Characteristics, chronology and controls on natural fractures in tight sandstone reservoirs of the Triassic Chang 6 Member, Yanchi area, Ordos Basin, China

Characteristics, chronology and controls on natural fractures in tight sandstone reservoirs of the Triassic Chang 6 Member, Yanchi area, Ordos Basin, China | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Characteristics, chronology and controls on natural fractures in tight sandstone reservoirs of the Triassic Chang 6 Member, Yanchi area, Ordos Basin, China Shangfeng Yang, Jinfeng Ruan, Miao Li, Ma Suo, Bohua Zhu, Jia Zhao, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8438007/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 13 You are reading this latest preprint version Abstract The Triassic Chang 6 Member is a significant oil layer in the Ordos Basin, north-west China, and is considered to be a tight sandstone reservoir. Natural fractures have significantly exerted enormous influence on the reservoir quality. This study employs similar outcrops, cores, imaging logs, thin sections, scanning electron microscopy (SEM), fluid inclusions and stable isotope analyses to investigate the characteristics, chronology and controlling factors impacting fracture development in tight sandstones. There are four recognized types of natural fractures in the Chang 6 Member: 1) tectonic shear, 2) extension, 3) bedding-parallel, and 4) micro. Tectonic shear fracture plays a predominant role in the reservoir modification, with two sets of crosscutting strikes (E-W and ENE-WSW), high-dip angle, middle width and fillings (i.e. calcite, ankerite and quartz). In detail, the E-W oriented fractures occur with fills, but without in the ENE-WSW oriented ones. According to C-O isotope and fluid inclusion microthermometry, the fracture filling of calcite is characterized by 18 O (δ 18 O PDB varying from − 21.30‰ to -18.30‰, mean = -20.00‰, and corresponding to the O isotope calculated temperature from 62.1℃ to 85.3℃ with an average of 74.4℃), 13 C (δ 13 C PDB varying between − 5.70‰ and − 3.10‰, mean = -4.10‰) and lower homogenization temperatures (Th's) ranging from 71.2℃ to 92.7℃, mean = 80.3℃. The fracture filling of ankerite is abundant in 16 O (δ 18 O PDB varying from − 25.60‰ to -17.50‰, mean = -21.80‰, and corresponding with the O isotope calculated temperature from 82.1℃ to 121.5℃ with an average of 103.2℃), 12 C (δ 13 C PDB varying between − 7.10‰ and − 5.30‰, mean = -6.06‰) and higher Th's ranging from 100.6℃ to 112.1℃, mean = 105.1℃. For the quartz fracture filling, Th's mainly sits between 120.5℃ and 129.8℃, mean = 122.2℃. Combining with mineralization and burial-thermal history, the Chang 6 natural fractures are thought to develop during three periods: 1) the Yanshanian Ⅰ episode during the end of the Jurassic to the Early Cretaceous, 2) the Yanshanian Ⅱ episode in the middle of the Cretaceous, and 3) the Himalayan episode during the end of the Cretaceous to the Paleogene. Historically, it was documented the fractures developed during only two periods (i.e. the end of the Jurassic and the end of Cretaceous to the Paleogene) in the past decades, but changed with the advances in this chronology analysis. When it comes to fracture density, it's constricted by sandstone thickness; but it increases first then decreases with the increase in net-gross-ratio (NGR). Mineralogically, fracture density correlates positively with rigid component contents (i.e. quartz, feldspar, dolomite and calcite cements), but negatively with plastic composition (i.e. rock fragment, clay, and mica). Porosity, to some extent, restricts fractures in the way of strain accommodation by coordination and adjustment between the pore system and its filling fluids. This study provides insights into when natural fractures occur and how sedimentary factors and modal compositions influence fracture density of tight sandstones. Earth and environmental sciences/Planetary science Earth and environmental sciences/Solid earth sciences Natural fracture Tight sandstone Triassic Chang 6 Member Yanchi area Ordos Basin Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 01 Apr, 2026 Reviews received at journal 31 Mar, 2026 Reviewers agreed at journal 25 Mar, 2026 Reviewers agreed at journal 03 Mar, 2026 Reviews received at journal 30 Jan, 2026 Reviews received at journal 19 Jan, 2026 Reviewers agreed at journal 10 Jan, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers invited by journal 08 Jan, 2026 Editor assigned by journal 08 Jan, 2026 Editor invited by journal 08 Jan, 2026 Submission checks completed at journal 05 Jan, 2026 First submitted to journal 05 