，初始生产结果呈趋势，该区域的邻井产量未受枯竭影响。与之前未对母井进行压裂的Y3井相比，Y3井的初始产量(IP)和EUR比邻井低，受枯竭影响明显。此外，重复压裂母井A1的EUR值有所提高，而非重复压裂母井X1的EUR值则有所下降。综上所述，在邻井母井上泵入优化的压裂液，既能保护母井储量，又能提高子井的产量。
{"title":"An Eagle Ford Case Study: Improving an Infill Well Completion Through Optimized Refracturing Treatment of the Offset Parent Wells","authors":"M. Garza, J. Baumbach, James Prosser, S. Pettigrew, Kirsten Elvig","doi":"10.2118/194374-MS","DOIUrl":"https://doi.org/10.2118/194374-MS","url":null,"abstract":"\u0000 This case study reviews Noble Energy's completion design, execution, and results of an Eagle Ford infill well B3 and the refracturing (refrac) treatments pumped on the direct offsets referred to in this paper as wells A1 and A2. The refrac stimulations were planned to serve the joint purpose of frac hit protection of the existing parent wells' reserves and re-pressurization of depleted zones to improve the performance of the infill child well. Both chemical diversion and mechanical diversion pods were utilized on the bullhead style refrac to optimize lateral placement of fracturing fluid and proppant.\u0000 The A1 refrac was pumped first with a larger job size of proppant, water, and diversion material. The A2 refrac, pumped second, was half the size of the A1. Instantaneous shut-in pressure (ISIP) and diversion pressure response data was captured at each stage for both wells. Infill well B3 was completed last with normal plug-and-perf operations and the optimum job size of the time. The child well B3 production will be compared to offset wells with no depletion risk as well as to a 2014 vintage infill (Y3) well that was completed with no refrac on the direct offsets (X1 and X2).\u0000 The A1 refrac data showed a gradual trend of increasing ISIP and treating pressure throughout the job indicating a more uniform stimulation of the lateral. There is a sustained production uplift resulting in a 36% improvement in estimated ultimate recovery (EUR). The A2 refrac data showed anomalous ISIP and pressure spikes mid-way through the job indicating the stimulation was not accessing the entire lateral. This blockage downhole was caused by being too aggressive with the concentration of pods pumped per stage. Since the A2 was not effectively re-pressurized, there was negligible change to EUR when the well was returned to production. In comparing the two refracs, we concluded that a larger job (increased proppant, fluid, and diversion) with less concentrated but more frequent diversion drops will increase lateral coverage and more effectively protect the parent well reserves.\u0000 The surface treating pressures of the infill B3 indicate new rock was stimulated and initial production results trend with offset well production of the area showing no impact from depletion. Contrasting this with the prior infill Y3 completed with no refracs on parent wells, the Y3 has lower initial production (IP) rates and EUR when compared to its offset wells showing an obvious impact from depletion. Additionally, the refrac'd parent well A1 saw an improvement in EUR while the non-refrac'd parent X1 saw EUR degradation. In conclusion, pumping optimized refracs on the offset parent wells will both protect parent well reserves and improve the performance of the child well.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87317638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Fu, Ji-xiang Huang, R. Settgast, J. Morris, F. Ryerson
A hydraulic fracture's height growth is known to be affected by many factors that are related to the layered structure of sedimentary rocks. While these factors are often used to qualitatively explain why hydraulic fractures usually have well-bounded height growth, most of them cannot be directly and quantitatively characterized for a given reservoir to enable a priori prediction of fracture height growth. In this work, we study the role of the "roughness" of in situ stress profiles, namely alternating low- and high-stress among rock layers, in determining the tendency of a hydraulic fracture to propagate horizontally versus vertically. We found that a hydraulic fracture propagates horizontally in low-stress layers ahead of neighboring high-stress layers. Under such a configuration, a fracture mechanics principle dictates that the net pressure required for horizontal growth of high-stress layers within the current fracture height is significantly lower than that required for additional vertical growth across rock layers. Without explicit consideration of the rough stress profile, the system behaves as if the rock is tougher against vertical propagation than it is against horizontal fracture propagation. We developed a simple relationship between the apparent differential rock toughness and characteristics of the stress roughness that induce equivalent overall fracture shapes. This relationship enables existing hydraulic fracture models to represent the effects of rough in situ stress on fracture growth without directly representing the fine-resolution rough stress profiles.
