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Geological Expertise in Oil and Gas Exploration

(Graphic from Oil & Gas Portal)

Geologists use a variety of tools to discover underground pockets of crude oil and natural gas. Without their expertise, the oil and gas industry would not exist.

Exploration

The first thing geologists must determine is the location of geological formations that can trap oil and gas underground. They do this by determining what kind of sedimentary rocks form the reservoir and what kind of chemical elements are present in the rocks. If sandstones and carbonates are present, this is a good indication that ancient organic matter once existed in that area which decayed and formed hydrocarbons. The hydrocarbons became trapped underground in the form of crude oil and natural gas (Busby, 1999, p. 15).

Geological methods include drawing maps of the surface and subsurface region and gathering rock samples.

Topographical maps in 2-D and 3-D visualize layers of rock and the horizontal and vertical placement of those layers. Rock formations are given a two-part name, the geographical location, which is usually the name of the nearby town, and the predominant type of rock (Busby, 1999, p. 19).

Subsurface maps include three elements: structural, which shows the elevation of rock layers; isopach, which indicates thickness; and lithofacies, which reveal variations in a single layer of rock (Busby, 1999, p. 20).

When geologists take rock samples, they extract samples from the core and gather “cuttings” (rock chips) for “assessing the formation’s lithology, hydrocarbon content, and ability to hold and produce gas” (Busby, 1999, p. 20). If they can figure out how the rock layers were formed, they can determine if the conditions were right for “the generation, accumulation, and trapping of hydrocarbons” (Busby, 1999, p. 21).

Geochemical methods use chemical and bacterial analyses of soil and water samples from the surface and the area around underground gas and oil deposits to determine the presence of hydrocarbons. “Micro-seeps” of petroleum can be detected in this way (Busby, 1999, p. 21).

Vitrinite reflectance uses a reflectance microscope to measure the percentage of light which is reflected from vitrinite (plant organic matter found in shale). The percentage can indicate the presence of gas and oil (Busby, 1999, p. 21).

Geophysical methods use sound waves (seismic vibration) to “determine the depth, thickness, and structure of subsurface rock layers and whether they are capable of trapping natural gas and crude oil” (Busby, 1999, p. 22). Computers are used to gather and analyze the data. Geologists can now use 2D, 3D, and 4D seismic imaging in their analysis (Natural Gas, 2013).

On land, explosives and vibrations are used to generate sound waves. The energy that bounces off the rock layers is detected as echoes by sensors called geophones (jugs) (Busby, 1999, p. 23).

Bright spots and flat spots can reveal where deposits of gas-oil and gas-water deposits might exist underground. Amplitude variation with offset (AVO) and geology related imaging programs (GRIP) can enhance the resolution and analysis of bright spots (Busby, 1999, p. 24).

“Cross-well” seismic technology uses seismic energy in one well and sensors in nearby wells to retrieve high-resolution images that have been used successfully in determining the presence of crude oil. It is now being used in natural gas exploration (Busby, 1999, p. 24).

Gravity meters are used to detect salt domes and other rock formations capable of trapping gas and oil. Magnetometers detect the thickness of basement rock and find faults. Computer models create hypothetical pictures of subsurface structures from mathematical computations (Busby, 1999, p. 25).

Drilling

Once geologists determine the geological and economic feasibility of drilling a well, a group of geologists, geophysicists, and engineers pinpoint the site for the well and its potential reservoir. They decide how deep the well should be. The average well is about 5,800 feet deep in the United States. The drilling company must then get permission to drill from the owners of the land and determine who owns the mineral rights.  They sign a lease to use the land for a certain length of time.  The drilling company then breaks ground (spudding) and keeps well logs (measurements) to determine the possibility of gas and oil formation and the porosity and permeability of the rock. The contractors who own the drilling rigs sign an agreement to drill to a certain depth and detail what equipment they will need. A pit is dug at the site and lined with plastic that holds unnecessary materials (Busby, 1999, p. 29-30).