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8438007","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":572480137,"identity":"4bdd7f99-5a3b-49d1-b494-9c9049fe1118","order_by":0,"name":"Shangfeng Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwUlEQVRIiWNgGAWjYLACxgY5OSDFRpIWY2OYFgmitSQ2EK3F4EaOmeTPHQbpG443P3vAuMOmjigt0rxnDHI3nDlmbsB4Jo2wLWa3c7dJM7b9yd1wI8FMgrHtMHFaJH+2GaQb3H/+DajlP3FaJHjbDBIMbvCAbDlAWIv9/fefrYFaDGeeySmTSGxLlmwgpEWy51jiTaDD5PmOH98m8bHNjp+gLUDAAnaLwgEgkUCMeiBg/gAi5Qk6aBSMglEwCkYsAAA9VD7184ZpEgAAAABJRU5ErkJggg==","orcid":"","institution":"Sinopec Geophysical Research Institute Co., Ltd.","correspondingAuthor":true,"prefix":"","firstName":"Shangfeng","middleName":"","lastName":"Yang","suffix":""},{"id":572480140,"identity":"f31104a2-e509-47a5-90a7-0f884a251cf2","order_by":1,"name":"Jinfeng Ruan","email":"","orcid":"","institution":"The Fifth Oil Production plant, PetroChina Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Jinfeng","middleName":"","lastName":"Ruan","suffix":""},{"id":572480141,"identity":"547523e6-7780-42f7-8214-8f74a42d09a5","order_by":2,"name":"Miao Li","email":"","orcid":"","institution":"The Fifth Oil Production plant, PetroChina Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Miao","middleName":"","lastName":"Li","suffix":""},{"id":572480142,"identity":"b21e1627-a27f-4ae5-ba7f-bc2ca22858ee","order_by":3,"name":"Ma Suo","email":"","orcid":"","institution":"The Fifth Oil Production plant, PetroChina Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Ma","middleName":"","lastName":"Suo","suffix":""},{"id":572480143,"identity":"3d139f26-3b95-44c5-aceb-db8091b23ddc","order_by":4,"name":"Bohua Zhu","email":"","orcid":"","institution":"Sinopec Geophysical Research Institute Co., Ltd.","correspondingAuthor":false,"prefix":"","firstName":"Bohua","middleName":"","lastName":"Zhu","suffix":""},{"id":572480144,"identity":"9515f84a-34a7-4f6d-b10b-8695f7f8a0f2","order_by":5,"name":"Jia Zhao","email":"","orcid":"","institution":"The Fifth Oil Production plant, PetroChina Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Jia","middleName":"","lastName":"Zhao","suffix":""},{"id":572480145,"identity":"c323fdca-e840-4a5e-9896-5c481207aeb6","order_by":6,"name":"Huan Zhao","email":"","orcid":"","institution":"The Fifth Oil Production plant, PetroChina Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Huan","middleName":"","lastName":"Zhao","suffix":""},{"id":572480146,"identity":"59e6ebb6-7b3f-4380-8abe-7a0416eb8095","order_by":7,"name":"Zhidong Bao","email":"","orcid":"","institution":"College of Geosciences, China University of Petroleum (Beijing)","correspondingAuthor":false,"prefix":"","firstName":"Zhidong","middleName":"","lastName":"Bao","suffix":""},{"id":572480147,"identity":"70f8610c-bc56-47cf-be67-268714ed58a5","order_by":8,"name":"Fei Li","email":"","orcid":"","institution":"Sinopec Geophysical Research Institute Co., Ltd.","correspondingAuthor":false,"prefix":"","firstName":"Fei","middleName":"","lastName":"Li","suffix":""},{"id":572480148,"identity":"a95c7d78-b215-4766-b4b0-7bb54cb60ff0","order_by":9,"name":"Hongzhu Chen","email":"","orcid":"","institution":"Sinopec Geophysical Research Institute Co., Ltd.","correspondingAuthor":false,"prefix":"","firstName":"Hongzhu","middleName":"","lastName":"Chen","suffix":""},{"id":572480152,"identity":"8497ded8-d4b5-406e-9e1c-9ba26ed68402","order_by":10,"name":"Jinjiang Shen","email":"","orcid":"","institution":"Exploration and Development Technology Research Center of Yanchang Oilfield CO., Ltd.","correspondingAuthor":false,"prefix":"","firstName":"Jinjiang","middleName":"","lastName":"Shen","suffix":""},{"id":572480153,"identity":"1cce72f8-1578-4e17-b4bf-6e3570a0ef98","order_by":11,"name":"Wei Lu","email":"","orcid":"","institution":"The Fifth Oil Production plant, PetroChina Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Lu","suffix":""}],"badges":[],"createdAt":"2025-12-24 02:23:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8438007/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8438007/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":100363793,"identity":"5add1210-9ed6-493b-86ad-cf3a786e5ac0","added_by":"auto","created_at":"2026-01-16 07:51:47","extension":"doc","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":18129920,"visible":true,"origin":"","legend":"","description":"","filename":"FractureManuscriptLastVersion.doc","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/1ef203687d4bf1d03a0f458b.doc"},{"id":100078705,"identity":"d40781ce-16f9-4c21-9d73-5c8c57c8afce","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":13621,"visible":true,"origin":"","legend":"","description":"","filename":"6113e9a821a74d3f9fb540153b6bc118.json","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/cb186a6a02d55fc71447e622.json"},{"id":100364860,"identity":"66290c65-ea02-49e6-b166-b61bca71e29a","added_by":"auto","created_at":"2026-01-16 07:54:25","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":174264,"visible":true,"origin":"","legend":"","description":"","filename":"6113e9a821a74d3f9fb540153b6bc1181enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/34fb9568b53125fea76e0bcb.xml"},{"id":100078708,"identity":"e6fa8a4f-9fb3-403d-8dfa-845401dc3870","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"jpeg","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2137548,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/ff8ee59a5a685cfac8058492.jpeg"},{"id":100365023,"identity":"73c02775-b6b5-4797-a316-fa75206ec5f0","added_by":"auto","created_at":"2026-01-16 07:54:35","extension":"jpeg","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":338853,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage10.