Oil and Gas Engineering Concepts Quiz

Final Exam Material

• Key points for the final exam include increasing pressure bursts and listening to and understanding audio information.
• Additional topics cover bit types, drilling action, and formation strength.
• Roller-cone/rock bits have milled teeth or tungsten carbide inserts (TCI).
• Milled tooth bits have cutting structures made of milled steel.
• TCI bits have cutting structures made of hard inserts pressed into a cone.
• These bits are suitable for various formation types and applications.
• The shape of the teeth on the cutting structure affects drilling action.
• Larger teeth result in more aggressive cutting structures for softer formations.

Bit Types: Roller-Cone / Rock Bits

• Two types exist: milled tooth or tungsten carbide insert (TCI)
• Milled tooth bits - cutting structure milled from steel
• TCI bits - cutting structure made of hard inserts pressed into a cone
• Suitable for many formation types and applications
• Cutting action causes rock crushing and scraping
• Teeth shape affects drilling
• Larger teeth mean more aggressive cutting, used in softer formations

Formation Strength & Bit Properties

• Formation strength is linked to insert/tooth spacing and properties.
• Soft formations use wide spacing with long, sharp inserts/teeth; high ROP and high cleaning flow rate.
• Medium formations have relatively wide spacing with shorter & stubbier inserts/teeth; relatively high ROP and relatively high cleaning flow rate.
• Hard formations use close spacing with short, rounded inserts/teeth; relatively low ROP and relatively low cleaning flow rate.

Fixed Cutter/Drag Bit - PDC

• PDC bits have no moving parts, a key advantage over roller-cone bits
• Rock failure is by shear rather than crushing in PDC bits, requiring less energy
• Steel-PDC bits are made of high-performance alloy steel
• Structurally stronger than matrix bits
• Easier to manufacture
• Dimensionally more accurate and repeatable
• Matrix bits are cast from tungsten carbide grains with a metallic binder.
• More resistant to abrasion and erosion than steel bits
• Preferred for smaller diameter holes where the body of the bit is likely to cause failure

Fixed Cutter Bit - Impreg & Diamond Bits

• Matrix PDC body (made from materials like tungsten carbide)
• Matrix is impregnated with embedded diamonds to prevent breakage
• Diamonds are small, leading to smaller depth of cuts
• Used with turbodrills or high-speed PDMs
• Sensitive to shocks and vibrations

Bit Selection

• Bit selection is based on formation description and unconfined compressive strength
• Suitable bit types are chosen based on formation hardness
• Bit selection considers economic factors, time savings, rig costs, and bit prices (next slide)
• The criteria also includes directional requirements and that the operating envelope for PDC's continues to expand

Drill String - DS

• The drill string (DS) transmits rotary power (torque) to the bit, provides weight-on-bit (WOB), and controls well trajectory, transporting drilling fluid to the bit.
• Monitoring and logging while drilling (MWD/LWD) are enabled through mud pulse telemetry
• Future monitoring will be done with wired/intelligent drillpipe

Drill String Components

• The drill string includes various components like the Kelly, Rotary Table, Top Drive, Mud Motor, Drill Collars, Stabilizers, and Bottom-Hole Assembly (BHA).

Drill Pipe

• Lengths range from 18-22 ft (now obsolete), 27-30 ft, and 38-45 ft
• Common sizes are: 3 ½", 4 ½", 5", in addition to others
• Larger drill pipe is selected for larger diameter hole sizes, lower frictional losses, and increased torsional strength
• API standards classify and indicate grades and strengths.

Drill Collars

• Large diameter, thick and heavy-duty tubes
• Connected by threading similar to the drill pipe
• Provide weight at the bottom of the well and are designed for compressive loads.
• It is common to avoid exceeding 80% of the buoyed drill collar weight.

Heavy-Wall Drill Pipe (HWDP)

• Lies in between drill collars and regular drill pipe in terms of weight
• Special tubes with wear pads in the middle (central wear pad) and long tool joints
• More resilient to fatigue and compression
• Used in slim-hole and high deviation drilling applications, due to less friction and reduced differential sticking risk

Stabilizers

• Centralize the drill string in the hole
• The location of stabilizers along the string, their size, and hole size all impact their effectiveness
• They act as a fulcrum in directional drilling operations

Miscellaneous String Components

• Subs, floats subs, circulators, bent subs, and more are included here as necessary components.

Rotary Steerable Systems (RSS)

• Steers by applying side load at the bit
• Active cutting structuring and gauge used to cut sideways into the formation
• The design uses short gauge bits as an advantage for quick responses.
• Active/responsive steering is a benefit but can lead to hole spiraling
• Alternatively, Point-the-bit steers by pointing or tilting the bit in the preferred wellpath without need for side loading
• Longer gauge bits are used to prevent hole spiraling

Downhole Motors (PDMs)

• Positive displacement motors (PDM's) consist of various components: Dump or Bypass valve, Power Assembly (rotor - stator), Connecting Rod / Universal Joint, Bearing in Drive Shaft / Sub, and Bit Sub.
• Types of PDMs include Mono Lobe and Multi Lobe types

Well Path Design

• Special case one and two discuss well path design in vertical and horizontal situations
• Formulas are used to calculate axial, horizontal, and vertical changes

Typical 2-D Well Profiles

• Three major types are shown: Type 1 is a vertical well, Type 2 is a well with a build section, and Type 3 is a continuous build well, used for directional drilling