Rotary drills, driven by a diesel engine, are the most common type of drill used because they can drill hundreds and even thousands of feet per day. The drill bit must be changed after 40 to 60 hours of drilling. Other drilling techniques include directional drilling, which allows drilling in multiple directions, horizontal drilling, which is used to enhance gas recovery and to inject fracturing fluids, and offshore drilling, which uses special equipment to drill in ocean water (Busby, 1999, p. 31-35).

Some of the drilling problems that come up include drilling a dry hold; a breakage inside the well; things falling into the well; and high pressures underground causing gas or water to flow into the well, changing the balance of the pressure in the well. Drilling must be halted then and the problem corrected (Busby, 1999, p.33).

Geologists use various tests to measure the probability that the well will produce enough oil and gas. Drilling-time measurements measure the rate of the bit’s penetration into the rock; mud logs measure the chemistry of mud and rock cuttings, looking for traces of gas; wireline logs sense electrical, radioactive, and sonic properties of rocks and fluids; electrical logs test rock for resistivity; gamma ray logs measure radioactivity; neutron logs measure rock density; caliper logs test the type of rock; dip logs look for the placement of rock layers; sonic/acoustic velocity logs measure the speed at which sound travels through rock. Traditionally, these tests were conducted on bare, uncased wells. But new technology allows testing to be done with the casing in place (Busby, 1999, p. 36-37).

If the well comes up dry, the well is plugged up and abandoned. If the well holds promise of a productive well, the bare well is “cased, or lined with metal pipe to seal it from the rock” (Busby, 1999, p.29). A foundation of cement is created. Then the casing is drilled with holes so gas can flow into the well. The flow rate of the gas is measured, and if productive, valves and fittings are installed in order to control the flow. Oil and gas products are separated at the wellhead. A gathering system is built after several wells are completed. Flow lines gather gas from several wells and transport it to a centralized processing facility (Busby, 1999, p. 37-38).

Transmission

“The pipeline industry carries natural gas from producers in the field to distribution companies and to some large industrial customers” (Busby, 1999, p. 43) through large pipes with high pressures, from 500 to 1,000 psi or 3,400 to 6,900 psi). Compressor stations along the lines maintain the pressures in the pipes. “As of the 1990s, more than 300,000 miles of gas pipelines criss-cross the United States, serving nearly 60 million gas customers” (Busby, 1999, p. 43).

Pipes are laid in trenches and coated inside with chemicals to prevent corrosion, improve light reflection, reduce water retention, reduce absorption of gas odorants, and to improve gas flow (Busby, 1999, p. 46-47).

Gas demand depends on weather, the season, and its use in power generation. Pipeline operators try to spread the costs over the whole year. Gas meters are used “to reduce costs and increase the accuracy of gas flow measurement” (Busby, 1999, p. 51).

Pipeline inspection and maintenance have to be done on a regular basis to detect gas leaks, address corrosion, repair damage, and to keep the gas flowing smoothly (Busby, 1999, p.  51-53).

Economic Concerns

During exploration, there is no guarantee that all the money spent on research, testing, and drilling will be recouped. If a well is productive, royalties must be paid to the owner of the mineral rights after all production costs are paid. State and federal governments regulate how many wells can exist per 640 acres and how much gas and oil can be produced over a certain time period. Offshore drilling, which has become more common, is very expensive because these oil rigs use special equipment and can drill as deep as 10,400 feet. When wells are losing pressure and running dry, companies must spend money on well stimulation. In fact, companies give priority to this because it costs less than exploring for new wells. It’s been estimated that the oil and gas companies spend roughly $5 billion on treating natural gas before it is ever transmitted through a pipeline. Pipelines and compressor stations must be built, inspected, repaired, and maintained. Environmental regulations cost companies money on research and new technologies (Busby, 1999, p. 15-54).

If oil and gas supplies diminish or are suddenly cut off, access to energy is decreased, and costs sky-rocket. When pipelines break or oil rigs are damaged or destroyed, this causes a disruption in the oil and gas supply. If the disruption lasts long enough, it can raise costs to the consumer. Political conflicts affect oil and gas supplies, energy costs, and the ability of companies to find new sources (Busby, 1999, p.15-54).

