Wuerxun Depression Hydrocarbon Accumulation Mechanism And The Main Controlling Factors

On the basis of study to structure and sedimetary background, accumulation conditions of generation, reservoirs, caprocks, traps and migration in Wuerxu depressions are completely and systemly studied. Using oil or gas drilling data and oil or gas displays, tapes of oil or gas reservoirs and their distribution in Wuerxun deperession are summarizd. Four kinds of oil or gas reservoirs are found, they are structural oil or gas reservoirs, lithological oil or gas reservoirs, structural-lithological oil or gas reservoirs and basement rock weathering crust oil or gas reservirs. Most of oil or gas reservoirs distribute from k1n2 to k1d2 in section, but the number of oil or gas reservoirs in k1n is more than that in k1d2 Most of oil or gas reservoirs distribute in Surennuoer structural zone and Bayantala structural zone in plane, but the number of oil or gas reservoirs in Surennuoer structural zone is more than that in Bayantala structural zone. According to the relation between oil or gas reservoirs and main accumulating conditions, the factors controlling accumulation and distribution of oil or gas reservoirs were completely and systemly studied. Time and space matching relation between sourcerock and caprock, sedimentary environment, faults and traps are main factors controlling oil or gas accumulation and distribution. On the basis of generation and expulsion hydrocarbon history of source rock, seal formation history of cap rock, formation history of trap, active history of fault, oil or gas accumulation period by use of illite's ages, main oil or gas accumulation period was determined to be from the end of Yimin formation to the early of Qingyuangang formation. On the basis of that, according to types of oil or gas reservoirs, four kinds of oil or gas accumulation models fit to Wuerxun depression are reduced, they are the model of oil or gas migrating and accumulating in sandstone lens or fracture traps of source rock, the model of oil or gas accumulating in fault-block or fault-screened traps through vertical migration, the model of oil or gas accumulating in structural-lithological traps migrating laterally in short instance through sandrock, the model of gas from mantle accumulating in basement rock weathering crust or structural traps migrating through deep and big faults. Based on the above, favorable exploration areas in Wuerxun depression are predicted. The most favorable exploration areas of k1n2 are Surennuoer structural zone, Huangqimiao structural zone. The favorable exploration areas are Tongbomiao structural zone, Wudong slope zone, Wuxi fault zone, Wuzhong structural zone and Bayantala structural zone. The most favorable exploration areas of k1d2 are Surennuoer structural zone, Huangqimiao struvctural zone, Tongbomiao structural zone, Wuxi fault zone, Wuzhong structural zone. But The most favorable exploration areas for carbon dioxide gas are Surennuoer southern structural zone, Huangqimiao southern structural zone and line intersection of Wuxi fault zone, Wuzhong structural zone, Bayantala structural zone. Huang yi-1, Suwu-7 and Sushiyi-9 traps of kin: and Bayi-9, Bayi-10 and Suer-1 traps of k1d2 are considered to be the most farorable traps for oil or gas to be drilled.