Abstract: The marine sequences in the unmodified foreland region of Tarim Basin had experienced multiple stages of hydrocarbon accumulation with alternative later adjustment, destruction and preservation processes. Consequently, the distribution of oil and gas reservoirs in the study area today is very complicated. The article proposed that both source rocks and cap rocks had played roles in controlling the distribtuion of oil and gas reservoirs and suggested that the interaction between favorable timing of hydrocarbon generation with formation of cap rocks as well as the sealing capacity of cap rocks are the key factors that had affected the distribution of oil and gas reservoirs. Macroscopically, different collocation of source/cap rocks had determined where and how the oil/gas-bearing formations were located. Based on this understanding, the paper also discussed the distribution pattern of oil and gas reservoirs and predicted potential exploration targets for middle-and large-sized oil and gas fields in the study area.

Key words: source/cap rock controlling hydrocarbon accumulation, oil and gas distribution, exploration target, unmodified foreland region, Tarim Basin