Dawn Pisturino

Thomas Edison State University

October 22, 2020; March 18, 2022

Copyright 2020-2022 Dawn Pisturino. All Rights Reserved!

Busby, R.L. (Ed.). (1999). Natural Gas in Nontechnical Language. Tulsa, OK: PennWell.

Natural Gas. (2013). Natural gas and the environment. Retrieved from

       http://www.naturalgas.org

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Evolution of Natural Gas in America

The natural gas industry is so vital to the functioning and prosperity of the United States that a depletion of natural gas resources would cripple the whole country.  Roughly 25% of the energy used in the United States comes from natural gas.  From manufacturing uses to home energy consumption, natural gas plays an important role in everyday life, even if American consumers are unaware of it (Busby, 1999, p. xviii).

       Natural gas is a natural resource that has developed over millions of years of plant and animal decomposition.  It is often found at the bottom of bodies of water that have existed for eons, such as oceans and lakes.  Plant and animal matter that became buried before decomposition or became lodged in anaerobic water, such as a stagnant pond, avoided oxidation.  As sand, mud, and other materials collected on top of the organic matter over long periods of time, these materials solidified into rock.  The organic matter was preserved by the rock. Years and years of pressure and heat turned the organic matter into gas and oil.  “Coal, shale, and some limestones have a dark color that comes from their rich organic content.  Many sedimentary basins are gas-prone and produce primarily natural gas” (Busby, 1999, p. 2-3).

       The average composition of natural gas, after processing, is 88% methane, 5% ethane, 2% propane, and 1% butane (Busby, 1999, p. 2).  The natural gas widely used today is, therefore, largely methane, “a colorless, odorless gas that burns readily with a pale, slightly luminous flame (Busby, 1999, p. 1).  The by-products of burning natural gas are mostly water vapor and carbon dioxide, making it “the cleanest burning fossil fuel” (Busby, 1999, p. 1).

       Methane is used in making solvents and other chemical compositions.  Propane and butane are separated from natural gas and sold as separate fuels. Liquified petroleum gas (LPG) is mostly propane and used as a fuel in rural areas where pipelines do not exist.  When carbon dioxide and helium are recovered from natural gas, they are often used to boost production in old oil fields.  Helium that is recovered from natural gas is used to fill balloons and blimps.  It is also widely used in the electronics industry.  Hydrogen sulfide, which is very corrosive, must be removed from natural gas before it is transmitted through pipelines or it will damage vital parts of gas wells and pipes (Busby, 1999, p. 1-2).

       Wood that has been subjected to high temperatures over time, turns into coal.  Coal seam gas is primarily methane. At depths with cooler temperatures, bacteria produce microbial gas, which is largely methane. Thermogenic gas develops at lower depths and with temperatures greater than 300 degrees Fahrenheit.  Trapped in underground reservoirs, high temperatures sometimes “gasify” the heavier hydrocarbons.  When the temperature cools, the gas re-liquifies and forms a condensate, which is largely pure gasoline. This is known as “wet” gas.  “Dry” gas is composed of pure methane.  Natural gas liquids (NGL) are composed of butane, propane, ethane, and gasoline condensate.  At depths greater than 18,000 feet, high temperatures turn oil into natural gas and graphite (Busby, 1999, p. 3-4).

       “Most deep wells are drilled in search of natural gas . . . [because] most gas that has been generated over the ages has been lost rather than trapped, which is why many exploratory wells are unproductive” (Busby, 1999, p. 3-4).  The reservoir rock holding the gas must be porous as well as permeable to allow for containment and access.

       Although people in the past were aware of natural gas, it was not until the 1800s that gas began to be developed and used for various purposes.  Coal gas began to be utilized in gas lighting in America and Europe, which allowed factories and businesses to operate for longer hours and families to engage in more social activities in the evenings (Busby, 1999, p. 5-6).

