松辽盆地地层水化学特征及其流体—岩石相互作用探讨

GEOCHEMISTRY OF FORMATION WATER AND ITS CONTROLLING FACTORS, CASE STUDIES ON THE SONGLIAO BASIN

地层水化学的空间分布特征研究是追踪流体运移及油气运移、聚集的重要手段之一。通过对松辽盆地水化学测试数据的分析,阐明了该盆地水化学特征的空间分布规律及其所反映的流体-岩石相互作用过程,指出水化学的时间演化特征受流体-岩石相互作用的控制。再通过研究水化学中C l--HCO3-和N a+-K+-Ca2+的关系进一步阐明了该盆地地层水早期为富含HCO3-的低盐度流体,含钠矿物(N aC l)与碳酸盐矿物的溶解作用导致了流体中各种离子及流体盐度的增高,随后的钠长石化作用导致流体中Ca2+的富集与N a+的亏损,形成了CaC l2型流体。最后指出松辽盆地水化学特征所反映的流体-岩石相互作用过程得到了其它地质观察的证明,认为地层水化学可以示踪流体-岩石相互作用过程,有广泛的用途。

The geochemistry of formation water is a common way to trace the fluid flow and hydrocarbon accumulation. This paper focused on the space distribution of the geochemistry of the formation water in Songliao basin and its indication for the water rock interaction processes. The Cl^--HCO3^- and Na^＋-K^＋-Ca^2＋ relationships show that the initial water-rock interaction was the dissolution of NaCl and calciumbearing carbonate,which resulted in the increasing of Na^＋-K^＋-Ca^2＋-Cl^- and salinity. The succeeding water-rock interaction was multaneously and formed C albitization, which led to the decreasing of Na^＋ and the increasing of Ca^2＋ simuhaneously and formed CaCl2 type fluid. The above analyses show that the geochemistry evolution of the formation water is governed by the water-rock interaction, while its space distribution was controlled by the hydrological conditions. The analyzed water rock interaction process has been proved by other geological observations, which proves that the fluid geochemistry can be used to trace the fluid-rock interaction processes and have a broad usage in practice.