塔河地区奥陶系油田水分布与运动学特征研究

Distribution and Kinetic Characteristics of Hydrothermal Fluid from Ordovician Oil Field in the Tahe Area

塔河油田是我国最大的陆上整装碳酸盐岩油田,其油田水分布与运动特征反映了油气运移规律。该区奥陶系油田水现今总体矿化度高,南北向存在从低到高再到低的3个矿化带,各带内平面分割性强,纵向层间差异大。塔河油田奥陶系的流体经历了多期次活动,奥陶系储层共捕获了4～5期盐水包裹体,其均一温度范围集中在60～80℃,90～105℃,110～140℃和145～170℃,盐度集中在0.5%～4%、5%～10%、10%～13%、14%～18%、>18%,反映出奥陶系储层曾经历过了4～5期热流体活动,对照埋藏史与油气运移史,高盐度流体活动与油气运移具有良好的匹配关系,油田水化学指标(油田水变质系数、碳酸盐岩平衡系数等)反映出塔河油区现今保存条件良好。井剖面包裹体纵向温度、盐度纵向不规则变化表明流体的活动以侧向运移为主。流体势分析说明运移方向不仅包括塔河东、南面是烃源岩方向,而且具有高流体势的西面也可能是油气来源方向。

Tahe Oilfield is one of the largest oilfields among the terrestrial carbonate reservoirs in China. The distribution and characteristics of hydrothermal fluid reflect the conditions and state of hydrocarbon migration and preservation. The present Ordovician Tahe Oilfield is highly mineralized and consists of three zones whose mineralization decreases gradually from south to north, and TDS is also distributed heterogeneously. The hydrothermal fluid in the Tahe Oilfied experienced multiphase activities. Inclusion study shows 4 to 5 kinds of inclusions found were trapped in the Ordovician reservoir with a wide range of homogeneous temperatures, namely 60-80℃, 90-105℃, 110-140℃ and 145-170℃, and a wide range of salinity, 0.5%-4%, 5%-10%,10%-13%, 14%-18%, 〉18%, correspondingly. Combined with depositing and migration history, high-salinity fluid activity has a good relation to oil migration. Vertical discontinuity of temperature and salinity may suggest a dominantly lateral migration. Analysis of the hydrothermal fluid potential shows hydrocarbon source was distributed around not only the south and east of the Tahe Oilfield but the west side with a high fluid potential.