徐波. 东海盆地西湖凹陷天台反转带花港组地层水地球化学特征及其成因[J]. 海洋地质与第四纪地质, 2021, 41(3): 62-71. DOI: 10.16562/j.cnki.0256-1492.2020122101
引用本文: 徐波. 东海盆地西湖凹陷天台反转带花港组地层水地球化学特征及其成因[J]. 海洋地质与第四纪地质, 2021, 41(3): 62-71. DOI: 10.16562/j.cnki.0256-1492.2020122101
XU Bo. Geochemistry and genesis of the formation water in Huagang Formation of the Tiantai Inversion Zone, the Xihu Depression of the East China Sea Basin[J]. Marine Geology & Quaternary Geology, 2021, 41(3): 62-71. DOI: 10.16562/j.cnki.0256-1492.2020122101
Citation: XU Bo. Geochemistry and genesis of the formation water in Huagang Formation of the Tiantai Inversion Zone, the Xihu Depression of the East China Sea Basin[J]. Marine Geology & Quaternary Geology, 2021, 41(3): 62-71. DOI: 10.16562/j.cnki.0256-1492.2020122101

东海盆地西湖凹陷天台反转带花港组地层水地球化学特征及其成因

Geochemistry and genesis of the formation water in Huagang Formation of the Tiantai Inversion Zone, the Xihu Depression of the East China Sea Basin

  • 摘要: 通过对西湖凹陷天台反转带花港组20口井地层水地球化学特征进行研究,进一步揭示地层水成因、来源以及保存条件。研究结果表明,花港组地层水离子组成以Cl、Na+、Ca2+以及HCO3为主,其中Na+和Cl浓度与矿化度(TDS)之间呈现较好的线性关系,具有高浓缩地层水的特征。水型以氯化钙Ⅳ型和Ⅴ型为主;钠氯系数和脱硫系数均较小,远低于海水;钙镁系数高于深层水,均指示花港组地层封闭性好,处于交替停滞带,有利于油气的聚集与保存。Na+轻微亏损主要受钠长石化作用影响;Ca2+富集除了钠长石化作用外,有机质成熟过程中伴生的有机酸,对长石和含钙矿物的溶蚀作用,也促进地层水中Ca2+的富集;Mg2+亏损可能与高岭石、绿泥石以及白云岩化紧密相关。花港组地层水来源于陆相沉积水,受沉积环境、水-岩反应、蒸发浓缩作用以及流体混合作用共同控制,表现出富Ca2+,贫Mg2+,略微贫Na+的特点。

     

    Abstract: Based on the geochemical features of the formation water in Huagang Formation collected from 20 wells on the Tiantai structure of Xihu Depression, the genesis, source and preservation conditions of the formation water are discussed in this paper. The water is dominated by Cl, Na+, Ca2+ and HCO3. And the concentrations of Na+ and Cl show an obvious linear relationship with TDS which suggests a kind of highly concentrated formation water. The water is mainly of types CaCl2 Ⅳ and Ⅴ. r(Na+)/r(Cl) and 100×(rSO42−)/r(Cl) are lower than those in seawater; while r(Ca2+)/r(Mg2+) are higher in deep water. All of these features indicate that the Huagang Formation has effective sealing capability and is deposited in an alternative stagnation zone, which is conducive as well to oil and gas accumulation and preservation. The slight loss of Na+ is mainly caused by albitization. In addition to the formation of sodium feldspar, organic acids associated with the maturation of organic matter and the dissolution of feldspar and calcium-bearing minerals, also promoted the enrichment of Ca2+ in the formation water. The deficiency of Mg2+ may be closely related to the formation of kaolinite and chlorite in addition to dolomitization. The formation water of Huagang Formation originally came from land water and therefore is controlled by sedimentary environment, water-rock reaction, evaporation and concentration and fluid mixing characterized by rich Ca2+, poor Mg2+ and slightly poor Na+.

     

/

返回文章
返回