{"title":"Cracking Canisp: Deep void evolution during ancient earthquakes","authors":"","doi":"10.1144/geosci2019-003","DOIUrl":"https://doi.org/10.1144/geosci2019-003","url":null,"abstract":"","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86898669","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}
{"title":"Eruptions and ships","authors":"","doi":"10.1144/geosci2019-002","DOIUrl":"https://doi.org/10.1144/geosci2019-002","url":null,"abstract":"","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88694339","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}
{"title":"Distant Thunder: Romance of the Fossiles","authors":"","doi":"10.1144/geosci2019-006","DOIUrl":"https://doi.org/10.1144/geosci2019-006","url":null,"abstract":"","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":"632 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73319560","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}
{"title":"Southwest Britain inspires through the ages","authors":"","doi":"10.1144/geosci2019-005","DOIUrl":"https://doi.org/10.1144/geosci2019-005","url":null,"abstract":"","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81170923","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}
Coring adjacent to a hydraulically fractured horizontal well in Eagle Ford shale by Conoco-Phillips has revealed several closely spaced parallel hydraulic fractures (separated only by few inches) propagating in the direction perpendicular to the wellbore axis. The number of observed hydraulic fractures greatly exceed the number of clusters according to the recent paper titled "Sampling a Stimulated Rock Volume: An Eagle Ford Example". The observed behavior is contrary to the conventional practice of hydraulic fracture modeling where often a single fracture from each perforation cluster. This assumption stems from a simplified concept of the stress shadow that inhibit the growth of multiple parallel fractures under very tight spacing. In this study we show that correct modeling can in fact capture the field observed fracture clusters or swarms of closely-spaced fractures. Numerical model based on displacement discontinuity method is used to simulate non-planar hydraulic fracture propagation. Fracture deformation, fluid flow and perforation friction are fully coupled. Fracture propagation from a single cluster consisting of 20 perforations under 1800 phasing spanning 5 ft is considered. The effect of controlling parameters such as far-field stress contrast, perforation properties, and fracture toughness on multiple hydraulic fracture growth from a cluster of perforations is studied. The results show that closely spaced fracture clusters or swarms can occur for a certain range of conditions and operational parameters. The in-situ stress contrast, perforations conditions, and injection rates exert a significant influence. Under the right conditions, closely-spaced fractures can extend to distances exceeding tens of feet from the wellbore. Early termination and/or coalescence of closely spaced fractures can also occur. To our knowledge, our modeling results are the only ones that can explain the data from the Conoco-Phillips field observations regarding the occurrence of fracture swarms. The resuts show that the assumption of a single fracture per cluster does not hold true under all conditions. Moreover, such assumption would significantly underestimate stimulated rock volume near the wellbore. Finally, our results capture the injection pressure data which can be used as a diagnostic tool to infer the perforation effectiveness (i.e., the number of perforations that are in contact with fluid flow).
{"title":"Simulation and Analysis of Fracture Swarms Observed in the Eagle Ford Field Experiment","authors":"V. Sesetty, A. Ghassemi","doi":"10.2118/194328-MS","DOIUrl":"https://doi.org/10.2118/194328-MS","url":null,"abstract":"\u0000 Coring adjacent to a hydraulically fractured horizontal well in Eagle Ford shale by Conoco-Phillips has revealed several closely spaced parallel hydraulic fractures (separated only by few inches) propagating in the direction perpendicular to the wellbore axis. The number of observed hydraulic fractures greatly exceed the number of clusters according to the recent paper titled \"Sampling a Stimulated Rock Volume: An Eagle Ford Example\". The observed behavior is contrary to the conventional practice of hydraulic fracture modeling where often a single fracture from each perforation cluster. This assumption stems from a simplified concept of the stress shadow that inhibit the growth of multiple parallel fractures under very tight spacing. In this study we show that correct modeling can in fact capture the field observed fracture clusters or swarms of closely-spaced fractures.\u0000 Numerical model based on displacement discontinuity method is used to simulate non-planar hydraulic fracture propagation. Fracture deformation, fluid flow and perforation friction are fully coupled. Fracture propagation from a single cluster consisting of 20 perforations under 1800 phasing spanning 5 ft is considered. The effect of controlling parameters such as far-field stress contrast, perforation properties, and fracture toughness on multiple hydraulic fracture growth from a cluster of perforations is studied.\u0000 The results show that closely spaced fracture clusters or swarms can occur for a certain range of conditions and operational parameters. The in-situ stress contrast, perforations conditions, and injection rates exert a significant influence. Under the right conditions, closely-spaced fractures can extend to distances exceeding tens of feet from the wellbore. Early termination and/or coalescence of closely spaced fractures can also occur.\u0000 To our knowledge, our modeling results are the only ones that can explain the data from the Conoco-Phillips field observations regarding the occurrence of fracture swarms. The resuts show that the assumption of a single fracture per cluster does not hold true under all conditions. Moreover, such assumption would significantly underestimate stimulated rock volume near the wellbore. Finally, our results capture the injection pressure data which can be used as a diagnostic tool to infer the perforation effectiveness (i.e., the number of perforations that are in contact with fluid flow).","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75179242","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}
