东濮凹陷古近系致密砂岩气成因与充注差异

中国东部深层古近系致密砂岩气是今后油气勘探的重要接替领域。以东濮凹陷深层古近系致密砂岩气为例,根据天然气组分、碳同位素及储层沥青等分析了天然气成因,从储层致密化及油气充注期等方面,研究了深层洼陷带、斜坡带致密砂岩气充注差异,并划分了气藏成因类型。结果表明,东濮凹陷洼陷带以腐泥型干酪根裂解气为主,并混有原油裂解气,储层在东营组沉积期和明化镇组沉积中期均演化为致密储层,普遍存在东营组沉积中后期—东营组抬升初期、明化镇组沉积后期—第四纪2期油气充注;东濮凹陷斜坡带以原油裂解气为主,储层在明化镇组沉积中期演化为致密储层,以东营组沉积中后期—东营组抬升初期油气充注为主。根据天然气成因、储层致密化进程及其与油气充注期的关系,将东濮凹陷深层古近系致密砂岩气藏划分为2种成因类型:洼陷带2期致密混合型气藏,斜坡带晚期致密原油裂解型气藏。

Genesis and charge difference of Paleogene tight sandstone gas in Dongpu sag

Deep Paleogene tight sandstone gas in eastern China is the important substitute area for oil and gas exploration. Taking the deep Paleogene tight sandstone gas of Dongpu sag as an example, the natural gas genesis is analyzed according to natural gas composition, carbon isotope and reservoir bitumen. Then the charging differences of tight sandstone gas between deep sag zone and slope zone are studied in terms of reservoir densification, and hydrocarbon charging stage, etc., and the genetic types of gas reservoir are also divided. The results show that the sag zone of Dongpu sag is dominated by sapropel-kerogen pyrolysis gas, mixed with oil cracking gas. The tight reservoir was formed in Dongying period and middle Minghuazhen period, and this zone commonly underwent two hydrocarbon-charging stages, i.e., the mid-late Dongying sag period-the early Dongying uplift period and the late Minghuazhen deposition period-the Quaternary. The slope zone of Dongpu sag is dominated by oil cracking gas, and the tight reservoir was formed in middle Minghuazhen period, and mainly experienced the hydrocarbon charging in the mid-late Dongying sag period-the early Dongying uplift period. According to natural gas genesis, reservoir densification process and its relationship to hydrocarbon charging stage, the deep Paleogene tight sandstone gas reservoir in Dongpu sag is classified into two genetic types, i.e., dual-stage mixed tight reservoir in sag zone and the late oil-cracking gas reservoir in slope zone.