Abstract

This study was carried out to evaluate the extent of carbonate crash in some Niger Delta oil wells and the levels of heavy metals (HMs) and rare earth elements (REEs) as useful fingerprinting tools in the characterization of the oil wells. Thirty-nine (39) rock samples were collected from three (3) oil wells in the Niger Delta, Nigeria. The carbonate contents were determined using Chittick apparatus while the elemental concentrations were determined using Atomic Absorption Spectrophotometry. Results of the study indicated that the carbonate contents of the rock samples decreased with increasing depth, due to a possible higher-than-average dissolution of CaCO₃ and/or excess bio-SiO₂ production. Among the investigated HMs, manganese had the highest mean concentration while nickel had the lowest mean concentration. Cerium had the highest mean concentration while lanthanum had the lowest mean concentration among the REEs. Mean V/Ni ratios of Oil Well 1 (3.21) indicated marine organic matter input while Oil Well 2 (2.47), and Oil Well 3 (2.16) indicated organic matter input of both marine and terrestrial sources. V/(V + Ni) ratios (>0.5) of the oil wells indicated that the organic matter was deposited under anoxic conditions. Variations in the distribution patterns of HMs, REEs, and carbonate content of the rock samples of Niger Delta oil wells indicated that the organic matter source and depositional environment were quite similar.

摘要

本研究旨在评估尼日尔三角洲一些油井中碳酸盐崩塌的程度以及重金属 (HMs) 和稀土元素 (REE) 的含量，作为油井表征中有用的指纹工具。从尼日利亚尼日尔三角洲的三 (3) 口油井中采集了三十九 (39) 个岩石样品。碳酸盐含量使用 Chittick 仪器测定，而元素浓度使用原子吸收分光光度法测定。_{研究结果表明，由于 CaCO 3}的溶解可能高于平均水平和/或过量的 bio-SiO ₂，​​岩石样品的碳酸盐含量随着深度的增加而降低生产。在所研究的 HMs 中，锰的平均浓度最高，而镍的平均浓度最低。在稀土元素中，铈的平均浓度最高，而镧的平均浓度最低。油井 1（3.21）的平均 V/Ni 比表示海洋有机质输入，而油井 2（2.47）和油井 3（2.16）表示海洋和陆源有机质输入。油井的V/(V+Ni)比值(>0.5)表明有机质在缺氧条件下沉积。尼日尔三角洲油井岩样中HMs、REEs和碳酸盐含量分布规律的变化表明，有机质来源和沉积环境较为相似。