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/e3b044446c7dde7168222def.jpeg"},{"id":100078702,"identity":"9f4f3b6b-3068-41f9-8598-126b2b6a39ec","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"jpeg","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":184318,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage11.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/37bc54601de77ff19bb900b0.jpeg"},{"id":100364937,"identity":"619a082e-511d-4c3e-9551-e2eaf04db9f0","added_by":"auto","created_at":"2026-01-16 07:54:30","extension":"jpeg","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":101223,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage12.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/d097364a4f5b55c58b9b8a16.jpeg"},{"id":100364800,"identity":"ea889f3a-8cd5-4465-bf4b-c7ee87e908b0","added_by":"auto","created_at":"2026-01-16 07:54:19","extension":"jpeg","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":422445,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage13.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/f7091ab9152ed21d697216e9.jpeg"},{"id":100364564,"identity":"f1fe1a98-6636-4458-87c6-b0554b9ae093","added_by":"auto","created_at":"2026-01-16 07:53:55","extension":"jpeg","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":131550,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage14.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/2d22e66e4d0c4a8effa71b51.jpeg"},{"id":100364147,"identity":"73865ab6-4337-4248-aa29-a4487ed74ded","added_by":"auto","created_at":"2026-01-16 07:52:41","extension":"jpeg","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":171827,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage15.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/17779e1056b0d293bb134339.jpeg"},{"id":100365390,"identity":"d2d2feff-2662-49da-a255-ecde5ff7b03a","added_by":"auto","created_at":"2026-01-16 07:55:10","extension":"jpeg","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1135800,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage16.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/dfd15834a091b7dd0a4ed7b1.jpeg"},{"id":100364714,"identity":"3c121da5-d8a1-4a2a-b388-24456bd5e1c3","added_by":"auto","created_at":"2026-01-16 07:54:14","extension":"jpeg","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":292362,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage17.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/f76baebad7983f56f7cc22c0.jpeg"},{"id":100078717,"identity":"6b081841-f798-44fc-8feb-ae9eefa698fb","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"jpeg","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1149078,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage18.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/797bf28143c6dbd5810bac08.jpeg"},{"id":100364771,"identity":"ab2f746c-453e-43d7-9b0d-53363812fcc2","added_by":"auto","created_at":"2026-01-16 07:54:18","extension":"jpeg","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":657231,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage19.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/b2ff3ca9a3f4d95e4b87d0ae.jpeg"},{"id":100078710,"identity":"fab6878d-1d60-4978-9564-1ef9c3527938","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"jpeg","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":449808,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/c9d70421d14afa432f72e7fd.jpeg"},{"id":100364869,"identity":"793ad6e0-553a-48e1-8e78-f293d3937285","added_by":"auto","created_at":"2026-01-16 07:54:26","extension":"jpeg","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2655168,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/5428360b2eb35e13a6ed7b58.jpeg"},{"id":100078734,"identity":"3e33d844-8a60-4716-93f2-daeabc4466c7","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"jpeg","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":921856,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/3e5876c79d28150150503fdb.jpeg"},{"id":100365647,"identity":"50603582-7043-4c4d-9676-06a5211687b0","added_by":"auto","created_at":"2026-01-16 