再论塔里木盆地古隆起的形成期与主控因素

塔里木盆地发育不同类型、不同特征的古隆起,前人对于古隆起的成因、构造演化等方面的认识存在着较多分歧,影响了该区油气勘探的思路与部署。为此,基于新的地震资料与钻井资料,针对该盆地深层海相碳酸盐岩地层,开展了区域地震资料解释与构造解析研究,结合构造剥蚀量成果恢复了古构造格局,进而探讨了古隆起的形成期及其主控因素。结果表明:(1)中奥陶世是塔里木盆地内部从伸展转向挤压的关键时期,地层、沉积与构造开始出现分异,在中奥陶世晚期一间房组沉积前,塔北、塔中、塔西南等三大碳酸盐岩古隆起已开始出现雏形,其形成时期相同且均为宽缓的近东西走向的褶皱古隆起;(2)前寒武纪发育近东西走向的塔南与塔北基底古隆起,制约了该区显生宙古隆起的发育与分布;(3)上述三大古隆起都是在基底古隆起的基础上受塔里木板块南缘聚敛作用而形成的挤压型古隆起,其构造特征相似且形成演化都具有继承性;(4)志留纪以来的多期强烈构造改造作用,影响并控制了现今古隆起的差异。结论认为:该盆地更为广阔的、深层保存条件好的继承性古构造区碳酸盐岩油气勘探潜力巨大。

Formation stage and controlling factors of the paleo-uplifts in the Tarim Basin: A further discussion

Various types of paleo-uplifts with different characteristics are developed in the Tarim Basin. Previously, there were multipleopinions on the paleo-uplifts origins and structural evolution, so the oil and gas exploration ideas and deployment in the Tarim Basinwere not developed smoothly. In this paper, regional seismic interpretation and structural analysis were carried out on the deep marinecarbonate rocks in this basin based on the new seismic and drilling data. Then combined with the structural denudation results, the paleostructural frameworks were reconstructed. And finally, the formation stage and main controlling factors of paleo-uplifts were discussed. Itis shown that the Middle Ordovician is the key period when regional extension was converted to compression in this basin, so stratigraphic,sedimentary and structural differences occurred. Before the deposition of Yijianfang Fm in late Middle Ordovician, three carbonate paleo-uplifts (i.e., the North, Central and SW Tarim paleo-uplifts) had begun to appear, and they are all broad-folding paleo-uplifts of nearlyE-W striking which were formed at the same stage. The distribution and development of the Phanerozoic uplifts in this basin are restrictedby the North and South Tarim basement paleo-uplifts of nearly E-W striking which were developed during Precambrian. It is indicatedthat the three Paleo-uplifts are compressional paleo-uplifts which were originated from the convergence activity of the southern platemargin based on the basement paleo-uplifts and they are all characterized by similar structural characteristics and inherited formation andevolution. The current differences of paleo-uplifts are controlled by multi-stage strong structural reworking since the Silurian. It is concludedthat the oil and gas exploration potential is immense in the carbonate reservoirs of well-preserved deep paleo structural zones in alarger area.