塔里木盆地顺北特深碳酸盐岩断溶体油气藏发现意义与前景

Significance and prospect of ultra-deep carbonate fault-karst reservoirs in Shunbei area, Tarim Basin

焦方正

Jiao Fangzheng

塔里木盆地顺北地区埋深7 000 m以下特深碳酸盐岩领域获得重大油气突破。通过对顺北特深油气田的构造演化、储层、油气藏特征与油气富集规律等的综合分析，认为该类油气藏为断溶体油气藏，具有沿断裂带整体含油、不均匀富集的特点。走滑断裂多期活动与流体溶蚀改造作用在中-下奥陶统碳酸盐岩层系形成良好的洞穴、裂缝及沿缝溶蚀孔洞型储集体；断裂带外围致密碳酸盐岩作为侧向封挡构成了物性圈闭。上覆巨厚却尔却克组泥岩作为区域封盖层，源自下寒武统的油气沿走滑断裂垂向运移聚集，以晚期成藏为主，断裂既是油气运移通道又是油气富集场所。该类型油气藏的发现展现了一种新的特深层油气富集成藏模式。目前，顺北油气田已发现落实了18条走滑断裂带，资源规模达17×10 t油当量，展示了顺北地区良好的勘探开发前景。

Oil and gas reservoirs discovered in the ultra-deep carbonates of a burial depth larger than 7 000 m in Shunbei area of Tarim Basin have gained attention from the industry.A comprehensive study was then carried out on the tectonic evolution,reservoir characteristics and oil and gas accumulation patterns in the area.The results show that the reservoirs are of fault-karst type,featuring pervasive distribution but uneven enrichment of oil in the whole fault zone.With caverns,fractures and along-fracture dissolved pores and vugs formed by multi-stage strike-slip faulting as well as dissolution and alteration,the Middle-Lower Ordovician carbonates were wonderful reservoirs with favorable properties.Tight carbonates at the periphery of the faulting zone served well as lateral barriers for the formation of lithologic traps.The overlaying massive mudstone in Queerqueke Formation was the regional seal,which caped the hydrocarbons being sourced from the Lower Cambrian and migrating up along the strike-slip faults. The accumulations were mostly formed at late stage.The faults acted both as hydrocarbon migration pathways and accumulation spots.The discovery of the reservoirs demonstrated a new hydrocarbon reservoiring pattern in the ultra-deep sequences.About 18 strike-slip faulting zones were identified in the area with a resource volume as high as 17×10 t oil equivalent,indicating a bright exploration and development future in the area.

10.11743/ogg20180201