07:55:29","extension":"jpeg","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1188627,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/0fb5e7068bd29c81c027abfe.jpeg"},{"id":100365418,"identity":"51041033-a117-4a49-8b95-de79ff602af5","added_by":"auto","created_at":"2026-01-16 07:55:11","extension":"jpeg","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1751142,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/42b4dc4087f600c1f45f675e.jpeg"},{"id":100078715,"identity":"8836f5f7-5aa9-4023-867c-c00ca50ff29d","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"jpeg","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":170496,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/6a3d51a740f0a8c4809bc33e.jpeg"},{"id":100364169,"identity":"14b2a00c-f915-496f-96ec-ea4834c7cfa7","added_by":"auto","created_at":"2026-01-16 07:52:45","extension":"jpeg","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":217391,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/5ec54cf8e3195f2db5274e83.jpeg"},{"id":100364596,"identity":"8755d2e8-aa85-40ba-bc1d-48b8f911a41a","added_by":"auto","created_at":"2026-01-16 07:53:59","extension":"jpeg","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":348543,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/8da72aab5067baa2233b0685.jpeg"},{"id":100365488,"identity":"835975fd-2f64-44b8-972b-9afef00da02c","added_by":"auto","created_at":"2026-01-16 07:55:15","extension":"png","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":606947,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/4bbac8e05707138d67001bd9.png"},{"id":100365062,"identity":"e3f2a414-1c4e-42e3-bf24-1ccecaa93d32","added_by":"auto","created_at":"2026-01-16 07:54:38","extension":"png","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":54449,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/6d420c7e7e8c06b364451256.png"},{"id":100078721,"identity":"b6dde60a-f30b-42a9-9301-f14b6f7b3b8c","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"png","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":105429,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/7d34c8217ccd9189a7676c7f.png"},{"id":100364901,"identity":"6641794a-21a1-4b1d-a513-23bca2f078e5","added_by":"auto","created_at":"2026-01-16 07:54:28","extension":"png","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":55434,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/555325fda96c1a41072081ba.png"},{"id":100078726,"identity":"0d065890-52db-441c-bfb8-c1883448371c","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"png","order_by":26,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":136541,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/67aa4e84d744dc4f43ac2520.png"},{"id":100365756,"identity":"b1d12c62-8ed9-49ed-81a2-216595c217da","added_by":"auto","created_at":"2026-01-16 07:55:35","extension":"png","order_by":27,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":32423,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage14.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/df62110827d5a8c1dd80da02.png"},{"id":100406146,"identity":"72686ef2-316e-4492-92ee-9aeba07287f1","added_by":"auto","created_at":"2026-01-16 12:44:38","extension":"png","order_by":28,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":113415,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage15.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/9d1372b05b7c3adfd84c4048.png"},{"id":100078723,"identity":"5c15324e-b041-4af5-bb1f-57b5e8f2cc31","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"png","order_by":29,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":607829,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage16.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/101694b4853080afe055d1d2.png"},{"id":100078729,"identity":"dd58cb21-0378-4271-9242-c2a619041c1c","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"png","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":47362,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage17.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/bdb9b8290710ea32cae3f5e3.png"},{"id":100364874,"identity":"8bf689a2-0d13-48d7-b866-8303d5feef06","added_by":"auto","created_at":"2026-01-16 07:54:26","extension":"png","order_by":31,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":203267,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage18.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/bcab3dc8228cb39afe7499b6.png"},{"id":100365586,"identity":"19909a08-0cf7-4173-bb67-24129851869a","added_by":"auto","created_at":"2026-01-16 07:55:24","extension":"png","order_by":32,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":170287,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage19.