Principles of Elemental Chemostratigraphy (eBook)

​Dr Neil W. Craigie first became interested in geology during his experiences of attending Boy Scout camps in the early 1980’s and this inspired him to embark on a BSc degree in Geology at the University of St. Andrews, Scotland, in 1988. After this, Neil wished to enter the petroleum industry but felt that he required additional qualifications, so he decided to complete an MSc degree in Petroleum Geology at the University of Aberdeen, Scotland.  Unlike many of his colleagues at that time, he preferred to work towards a PhD at the same university, instead of gaining employment immediately after graduation. This was awarded in 1998 on completion of his thesis on the chemostratigraphy and sedimentology of Middle Devonian lacustrine sediments encountered in the Orcadian Basin, NE Scotland. During this study Neil realized that, though chemostratigraphy could be employed as a stand-alone reservoir correlation technique, it worked best as part of a multidisciplinary approach to correlation. On completing his PhD, Neil worked as a Geologist for Scott Pickford Ltd until the year 2000, and then as a chemostratigrapher for Chemostrat Ltd and Ichron Ltd. He is currently employed as a “geological consultant” for Saudi Aramco in Dhahran, Saudi Arabia, where he works on and manages a range of chemostratigraphy projects. Since 1997, Neil has completed chemostratigraphy studies throughout Saudi Arabia, the North Sea (UK, Norwegian, Dutch and Danish sectors), Norwegian Sea, Barents Sea, Canada, USA, Bolivia, Brazil, Egypt, Algeria, Libya and Qatar. Most of these studies have involved the integration of chemostratigraphic, sedimentological and biostratigraphy data and some have taken the form of ‘near real time’ wellsite work. Neil has published numerous papers and is widely regarded as one of the world’s leading experts in the field of elemental chemostratigraphy. He is delighted to share his knowledge and experience of the technique with readers of this book. Outside work, Neil enjoys fishing, walking and spending time with his family.

1. Introduction1.1 History and development of chemostratigraphy as a subject1.2. Principal applications of chemostratigraphy1.3 commonly used terminology2. Sampling, sample preparation and analytical techniques2.1 sampling strategyHow sampling strategies are established, types of lithologies that should/should not be sampled, common errors during sampling.2.2 Sample preparationCorrect procedures for washing, grinding and ‘picking’ of samples and common errors2.3 Analytical techniquesMost commonly used techniques of ICP-OES, ICP-MS and XRF2.4 Less commonly used techniquesLaser based instruments, QEMSCAN, XRD2.5 Summary and conclusion3. Geochemistry and mineralogy3.1 The use of mineralogical dataThe use of petrographic, XRD, heavy mineral and QEMSCAN data to establish element:mineral links will be discussed in detail3.2 Application of statistical techniquesPrincipal Components Analysis, Eigenvector analysis and Correlation Coefficient analysis will be discussed in detail3.3 Graphical analysisUse of binary diagrams to establish element mineral links3.3 Elements associated with heavy minerals3.4 Elements associated with carbonate minerals and evaporites3.5 Elements associated with clay minerals, feldspars and micas3.6 Classification of sandstones using inorganic geochemical data3.7 Use of geochemical data to determine changes in source/provenance3.8 Use of geochemical data to determine changes in depositional environment3.9 Use of geochemical data to model changes in weathering/diagenesis3.10 Summary and conclusions 4. Principles of chemostratigraphy4.1. Choice of key/index elements and ratiosHow to choose particular elements for chemostratigraphic purposes4.2 Development of hierarchical schemes4.3 comparison with wireline log, lithostratigraphic, biostratigraphic and sedimentological dataSeveral case studies will be presented4.5 Application of statisticsApplications of Discriminant Function Analysis, Principal Components Analysis and Histograms4.6 Common mistakes made during the interpretation of inorganic geochemical data and the establishment of chemostratigraphic schemes4. 7 Summary and conclusion5. Applications of chemostratigraphy to clastic and carbonate depositional systems and unconventional reservoirs5.1 Clastic depositional environmentsThrough case studies, details will be provided on the specific applications of the technique to the correlation of sediments deposited in glacial, continental, shallow marine and deep marine environments5.2. Carbonate environmentsHow can the technique be used in carbonates? What are the unique challenges of using the technique in this system, compared with that of clastics” Various case studies will be presented in this section5.3. Application of chemostratigraphy to unconventional reservoirs6. Applications of chemostratigraphy at wellsiteInformation provided on the application of chemostratigraphy at wellsite, including the use of chemostratigraphy to place coring points, casing points and total depth (TD) picks.7. Summary and Conclusions