火山活动影响的局限水体生烃潜力分析:以准噶尔盆地东部石炭系巴塔玛依内山组为例

以准噶尔盆地东部白碱沟地区石炭系巴塔玛依内山组为例,通过详细野外地质调查及烃源岩生烃潜力分析,探讨火山岩体所围限的局限水体的生烃能力。在大规模的中基性火山活动后的间歇期内,巴塔玛依内山组形成了一套沉积岩与火山岩互层的序列,通过对层系内的暗色泥岩、凝灰质泥岩及劣质煤等潜在烃源岩的总有机碳含量(TOC)、镜质体反射率(Ro)和岩石热解分析(S_1,S_2,T_(max))的测试,发现该套烃源岩有机质丰度平均为8.24 mg/g,处于高成熟-过成熟阶段,属于Ⅲ型烃源岩。尽管该套烃源岩分布有限,但其单层厚度可达13 m,且间歇期内小规模,多期次的火山活动有助于有机质的生成保存。白碱沟地区火山喷发间歇期所形成的局限水体具有烃源岩发育条件,可成为邻近火山岩储层的有效烃源岩。

Hydrocarbon generating potential in restricted waters influenced by volcanic activities: a case study of Carboniferous Batamayineishan Formation in eastern Junggar Basin

In order to verify the hydrocarbon generating potential in restricted waters surrounded by volcanic rocks, detailed geological survey has been carried out with respect to the Carboniferous Batamayineishan Formation in Baijiangou, eastern Junggar Basin. A stratigraphic sequence of sedimentary and volcanic rocks interbedding formed in Batamayineishan Formation during the period of volcanic intermittent after a large-scale massive intermediate-basic volcanic activity.Source rocks, mainly include dark mudstone, tuffaceous mudstone, and inferior coal, have been sampled and analyzed for TOC, Ro, S1, S2, and Tmax. The source rocks are characterized by an averaged TOC of 8.24 mg/g, mature-over mature evolution stage, and Type Ⅲ kerogen. Though the lateral distribution of source rocks is limited by the volcanic rocks, the thickness of single layer of source rock can exceed 13 m, and the generation and preservation of organic matter have been benefited from frequent small scale volcanic activities during the sedimentation of source rocks. Based on the discoveries in Baijiangou outcrops, effective source rocks can be deposited in restricted waters that formed in volcanic intermittent period and expulse hydrocarbon to adjacent volcanic reservoirs.