Cyrille Defeu, Ryan Williams, Dan Shan, Joel Martin, D. Cannon, Kyle Clifton, Chad Lollar
Unconventional plays across the US are often made of stacked pays, typically ranging from a few hundred to thousands of feet thick. These stacked pay intervals are generally segregated into different formations as dictated by differences in geology, mineralogy, rock fabric, and fluid type. This proves to be a challenge because many stacked/staggered horizontal wells are required to provide effective coverage of the reservoir. Selecting the right landing location can become even more challenging in an environment with existing producing wells in adjacent formations because pressure depletion and its associated effects on fracture propagation necessitate consideration of vertical spacing and time. In this study, we outline an integrated approach that addresses a four-dimensional horizontal well placement challenge in the Midland basin's Wolfcamp A formation using advanced hydraulic fracture modeling to calibrate hydraulic fracture geometries and history match five producing wells in both Lower Spraberry and Wolfcamp B. The optimal landing location within the Wolfcamp A was determined based on an assessment of reservoir quality, rock mechanics, unique structural features, and depletion effects. These data were then combined to form a 4D geomodel that enabled a completion optimization study via modeling of the resulting complex hydraulic fracture geometry and subsequent hydrocarbon production. This integrated workflow, using a wide array of high-quality datasets and the input of experts from multiple disciplines, yielded a comprehensive assessment and clear recommendations for this challenging partially depleted stacked pay interval. Although this study is specific to the Midland basin's Lower Spraberry and Wolfcamp A and B formations, many sections of the workflow apply to other basins and their unique strata.
{"title":"Case Study of a Landing Location Optimization within a Depleted Stacked Reservoir in the Midland Basin","authors":"Cyrille Defeu, Ryan Williams, Dan Shan, Joel Martin, D. Cannon, Kyle Clifton, Chad Lollar","doi":"10.2118/194353-ms","DOIUrl":"https://doi.org/10.2118/194353-ms","url":null,"abstract":"\u0000 Unconventional plays across the US are often made of stacked pays, typically ranging from a few hundred to thousands of feet thick. These stacked pay intervals are generally segregated into different formations as dictated by differences in geology, mineralogy, rock fabric, and fluid type. This proves to be a challenge because many stacked/staggered horizontal wells are required to provide effective coverage of the reservoir. Selecting the right landing location can become even more challenging in an environment with existing producing wells in adjacent formations because pressure depletion and its associated effects on fracture propagation necessitate consideration of vertical spacing and time.\u0000 In this study, we outline an integrated approach that addresses a four-dimensional horizontal well placement challenge in the Midland basin's Wolfcamp A formation using advanced hydraulic fracture modeling to calibrate hydraulic fracture geometries and history match five producing wells in both Lower Spraberry and Wolfcamp B.\u0000 The optimal landing location within the Wolfcamp A was determined based on an assessment of reservoir quality, rock mechanics, unique structural features, and depletion effects. These data were then combined to form a 4D geomodel that enabled a completion optimization study via modeling of the resulting complex hydraulic fracture geometry and subsequent hydrocarbon production.\u0000 This integrated workflow, using a wide array of high-quality datasets and the input of experts from multiple disciplines, yielded a comprehensive assessment and clear recommendations for this challenging partially depleted stacked pay interval. Although this study is specific to the Midland basin's Lower Spraberry and Wolfcamp A and B formations, many sections of the workflow apply to other basins and their unique strata.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84849909","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}
Microseismic monitoring is generally the most reliable method for estimating stimulated fractured volume. Receivers used in microseismic monitoring measure only seismic events. That limitation explains why only a small portion of the energy budget during hydraulic fracturing can be estimated by information obtained from microseismic monitoring. We performed a series of numerical experiments to investigate the effects of rock mechanical properties and fracture friction characteristics on seismic efficiency and rupture velocity. We conducted numerical experiments using acoustic emission for saw-cut samples under triaxial loads and applied slip-weakening constitutive modeling for natural fractures to study how the Young's modulus and slip-weakening distance affect seismic efficiency and rupture velocity. Perhaps surprisingly, our results show that rocks with higher values of the Young's modulus have lower seismic efficiency generated from sliding on pre-existing natural fractures, while lower rigidity leads to higher seismic efficiency. These results do not contradict general beliefs about the effect of rigidity on fracability. More rigid rocks are more favorable for hydraulic fracturing and generate larger fracture networks; however, compared with less rigid rocks, fewer events would be detected seismically. The results also give insight into how to connect geomechanical numerical modeling of hydraulic fractures in naturally fractured reservoirs with microseismic data from the field and actual subsurface-generated fractured networks.
