Petroleum Exploration Prospect Research Of Permian In Yanbian Area

The petroleum geological research and resource exploration degree of Permian isvery low in Yanbian area, Jilin province. Based on field geological investigation,geochemical test, gravity-magnetic and seismic data, the author have systematicallystudied the distribution and occurrence of Permian, lithofacies paleogeography,characteristics of hydrocarbon source rocks, and analyzed the petroleum explorationperspective of Permian in Yanbian area.Permian has a wide distribution in Yanbian area, mainly including the upper andmiddle Permian. Based on gravity-magnetic data, there are thick Permian strata withburial depth in Dunhua basin of the northwest and Hunchun basin of the southeast. InMiddle Permian, the research area developed shoreland-shallow sea sedimentarysystem. The shallow sea was located in middle area along the northwest, while thesouthwest and northeast area was the shoreland. In Late Permian, crust uplifted, theresearch area was deposited in continental environment, and developed alluvial-lacustrine sedimentary system. The lacustrine facies deposited in most area, whilealluvial facies deposited in the southwest area.During Permian period, a large number of shallow sea and lacustrine darkmudstones were deposited in Yanbian area. Based on geochemical test, the darkmudstones are characterized by high abundance of organic matter, and most aremedium-good source rocks. The organic matter is typeⅡ-Ⅲ. But the maturity oforganic matter is not same in different regions. In the southwest and northeast area,the maturity of organic matter is high, and Ro is over4.0%; in the middle area(Tianqiaoling-Wangqing), Ro is at2.49%～5.76%, indicating that the hydrocarbonpotential is poor. Only in Hunchun basin of the southeast area, Ro is at1.26%～2.58%, which suggests that the source rocks are still in high mature-dry gas effective hydrocarbon generation stage and possess of a certain hydrocarbon generationpotential. According to preliminary estimate, the minimum quantity of oil resource is13046×104t, and the minimum quantity of gas resource is433.14×108m3in Permianof Hunchun basin, which presents a certain petroleum exploration prospect.Especially the west depression of Hunchun basin is provided with the favorablecondition of hydrocarbon accumulation in Hunchun Formation of Palaeogene. Andthe shale gas has the potential to accumulate in the thick dark mudstones ofJiefangcun Formation in Middle Permian. Therefore, the west depression in Hunchunbasin is the potential prospect region of Yanbian area.