Abstract: The Luotan1 well in the Maigaiti slope of Tarim Basin has made a new breakthrough in the Ordovician carbonate rocks, marking the first exploration breakthrough of a new type of Ordovician fault controlled karst carbonate reservoirs in the Maigaiti slope and marking the discovery of an important strategic replacement area in the slope area. Based on regional drilling, logging, seismic and other data, a comprehensive analysis of the laboratory data of well Luotan1 is carried out to further understand the reservoir formation conditions of Ordovician carbonate rocks in the Maigaiti slope. The formation of Ordovician carbonate fault controlled karst reservoirs in the Maigaiti slope is mainly related to strike slip fault activity, and is one of the three main reservoir formation models in the Maigaiti slope. At present, it has been discovered that hydrocarbon in the Maigaiti slope comes from the source rocks of the Cambrian Yuertus Formation, and the basement paleostructure controls the sedimentation and distribution of the Lower Cambrian source rocks. The slope area has three stages of hydrocarbon charging and accumulation: the Caledonian, Hercynian-Indosinian, and Himalayan periods. Hydrocarbon source rocks, paleotectonic evolution, and the faults connecting hydrocarbon source rocks control the multi-stage hydrocarbon accumulation. The fault active stages and fault penetrating layers determine the hydrocarbon enrichment layers and reservoir properties. The Maigaiti slope is characterized by well-developed Ordovician strike slip faults, with an extension distance of over 1000km, which control the distribution of fault controlled karst carbonate reservoirs and hydrocarbon reservoirs. It has clear zoning characteristics on the plane, with a large resource scale and strong deployability, demonstrating huge exploration potential. It is an important practical field for large-scale hydrocarbon exploration discovery and strategic succession in the southwestern Tarim Basin.

Key words: Maigaiti slope, Ordovician, Carbonate rocks, Fault controlled karst, Reservoir forming conditions, Exploration potential