麻江古油藏原生水晶中固体沥青包裹体的发现及地质意义

Discovery of Solid Bitumen Inclusions in Authigenic Rock Crystals in Majiang Paleo-oil Reservior and Its Geological Significance

在麻江古油藏坝固地区,产于下奥陶统红花园组碳酸盐岩储层晶洞中的大部分水晶中均含有固体沥青包裹体,其中一类为水晶生长过程中捕获白云岩晶洞中的储层沥青,可能代表了传统上认为的在加里东期被破坏的麻江古油藏。激光拉曼光谱分析显示该类固体沥青包裹体与白云岩晶洞中的储层沥青都具有较高的演化程度。根据流体包裹体显微测温和埋藏史分析,认为麻江古油藏存在印支期成藏的油气,结合流体包裹体与水晶中原生固体沥青包裹体的共生关系,为传统认为的麻江古油藏在加里东期被破坏提供了新证据,此外,还对印支期成藏油气的来源做了初步分析。

In the capacities of dolomite reservoir of Lower Ordovician Honghuayuan Formation in Bagu area, many rock crystals contain solid bitumen inclusions. One type of the inclusions was captured by rock crystals through their growing process from the solid bitumen of the capacities. This probably represents the Majiang paleo-oil reservior generally considered to have been destroyed during Caledon period. Laser Raman spectrum analysis demonstrates that both have high thermal maturity. The analysis of microthermometry and burial history suggests that there should exist Indosinian oil accumulation in the area of Majiang paleo-oil. This provides new evidence that Majiang paleo-oil reservior was destroyed during Early Paleozoic period combined with the co-existence relation of the fluid inclusions and solid bitumen in the rock crystals. Besides, a preliminary analysis of the source rocks of the existing Indosinian oil accumulation is made.