Resource Potential And Oil-gas Source In North-Central Langgu Sag

Langgu Sag suffered a strong tectonic movement in the late sedimentary stage,forming several units of complicated oil reservoirs.Various recognitions of hydrocarbon generation,hydrocarbon source and unspecific resource potential are still restraining exploration work.Based on laboratory analysis,sedimentation facies,logging and mud logging data,this study evaluates hydrocarbon source rock and describes source rock distribution for different objective layers in different parts of Langgu Sag.Petroleum source is compared associating with oil and gas geochemical characters in the north-central sag.Petroleum types are classified.Resource potential and reserves distribution are confirmed.It is summarized that Middle Shasan formation and Lower Shasan formation are primary hydrocarbon source rock.In Middle Shasan,high abundance source rocks develop in Caiyu-Wangzhuang-Gu'an and Hancui-Liuquan while Lower Shasan develop high abundance source rocks in northern Tongbo,western Bieguzhuang and adjacent Jiuzhou.Upper Shasi formation and Kongdian formation develop secondary hydrocarbon source rock.In Upper Shasi,high abundance source rocks develop in Hupoying-Liuquan and adjacent Yongqing while Kongdian develops high abundance source rock in western Yongqing-Niutuo.It is concluded that three types of oil exist in north-central Langgu Sag.Grade?oil exists in oilfields of Bieguzhuang,Zhongchakou and Quan 42 with source rock Upper Shasi.Grade?oil is discovered in northern Wangju,which is from good source rock of Lower Shasan.Sourcing from Lower Shasan,grade ? oil is found in most oilfields of Hexiwu tectonic zone and southern Wangju in Langgu sag.Three types of natural gas in north-central Longgu Sag are confirmed: associated natural gas,high-maturing condensate gas and biogas in shallow bed.It is suggested that the most favorable prospect in the future be the oil-gas enrichment of Daliuquan and Hexiwu tectonic zones.