济阳拗陷东营凹陷盐岩中的烃类包裹体 及其地质意义

本文报道在东营凹陷盐岩中发现大量烃类包裹体,这证实盐岩曾经失去封闭能力,成为油气运移通道。在对其盐水包裹体进行均一温度测试时发现,由于捕获压力与实验环境压力差异很大,再加上岩盐在水中溶解度随温度升高而增大,导致测温过程盐水包裹体体积变化和拉伸效应明显,所以同期盐水包裹体的均一温度出现较大波动,结果也不可靠,而纯烃类包裹体在一定程度上可以避免溶解度变化的影响,其均一温度有一定指示意义。通过对岩盐中的烃类包裹体均一温度初步校正,结合埋藏史和热史分析,认为至少存在两期与盐岩层变形有关的烃类流体活动,活动时期分别在东营期和明化镇期。流体对岩盐颗粒滑动和盐岩层变形有极其重要的影响,重结晶的岩盐晶体及其中的流体包裹体是流体作用的直接证据。盐岩中的流体来源、运移方向、活动期次和流体作用下的盐岩变形温度和压力是需要解决的关键问题,这对于了解含油气盆地中盐岩层对油气成藏的控制作用有重要意义。

Hydrocarbon Inclusions in Salt Rock of Dongying Sag, Jiyang Depression, and Their Geological Implications

This paper reports that hydrocarbon inclusions were found in halite of salt rocks from the Dongying depression, east of China. Hydrocarbon inclusions in halite indicate that the sealing capacity of salt rocks may be lost under special condition, oil and gas can migrate though them. The micro thermometry shows that the homogenization temperatures of aqueous inclusions in halite are not reliable because the volume of inclusions will change during heating. The change of volume was caused by two aspects, including difference between trapping pressure and pressure in lab, solubility of halite increasing with temperature. But the hydrocarbon inclusions can avoid the effect of solution, their homogenization temperatures are more reliable comparing to aqueous inclusions. Based on analysis of hydrocarbon inclusions in halite, we speculate that two activities stages of hydrocarbon fluid related to deformation of salt rock appeared in Dongying depression. The first stage was Dongying period, and the second one was Minghuzhen period, which were similar to stages of oil accumulation in Dongying depression. Fluids play an important role in salt grains moving and deformation of salt rocks. Recrystallization and fluid inclusions in halite are direct evidences for fluids activities. There are some key problems should be understood including where the fluids in halite came from and went, stages of fluids activities, the temperature and pressure of deformation under fluids adding. The answers of these questions are helpful to know how the salt rocks control accumulation oil and gas in hydrocarbon bearing basins.