Abstract:
Well Xiongtan 1 in Kalayuergun structural belt of western Tabei uplift, Tarim Basin, has made a major breakthrough in oil and gas exploration in the Upper Cambrian Xiaqiulitage Formation in September 2023. This is another significant oil bearing strata discovery that has been made since Cretaceous and Paleogene in Tabei area, demonstrating the three-dimensional multi-layer hydrocarbon accumulation in Tabei area. Based on comprehensively analyzing the structural styles, fault characteristics, as well as the drilling, logging and testing data of Well Xiongtan 1, the paper makes clear the source rock conditions, oil and gas channel, reservoir-cap conditions and trap types of Kalayuergun structural belt, and systematically summarizes the accumulation elements and modes of the Cambrian Xiaqiulitage Formation in Kalayuergun structural belt. Two sets of deep source rocks are developed in Tabei uplift. The hydrocarbon source correlation shows that the Cambrian Yuertusi Formation is the main source rock layer, and the potential source rock is developed in the pre-Cambrian rift trough. Tectonic movement is active in the study area, forming Caledonian, Hercynian and Himalayan faults. NNW-trending strike-slip faults are superimposed with NW- and EW-trending thrust faults, forming an interlaced fault system, which vertically communicates with deep source rocks and reservoirs. Traps of the Upper Cambrian Xiaqiulitage Formation were formed at an early stage, where multiple periods of oil and gas accumulation occurred; under the influence of strong compression in Late Hercynian period, several faults connected with source rocks and related structural traps were initially formed. As a result of the late tectonic movement, the whole area continued to uplift, and formed a large area of continuously distributed tectonic traps in the Upper Cambrian reservoir, capturing oil and gas in multiple stages. The hydrocarbon accumulation mode of "lower generation and upper reservoir, dredging by faults and near-source accumulation" is established. The research results reveal that the Cambrian Xiaqiulitage Formation in western Tabei uplift has a huge exploration prospect, and it is expected to become a new strategic replacement area for increasing reserve and production in the platform area of Tarim Basin.