Petroleum Production Engineering

• Petroleum production engineers are responsible for designing, managing, and optimizing production systems.
• Petroleum production engineering focuses on maximizing oil and gas production from reservoirs.
• These engineers work with reservoir, drilling, and processing engineers for efficient operations.

Learning Objectives

• Define petroleum production engineering and its role in the oil and gas industry.
• Identify the responsibilities of petroleum production engineers.
• Explain components of a typical petroleum production system.
• Analyze the characteristics and management of oil and gas reservoirs.

Responsibilities

• Evaluating inflow and outflow performance of wells.
• Designing completion systems to maximize oil and gas recovery.
• Selecting artificial lift equipment for wells.
• Optimizing surface facilities for efficient processing and transportation.

Production System Overview

• Reservoir: geological formation with hydrocarbons
• Well: a drilled hole that connects the reservoir to the surface
• Flowline: pipe connecting the well to surface facilities
• Separators: vessels that separate oil, gas, and water
• Pumps: equipment used to lift fluids to the surface
• Transportation pipelines: pipelines used to transport the produced hydrocarbons

Reservoir Characteristics and Management

• Porosity: the volume of empty spaces in the rock, representing storage capacity
• Permeability: the ability of rock to allow fluids to flow
• Reservoir Pressure Management: maintaining reservoir pressure for sustained production
• Enhanced Oil Recovery Techniques: Methods to improve oil recovery from depleted reservoirs.

Reservoir Types and Categories

• Conventional Reservoirs: found in porous/permeable rock, allowing easy flow of oil and gas.
• Unconventional Reservoirs: tight formations with lower permeability, requiring advanced extraction.
• Reservoir Rock Examples: sandstone, carbonate, and shale reservoirs, each with distinct properties.

Oil Reservoir Types

• Black Oil:
  • High molecular weight hydrocarbons with low gas-to-oil ratio (GOR) which, is typically less than 2,000 scf/stb.
  • Appears dark in color and is composed mostly of heavy hydrocarbons.
  • Low shrinkage when produced; oil volume is not significantly reduced as gas comes out of the solution.
  • Separate free gas and liquid oil are produced in the stock tank.
  • The liberated gas is primarily methane and heavier hydrocarbons.
• Volatile Oil:
  • High GOR between 2,000 to 3,500 scf/stb.
  • More dissolved gases in solution and significant volume shrinkage during production.
  • Lighter in color with higher API gravity (40°-50° API).
  • Gas evolves rapidly when pressure drops below bubble point pressure.
  • Produces more gas and condensate than black oil.
• Dead Oil:
  • No dissolved gas (GOR ≈0 sc/stb).
  • Extremely viscous, with very low API gravity (< 20° API).
  • Expand very little during production.
  • No gas liberation when pressure decreases.
  • Requires thermal recovery methods to reduce viscosity for production.
• High Shrinkage Oil:
  • A form of volatile oil with very high shrinkage factor upon pressure depletion.
  • Large amounts produce of gas upon initial production.
  • API gravity is above 45° API.
  • Shrinks significantly as the lighter fractions escape.
  • Often transitions to retrograde condensate behavior.
• Low Shrinkage Oil:
  • Similar to black oil but has very little shrinkage when pressure declines.
  • Low GOR, less than 500 scf/stb.
  • Produces mostly liquid oil with minimal gas liberation.
• Retrograde Condensate:
  • Exists as a single-phase gas in the reservoir that condenses into liquid upon production.
  • Composed of light hydrocarbons (C1-C7) with an API gravity greater than 50°.
  • GOR between 3,500 – 10,000 scf/stb.
  • Gas condenses into liquid when the pressure drops below the dew point.
  • High gas condensate yield but subject to retrograde liquid dropout, which reduces flow efficiency.

