This article relates to land based field jobs in the oil industry. Much of this also applies to offshore drilling, indoor, lab, office, and facility related jobs, but for the most part they are not addressed specifically. For most of this article, I use the word 'industry' to describe the oil industry as a whole. The word 'field' is used to describe a sector of the oil industry that involves on-site labor at varying locations, such as well drilling or seismic exploration.
From the time that a decision is made to begin field work on a land based project, there are four major industry sectors that are involved before the oil hits the refinery, each of which relying on many other supporting fields and industries.
Again, only major industry sectors which involve on-site labor at varying locations are included. There are many more industry fields which are involved in oil recovery that are not acknowledged here.
A brief description of the four core industry fields:
Site Survey and Preparation:
- Permitting. A land agent makes land access agreements with land owners on behalf of the oil company. All required permits from government agencies are also acquired.
- Survey and line cutting. A seismic line is surveyed in a specific location with pinflags or other markers designating geophone intervals. If required, the line is cleared of trees, snow, crop, or other obstructions.
- Seismic equipment layout. Geophones are planted in the ground at specific intervals, and are connected by cables to the recorder truck. A geophone is a sensitive directional microphone mounted in a weatherproof casing with a spike on the end.
- Recording of ground vibrations from a controlled source. Dynamite is the most common source-placed in drilled holes at specific intervals, followed by vibrator trucks/buggies and air guns. Many other sources are also used, both explosive and non-explosive. The array of geophones captures vibration measurements and passes them to the recorder. The result is a 3D map showing differences in density.
- Data is processed and analyzed off-site.
- Depending on the results, more exploration may be done or test wells may be drilled.
- Land acquisition. A land agent makes lease agreements with land owners on behalf of the oil company for wellsites and other above-ground sites, pipelines, and access roads. All required permits from government agencies are also acquired.
- Site or route selection. An oil company consultant coordinates with surveyors, land agents, land owners, and the oil company in choosing an acceptable location for the site; as well as routing for site access and pipelines.
- Soil samples may be taken to determine the suitability of the land for the proposed use.
- Survey. Surveyors place metal spikes or survey pins in the ground, as well as wooden stakes to mark the boundaries of the site, road, or pipeline. Survey is performed either using a 'total station'-laser measurment instrument- and a prism, or with Real Time GPS technology.
- If necessary, the site is cleared of trees, crop, or other obstructions.
- If necessary, earth moving equipment is brought in to level the ground, build approaches onto roads, or build crossings for other pipelines, roads, or wet areas.
- For a wellsite, a source of water for the drilling rig must be found or a water well must be drilled. A sump pit must be surveyed and dug either onsite or nearby for disposal of drilling mud and rock cuttings.
- Drilling. An appropriate drilling rig is chosen for the ground type, depth, angle of well bore, and other criterion. The rig is moved onsite and setup, and drilling commences. Depending on the ground and the depth of the hole, drilling may take less than a day or many months.
- Once a predetermined depth has been reached, the drill string and bit are removed from the hole and the well casing pipe is inserted into the borehole in sections to prevent it from collapsing. Concrete is pumped into the hole outside the casing pipe.
- The drill bit and string are reinserted into the hole and drilling continues in stages-- drill, run casing pipe, cement casing, test, repeat -- until core samples and downhole testing with wireline and other downhole equipment indicates that the optimum zone for production has been reached. The bore is also continuously monitored while drilling using measurement-while-drilling and logging-while-drilling tools that reside at the bottom of the hole.
- Perforating. Once the final depth is reached, a perforating gun is lowered into the casing to punch holes in the casing to allow oil to flow into the pipe from the reservoir rock. A smaller pipe is inserted into the casing through which the oil will flow. Some wells may be perforated in several different zones to allow production from multiple formations.
- Depending on the reservoir and the type of rock that holds the oil or gas, it may be necessary to pump acid or other chemicals and materials through the perforations to create channels for the oil to flow. Acid is used to dissolve channels in limestone, while proppants such as sand or crushed walnut shells are used in other formations to create channels and hold them open.
- To assist in the recovery of very heavy oils, a secondary hole may be drilled into the reservoir through which steam is injected to warm the oil and further pressurize the reservoir.
- Wireline and other testing. The hole is thoroughly tested with complex downhole measuring devices and core sample testing.
- The pump and sucker rod are inserted into the well, and a well head is mounted to the top of the casing.
- A pumpjack is placed over the well head and attaches to the sucker rod.
- For natural gas wells, a pumpjack is not necessary. The gas is simply collected and fed into pipelines.
- Pipelines are constructed to allow the gas or oil to be transported offsite and eventually to a refinery.
- Pipeline construction. Trenching equipment is used to dig a ditch for the length of the pipeline. Pipeline is then welded or glued together alongside the trench. It is thoroughly inspected and tested, and all joints are x-rayed and physically examined to ensure a complete seal before the pipe is placed in the ground and buried.
- Pressure testing. Pipeline valves are closed to quarantine a section of the system which may include above ground facilities as well as pipelines. That section is then pressurized with compressors and monitored for leaks.
- Inline site construction. Above ground facilities such as compressor stations and storage areas are surveyed and built along the pipeline as required.
- Refinery. The end of the line for crude oil gathering pipelines is the refinery, where the crude is distilled and processed to turn it into usable products like fuels, lubricating oils, plastics, and tires.
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