渤海湾盆地黄骅坳陷大港探区石炭系—二叠系天然气成藏主控因素及勘探方向

Main controlling factors and exploration prospectivity of Carboniferous-Permian play in Dagang exploration area,Huanghua Depression,Bohai Bay Basin

近年来,渤海湾盆地黄骅坳陷大港探区上古生界天然气勘探获得重大突破。从石炭系—二叠系含油气系统的烃源岩展布及生烃潜力、储层分布及物性、天然气成藏和富集规律等方面,开展地质、地球化学和测井的综合解释,对成藏主要因素进行深度剖析。结果表明:上古生界煤系烃源岩有机质丰度高、母质类型好,经历二次生烃,具备规模生气条件;储层以低孔、低渗碎屑岩为主,次生孔隙和裂缝发育,断层活动演化控制着油气的垂向分布,准原地烃源岩、次生改造储层和断层活动性是上古生界天然气成藏的主控因素,提出了黄骅坳陷上古生界天然气藏的主要成藏模式为“两期排烃、源储叠置、晚活调整充注”,认为大港探区上古生界天然气勘探潜力大,主要有利的勘探方向为洼中宽缓潜山带和斜坡断垒潜山带,预测乌马营—王官屯洼中、东光东翼低斜坡、歧北低斜坡是研究区未来规模勘探增储的3个有利目标区。

A significant breakthrough has been made in the Upper Paleozoic play in Dagang area of Huanghua Depression,Bohai Bay Basin over the past four years.This paper aims to analyze the key factors of hydrocarbon accumulation and identify the exploration prospective area.The geological,geochemical,logging and seismic data are allowed to investigate the source rock,reservoir distribution and properties,natural gas charging time and petroleum system model.The results show that the upper Paleozoic coal bedding source rocks have good organic matter with two peak periods of hydrocarbon generation.The reservoir responds low porosity and low permeability clastic rocks,but secondary pores and fractures have developed as a result of subsequent later tectonic movement.The origin source rock,secondary pore reservoir and the activity of faults are the key controlling factors for the gas accumulation.We build a petroleum system model as“two periods of hydrocarbon expulsion,source-sink superimposed,late fault activity reshape prospect,late gas charging”.The gentle high in the deep depression buried hill zone and slope of buried hill will be the promising exploration area.Three favorable target areas for future exploration are proposed:the slope area of Wumaying-Wangguantun sag,Dongguang Dongyi and Qibei.