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/49320ebf2e54ff4622626345.png"},{"id":100078735,"identity":"96387cb4-b112-4350-849f-d624d51918ec","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"png","order_by":33,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":166855,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/5452da14f59f64db474b3aba.png"},{"id":100078741,"identity":"f2029cec-f141-4313-89d3-5167a22b8f84","added_by":"auto","created_at":"2026-01-12 18:06:31","extension":"png","order_by":34,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1262286,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/730a228a33faca0993fdede1.png"},{"id":100078738,"identity":"436b33fe-f65a-4ee0-987b-257dd58ab6ac","added_by":"auto","created_at":"2026-01-12 18:06:31","extension":"png","order_by":35,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":858300,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/5e7cd7d942a0f619ae6f6aa9.png"},{"id":100078731,"identity":"85d2819c-64ed-4c28-ae20-8b25ea586401","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"png","order_by":36,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":340143,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/323cbaf078ae5f052995de7e.png"},{"id":100364314,"identity":"1764ebd2-e450-4640-b1ed-a8b5d8b6e3d9","added_by":"auto","created_at":"2026-01-16 07:53:24","extension":"png","order_by":37,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1287297,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/4abe8ca27e9d316c2e8cfa3b.png"},{"id":100078737,"identity":"320fa16c-fd4d-4fdc-b628-a3fb056126f7","added_by":"auto","created_at":"2026-01-12 18:06:31","extension":"png","order_by":38,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":41536,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/0d34f570569b05b8ffb3b2ad.png"},{"id":100078728,"identity":"b12818cf-6d03-44ce-8239-533e9e5c1867","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"png","order_by":39,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":49856,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/9860d480a9822f8e4af56372.png"},{"id":100078733,"identity":"365efda1-2105-4deb-a522-7fbd86b80f8e","added_by":"auto","created_at":"2026-01-12 18:06:30","extension":"png","order_by":40,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":57721,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/cbc386a778252cae9c85612d.png"},{"id":100364269,"identity":"abd639a3-828b-472b-a603-84f356719e21","added_by":"auto","created_at":"2026-01-16 07:53:11","extension":"xml","order_by":41,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":168222,"visible":true,"origin":"","legend":"","description":"","filename":"6113e9a821a74d3f9fb540153b6bc1181structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/4a1b2b6ff621f52d97fa2ffd.xml"},{"id":100365186,"identity":"03b3076c-666e-439f-863d-3c20fbe82442","added_by":"auto","created_at":"2026-01-16 07:54:47","extension":"html","order_by":42,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":184364,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1/040b2809a3487584a1f97fd8.html"},{"id":100413751,"identity":"b5935903-6179-48a9-8c84-f94dab646e32","added_by":"auto","created_at":"2026-01-16 13:18:06","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2562456,"visible":true,"origin":"","legend":"","description":"","filename":"FractureManuscriptLastVersion.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8438007/v1_covered_7bfd8221-79fe-4f61-89c5-c9877cc480f1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Characteristics, chronology and controls on natural fractures in tight sandstone reservoirs of the Triassic Chang 6 Member, Yanchi area, Ordos Basin, China","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Natural fracture, Tight sandstone, Triassic Chang 6 Member, Yanchi area, Ordos Basin","lastPublishedDoi":"10.21203/rs.3.rs-8438007/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8438007/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Triassic Chang 6 Member is a significant oil layer in the Ordos Basin, north-west China, and is considered to be a tight sandstone reservoir. Natural fractures have significantly exerted enormous influence on the reservoir quality. This study employs similar outcrops, cores, imaging logs, thin sections, scanning electron microscopy (SEM), fluid inclusions and stable isotope analyses to investigate the characteristics, chronology and controlling factors impacting fracture development in tight sandstones. There are four recognized types of natural fractures in the Chang 6 Member: 1) tectonic shear, 2) extension, 3) bedding-parallel, and 4) micro. Tectonic shear fracture plays a predominant role in the reservoir modification, with two sets of crosscutting strikes (E-W and ENE-WSW), high-dip angle, middle width and fillings (i.e. calcite, ankerite and quartz). In detail, the E-W oriented fractures occur with fills, but without in the ENE-WSW oriented ones. According to