GEO4210Introduction to PetroleumGeology and GeophysicsGeophysical Methods inHydrocarbon Exploration
About this part of the course Purpose: to give an overview of the basicgeophysical methods used in hydrocarbonexploration Working Plan:– Lecture: Principles Intro to Exercise– Practical: Seismic Interpretation excercise
Lecture Contents Geophysical Methods Theory / Principles Extensional Sedimentary Basins and itsSeismic Signature Introduction to the Exercise
Geophysical methods Passive:Method using the natural fields of the Earth, e.g. gravityand magnetic Active:Method that requires the input of artificially generatedenergy, e.g. seismic reflection The objective of geophysicsis to locate or detect the presence of subsurfacestructures or bodies and determine their size, shape,depth, and physical properties (density, velocity,porosity ) fluid content
Geophysical methodsMethodMeasured parameter“Operative” physicalpropertyGravitySpatial variations in thestrength of thegravitational field of theEarthDensityMagneticSpatial variations in thestrength of thegeomagnetic fieldMagnetic susceptibilityand remanenceElectromagnetic Response toElectric(SeaBedelectromagnetic radiation conductivity/resistivityLogging)and inductanceSeismicTravel times ofreflected/refractedseismic wavesSeismic velocity (anddensity)
Further reading Keary, P. & Brooks, M. (1991) An Introduction toGeophysical Exploration. Blackwell ScientificPublications. Mussett, A.E. & Khan, M. (2000) Looking into the Earth –An Introduction to Geological Geophysics. CambridgeUniversity Press. McQuillin, R., Bacon, M. & Barclay, W. (1984) AnIntroduction to Seismic Interpretation – ReflectionSeismics in Petroleum Exploration. Graham & Trotman. Badley, M.E. (1985) Practical Seismic Interpretation. D.Reidel Publishing php
Gravity Gravity surveying measures spatial variations inthe Earth’s gravitational field caused bydifferences in the density of sub-surface rocks In fact, it measures the variation in theaccelaration due to gravity It is expressed in so called gravity anomalies (inmilligal, 10-5 ms-2), i.e. deviations from apredefined reference level, geoid (a surface overwhich the gravitational field has equal value) Gravity is a scalar
Gravity Newton’s Universal Lawof Gravitation for smallmasses at the earthsurface: Spherical Non-rotating HomogeneousG M mG MF mg g 22RR––––G 6.67x10-11 m3kg-1s-2R is the Earth’s radiusM is the mass of the Earthm is the mass of a smallmassg is constant!
Gravity Non-sphericalEllipse of rotation RotatingCentrifugal forces es in the acceleration
NEllipse ofrotationEarth surfacecontinentEllipse of rotationGeoidoceanGeoid main sea-levelSphereGeoidgav 9.81 m/s2gmax 9.83 m/s2 (pole)gmin 9.78 m/s2 (equator)Anomaly
Magnetics Magnetic surveying aims to investigate the subsurfacegeology by measuring the strength or intensity of the Earth’smagnetic field. Lateral variation in magnetic susceptibility and remanencegive rise to spatial variations in the magnetic field It is expressed in so called magnetic anomalies, i.e.deviations from the Earth’s magnetic field. The unit of measurement is the tesla (T) which is volts·s·m-2In magnetic surveying the nanotesla is used (1nT 10-9 T) The magnetic field is a vector Natural magnetic elements: iron, cobalt, nickel, gadolinium Ferromagnetic minerals: magnetite, ilmenite, hematite,pyrrhotite
Magnetics Magneticsusceptibility, ka dimensionlessproperty which inessence is ameasure of howsusceptible amaterial is tobecomingmagnetized Sedimentary Rocks– Limestone: 10-25.000– Sandstone: 0-21.000– Shale: 60-18.600 Igneous Rocks– Granite: 10-65– Peridotite: 95.500-196.000 Minerals– Quartz: -15– Magnetite: 70.000-2x107
Magnetics Magnetic Force, H Intensity of inducedmagnetization, Ji Ji k · H Induced andremanentmagnetizationH Magnetic anomaly regional - residualJiJresJr
ElectromagneticsElectromagnetic methodsuse the response of theground to the propagationof incident alternatingelectromagnetic waves,made up of twoorthogonal vectorcomponents, an electricalintensity (E) and amagnetizing force (H) in aplane perpendicular tothe direction of travel
ElectromagneticsPrimary fieldTransmitterReceiverPrimary fieldSecondary fieldConductorElectromagnetic anomaly Primary Field – Secondary Field
Electromagnetics – Sea Bed LoggingSBL is a marine electromagnetic method that has the ability to map thesubsurface resistivity remotely from the seafloor.The basis of SBL is the use of a mobile horizontal electric dipole (HED) sourcetransmitting a low frequency electromagnetic signal and an array of seafloorelectric field receivers.A hydrocarbon filled reservoir will typically have high resistivity compared withshale and a water filled reservoirs.SBL therefore has the unique potential of distinguishing between ahydrocarbon filled and a water filled reservoir