Gas Reservoir Types

• Dry Gas:
  • Composed primarily of methane (CH4) with little to no heavier hydrocarbons.
  • GOR is extremely high at >100,000 scf/stb.
  • It does not condense into liquid at surface conditions.
  • Only gas is produced at reservoir and surface conditions.
  • No significant phase change occurs during production.
• Wet Gas:
  • Contains methane and significant heavier hydrocarbons such as ethane, propane and butane.
  • GOR between 50,000 – 100,000 scf/stb.
  • No liquid dropout in the reservoir, but liquid hydrocarbons may condense at the surface.
  • Gas is produced at the wellhead, but upon cooling at surface conditions, liquid hydrocarbons, like natural gas liquids or, NGLs form.
• Associated Gas Reservoir:
  • Found in oil reservoirs with a free gas cap sitting above the oil column.
  • GOR is variable, but typically higher than in black oil reservoirs.
  • Gas production occurs as the oil column depletes, with potential for gas cap expansion.
• Non-Associated Gas Reservoir:
  • Contains only free gas, with no underlying oil phase.
  • GOR is extremely high, meaning gas is usually dry or wet gas.
  • Only natural gas is produced with minimal liquid content.

Primary Recovery Mechanisms

• Water Drive:
  • A large aquifer surrounds or underlies the oil reservoir.
  • Water encroaches into the reservoir as oil is produced, displacing oil toward the wellbore.
  • Recovery Factor: 35-75%, the highest in primary drives
  • Pressure Decline: Minimal to moderate depending on aquifer size and strength.
  • GOR: Remains relatively stable unless gas breakthrough occurs.
  • Sustained oil production, but water cuts increase over time.
  • Strong initial well performance, but it may experience water breakthrough.
• Solution Gas Drive:
  • Initially, oil is saturated with dissolved gases at bubble point pressure.
  • Reservoir pressure drops as production occurs and gas comes out of solution forming free gas bubbles.
  • These gas bubbles expand and push oil toward the wellbore.
  • Recovery Factor: 5-30%
  • Pressure Decline: Rapid and severe.
  • GOR: Increases over time as more gas is liberated.
  • Oil Production: Declines rapidly because of poor sweep efficiency.
  • Initially strong, well performance declines quickly.
• Gas Cap Drive:
  • A free gas cap exists above the oil zone.
  • The gas cap expands downward, pushing the oil toward the wellbore as oil is produced.
  • Recovery Factor: 20-40%
  • Pressure Decline is Moderate because gas expansion helps maintain pressure.
  • GOR: Increases gradually as more gas production occurs.
  • Oil Production is more sustained than solution gas drive because of pressure support.
  • Well Performance is Better than solution gas drive, but production rate still declines over time.
• Gravity Drainage:
  • Oil moves downward because of gravitational forces in high permeability and steeply dipping reservoirs.
  • Gas migrates upward as oil flows down to the producing wells.
  • Recovery Factor: 50-70%, very efficient in thick, high-permeability reservoirs.
  • Pressure Decline: Slow and controlled.
  • GOR: Can be low or high, depending on gas cap behavior.
  • Oil Production is Sustained over long periods, with a slow decline.
  • Stable production is seen here, but it requires proper well placement.
• Expansion Drive:
  • This drive relies on the expansion of all reservoir fluids and the rock matrix when pressure decreases during production.
  • It includes expansion of oil, gas dissolved in oil, connate water, and the rock itself.
  • This drive does not have an external energy source to help maintain pressure, unlike other drive mechanisms.
  • Recovery Factor: 1-10%, very low
  • Pressure Decline is Very rapid
  • GOR: Remains relatively low, as gas does not come out of the solution early.
  • Oil Production: Declines quickly, meaning wells may become uneconomical early.
  • Well Performance is poor unless artificial lift or secondary recovery is implemented.
• Solution Gas Drive: - This includes a mix of solution gas drive, gas cap drive, and/or water drive. - The dominant drive mechanism depends on reservoir properties and fluid distribution - Recovery Factor: 20-50% which, depends on the dominant drive. - Pressure Decline is Moderate - GOR: Varies depending on the dominant drive. - Oil Production is more stable than pure solution gas drive but not as successful as pure water or gas cap drive. - Well Performance is intermediate between different drive mechanisms.