{"title":"Apparent Toughness Anisotropy Induced by Roughness of in Situ Stress: A Mechanism that Hinders Vertical Growth of Hydraulic Fractures and Its Simplified Modeling","authors":"P. Fu, Ji-xiang Huang, R. Settgast, J. Morris, F. Ryerson","doi":"10.2118/194359-MS","DOIUrl":"https://doi.org/10.2118/194359-MS","url":null,"abstract":"A hydraulic fracture's height growth is known to be affected by many factors that are related to the layered structure of sedimentary rocks. While these factors are often used to qualitatively explain why hydraulic fractures usually have well-bounded height growth, most of them cannot be directly and quantitatively characterized for a given reservoir to enable a priori prediction of fracture height growth. In this work, we study the role of the \"roughness\" of in situ stress profiles, namely alternating low- and high-stress among rock layers, in determining the tendency of a hydraulic fracture to propagate horizontally versus vertically. We found that a hydraulic fracture propagates horizontally in low-stress layers ahead of neighboring high-stress layers. Under such a configuration, a fracture mechanics principle dictates that the net pressure required for horizontal growth of high-stress layers within the current fracture height is significantly lower than that required for additional vertical growth across rock layers. Without explicit consideration of the rough stress profile, the system behaves as if the rock is tougher against vertical propagation than it is against horizontal fracture propagation. We developed a simple relationship between the apparent differential rock toughness and characteristics of the stress roughness that induce equivalent overall fracture shapes. This relationship enables existing hydraulic fracture models to represent the effects of rough in situ stress on fracture growth without directly representing the fine-resolution rough stress profiles.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85907178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Seyyed Mohammad Hashemi Najafi, D. Bousfield, M. Tajvidi
Cracking at the fold of publication and packaging paper grades is a serious problem that can lead to rejection of product. Recent work has revealed some basic mechanisms and the influence of various parameters on the extent of crack area, but no studies are reported using coating layers with known mechanical properties, especially for double-coated systems. In this study, coating layers with different and known mechanical properties were used to characterize crack formation during folding. The coating formulations were applied on two different basis weight papers, and the coated papers were folded. The binder systems in these formulations were different combinations of a styrene-butadiene latex and mixtures of latex and starch for two different pigment volume concentrations (PVC). Both types of papers were coated with single and double layers. The folded area was scanned with a high-resolution scanner while the samples were kept at their folded angle. The scanned images were analyzed within a constant area. The crack areas were reported for different types of papers, binder system and PVC values. As PVC, starch content, and paper basis weight increased, the crack area increased. Double layer coated papers with high PVC and high starch content at the top layer had more cracks in comparison with a single layer coated paper, but when the PVC of the top layer was low, cracking area decreased. No measurable cracking was observed when the top layer was formulated with a 100% latex layer.
{"title":"Cracking at the fold in double layer coated paper: the influence of latex and starch composition","authors":"Seyyed Mohammad Hashemi Najafi, D. Bousfield, M. Tajvidi","doi":"10.32964/TJ18.2.93","DOIUrl":"https://doi.org/10.32964/TJ18.2.93","url":null,"abstract":"Cracking at the fold of publication and packaging paper grades is a serious problem that can lead to rejection of product. Recent work has revealed some basic mechanisms and the influence of various parameters on the extent of crack area, but no studies are reported using coating layers with known mechanical properties, especially for double-coated systems. In this study, coating layers with different and known mechanical properties were used to characterize crack formation during folding. The coating formulations were applied on two different basis weight papers, and the coated papers were folded. The binder systems in these formulations were different combinations of a styrene-butadiene latex and mixtures of latex and starch for two different pigment volume concentrations (PVC). Both types of papers were coated with single and double layers. The folded area was scanned with a high-resolution scanner while the samples were kept at their folded angle. The scanned images were analyzed within a constant area. The crack areas were reported for different types of papers, binder system and PVC values. As PVC, starch content, and paper basis weight increased, the crack area increased. Double layer coated papers with high PVC and high starch content at the top layer had more cracks in comparison with a single layer coated paper, but when the PVC of the top layer was low, cracking area decreased. No measurable cracking was observed when the top layer was formulated with a 100% latex layer.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88012868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
For reasons of personal health and the environment, consumers are searching for “green” products. Packaging producers and consumers are seeing increased regulations set by authorities for packaging material and waste. Thus, interest in the development of renewable, sustainable fiber-based packaging products is growing. In recent years the paper industry has focused on finding substrates and the chemical suppliers have focused on developing different coating media to enhance properties. Sustainable paper and board barrier products are needed to create an alternative to the use of conventional packaging solutions containing plastics, perfluorocarbon, and wax. Typically, products with a water-based barrier coating are more expensive than conventional packaging solutions. Therefore, to make the new products with water-based barrier coatings cost competitive, the best achievable performance with the lowest coat weight is important so that production costs can be kept as low as possible. Results from pilot trials are presented that consider base stock (pretreated and non-pretreated), application methods by long- and short- (zero) dwell, and metering by rod and resilient tip. Laboratory evaluations of the coverage and barrier performance indicate the proper direction for obtaining a barrier.