Reflection SeismologyMarine multichannel seismic reflection data
Reflection SeismologyIncident rayAmplitude: A0Reflected rayAmplitude: A1Layer 1ρ1, v1Layer 2ρ2, v2ρ2, v2 ρ1, v1Acoustic Impedance: Z ρ·vReflection Coefficient: R A1/A0ρ 2 v2 ρ1v1 Z 2 Z1R ρ 2 v2 ρ1v1 Z 2 Z1Transmission Coefficient: T A2/A02 ρ1v1T ρ 2 v2 ρ1v1Transmitted rayAmplitude: A2-1 R 1R 0All incident energy transmitted (Z1 Z2)no reflectionR -1 or 1All incident energy reflectedstrong reflectionR 0Phase change (180 ) in reflected wave
Reflection Seismology Shotpoint interval 60seconds 25-120 receivers Sampling rate 4milliseconds Normal seismic lineca. 8 sTWT
Sedimentary Basins Hydrocarbon provinces are found in sedimentary basins Important to know how basins are formed Basin Analysis– Hydrocarbon traps– Stratigraphy of Source rock Reservoir rock Cap rock– Maturation of source rocks– Migration path-ways
Extensional Sedimentary Basins Offshore Norway – VikingGraben, Central GrabenLate Jurassic – EarlyCretaceousMature HydrocarbonProvince
Syn-RiftRotated Fault BlocksIncreasing Fault Displacement
Seismic Signature of ExtensionalSedimentary Basins
INTRODUCTION TO EXERCISE
Seismic Signature of ExtensionalSedimentary Basins – Offshore Norway
Stratigraphy – Offshore Norway
Summary Offshore Norway Main Rifting Event: Late-Jurassic – EarlyCretaceous Structural Traps – Fault bounded Main Reservoir: Upper Triassic – MiddleJurassic, containing Tarbert, Ness,Rannoch, Cook, Statfjord and Lunde Fms. Source Rock: Upper Jurassic, Heather Fm Cap Rock: Early Cretaceous
Exercise Interprete seismic line NVGTI92-105 Interprete pre-, syn- and post-riftsequences Interprete possible hydrocarbon traps Point out source-, reservoir, and cap-rock
geomagnetic field Magnetic “Operative” physical property Method Measured parameter. Further reading Keary, P. & Brooks, M. (1991) An Introduction to Geophysical Exploration. Blackwell Scientific Publications. Mussett, A.E. & Khan, M. (2000) Looking into the Earth – An Introduction to Geological Geophysics. Cambridge University Press. McQuillin, R., Bacon, M. & Barclay, W .
1 An Introduction to Geology 2 11. Geology: The Science of Earth 4 Physical and Historical Geology 4 Geology, People, and the Environment 5 21. The Development of Geology 6 Catastrophism 6 The Birth of Modern Geology 6 Geology Today 7 The Magnitude of Geologic Time 8 31. The nature of Scientific Inquiry 9 Hypothesis 10 Theory 10 Scientific .
GEOLOGY . is a Branch of Natural science deals with the study of the Earth, It is also known as Earth science. For studying the Earth in detail the subject of geology has been divided into various branches, which are as follows: 1. Mineralogy 2. Petrology 3. Structural geology 4. Civil Engineering geology 5. Mining geology 6. Economic geology 7.
Essentials of Geology Frederick K. Lutgens Edward J. Tarbuck Illinois Central College Illustrated by Dennis Tasa Prentice Hall Upper Saddle River, New Jersey 07458. Contents Preface xi 1 An Introduction to Geology The Science of Geology 2 Historical Notes about Geology 2 Catastrophism 3 The Birth of Modern Geology 3 Geologic Time 4 The Nature .
BU - B.Sc Geology- 2019-20 onwards - colleges Page 5 of 45 BHARATHIAR UNIVERSITY COIMBATORE 641 046 B.Sc., GEOLOGY I YEAR - I SEMESTER PAPER I-PHYSICALGEOLOGY Broad Objectives & Methodology: Geology is the study of the Earth as a whole. Physical Geology introduces different topics which define geology as a branch of Physical Geology.
Earth science includes many subdivisions of geology such as geochemistry, geophysics, geobiology and paleontology, as well as oceanography, meteorology, and astronomy. Units 1 through 4 focus on the science of geology, a word that means "study of Earth." Geology is divided into two broad areas—physical geology and historical geology.
estimation and exploration are dealt within mining geology. (xi) Civil Engineering Geology As a branch of geology, it deals with “all the geological problems that arise in the field of civil engineering along with suitable treatments”. Thus, it includes the construction of dams,
AA in Geology 35-38 credits General Geology, Dinosaurs and Earth History, Geology of National Parks, Oceanography, Astronomy, Physics, Chemistry Transfer courses for lower-division coursework General Geology, Dinosaurs and Earth History, Physics, Chemistry, Calculus 4-year
engineering geology, soil mechanics or rock mechanics can be based. They are not conceived as a course and text on engineering geology. We have, however, extended the scope of the book beyond what is geology in the strict sense to include engineering applications of geology.