Geochemistry and origin of formation waters in the western Canada sedimentary basin—III. Factors controlling chemical composition☆
Geochemistry and origin of formation waters in the western Canada sedimentary basin—III. Factors controlling chemical composition☆
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DOI：
10.1016/0016-7037(71)90088-3
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发表时间：
1971-06
影响因子：
5
通讯作者：
B. Hitchon;G. K. Billings;J. E. Klovan
中科院分区：
文献类型：
--
作者：
B. Hitchon;G. K. Billings;J. E. Klovan
据报道，加拿大阿尔伯塔省油田和气田的78个地层水中含有20种主要和次要的化学成分。利用已公布的孔隙体积和氯度分布数据，给出了加拿大西部沉积盆地地层水的体积加权平均组成。对Q型、R型和二阶R型因子分析的结果进行了列表和解释。体积加权平均组成与现今海水相似，是地层水中大部分溶解盐类最终来源于海水的有力证据。淡水补水稀释和膜过滤浓缩是控制化学成分的主要因素。它们共同产生了从淡水到盐水的化学种群，这一点得到了Q模式分析的证实。与海水相比，体积加权平均地层水获得了氯化钠，这在R型分析中是作为一个单独的因素出现的，定量计算表明，中泥盆世蒸发岩层已经溶解了足够的盐岩来解释观测到的氯化钠增加，而从盆地层状蒸发岩中溶解的盐酸盐平衡已经并正在丢失到地表。镁和钙在不同因素中的存在，结合定量计算，表明体积加权平均地层水中镁的离子平衡损失和钙的增加不能归因于白云石化作用。同样，SO4的总损失也不是由于硫化氢的转化。绿泥石的形成可能是镁流失的原因。因子研究表明，控制化学成分的其他因素包括粘土上的阳离子交换，从泥质岩石的粘土部分以及有机质中解吸的可能的溴和碘的贡献，以及Ca-CO_3和Sr-SO_4浓度的溶解度控制。
Twenty major and minor chemical components are reported for 78 formation waters from oil fields and gas fields in Alberta, Canada. Using published pore volume and chlorinity distribution data, a volume-weighted mean composition of formation waters in the western Canada sedimentary basin is presented. The results of Q-mode, R-mode, and second-order R-mode factor analyses are tabulated and interpreted. The volume-weighted mean composition is similar to that of present day sea water and is compelling evidence for an ultimate origin from sea water of the major portion of the dissolved salts in the formation waters. Dilution by fresh water recharge and concentration by membrane filtration are the major factors controlling chemical composition. Together, they produce a chemical population ranging from freshwater to brines which is confirmed by the Q-mode analysis. Compared to sea water, the volume-weighted mean formation water has gained NaCl, which occurs as a separate factor in the R-mode analysis, and quantitative calculations demonstrate that sufficient halite has been dissolved from Middle Devonian evaporite beds to account for the observed gain in NaCl, and that the balance of halite dissolved from bedded evaporites in the basin has been, and is being, lost to the surface. The presence of Mg and Ca in separate factors, together with quantitative calculations, indicate that the ionically balanced loss of Mg and gain of Ca in the volume-weighted mean formation water cannot be attributed to dolomitization. Similarly, the total loss of SO4is not due to conversion of H2S. Chlorite formation could account for the loss of Mg. Other factors controlling chemical composition and suggested by the factor study include cation exchange on clays, a probable contribution of Br and I by desorption from the clay fraction of argillaceous rocks, as well as from organic matter, and solubility control of Ca-CO3and Sr-SO4concentrations.