川西坳陷陆相脉冲式波动“二元”层序特征研究

LST and T-HST featured by impulse in continental sequences in the Western Sichuan Depression

张庄 叶素娟 杨克明 朱宏权 杨映涛 李旻 张世华

Zhang Zhuang Ye Sujuan Yang Keming Zhu Hongquan Yang Yingtao Li Min Zhang Shihua

成都理工大学 能源学院, 成都 610059 2. 中国石化 西南油气分公司 勘探开发研究院, 成都 610041 3. 中国石化 西南油气分公司, 成都 610041

College of Energy Resources, Chengdu University of Technology, Chengdu, Sichuan 610059, China 2. Exploration and Production Research Institute of SINOPEC Southwest Oil & Gas Company, Chengdu, Sichuan 610041, China 3. SINOPEC Southwest Oil & Gas Company, Chengdu, Sichuan 610041, China

将层序地层学基本原理与压性盆地控制因素相结合,充分运用野外露头、钻井岩心、测井、地震等资料,对川西坳陷陆相层序结构特征进行了分析。认为川西坳陷周缘山系的幕式逆冲挤压作用是控制川西前陆盆地层序地层及沉积充填样式的主导性因素,它是一个"应力长期缓慢积累、短期瞬时释放"的脉冲式波动过程。这种周期性的幕式逆冲挤压和松弛过程导致湖平面(或基准面)以及可容空间的变化呈现出周期性、脉冲式波动的"二元"突变特征。层序的低位体系域主要发育辫状河、三角洲等粗粒沉积体,而层序上部的湖侵-高位体系域则主要为半深湖的细粒沉积体,在垂向上构成了极好的三角洲相砂体与湖相泥岩广覆式间互的沉积充填特征,形成了良好的生储盖组合和圈闭条件。因此,在油气勘探中,层序底部的粗碎屑可以形成的岩性油气藏及构造-岩性油气藏是重要的勘探对象,同时,针对层序上部在湖盆边缘可能形成的岩性油气藏也应引起重视。

According to the basic concepts of sequence stratigraphy and the controlling factors of compressional basins, the continental sequences in the Western Sichuan Depression were studied, based on field outcrops, well cores and logging and seismic data. The episodic compressions of surrounding mountains controlled the sequence stratigraphy and sedimentary infill pattern in the western Sichuan foreland basins. Stress accumulated slowly for a long time, and released instantly. Lake-level (basal level) and accommodation space changed in response to periodic compression and relaxation, resulting in LST (Lowstand System Tract) and T-HST (Transgressive-Highstand System Tract). Coarse-grained sedimentary bodies such as braided river and delta are dominant in LST, while T-HST in the upper part of the sequence is composed of fine-grained semi-deep lacustrine sediments. Vertically, delta facies sand bodies are interbedded with lacustrine mudstones, favorable for hydrocarbon generation, accumulation, preservation and trap formation. Lithologic reservoirs and lithologic-tectonic reservoirs formed by coarse grains at the bottom of the sequence are important exploration targets. Meanwhile, lithologic reservoirs in the upper part of the sequence on the basin margin provide additional opportunities.

国家科技重大专项"四川盆地碎屑岩层系大中型油气田形成规律与勘探方向(二期)"(2011ZX05002-004)资助。

https://doi.org/10.11781/sysydz201603303