Types of Oil and Gas Wells Based on Purpose

• Exploratory Well: used to discover and evaluate potential hydrocarbon reserves.
• Appraisal Well: used to define the size and shape of the discovered reservoir and estimate its production potential.
• Relief Well: used to control and mitigate blowouts in compromised wells.
• Infill Well: used to enhance recovery and optimize production within existing fields.
• Production Well: acts as a path for fluid flow from reservoir to the surface.
• Observation Well: used to monitor reservoir conditions, like pressure, temperature, and fluid movement.
• Development Well: used to produce hydrocarbons from a known reservoir.
• Injection Well: used to inject fluids (water or gas) into a reservoir, maintaining pressure and enhancing oil recovery.

Oil and Gas Well Components

• Conductor Casing: provides stability to the wellbore and protects from surface contamination.
• Surface Casing: protects freshwater zones and provides structural support.
• Intermediate Casing: isolates zones with varying pressures or formations.
• Production Casing: isolates wellbore in the productive formation and guides production fluids.
• Tubing: delivers oil or gas to the surface through the production casing.

The Wellhead

• Wellhead: a critical component that serves as the interface between the reservoir and surface facilities.
• It houses essential components for controlling and regulating hydrocarbon flow to enable safe and efficient production.
• Key components include the Christmas tree, tubing head, casing head, and flowline. -Christmas tree: controls flow of oil and gas, complex valve assembly -Tubing head: connects the production tubing to the wellhead -Casing head: secures the production casing and provides a connection point for surface equipment. -Flowline: carries produced hydrocarbons to surface processing facilities.

Surface Facilities and Equipment

• Separators: separate oil, gas, and water into individual streams.
• Storage tanks: store oil and gas before transportation.
• Compressors and pumps: transport and boost the pressure of oil and gas.
• Pipeline systems: transport produced oil and gas to refineries and consumers.

Types of Separators by Geometry

• Spherical Separators: used for smaller volumes of oil and gas and higher gas-to-liquid ratios.
• Vertical Separators: designed to handle larger volumes of oil and gas.
• Horizontal Separators: used for larger volumes of gas and lower gas-to-liquid ratios.

Types of Separators by Phase Separation

• Two-Phase Separators: typically used in wells with low water production, separates oil and gas
• Three-Phase Separators: commonly used in wells with high water production, separates oil, gas, and water

Pumps and Compressors

• Compressors: this increases the pressure of natural gas for transportation through pipelines, employing either centrifugal or reciprocating designs to reduce gas volume and increase pressure.
• Key applications include boosting gas pressure for long-distance transport, gas lift operations, and injection into reservoirs for enhanced oil recovery.
• Pumps: they transport oil and water to processing facilities, use of centrifugal or positive displacement to move fluids.
• Centrifugal pumps - for high-volume transfer
• Positive displacement pumps for high-pressure applications
• Common uses include transferring crude oil from storage tanks to pipelines, water injection for pressure maintenance, and pumping produced water for disposal or treatment.

Types of Pumps and their applications

• Dynamic pumps: used for high-volume transfer of fluids, like transferring crude oil from storage tanks to pipelines.
• Positive displacement pumps: ideal for high-pressure applications like water injection for pressure maintenance in oil reservoirs.

Dynamic vs Positive pumps

• Pipeline systems are the backbone of oil and gas transportation, connecting production sites to refineries, storage facilities, and end consumers.
• Crucial for efficiently moving large volumes of oil and gas over long distances and traversing challenging terrains.
• Key Components - they are designed with various components like pumps, valves, and control systems to ensure safe and reliable transportation.

Production Optimization and Future Trends

• Real-time monitoring: monitoring production data in real-time to optimize performance.
• Data analytics: using data analytics and artificial intelligence to improve decision making.
• Sustainability: environmental considerations and sustainable practices.
• Emerging Technologies: implementing new technologies to enhance production.