化学元素在英国北海深水浊积油田精细小层划分的实践应用

    Application of Chemical Elements for Stratigraphic Division of Deepwater Turbidite Sandstone Oilfield in the North Sea, UK

    • 摘要: 深水浊积砂岩油田开发井距大、储层横向变化快、空间展布不规则,小尺度地层划分对比往往借助高分辨率地震资料。当地震资料难以满足精度要求时,利用常规地层对比方法往往效果不佳。本文以英国北海BD油田为例,通过岩芯和岩屑矿物分析,优选出对古物源、古气候、古沉积环境等沉积控制因素敏感的地球化学元素,按照“层次递进”的思路,首先基于深海泥岩背景建立宏观地层格架,再进行内部砂体的精细对比,进而建立研究区无机地球化学沉积序列,并对深水浊积砂岩地层进行了精细划分。研究表明:针对研究区识别到的近50种矿物元素研究分析,通过主成分分析共筛选出3个主成分(PC1、PC2、PC3);PC1为泥岩相匹配的共生矿物组合;PC2为与砂岩相匹配的共生矿物组合;PC3指示后期成岩程度;基于砂泥岩共生矿物元素分析,遴选出可分辨泥岩和砂岩的共生矿物关键元素比率(砂岩识别出6类;泥岩识别出5类)来定义识别目的层不同期次的泥岩段单元和砂岩段单元,从而建立适用于该区的化学地层学地层识别划分标准。基于共生矿物元素的地球化学地层特征,将该区目的层共划分出6套泥岩层系(CP0—CP5)、7套砂岩层系(SP0—SP6)。该类方法为类似油田的小层精细划分对比可提供参考依据。

       

      Abstract: Generally deep-water turbidite sandstone shows the characteristics of less well, fast lateral change and irregular spatial distribution, and its stratigraphic division and comparison often rely on high-resolution seismic data. When seismic cannot meet the accuracy requirements, conventional stratigraphic correlation methods often have poor results. This article takes the BD oilfield in the North Sea of the UK as an example, and through core and rock fragment mineral analysis, geochemical elements that are sensitive to sedimentary control factors such as ancient sources, ancient climate, and ancient sedimentary environment are selected. Following the idea of "hierarchical progression", a macroscopic stratigraphic framework is first established based on the deep-water turbidite mudstone background, then fine comparison of internal sand bodies is done following the above macroscopic framework. Finally, an inorganic geochemical sedimentary sequence is established in the target area. And the deep-water turbidite sandstone formation is finely divided. Research shows that based on the analysis of nearly 50 identified mineral elements in the target area, three principal components (PC1, PC2, PC3) are selected through principal component analysis; PC1 is a symbiotic mineral combination that matches mudstone; PC2 is a symbiotic mineral combination that matches sandstone; PC3 indicates the degree of late diagenesis; Based on the analysis of coexisting mineral elements in sandstone and mudstone, the key element ratios of distinguishable coexisting minerals in mudstone and sandstone (6 types identified in sandstone and 5 types identified in mudstone) are selected to define the identification of mudstone and sandstone units in different stages of the target layer, thereby establishing a chemical stratigraphy stratigraphic identification and division standard applicable to the area. Based on the geochemical stratigraphic characteristics of coexisting mineral elements, the target layers in this area are divided into 6 sets of mudstone layers (CP0 to CP5) and 7 sets of sandstone layers (SP0 to SP6). This type of method can provide a basis for fine comparison of small layers similar to oil fields.

       

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