       One of the first inventors to experiment with coal gas was William Murdoch.  His experiments were so successful that his employer, Boulton & Watt, expanded its business to include “installing gas lighting in English factories” (Busby, 1999, p. 6).  The city of Birmingham adopted gas lighting, which inspired great demand for this new technology (Busby, 1999, p. 6).

       One of the first gas lights, the Thermolamp, was invented by Philippe Leon in France in 1799.  He patented a process to generate gas from wood and put it on display in Paris in 1802.  But the French government rejected the idea of a massive lighting system fueled by gas (Busby, 1999, p. 6).

       In 1807, Frederick Winsor “staged the first gas street-lighting display in London” (Busby, 1999, p. 6).  He had found a way to pipe large quantities of gas via a centralized system and founded his own public gas distribution company in 1812 (Busby, 1999, p. 6).

       By 1819, London had installed approximately 300 miles of gas pipes that supplied more than 50,000 gas burners.  The pipes were made of wood, but these were eventually replaced by metal pipes (Busby, 1999, p. 6).                                                                                                                                        

       In America, Charles Peale began testing gas lighting in Philadelphia in 1802.  The city of Baltimore hired his son, Rembrandt Peale, to install a gas lighting system in 1816.  The first gas utility company in America was born in that year, and more sprouted up along the East coast.  The first gas company in the southern states was established in New Orleans (Busby, 1999, p. 6).

       America could boast around a thousand companies selling coal gas for lighting by the end of the 19th century.  And most major cities around the world had adopted gas lighting (Busby, 1999, p. 6).

       Most consumer gas distribution was not metered but delivered at a flat rate, which was based on the number of hours of use and the number of lights in a household or business.  A gas meter was invented in 1815.  By 1862, gas meters – which monitor the volume of gas used – were being used in London.  Coin-operated meters became available in the 1890s which allowed poorer consumers to utilize gas energy as they could afford it (Busby, 1999, p. 7).

       “Coke is a solid, porous by-product of gas manufacturing that can also be used for domestic heating” (Busby, 1999, p. 8).  The evolution of the iron and steel industries created a demand for blast-furnace coke that led to the development of the push-through-coke oven.  The demand for coke oven gas increased until it “constituted 18.7% of all manufactured gas” (Busby, 1999, p. 8) in 1920.

       As new uses for gas were discovered, developed, and implemented, “the first gas range in the U.S. was built around 1840” (Busby, 1999, p. 8).  The Goodwin Company introduced the Sun Dial Stove in 1879.  Two more gas stove manufacturers opened within four years.  And in 1887, the first gas appliance store opened in Providence, Rhode Island.  By 1900, cooking with gas had outstripped gas lighting and gas heating (Busby, 1999, p. 8).                                                                                                            

       Using gas to heat water storage tanks became popular in the 1860s.  The year 1883 saw the first circulating water heater come onto the market.  A water heater with a thermostat was introduced a few years later. Gas distribution was fast becoming a household necessity (Busby, 1999, p. 9).

       Natural gas was frequently discovered in the 1800s when people drilled for water, but the gas was ignored.  It was not until 1821 that William Hart drilled the first natural gas well and piped it through wooden pipes to neighbors’ homes.  This same gas was used to light up the City of Fredonia, New York a few years later (Busby, 1999, p. 9).

       Gas wells were drilled in Pennsylvania, New York, and West Virginia throughout the 1830s and 1840s.  But gas pipes were still primitive and only able to transport gas to customers near the gas wells (Busby, 1999, p. 10).

       The first natural gas company opened in Fredonia, New York in 1865.  When oil was discovered in Titusville, Pennsylvania, an oil rush ensued that diminished the importance of natural gas.  “Gas produced along with oil was usually just burned off, or flared” (Busby, 1999, p. 10).

       Andrew Carnegie, the famous steel magnate, documented in 1885 that 10,000 tons of coal had been replaced by natural gas.  But as the supply of natural gas became depleted, steel makers were forced to revert to using coal again by 1900.  This pattern repeated itself for the next 25 years.  Wastefulness and leakage were the main culprits (Busby, 1999, p. 10).

