Reservoir Development Tools

1. Chapter 2 (Part 3) Reservoir Development Tools

2. Reservoir Development Tools • When information indicates a strong possibility of hydrocarbons oil companies will typically drill an exploratory well. • While drilling geologist monitor the well through core samples, well logs, and test results. • Geologist combine all the information and try to predict the production possibility of the formation.

3. Well Logs • Log: Record of information about the formations the well has been drilled through. • Typically two types: • Drillers Logs • Wire line Logs • Electric Logs • Radioactivity Logs • Acoustic Logs

4. Driller’s Log • Record of the kinds of rocks and fluids encountered at different depths and anything else of interest. • Mainly when formations are alternating from soft to hard rock – How long it took to drill through a particular formation. • Good drillers can correlate the time/data with other wells in the area and different formations.

5. Driller’s Log

6. Wire Line Logs • Wire Line: A metal line that can be run down the hole with a tool attached. • Conductor Line: Wire line that can carry electricity to the tool. (Both are commonly called “Wireline”) • Wire Line involves complex calculations and interpretation of the information the tool relays to the surface. • Logging Specialist use the data to compare, correlate and track the depth of formations. • Sonde: Instrument lowered down hole that relays all the information back to the surface.

7. Wire Line Logs

8. Electric Logs • Spontaneous Potential (SP) Log • Records weak electrical currents that flow naturally in the rock next to the wellbore (Natural Electricity) • Shows the boundaries and thickness of each layer of rock • Easiest and most basic log – therefore the most common • Induced Electricity Log • Electrical signal is emitted by the sonde through the formation and relays it back to the receiver at the surface. • Receiver measures the formations resistance to current or how well it conducts current. • Resistivity Log: Records resistance • Induction Log: Records conductivity

9. Nuclear Logs • Radioactivity Logs • Measure natural and induced radioactivity in formations • Gamma Ray Log: • Records gamma particles (Gama Rays) that the formation gives off naturally. • Useful in identifying shale and clay-filled formations • Neutron Log: • Sends Neutrons through the formation, when they collide with hydrogen it slows them down. This slowness is recorded when a lot of hydrogen is present in the formation.

10. Acoustic Logs • Acoustic/Sonic Log: • Sonde emits a sound wave through the formation that is recorded. • How fast the sound travels depends on the density of the rock. • The more porous the rock the faster the sound waves travel.

11. Wire Line Logs

12. Sample Logs • Physical samples of the well bore. • Typically Two Types: • Core Samples • Cutting Samples

13. Core Samples • Core: Slender column of rock that shows the sequence of rock as they appear within the earth. • Coring Bit: Substituted for the drilling bit, it has a hollow center that enables the recovery of a sample. • Typically length ranges from 25 to 60 feet. • When it is brought to the surface it is packaged and sent to a lab for analysis.

14. Core Samples

15. Cutting Samples • Cuttings: rock that is broken up from the well bore. • As the cuttings flow out of the hole they are recovered by geologist/mud engineers and studied. • Not all cuttings come from the bottom, some are sloughed off from the sides at various depths. • Not as accurate as a core sample, but it is still widely used and offers useful data to geologists/mud engineers regarding the condition and characteristics of the hole.

16. Drill Stem Test • Drill Stem Test (DST): • Primary way to test a formation that has just been drilled. • Formation fluids flow into perforated holes in the tool where the pressure is recorded . • When the pressure is recorded valves inside the tool close trapping the fluid inside the tool to be used later as a sample for analysis

17. Drill Stem Test Seals off well bore for reading only formation fluid Formation Fluid and Pressure Fluid is trapped inside once measurements have been made

18. Strat Test • Stratigraphy: • The study of the origin, composition, distribution, and sequence of rock strata. • Strat Test: • Drill a hole primarily to obtain geological information, mainly in exploration work. • Borehole that exposes complete sections of formations • Stratographers analyze the cuttings to create a cutting log and look for hydrocarbons. • Geologist try to follow beds of rock from well to well.

19. Stratigraphic Correlation • Stratigraphic Correlation: • The process of comparing geological formations. • Scientists use data from other wells and compare them to predict other sources (formations) of hydrocarbons. • Use of drillers logs, sample logs, electrical logs, composition of formations, and area data are common methods. • Sequence Stratigraphy: • Scientist use seismic surveys and deduce how the environment existed when a rock layer first formed.

20. Stratigraphic Correlation

21. Maps • Base Maps • Show existing wells, property lines, roads, buildings and other man made features. • Topographic Maps • Show surface features such as mountains and valleys • Bouger Gravity Map • Underground formations developed from gravity surveys.

22. Contour Maps (see pg. 43) • Depicts geologic structure and thickness of formations • Structural Map • Depicts the depth of a specific formation from the surface of the formation • Isopach Map • Shows the thickness of a formation. Used mainly to calculate how much hydrocarbon remains in a formation. • Lithofacies Map • Shows the character of the rock itself and how it varies horizontally within the formation. • Biofacies Map: Shows the variations in occurrence of fossil types

23. Vertical Cross Sections • Represents a portion of the crust as though it were sliced • Shows the structures and fault patterns • Show anticlinal and fault traps • Horizontal variations I type and thickness of rock

24. Vertical Cross Sections

25. Questions • 1. When do oil companies typically drill an exploration well? • 2. List the two typical types of well logs. • 3. List the three types of wire line logs. • 4. What is a sonde? • 5. List the two types of sample logs typically used. • 6. What is the difference between a coring bit and standard drilling bit. • 7. Define cuttings. • 8. What is a DST? • 9. Define stratography. • 10. List the three types of maps commonly used in the oil industry.