准噶尔盆地东部中二叠统咸化湖相烃源岩生气潜力及天然气勘探意义

Gas-generating potential of the Middle Permian saline lacustrine source rocks and significance for natural gas exploration in the eastern Junggar Basin

冯德浩 刘成林 杨海波 韩杨 杨小艺 苏加佳 李国雄 张景坤

Dehao FENG Chenglin LIU Haibo YANG Yang HAN Xiaoyi YANG Jiajia SU Guoxiong LI Jingkun ZHANG

中二叠统咸化湖相页岩是准噶尔盆地东部最重要的烃源岩，研究其生气潜力及成藏贡献对油气勘探具有重要的意义。根据近年来新钻井的录井、岩石学、有机地球化学、半开放体系热模拟实验及天然气地球化学分析数据，系统评价了中二叠统咸化湖相烃源岩的生气潜力，研究了天然气成因和来源，提出了有利的天然气勘探领域。研究表明：①东道海子凹陷中二叠统咸化湖相烃源岩厚度自边缘向凹陷中心逐渐增大，凹陷中部厚度普遍超过350 m，最厚可达600 m。阜康凹陷存在2个中二叠统咸化湖相烃源岩厚度高值区，其中东北缘烃源岩厚度主要为200 ~ 250 m，中南部烃源岩厚度超过400 m。阜康凹陷和东道海子凹陷中二叠统咸化湖相烃源岩以中等—极好烃源岩为主，发育倾油型生烃母质，具有厚度大、滞留烃含量高、普遍达到生气窗的特点，具备规模生气潜力。②准噶尔盆地东部发现来自于咸化湖相烃源岩生成的油型气，主要分布在阜康凹陷、东道海子凹陷和阜康断裂带，克拉美丽气田和彩南油气田煤型气也混有中二叠统生成的油型气。③阜康凹陷和东道海子凹陷超深层是油型气勘探的有利地区，主要包括源外常规气、源内致密气和源内页岩气3个有利的天然气勘探领域。

The Middle Permian saline lacustrine shales are identified as the most significant source rocks in the eastern Junggar Basin. Investigating their gas-generating potential and contribution to gas accumulation holds great significance for hydrocarbon exploration. Based on logs of wells newly drilled in recent years， as well as data from petrology， organic geochemistry， semi-open pyrolysis simulation experiments， and natural gas geochemical analysis， we systematically evaluate the gas-generating potential of the Middle Permian saline lacustrine source rocks， clarify the origin of natural gas from within， and delineate favorable targets for natural gas exploration. The results indicate that in the Dongdaohaizi Sag， the thickness of the Middle Permian saline lacustrine source rocks increases gradually from its margin to center， generally exceeding 350 m and reaching a maximum of 600 m at the center. In the Fukang Sag， two zones of thick Middle Permian saline lacustrine source rocks are determined， namely the northeastern margin and the south-central portion， where the source rock thicknesses primarily range from 200 to 250 m and exceed 400 m， respectively. The Middle Permian saline lacustrine source rocks in both sags principally exhibit medium to excellent quality， with oil-prone kerogen widely developed which is characterized by considerable thicknesses， high contents of retained hydrocarbons， and generally entering the gas window stage. All these suggest the potential for large-scale gas generation. The petroliferous gas generated by the Middle Permian saline lacustrine source rocks has been discovered in the eastern Junggar Basin， distributed primarily in the Fukang Sag， Dongdaohaizi Sag， and the Fukang fault zone. Besides， the petroliferous gas generated from the Middle Permian source rocks is also found mixed with the coal-derived gas in the Kelameili gas field and the Cainan oil and gas field. The ultra-deep reservoirs in the Fukang and Dongdaohaizi sags in the eastern Junggar Basin are favorable for the exploration of petroliferous gas， which can be divided into three favorable gas exploration zones： conventional gas outside source rocks， tight gas inside source rocks， and shale gas inside source rocks.

10.11743/ogg20240507