The second stage of karstification took place after the limestones folded.
Cañaveras, J. C., Calvo, J. P., García del Cura, M. A., Sanz-Montero, M.E. 2003, 'Rasgos morfologicos y petrologicos del paleokarst de la unidad superior del miocenode la cuenca de Madrid', Estudios Geologicoshttp://estudiosgeol.revistas.csic.es/index.php/estudiosgeol/article/view/84/81. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Internal gypsum karstification proceeded mainly under confined hydrogeological conditions.
Klimchouk A. 1996, 'Gypsum karst in Western Ukraine', International Journal of Speleologyhttp://ijs.speleo.it/pdf/6.64.25_Klimchouk_Ukraine.pdf. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
This region must have been significantly elevated from the karstification (erosion) base.
Ekmekci Mehmet, Lutfu Nazik 2004, 'Evolution of Golpazari-Huyuk karst system (Bilecik-Turkey): indications of morpho-tectoniccontrols', International Journal of Speleologyhttp://www.ijs.speleo.it/pdf/61.519.33_Ekmekci.Nazik.pdf. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Additionally, supergene karstification and structural fractures improve reservoir physical properties.
Jianyong Zhang, Xinfeng Ni, Xingning Wu, Wenzheng Li, Yi Hao, Yanna Chen, Xueju Lü,Mingfeng Gu, Han Tian, Mao Zhu 2018, 'Main controlling factors and distribution of high-quality deep dolomite reservoirsin typical cratonic basins in China', Journal of Natural Gas Geosciencehttp://www.sciencedirect.com/science/article/pii/S2468256X18300312. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
These hypogenic systems involve confined aquifers with upwards flow, responsible for their karstification.
Alberto Sendra, Policarp Garay, Vicente M. Ortuño, José D. Gilgado, Santiago Teruel,Ana Sofia P.S. Reboleira 2014, 'Hypogenic versus epigenic subterranean ecosystem: lessons from eastern Iberian Peninsula',International Journal of Speleologyhttp://scholarcommons.usf.edu/ijs/vol43/iss3/2/. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Especially, epigenic karstification and its resulted reservoir-seepage spaces have always been the focal points in researches.
Yuqiang Jiang, Yifan Gu, Xun Zhu, Wei Xu, Yao Xiao, Junliang Li 2017, 'Hydrothermal dolomite reservoir facies in the Sinian Dengying Fm, central SichuanBasin', Natural Gas Industry Bhttp://www.sciencedirect.com/science/article/pii/S2352854017301122. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Four different paleo-karstification periods were identified according to the carbon and oxygen isotopic characteristics of calcite.
Zhang Qingyu, Liang Bin, Qin Fengrui, Cao Jianwen, Dan Yong, Hao Yanzhen, Li Jingrui,Muhammad Aqeel Ashraf 2016, 'Geochemical Characteristics and Paleoenvironmental Signi cance of the Ordovician PaleokarstReservoir in the Maigaiti Slope of Tarim Basin', Earth Sciences Research Journalhttps://revistas.unal.edu.co/index.php/esrj/article/view/54142. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Drilled wells are located mainly in the northern karst depression which has weak karstification and heavy filling.
Guanghui WU, Honghui LI, Liping ZHANG, Chenglin WANG, Bo ZHOU 2012, 'Reservoir-forming conditions of Ordovician weathering crust in the Maigaiti slope,Tarim Basin, NW China', Petroleum Exploration and Developmenthttp://www.sciencedirect.com/science/article/pii/S1876380412600287. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
In the deep slow flow zone with over weak karstification, there are sedimentary and filling activities.
Jiang HE, Shaoxian FANG, Fanghao HOU, Ronghui YAN, Zhongjun ZHAO, Jian YAO, XiujunTANG, Guorong WU 2013, 'Vertical zonation of weathered crust ancient karst and reservoir evaluation and prediction—Acase study of M55–M51 sub-members of Majiagou Formation in gas fields, central OrdosBasin, NW China', Petroleum Exploration and Developmenthttp://www.sciencedirect.com/science/article/pii/S1876380413600750. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)