Geochemistry is the science of investigation of chemical variations in sediments and rocks. Variations in elements happen during some geological processes such as weathering, diagenesis and burial of sediments. Geochemistry covers a wide area of scientific subjects; each of them needs special training and study. All subdivisions of geochemistry are presented in following flowchart.
The most notable subjects of geochemical studies in petroleum geology include low-temperature (sedimentary) geochemistry and its subsidiaries.
Organic geochemistry deals with geochemical variations of living organism and their transformation into hydrocarbon. Moreover, determination of source, formation mechanism and evolution of hydrocarbon fluids all are the subjects of organic geochemistry. Thermal maturation of organic matters in source rocks and characterizing chemical composition of oil and gas are the most notable outputs of organic geochemistry.
Isotopic and elemental geochemistry makes it possible to reconstruct the past climatic condition and evolution of rocks and sediments throughout various geological processes. Stable (C, O, S) and radiogenic (Sr) isotopes provide important data about depositional and post-depositional (diagenetic) evolutions of rocks. Absolute dating of stratigraphic sequences in hydrocarbon fields and correlation of reservoir rocks based on their geochemical signatures are among the most useful applications of this part of geochemistry.
Geochemistry research group in upstream unit of the MAPSA Company has completed some geochemical studies by integrating the knowledge of Iranian scientists and technology of some joint companies in England, Canada, Spain and USA. This group aims to stablish a standard geochemistry laboratory, due to the growing trend in geochemical studies in exploration and production plans of National Iranian Oil Company (NIOC). Now some important geochemical analyses are available in the MAPSA Company which are summarized in following table.
|1||Vitrinite reflectance (Ro%)||15||Fission Track (Apatite and Zircon) analysis|
|2||Elemental analyses (Ni, V, Co)||16||Stable isotopes (C, O, N, S) analysis|
|3||Liquid Chromatography (LC)||17||Strontium (Sr) isotope analysis|
|5||GC-saturate||19||Fluid inclusion analysis|
|6||GC-aromatic||20||Trace and rare-earth elements (REEs) analysis|
|7||GC-FID SIM||21||XRD and XRF analysis|
|8||GC*GC||22||C, H, S isotopes in gas samples|
|9||Gas composition||23||C isotope (oil, rock, bitumen)|
|10||GC-MS||GC-MS||24||Ar/He isotopes in gas samples|
|14||Rock-Eval analysis||28||CSIA (Carbon Specific Isotope Analysis) for C1-C35|
The main tools for these analyses are:
Sample Preparation Facility
Atomic Absorption Spectroscopy
Scanning Electron Microscopy
Fluid Inclusion Thermometric and Spectroscopic Analysis
Laser Ablation ICP-MS
Stable Isotope Mass Spectrometry
Gas chromatography mass spectrometer (GC-MS)