基于微渗漏模拟实验的油气化探异常机理

对于油气化探异常形成的机理,早期国内外学者提出不同的油气化探异常模型,由于地质条件和烃类微渗漏的复杂性,难以从三维角度进行刻画和论证,同时又未见实验模拟证据的支持,使异常成因解释模糊,影响了化探技术的发展和在油气勘探中的广泛应用。针对上述问题,研制了系统的物理模拟实验装置,对油气聚集成藏后烃类物质穿过上覆地层微渗漏至地表的过程进行了实验室模拟。实验结果较好地反映了烃类垂向微渗漏的空间效应,在一定程度上揭示了油气化探异常由源及表的形成过程和基本规律。发现了烃类微渗漏具有幕式运移特点,揭示了油气垂向微渗漏过程中"羽状"涌流的存在。实验模拟结果与已知油气藏上方化探异常的观测数据具有较好的吻合性,表明"压力驱动、裂隙渗透"可能是油气化探异常形成的主要原因,不存在千篇一律的化探异常模式。取得的认识丰富了油气地球化学勘探的基础理论,促进了化探技术的持续发展,对油气运移、聚集理论的研究有一定的借鉴意义。

Mechanisms of geochemical anomalies in prospecting for oil and gas based on laboratory simulation of microseepage

Scholars previously proposed various models for the formation mechanism of geochemical anomaly prospecting for oil and gas. Because of geological conditions and complicated hydrocarbon microseepage, it is difficult to characterize and demonstrate from the three dimensional angle. Meanwhile, there has been no support evidence from experimental simulation, thus leading to an ambiguous interpretation for the cause of geochemical anomaly, which influences the development of geochemical exploration technology and extensive application in oil-gas exploration. To solve the above problems, the physical simulation experimental equipment was systematically developed to conduct laboratory simulation on the microseepage process of hydrocarbon through overlying strata to the surface after accumulation. The experimental results well reflect the spatial effect of vertical hydrocarbon microseepage, and to some extent reveal the formation process and basic law of geochemical anomaly prospecting for oil and gas from source to surface. It is found that hydrocarbon microseepage has the characteristics of episodic migration, thus revealing the "plume" flashy flow in vertical hydrocarbon microseepage process. The simulation results are in accord with geochemical anomaly data observed above the known reservoir, indicating that "pressure driven, fracture permeability" may be the main causes for geochemical anomaly and there is no unchanging geochemical anomaly pattern. The conclusions enrich the basic theories regarding petroleum geochemical exploration, promote the sustainable development of geochemical exploration technology, and also have some reference significance for studying the theories of hydrocarbon migration and accumulation.