Geochemistry and origin of deep-seated cracked gas on the northern slope of the Dongying Sag,Shandong Province

• Published in: 中国地球化学学报（英文版） Vol. 30; no. 3; pp. 353 - 358
• Main Authors: CHANG Xiangchun, HAN Zuozhen, XU Youde, SHANG Xiaofei, YAN Chengpeng
• Format: Journal Article
• Language: English
• Published: Shandong provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals, Shandong University of Science and Technology,Qingdao 266510, China%Geological Scientific Research Institute of Shengli Oilfield Company, SINOPEC, Dongying 257001, China 2011
• Subjects: cracking gas:source rock:geochemistry:Dongying Sag
• DOI: 10.1007/sl1631-011-0519-1
• ISSN: 1000-9426

P618.130.1; Deep-seated cracked gas exploration was achieved great breakthrough in Es4L of the Minfeng area on the northern slope of the Dongying Sag.Carbon isotopic and molecular compositions studies revealed the characteristics of wet gas and a normal trend of carbon isotopic composition.Empirical cutoff points of δ13C2 and δ13C3 and light hydrocarbon compositions distinguished the cracking gas as sapropelic gas.Variations in i/nC5,i/nC4 and δ13C2 further confirmed that the gas was cracked from residual kerogen.Source characteristics indicated that the gas was derived from mature-highly mature source rocks of Es4 with kerogen type Ⅱ being dominant mixed with some oil-cracking gas.Burial history modeling indicated that there were two hydrocarbon charging periods in Es4L reservoirs.The first period refers to the Guantao-Minghuazhen stage dominated by oil charging,while the second period refers to the Minghuazhen stage and has been dominated by cracked gas charging till now.