C-O isotope and fluid inclusion microthermometry, the fracture filling of calcite is characterized by \u003csup\u003e18\u003c/sup\u003eO (δ\u003csup\u003e18\u003c/sup\u003eO\u003csub\u003ePDB\u003c/sub\u003e varying from \u0026minus;\u0026thinsp;21.30\u0026permil; to -18.30\u0026permil;, mean = -20.00\u0026permil;, and corresponding to the O isotope calculated temperature from 62.1℃ to 85.3℃ with an average of 74.4℃), \u003csup\u003e13\u003c/sup\u003eC (δ\u003csup\u003e13\u003c/sup\u003eC\u003csub\u003ePDB\u003c/sub\u003e varying between \u0026minus;\u0026thinsp;5.70\u0026permil; and \u0026minus;\u0026thinsp;3.10\u0026permil;, mean = -4.10\u0026permil;) and lower homogenization temperatures (Th's) ranging from 71.2℃ to 92.7℃, mean\u0026thinsp;=\u0026thinsp;80.3℃. The fracture filling of ankerite is abundant in \u003csup\u003e16\u003c/sup\u003eO (δ\u003csup\u003e18\u003c/sup\u003eO\u003csub\u003ePDB\u003c/sub\u003e varying from \u0026minus;\u0026thinsp;25.60\u0026permil; to -17.50\u0026permil;, mean = -21.80\u0026permil;, and corresponding with the O isotope calculated temperature from 82.1℃ to 121.5℃ with an average of 103.2℃), \u003csup\u003e12\u003c/sup\u003eC (δ\u003csup\u003e13\u003c/sup\u003eC\u003csub\u003ePDB\u003c/sub\u003e varying between \u0026minus;\u0026thinsp;7.10\u0026permil; and \u0026minus;\u0026thinsp;5.30\u0026permil;, mean = -6.06\u0026permil;) and higher Th's ranging from 100.6℃ to 112.1℃, mean\u0026thinsp;=\u0026thinsp;105.1℃. For the quartz fracture filling, Th's mainly sits between 120.5℃ and 129.8℃, mean\u0026thinsp;=\u0026thinsp;122.2℃. Combining with mineralization and burial-thermal history, the Chang 6 natural fractures are thought to develop during three periods: 1) the Yanshanian Ⅰ episode during the end of the Jurassic to the Early Cretaceous, 2) the Yanshanian Ⅱ episode in the middle of the Cretaceous, and 3) the Himalayan episode during the end of the Cretaceous to the Paleogene. Historically, it was documented the fractures developed during only two periods (i.e. the end of the Jurassic and the end of Cretaceous to the Paleogene) in the past decades, but changed with the advances in this chronology analysis. When it comes to fracture density, it's constricted by sandstone thickness; but it increases first then decreases with the increase in net-gross-ratio (NGR). Mineralogically, fracture density correlates positively with rigid component contents (i.e. quartz, feldspar, dolomite and calcite cements), but negatively with plastic composition (i.e. rock fragment, clay, and mica). Porosity, to some extent, restricts fractures in the way of strain accommodation by coordination and adjustment between the pore system and its filling fluids. This study provides insights into when natural fractures occur and how sedimentary factors and modal compositions influence fracture density of tight sandstones.\u003c/p\u003e","manuscriptTitle":"Characteristics, chronology and controls on natural fractures in tight sandstone reservoirs of the Triassic Chang 6 Member, Yanchi area, Ordos Basin, China","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 18:06:19","doi":"10.21203/rs.3.rs-8438007/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-01T04:02:25+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-31T14:29:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"20623776762040943347718213568674512991","date":"2026-03-25T09:03:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"158797397825604617976177683138034341978","date":"2026-03-03T09:17:39+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-30T15:25:50+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-19T12:19:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"21840435038051478446290901613151688350","date":"2026-01-10T11:13:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"248599616788374710737500295534077791191","date":"2026-01-08T11:16:16+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-08T10:57:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-08T10:35:39+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-01-08T05:08:49+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-06T01:18:32+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-01-06T01:10:33+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"09c4b5a3-2955-4e22-9439-d3887a986ce1","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[{"id":60921274,"name":"Earth and environmental sciences/Planetary science"},{"id":60921275,"name":"Earth and environmental sciences/Solid earth sciences"}],"tags":[],"updatedAt":"2026-04-01T04:09:27+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-12 18:06:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8438007","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8438007","identity":"rs-8438007","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}