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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。
Based on the data of regional geology, earthquake, drilling and oil-gas geochemistry, this paper analyzes the basic elements of hydrocarbon accumulation, that is, the characteristics of source rocks, the types of reservoirs and traps, the hydrocarbon migration and accumulation system and the risk analysis of hydrocarbon accumulation Middle and deep natural gas accumulation conditions and main controlling factors in Eastern China. According to the geo-geochemical analysis of the shallow natural gas in Ledong, the genesis of natural gas is of mature-high-mature coal gas, and the hydrocarbon sources mainly come from the Middle Miocene Middle Meishan Formation-Huangliu Formation mature-high-mature partial humic hydrocarbon source rock , While the deep well drilling of L22-1-7 further confirmed the existence of this set of source rocks, indicating that there are hydrocarbon source conditions and good hydrocarbon source material in the middle and deep layers of this area. Although the exploration of the individual wells in the middle and deep reservoirs of Ledong district reveals its development and the deviation of reservoir properties, it is still impossible to deny the whole area. According to the analysis of seismic geology data, the middle and deep reservoir types are dominated by low-grade sandstones and mostly belong to the low-level shore bar, slope fan, pelvic floor fan, Storage properties. In addition, the strong mud diapirism in Ledong District resulted in the longitudinal deformation and fracture system of the diapir of the diapir, and also provided the high-velocity coalescence channel for vertical migration and accumulation of deep natural gas. Although there are still many exploration risks and some uncertain factors in the Ledong area, especially the key accumulation control factors such as reservoir distribution and physical properties, as well as the risk of non-hydrocarbon gas, there are still some natural gas in the middle and deep layers Reservoir conditions and exploration prospects are beyond doubt.