{"title":"Bridging Geomechanical and Geophysical Numerical Modeling: Evaluation of Seismic Efficiency and Rupture Velocity with Application to Estimating the Fractured Network Generated by Hydraulic Fracturing","authors":"F. Sheibani, B. Hager","doi":"10.2118/194307-MS","DOIUrl":"https://doi.org/10.2118/194307-MS","url":null,"abstract":"\u0000 Microseismic monitoring is generally the most reliable method for estimating stimulated fractured volume. Receivers used in microseismic monitoring measure only seismic events. That limitation explains why only a small portion of the energy budget during hydraulic fracturing can be estimated by information obtained from microseismic monitoring.\u0000 We performed a series of numerical experiments to investigate the effects of rock mechanical properties and fracture friction characteristics on seismic efficiency and rupture velocity. We conducted numerical experiments using acoustic emission for saw-cut samples under triaxial loads and applied slip-weakening constitutive modeling for natural fractures to study how the Young's modulus and slip-weakening distance affect seismic efficiency and rupture velocity. Perhaps surprisingly, our results show that rocks with higher values of the Young's modulus have lower seismic efficiency generated from sliding on pre-existing natural fractures, while lower rigidity leads to higher seismic efficiency. These results do not contradict general beliefs about the effect of rigidity on fracability. More rigid rocks are more favorable for hydraulic fracturing and generate larger fracture networks; however, compared with less rigid rocks, fewer events would be detected seismically. The results also give insight into how to connect geomechanical numerical modeling of hydraulic fractures in naturally fractured reservoirs with microseismic data from the field and actual subsurface-generated fractured networks.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86930279","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}
Wenyue Xu, R. Prioul, T. Bérard, X. Weng, O. Kresse
This work introduces a new set of energy-balance-based criteria for the vertical growth of a plain-strain planar hydraulic fracture across a horizontally laminated reservoir formation with heterogenous layer properties and multiple weak interfaces. Combined with Coulomb's friction law for mechanical balance along sliding interfaces, these criteria were built into a novel semi-analytical model of fractional fracture height growth. The model was then applied to investigate the growth of hydraulic fractures in an idealized symmetric three-layer rock formation, with the upper and lower layers acting as barriers to the growth. Preliminary modeling results show how the vertical growth of a hydraulic fracture is influenced by the various mechanical/energy barriers. Three primary types of barrier behaviors are identified. A stress barrier leads to gradually increasing fluid pressure when the barrier layer is crossed. A toughness/modulus barrier, on the other hand, results in an immediate sharp increase in fluid pressure followed by gradual decline in pressure. The effect of individual sliding interfaces is similar to that of a toughness/modulus barrier. The cumulative effect becomes more important when multiple closely spaced interfaces are present. A formation layer containing multiple closely spaced weak interfaces behaves collectively much like a stress barrier.
{"title":"Barriers to Hydraulic Fracture Height Growth: A New Model for Sliding Interfaces","authors":"Wenyue Xu, R. Prioul, T. Bérard, X. Weng, O. Kresse","doi":"10.2118/194327-MS","DOIUrl":"https://doi.org/10.2118/194327-MS","url":null,"abstract":"\u0000 This work introduces a new set of energy-balance-based criteria for the vertical growth of a plain-strain planar hydraulic fracture across a horizontally laminated reservoir formation with heterogenous layer properties and multiple weak interfaces. Combined with Coulomb's friction law for mechanical balance along sliding interfaces, these criteria were built into a novel semi-analytical model of fractional fracture height growth. The model was then applied to investigate the growth of hydraulic fractures in an idealized symmetric three-layer rock formation, with the upper and lower layers acting as barriers to the growth. Preliminary modeling results show how the vertical growth of a hydraulic fracture is influenced by the various mechanical/energy barriers. Three primary types of barrier behaviors are identified. A stress barrier leads to gradually increasing fluid pressure when the barrier layer is crossed. A toughness/modulus barrier, on the other hand, results in an immediate sharp increase in fluid pressure followed by gradual decline in pressure. The effect of individual sliding interfaces is similar to that of a toughness/modulus barrier. The cumulative effect becomes more important when multiple closely spaced interfaces are present. A formation layer containing multiple closely spaced weak interfaces behaves collectively much like a stress barrier.","PeriodicalId":10957,"journal":{"name":"Day 1 Tue, February 05, 2019","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80991735","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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