FE 02-01 Introduction

Nội dung text: FE 02-01 Introduction

1. Seminar Objectives • How hydrocarbons are formed • The search for oil and gas • Present the parts of the rig • Outline the steps taken in drilling and completing a well • Overview of basic mud logging operations
2. Life and Geologic Time • The presence of C,H,N and O created the conditions of life on Earth • First bacteria appeared 3.5 billion yrs ago • Oil and gas derived entirely from decayed organic matter
3. Maturation • Maturation is the “cooking” of organic matter trapped in sedimentary layers • Increasing heat and pressure causes kerogen to form • Source rocks are rocks that contain sufficient substances to generate oil and gas • When a source rock starts to generate oil or gas it is said to be mature
4. Oil Window • Special environment where oil is generated • The temperature in the oil window: – 65º and 150º C
5. Oil and Gas Windows
6. Primary Vs. Secondary Migration • Primary Migration – release of oil from kerogen and its movement in the narrow pores and capillaries of the source rock • Secondary Migration – movement of hydrocarbons away from the source rock
7. Entrapment • Oil and gas fields need to be trapped in permeable reservoir rocks and capped by a seal called a cap rock
8. Traps • 2 main types of traps: – Structural traps – Stratigraphic traps • Traps must exist before hydrocarbon generation ceases
9. Stratigraphic Traps • Traps that result when the reservoir bed is sealed by other beds or by a change in porosity or permeability within the reservoir bed itself • Examples: – a tilted or inclined layer of petroleum-bearing rock is cutoff or truncated by an essentially horizontal, impermeable rock layer – petroleum-bearing formation pinches out – reservoir bed is surrounded by impermeable rock – change in porosity and permeability in the reservoir itself
10. End of Topic
11. Buried Treasure • Oil seeps used for medicinal purposes, lighting fuel, caulking boats and for military purposes • Industrial Revolution – saw a need for better source of fuel • First oil well completed by Edwin Drake in 1859
12. The Decision to Explore • Oil Exploration is undertaken by a variety of people for a variety of reasons such as: – Governments • Development of local resources reducing dependence upon others • Development of industry / Employment – Private Companies • Financial Gain
13. Private Oil Companies • Majors – Shell – Exxon Mobil – BP-Amoco-Arco – Chevron-Texaco • Independents (range from Multi-national to local) – Lasmo – Gulf Resources – Unocal
14. Where to Drill? • This decision is made at a variety of levels: – Global: • Which Country/Basin should we drill in? – Economic Terms? – Political Stability? – Availability of prospective acreage? – Market / Infrastructure? • This decision is part of a companies overall strategy, made by upper management and “New Ventures” explorationists.
15. Sedimentary Basins • Areas of extensive and prolonged subsidence where large accumulations of sediments occur and are hosts of hydrocarbon deposits • 600 known sedimentary basins of which 160 sedimentary basins have yielded oil but only 26 are significant producers • Exploration has occurred in another 240 basins, but no discoveries • The most predominant sedimentary basin is the Arabian-Iranian basin (>20 super giant fields)
16. The Job of the Geologist • Observe, explore and record any clues related to hydrocarbons • Reconstitute a scenario to identify places of oil/gas accumulations • Work with other specialists
17. Gravimetry • Gravity surveys can be used to map the extent or depth of sedimentary basins or even individual hydrocarbon prospects. • Gravimetry - the measurement of gravitational acceleration over an area, usually presented as a map or profile of Bouguer or free-air anomalies
18. Seismic Survey • Measure the travel time of sound waves generated by a “shock” applied to the ground or sea • More costly than gravimetry and magnetometry • But essential to discovering oil and gas fields
19. Offshore Seismic 1. Seismic vessel 2. Hydrophones – More data obtained offshore than onshore
20. Seismic Interpretation 1. Isochronic lines – points on the ground at which the waves take exactly the same time to be reflected / refracted at the surface 2. 3-D Seismic Maps Seismic profile Depth section based on seismic profile
21. Where to Drill • The decision where to drill is based partly on science and partly on gambling. • The site for a wildcat (exploration well) is usually above the thickest part of the stratum thought to contain hydrocarbons.