东营凹陷水化学场成因及其与超压系统耦合关系

Hydrochemistry field origin and its coupling relationship with overpressure system, Dongying depression

关键词:  东锊凹陷  超系统  矿化度特征  离子特征  水-岩相互作用  原油分布与保存

Key words:  Dongying depression  overpressure system  salinity characteristics  ions characteristics  water-rock interaction  oil distribution and preservation

摘要:

以研究K2000余U探并的实测地和油田水化学资料以及149个流体包裹体古压力模拟结果等为基础,利用 地层水中阴R丨离子平衡关系和水-岩相互作用的特点,考察东旮凹陷水化学场的成因特征及其与超压系统演化特怔 的耦合关系以及对原油保存条件的影响。结果表明:在垂问上.2. 2 km之上常压系统(沙二段至馆陶组)地位水矿化 度一般低于100 g/L,属于咸水,而2. 2 I?之下的超压系统(沙PN和沙三段)部分地戻水矿化度高于100 g/L,最高达 336 r/L,属于盐水:在平面上.东营凹陷东部地W水矿化度高于西部,北带卨于南部，沙=和沙二段高矿化度地层水 在W陷中心沿断裂带分布，沙四段地层水矿化度以东营北带洼陷IX为中心呈环带状向外减小;在水化学场和超压系 统耦合作用下，超压流体封存箱中的水-岩相迂作用对凹陷中心氣化钙型高矿化度地E水的形成有重要作用，高 矿化度地层水的形成某种程度上受到沙四段蒸发岩地层中盐类溶解作用的影响；不同地区和层位的原油密度不同，在凹陷边缘常压带为开启的水文地质系统,地表水渗入作用导致地M水矿化度降低，原油的轻组分散失，密度增加， 油气保存条件较差，iwm陷中心超压顶面附近和超压系统内部处于封闭性较好的水文地质系统,原油密度多小于 0. 9 R/cm³,油气保存条件较好。

Abstract:

According to the measured pressure of formation，hydroohemistry data from more than 2 000 wells in oilfield, and the paleao-pressure from 149 fluid inclusion thermodynamics modeling in Dongying depression, the mass balance relation of cation and anion was calculated to study the water-rock interaction. Based on these, the generation process of the formation water and its relation to the pressure evolution and oil preservation conditions were analyzed. The results show that in the vertical, the formation water salinity is lower than 100 g/L in the normal pressure system (from Es2 to Qp) with the depth above 2. 2 km, and the formation water belongs to salt water. The formation water salinity is higher than 100 g/L and the highest value is 336 g/L in the overpressure system ( Ea4 and Es,) wilh the depth under 2.2 km, and the formation water belongs to saline. In the plane, the. formation water salinity in the east of Dongying depression is higher than that in the west, and the saJinily in the north is higher than that in the south. The high salinity formation water in Es2 and Es5 distributes along the fault zones of depression center. The formation water salinity in Es4 reduces from the center of north depression to the outside, exhibiting zonal distribution. For the coupling relation between hydrochemical field and overpressure system, water-rock interaction in overpressure fluid compartment has a signification impact on forming high salinity CaCl2 formation water in the center depression. The forming of high salinity formation water was influenced by the salt dissolution of evaporite forma-tion in Es4. The density from different member and area is different. The depression edge normal pressure zone is an open hydro-geological system. The formation water salinity is reduced by inflltration of surface water. The oil light components are lost and oil density increases. The oil preservation conditions of the zone are poor, but the top and inside of overpressure system in the center of depression is a closed hydro-geological system. Most of oil density is lower than 0.9 g/cm³，and the oil and gas preservation conditions are good.