HYDROCARBON

• Hydrocarbons are organic compounds composed solely of hydrogen (H) and carbon (C) atoms. Hydrocarbons, including natural gas, coal, crude oil, and petroleum, primarily reside within subterranean rock formations. These formations often take shape beneath layers of more resilient rock, forming underground reservoirs that prevent the hydrocarbons from rising to the surface and dispersing.
• Assessing these reservoirs requires expertise in petroleum geology, employing various tools and methodologies to evaluate factors like porosity and permeability. Porous rocks can hold larger quantities of hydrocarbons, while permeable ones facilitate the flow of hydrocarbons. Kerogen, organic matter clusters, serves as the primary source of hydrocarbons within these formations and can originate from lacustrine, marine, or terrestrial ecosystems. The breakdown of kerogen within heated and compacted rocks yields different hydrocarbon types: waxy oils from lacustrine kerogen, oil and gas from marine kerogen, and light oils, gas, and coal from terrestrial kerogen.
• Identifying source rocks, understanding their geophysical and thermal properties, and estimating their hydrocarbon-yielding potential are critical tasks undertaken by petroleum geologists. This involves a combination of observational data analysis, modelling, and exploratory drilling to assess the reservoir's capacity accurately.
• Upon confirming a profitable hydrocarbon reservoir, drilling operations commence to extract these valuable resources.

3. Hydrocarbon Extraction Techniques

To efficiently extract hydrocarbons from reservoirs while safeguarding their integrity, drilling and reservoir engineers employ a range of specialized methods.

• The initial step involves drilling a production well, strategically positioned to maximize drainage from the reservoir. Using drilling machines, engineers bore through the rock formations using a drill bit attached to a drill pipe. Drill collars provide weight and stability to the drilling process.
• As drilling progresses, steel casings slightly narrower than the borehole diameter are lowered into the well. Cement slurry is then pumped between the outer surface of the casings and the wellbore. Once solidified, this cement casing prevents cave-ins and the influx of surrounding fluids into the well.
• Drilling fluid, circulated through the drill string, serves multiple functions. It cools the drill bit, carries rock cuttings to the surface, and maintains wellbore stability. Careful pressure control is crucial to prevent hydrocarbons from surging into the wellbore uncontrollably.
• Mechanical valves known as blowout preventers are integrated into modern drilling setups to manage pressure and prevent uncontrolled release of hydrocarbons. These devices trap potential gushers within the wellbore, ensuring operational safety.
• The process of recording and analyzing rock cuttings by depth to assess their properties is termed mud-logging. This helps engineers evaluate reservoir characteristics and make informed decisions during drilling operations.
• As drilling progresses, the drill pipe length is extended by adding sections. Additionally, drill bits may be replaced as needed to maintain drilling efficiency.

Modern drilling rigs equipped with generators and batteries facilitate these processes. Offshore rigs incorporate additional features to enhance stability and facilitate extraction through water columns.

4. Hydrocarbon Extraction Process

1. Completion Stage: After drilling the production well, engineers proceed to prepare it for hydrocarbon drainage, a process known as completion. The drill string is removed from the borehole, and small perforations are made in the casing. In many cases, the pressure differential between the well and surrounding rock is adequate for hydrocarbons to flow into the wellbore naturally. As hydrocarbons ascend, they are guided upward through a narrower tube installed at the top, ensuring unidirectional flow.
2. Production Stage: Upon commencement of hydrocarbon flow, the production stage begins, where controlling systems at the wellhead regulate outflow using valves. In instances where natural pressure is insufficient to lift hydrocarbons to the surface, pump jacks are employed. These devices, often seen in oil-rich regions like the American Midwest, utilize a piston-driven mechanism powered by engines to extract hydrocarbons from the wellbore. Some older wells may require maintenance or component replacement (workovers) to optimize production.
3. Phases of Well Production:

1. Primary Phase Relies on natural processes such as reservoir-to-well pressure differentials and buoyancy effects to facilitate hydrocarbon flow.
2. Secondary Phase Involves artificial pressure enhancement techniques, such as water injection or dilution of hydrocarbon mixtures, to sustain production rates.
3. Tertiary Phase Utilizes enhanced recovery methods to extract remaining hydrocarbons. One common technique is steam injection, where waste heat from an on-site gas turbine is used to generate steam. Injected steam reduces the viscosity of heavy-oil hydrocarbons, facilitating their flow, while pressure assists in extraction. The recovery profile typically yields about 15%, 45%, and 15% of hydrocarbon volume during the primary, secondary, and tertiary phases, respectively.

5. Environmental Considerations

• Extraction rates serve as indicators, signalling when a well may cease production. Economic viability plays a pivotal role, prompting contractors to halt extraction when profitability diminishes, even if the well isn't fully depleted.
• Abandoned wells require proper sealing to prevent hydrocarbons and accumulated gases from escaping into the surroundings. Plugs can be either temporary or permanent, depending on the project's future intentions. However, inadequate plugging can lead to plugging deterioration and failure, posing environmental risks, especially when disturbances occur nearby.
• Decommissioning wells, whether on land or offshore, is the most comprehensive approach to concluding operations. However, this process is often prohibitively expensive and commercially unfeasible for project proponents. Improperly abandoned wells contribute significantly to methane emissions, compounding the environmental impact of hydrocarbon extraction.
• A 2018 study revealed alarming statistics, estimating that 9,000 oilfields across 90 countries released approximately 1.7 billion tonnes of carbon dioxide in 2015 alone. This underscores the critical importance of responsible well abandonment and decommissioning practices to mitigate greenhouse gas emissions and environmental degradation associated with hydrocarbon extraction.