祁连山冻土区含天然气水合物层段的油气显示现象

Oil and Gas Indications at Gas Hydrate-bearing Intervals in the Qilian Mountain Permafrost

以祁连山冻土区天然气水合物钻孔DK-2孔为例,对含油气显示岩心样品进行了储集岩热解分析,结合野外观察到的含油气显示现象,讨论了油气显示性质及其对水合物的可能指示意义。野外观察到的油迹、油斑、油浸、油染等不同级别油气显示现象大多产出在细砂岩、中砂岩中,部分产出在粉砂质泥岩夹薄层碳酸盐岩接触面及裂隙中,它们均得到室内储集岩热解分析结果的证实。油气显示所指示原油性质以中质油、重质油为主,少部分为超重油,甚至为沥青。钻孔中油气显示现象与水合物密切伴生,特别是水合物产出深度段或下部常见具中质油特征的油气显示,或可作为水合物一种指示。

In this paper a case was set in the gas hydrate drilling hole of DK - 2 in the Qilian Mountain perma- frost. Oil and gas indication-bearing core samples were analyzed with reservoir pyrolysis, and in combination with field observation of oil and gas indications, the nature of oil and gas indications and their possible indica- tive implication to gas hydrate were discussed. The field-observed oil and gas indication phenomena such as va- rious kinds of oil trace, oil patch, oil immersion and oil staining, mostly occurred within fine sandstone, medi- um sandstone, and partly on interfaces between silt mudstone and carbonate lamina or within their fissures, which were proven by indoor reservoir pyrolysis results. The nature of oil and gas indications showed that the crude oil was mainly composed of medium-weighted oil or heavy-weighted oil with minor over-heavy-weighted oil and even with asphalt. In the drilling hole, the oil and gas indications were closely associated with gas hydrate, and especially those characterized by medium-weighted oil within or just below gas hydrate occurrence interval could be a sign for gas hydrate occurrence.