【摘要】 根据区域地质、地震、钻井及油气地球化学等资料,从油气成藏基本要素,即烃源岩特征、储层及圈闭类型、油气运聚系统及成藏风险分析等方面入手,深入剖析乐东区中深层天然气成藏条件及主控因素。根据乐东区浅层天然气地质地球化学分析,天然气成因类型属成熟—高熟煤型气,其烃源主要来自中新统中深层梅山组—黄流组成熟—高成熟偏腐殖型烃源岩,而L22-1-7深探井钻探则进一步证实了该套烃源岩的存在,表明该区中深层具备烃源条件及良好烃源物质基础。乐东区中深层储层虽然个别探井揭示其发育及储集物性偏差,但尚不能否定全区。通过地震地质资料分析,该区中深层储层类型以低位域砂岩为主,多属于强制海退形成有关的低位滨岸砂坝、斜坡扇、盆底扇及水道砂等,预测其具有较好储集物性。再者,乐东区泥底辟活动强烈,泥底辟上拱刺穿形成了纵向断裂及裂隙系统,亦为深部天然气垂向运聚成藏提供了高速运聚通道。乐东区中深层天然气成藏,尽管目前尚存在诸多勘探风险和一些不确定因素,尤其是储集层分布及物性这个关键成藏控制因素,以及非烃气风险等仍然存在,但中深层具备天然气成藏条件及勘探前景是不容置疑的。更多还原

【Abstract】 The prospecting of mid-deep layers of Ledong area in the Yinggehai Basin is at the exploration stage at present.Based on regional geology,seismic data,boreholes as well as geochemical data,the conditions of natural gas accumulation and its controlling factors of the middle-deep layers in Ledong area were analyzed,including the characteristics of source rocks,the styles of reservoirs and traps,petroleum conduction system and accumulation risks.According to the geochemical features of the natural gas in the shallow layers,they belong to mature-high mature coal-derived gas,which is sourced from the mature-high mature humic source rocks in the Miocene Meishan-Huangliu Formations.Moreover,the drilling of well L22-1-7 confirmed the existence of this set of source rocks and it indicated that Ledong area has a good condition of source rocks.Although individual borehole revealed that the development and the reservoir physical properties of the middle-deep layers in Ledong area were not promising,we can′t ignore the whole area.The seismic and geologic data showed that the styles of reservoirs of the middle-deep layers in Ledong area are dominated by low stand sandstones,including coastal sand dams,slope fans,floor fans and channel sandstones,etc.,which were formed in the forced regression environment and should have good physical properties.What′s more,vertical faults and microcracks system resulted from upwarping and piercing forces of diapirs in Ledong area provided high efficient conduction pathways for vertical migration and accumulation of deep hydrocarbons.Though there are many exploration risks and some uncertain factors in the hydrocarbon accumulation of middle-deep layers in Ledong area,especially the key controlling factor on the distribution and physical properties of reservoirs,and nonhydrocarbon gas risks,the middle-deep layer gas accumulation conditions and exploration prospects are unassailable.更多还原