Unconventional Wells / Casing Schemes

• Surface + production, with multiple surface casing options, depending on the specifics of the formation
• Multiple surface casing possible, often in normally pressured formations
• In geo-pressured formations, intermediate casings are also part of the design

Casing Design / Barrier Design

• Different types include conventional, secondary barriers, and cemented completion casing

API Casing Grades

• Standardized casing grades with minimum yield strengths, maximum yield strengths, and minimum tensile strengths provided

Effect of Environment

• Temperatures have a significant impact on mechanical properties in casing
• Yield strength decreases while toughness increases with higher temperature.
• Presence of gases like CO2 and H2S reduces steel's toughness

Casing Design Considerations

• Human lives and the environment are critical factors for consideration during design
• The system's behavior under different loads must be modeled and controlled considering Mechanical equipment properties
• Operational limits and safety margins need to be set and communicated

Design Philosophy/ Working Stress

• Explains the concept of maximum load and minimum resistance, with built-in safety factors when considering working stress

Loads and Force on Casing

• Loads acting upon the casing/strings during periods such as drilling, completions, stimulation, workovers, production, abandonments, and decommissions

Casing Failure Example

• Various load cases exist including uniaxial tension, compression, burst, collapse (with and without internal pressure), and biaxial collapse

Types of Casing Failures: Burst

• Pipe burst occurs when the internal pressure (P₁) exceeds external pressures (P₂) such that the pipe exceeds its API yield stress
• Pressure testing and shut-in operations need careful consideration and documentation

Casing Point Selection

• Regulatory issues like shallow aquifers and production zone coverage need consideration
• Geologic considerations, like unusual formations, pore pressures, and unstable ground conditions, impact casing point
• Pressure tolerance, for handling kicks, also guides casing point selection

"Top-Down" Casing Point Selection

• Hydrostatic pressure needs to be greater than pore pressure to prevent influx and less than “formation strength” to avoid fractures
• Maintaining margin on limiting values, for safety, is discussed

Well Path Design – Special Cases

• Special case one and two provide formulas calculating axial, horizontal, and vertical changes and considering constant azimuth and 90° deviation respectively

Typical 2-D Well Profiles

• Type 1, 2, and 3 provide graphical representation for vertical, build/hold, and continuous build directional drilling schemes

Cementing Optimization

• Four possible means of optimizing cementing, with respect to displacement efficiency, are mud conditioning, pipe rotation, standoff, and turbulent flow
• Mud conditioning, pipe rotation, standoff, and turbulent flow techniques are used in different ways, depending on the need

Cement Composition

• The mineral makeup and composition of cement are noted

Cement Grades and Chemistry

• Categorizes cement grades based on ASTM standards in terms of contents of C3S, C2S, C3A, C4AF, and fineness(cm2/g)
• Describes methods of obtaining particular properties, such as high early strength, better retardation, low heat of hydration, and resistance to sulfate attack

Other Reasons for Cementing

• Well tubular support
• Preventing wellbore/tubular collapse, borehole instability, and mud losses
• Corrosion protection and kick-off plugs
• Well abandonment

Cement Water Requirements

• Water requirements by weight of cement for different API classes (A & B, C, D, E, F, H & G) are noted

Schematic of Heat Evolution for Portland

• Stages 1, 2, 3, 4, and 5 discuss pre-induction, dormant induction, acceleration, deceleration, and steady state, respectively.
• Chemical action, including hydration and gel formation (exothermic), slow gel formation, grain hydration and water filling spaces (exothermic), setting phase and gel hydrate intergrowth, and hardening via further C3S hydration
• Time scales are noted

Cement Additives and Roles

• Different additives, their use, chemicals, and benefits are listed

Casing Centralization

• Different percentages of casing centralization in relation to mud and cement are noted

Wellpath Design: Special Cases

• Provides equations and methods to design well paths considering both vertical and horizontal situations, 90° deviation and constant azimuth

Typical 2-D Well Profiles

• Describes and displays graphical representation of the major types of directional drilling schemes including vertical, build section, tangent section and drop off section and continuous build well

Example 3/4 Solutions

• Solutions to a couple of casing design examples are demonstrated, that is applicable to both "Top-Down" & "Bottom-Up" methods of design

Design Process: Conventional Casing OD Selection

• Explains the conventional design process graphically exhibiting relationships between casing selection and Bit and hole sizes.

The Value of Cementing

• Expounds on the importance of cementing during well operations
• Discusses some of the reasons relating to completion, productivity, environment and cost over the entire life of the well.

Casing/Liner Cementation

• Illustrates the use of cementing during the placement of casing and liner pipes

Cement Evaluation: Bond Logging

• Describes the methods and concepts of bond logging to evaluate cement quality and its bonding to surround formations.

Cementing Problems

• Highlights some of the potential issues relating to cementation operations, including problems with casing centralization, and other similar scenarios

Additional Topics

• Further topics include slide steering processes both I and II, different types of directional drilling systems, and definitions of terms like dog leg severity (DLS), and others which may prove relevant to the specifics required for the final exam.

Test your knowledge on important concepts in oil and gas engineering, including casing grades, bit types, and mechanical properties of steel. This quiz covers key topics essential for professionals in the field and aims to enhance your understanding of drilling and casing design. Challenge yourself with questions about yield strength, temperature effects, and bit advantages.