{"title":"Optimization of coating with water-based barriers","authors":"Tommy Larsson, P. Emilsson","doi":"10.32964/TJ18.2.111","DOIUrl":"https://doi.org/10.32964/TJ18.2.111","url":null,"abstract":"For reasons of personal health and the environment, consumers are searching for “green” products. Packaging producers and consumers are seeing increased regulations set by authorities for packaging material and waste. Thus, interest in the development of renewable, sustainable fiber-based packaging products is growing. In recent years the paper industry has focused on finding substrates and the chemical suppliers have focused on developing different coating media to enhance properties. Sustainable paper and board barrier products are needed to create an alternative to the use of conventional packaging solutions containing plastics, perfluorocarbon, and wax. Typically, products with a water-based barrier coating are more expensive than conventional packaging solutions. Therefore, to make the new products with water-based barrier coatings cost competitive, the best achievable performance with the lowest coat weight is important so that production costs can be kept as low as possible. Results from pilot trials are presented that consider base stock (pretreated and non-pretreated), application methods by long- and short- (zero) dwell, and metering by rod and resilient tip. Laboratory evaluations of the coverage and barrier performance indicate the proper direction for obtaining a barrier.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74945330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cracking at the fold is a serious issue for many grades of coated paper and coated board. Some recent work has suggested methods to minimize this problem by using two or more coating layers of different properties. A discrete element method (DEM) has been used to model deformation events for single layer coating systems such as in-plain and out-of-plain tension, three-point bending, and a novel moving force picking simulation, but nothing has been reported related to multiple coating layers. In this paper, a DEM model has been expanded to predict the three-point bending response of a two-layer system. The main factors evaluated include the use of different binder systems in each layer and the ratio of the bottom and top layer weights. As in the past, the properties of the binder and the binder concentration are input parameters. The model can predict crack formation that is a function of these two sets of factors. In addition, the model can predict the flexural modulus, the maximum flexural stress, and the strain-at-failure. The predictions are qualitatively compared with experimental results reported in the literature.
{"title":"Discrete element method to model cracking for two layer systems","authors":"Dan Varney, D. Bousfield","doi":"10.32964/TJ18.2.101","DOIUrl":"https://doi.org/10.32964/TJ18.2.101","url":null,"abstract":"Cracking at the fold is a serious issue for many grades of coated paper and coated board. Some recent work has suggested methods to minimize this problem by using two or more coating layers of different properties. A discrete element method (DEM) has been used to model deformation events for single layer coating systems such as in-plain and out-of-plain tension, three-point bending, and a novel moving force picking simulation, but nothing has been reported related to multiple coating layers. In this paper, a DEM model has been expanded to predict the three-point bending response of a two-layer system. The main factors evaluated include the use of different binder systems in each layer and the ratio of the bottom and top layer weights. As in the past, the properties of the binder and the binder concentration are input parameters. The model can predict crack formation that is a function of these two sets of factors. In addition, the model can predict the flexural modulus, the maximum flexural stress, and the strain-at-failure. The predictions are qualitatively compared with experimental results reported in the literature.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81797795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Process issues such as blade deposits, scratches, spits, and defects on the coating surface develop during blade coating of paper at high solids content and fast machine speeds. Coatings that contain high aspect ratio pigments display these issues at lower solids concentrations and slower web speeds than spherical or block shaped pigments. The shape of the pigment particles influences the characteristics of the coating formulation after drying, and high aspect ratio pigments can lead to high gloss surfaces that have good printing properties and are of interest in barrier coatings. The rheology, particle packing, and water retention are all functions of the pigment shape and size distribution. The base sheet properties of porosity, surface roughness, and permeability interact with the coating and the blade coater operating conditions. The possible causes of poor runnability are part of an interrelated and complex system. A cylindrical laboratory coater (CLC) was utilized to determine the speed at which operational and quality issues begin at varying solids concentration for two pigments with different shape factors on two different paper surfaces with varying absorption rates. An operational window was developed for both pigments. Characteristics of the pigment suspensions were explored in order to find a relationship with the onset of operational problems. The high shear rate viscosity of these suspensions did not explain the operational windows. The difference between the solids concentration and the immobilization solids, which is a function of the shape factor, has a linear relationship to the runnability limits. This could be ascribed to the tight packing structure of the particles as the solids content approaches the immobilization solids.
