Shale gas in China: Characteristics, challenges and prospects (II)

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• 作者：Caineng ZOU^a ; ^{zcn@petrochina.com.cn" class="auth_mail" title="E-mail the corresponding author} ; Dazhong DONG^a ; ^b ; Yuman WANG^a ; Xinjing LI^a ; Jinliang HUANG^a ; Shufang WANG^a ; Quanzhong GUAN^a ; Chenchen ZHANG^a ; Hongyan WANG^b ; ^c ; Honglin LIU^c ; Wenhua BAI^c ; Feng LIANG^c ; Wen LIN^c ; Qun ZHAO^c ; Dexun LIU^c ; Zhi YANG^a ; Pingping LIANG^c ; Shasha SUN^c ; Zhen QIU^c
• 关键词：shale gas field ; economic sweet spot ; micro gas reservoir ; horizontal well ; factory-like production ; volume fracturing ; development cost ; resource potential ; favorable target
• 刊名：Petroleum Exploration and Development
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：43
• 期：2
• 页码：182-196
• 全文大小：5755 K

文摘

This paper mainly discusses the industrialization progress, “sweet spot” evaluation criterion, E&P technologies, success experiences, challenges and prospects of China's shale gas. Based on the geologic and engineering parameters of the Fuling, Changning and Weiyuan shale gas fields in the Sichuan Basin, this paper points out that China's shale gas has its particularity. The discoveries of super-giant marine shale gas fields with high evolution degree (R_o=2.0%−3.5%) and ultrahigh pressure (pressure coefficient=1.3−2.1) in southern China is of important scientific significance and practical value to ancient marine shale gas exploration and development to China and even the world. It's proposed that shale gas “sweet spots” must be characterized by high gas content, excellent frackability and good economy etc. The key indicators to determine the shale gas enrichment interval and trajectory of horizontal wells include “four highs”, that is high TOC (>3.0%), high porosity (>3.0%), high gas content (>3.0 m³/t) and high formation pressure (pressure coefficient>1.3), and “two well-developed” (well-developed beddings and well-developed micro-fractures). It's suggested that horizontal well laneway be designed in the middle of high pressure compartment between the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation. The mode of forming “artificial shale gas reservoir” by “fracturing micro-reservoir group” is proposed and the mechanisms of “closing-in after fracturing, limiting production through pressure control” are revealed. Several key technologies (such as three-dimensional seismic survey and micro-seismic monitoring of fracturing, horizontal wells, “factory-like” or industrialized production mode, etc.) were formed. Some successful experiences (such as “sweet spot” selection, horizontal well laneway control, horizontal length optimization and “factory-like” production mode, etc.) were obtained. The four main challenges to realize large-scale production of shale gas in China include uncertainty of shale gas resources, breakthroughs in key technologies and equipment of shale gas exploration and development below 3 500 m, lower cost of production, as well as water resources and environment protection. It is predicted that the recoverable resources of the Lower Paleozoic marine shale gas in southern China are approximately 8.8×10¹² m³, among which the recoverable resources in the Sichuan Basin are 4.5×10¹² m³ in the favorable area of 4.0×10⁴ km². The productivity of (200−300)×10⁸ m³/a is predicted to be realized by 2020 when the integrated revolution of “theory, technology, production and cost” is realized in Chinese shale gas exploration and development. It is expected in the future to be built “Southwest Daqing Oilfield (Gas Daqing)” in Sichuan Basin with conventional and unconventional natural gas production.