{"title":"Operational limits of blade coating associated with high aspect ratio pigments: Part II—cylindrical laboratory coater","authors":"Lisa Weeks, P. Gane, Tony Lyons, D. Bousfield","doi":"10.32964/TJ18.2.133","DOIUrl":"https://doi.org/10.32964/TJ18.2.133","url":null,"abstract":"Process issues such as blade deposits, scratches, spits, and defects on the coating surface develop during blade coating of paper at high solids content and fast machine speeds. Coatings that contain high aspect ratio pigments display these issues at lower solids concentrations and slower web speeds than spherical or block shaped pigments. The shape of the pigment particles influences the characteristics of the coating formulation after drying, and high aspect ratio pigments can lead to high gloss surfaces that have good printing properties and are of interest in barrier coatings. The rheology, particle packing, and water retention are all functions of the pigment shape and size distribution. The base sheet properties of porosity, surface roughness, and permeability interact with the coating and the blade coater operating conditions. The possible causes of poor runnability are part of an interrelated and complex system. A cylindrical laboratory coater (CLC) was utilized to determine the speed at which operational and quality issues begin at varying solids concentration for two pigments with different shape factors on two different paper surfaces with varying absorption rates. An operational window was developed for both pigments. Characteristics of the pigment suspensions were explored in order to find a relationship with the onset of operational problems. The high shear rate viscosity of these suspensions did not explain the operational windows. The difference between the solids concentration and the immobilization solids, which is a function of the shape factor, has a linear relationship to the runnability limits. This could be ascribed to the tight packing structure of the particles as the solids content approaches the immobilization solids.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81640761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Operational issues, such as stalagmite formations, scratches, or spits, develop during blade coating of high solids coatings at high web speeds. Coatings that contain high aspect ratio pigments exhibit these difficulties at lower solids concentrations and slower machine speeds than coatings comprised of more spherical shaped pigments. There are a number of potential reasons behind this phenomenon, but a clear mechanism is not well established. Using a bench top blade coater without a base sheet, the goal of this study is to understand the operational limits that occur due to the coating suspension interacting with the blade. Pigment suspensions are applied in excess in front of the blade. A camera mounted near the blade exit is used to detect defects and buildup on the backside of the blade. The machine speed at which deposits on the blade first appear was determined for three pigments having different shape factors and at varying weight fractions. A Newtonian fluid was also used in the coating device. A runnability window based on shape factor and solids content was developed. Small changes in the solids concentration displayed changes in the speed at which blade deposits begin to appear. No operational issues could be produced using the Newtonian fluid. Presence of the particles at solids concentration nearing their immobilization solids mustbe contributing to the development of runnability issues.
{"title":"Operational limits of blade coating associated with high aspect ratio pigments: Part I—bench top blade coater","authors":"Lisa Weeks, P. Gane, Tony Lyons, D. Bousfield","doi":"10.32964/TJ18.2.123","DOIUrl":"https://doi.org/10.32964/TJ18.2.123","url":null,"abstract":"Operational issues, such as stalagmite formations, scratches, or spits, develop during blade coating of high solids coatings at high web speeds. Coatings that contain high aspect ratio pigments exhibit these difficulties at lower solids concentrations and slower machine speeds than coatings comprised of more spherical shaped pigments. There are a number of potential reasons behind this phenomenon, but a clear mechanism is not well established. Using a bench top blade coater without a base sheet, the goal of this study is to understand the operational limits that occur due to the coating suspension interacting with the blade. Pigment suspensions are applied in excess in front of the blade. A camera mounted near the blade exit is used to detect defects and buildup on the backside of the blade. The machine speed at which deposits on the blade first appear was determined for three pigments having different shape factors and at varying weight fractions. A Newtonian fluid was also used in the coating device. A runnability window based on shape factor and solids content was developed. Small changes in the solids concentration displayed changes in the speed at which blade deposits begin to appear. No operational issues could be produced using the Newtonian fluid. Presence of the particles at solids concentration nearing their immobilization solids mustbe contributing to the development of runnability issues.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77967545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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