       The first long-distance wooden pipeline was built between West Bloomfield and Rochester, New York in the 1870s when a large reservoir of natural gas was discovered in West Bloomfield.  The gas was transported through this 25-mile pipeline (Busby, 1999, p. 10).

       Indiana Gas and Oil Company laid a 120-mile parallel pipeline made of wrought iron in 1891 that used high pressure (525 psi) to transmit natural gas to Chicago from the gas field in Indiana.  The company started using manufactured gas when the natural gas supply ran out in 1907 (Busby, 1999, p. 10-11).

       Oxyacetylene welding was invented in 1911 which sped up development of seamless steel pipe in the 1920s.  Natural gas could now be transmitted at higher pressures and in larger quantities and to longer distances, which boosted profitability for natural gas companies and helped them compete with other fuels.  The natural gas industry continued to expand until the Great Depression, which slowed down economic activity across the country.  As soon as World War II was over and the economic climate improved, the industry began to boom again (Busby, 1999, p. 11-12).

       Natural gas is one of the main fuels used in the food processing industry in the United States.  Large boilers are used to create process steam, which is used in “pasteurization, sterilization, canning, cooking, drying, packaging, equipment clean-up, and other processes” (Busby, 1999, p. 87). Natural gas energy saves companies money when they install “high-efficiency, low-emission natural gas-fired boilers” (Busby, 1999, p. 87). 

       Large amounts of hot water are also needed for “cleaning, blanching, bleaching, soaking, and sterilization” (Busby, 1999, p. 87).  High-efficiency industrial water heaters are used routinely in food processing.  Gas appliances are also used for “drying, cooking, and baking, as well as for refrigeration, freezing, and dehumidification” (Busby, 1999, p. 87).

       Tyson Foods has made a commitment to reduce energy use and produce fewer emissions that puts them at the top of the food processing industry.  As of 2019, they were using 42.15%

non-renewable fuels (including natural gas), 15.72% electricity, and 0.45% renewable energy (wind and solar power).  They are using renewable fuels like biogas from their waste treatment plants in their plant boilers in order to reduce their natural gas use.  They used about 666 million cubic feet of biogas in their boilers in 2019.  Although their energy use went up in 2019, their emissions went down.  The company is reusing process water in their plants to reduce water use.  And it is considering natural gas, electrification, and hydrogen fuel for their transportation fleet (Tyson Sustainability, 2019).

       “Natural gas . . . is the cleanest burning fossil fuel, and emits very few pollutants into the atmosphere” (Natural Gas, 2013).  Although Tyson is already using natural gas in its plants, it might want to consider using natural gas to generate its own electricity in order to free itself from dependency on local electric companies.  This could save them money in the long run, especially as electricity rates go up and electricity delivery reliability goes down.  This, however, would require a large capital investment that Tyson might not want to make (Natural Gas, 2013).

       But Tyson is already using boilers that produce steam, and this steam could be used to generate electricity.  If the boiler keeps running, “the steam can be diverted to a turbine for generating power” (Busby, 1999, p. 87-88).  This is called cogeneration because “waste heat is recovered and used” (Busby, 1999, p. 87).

       Although most power plants have been fueled by coal, there has been a push towards using natural gas because this reduces emissions of sulfur dioxide, nitrogen oxides, soot, and smoke (Busby, 1999, p. 88).  “Natural gas can be used to produce electricity either directly, in a gas-powered turbine, or indirectly, in a steam-powered turbine (using steam from a gas-fired boiler)” (Busby, 1999, p. 89).  The natural gas also serves to increase boiler efficiency.

       Natural gas demand is expected to increase in the future as consumers expect energy efficiency regulations to reduce emissions in the atmosphere and industries are pressured to use low-carbon fuels.  Natural gas is a clean, reliable, and efficient energy source that can be used with confidence in the residential, commercial, and industrial settings.

Dawn Pisturino

Thomas Edison State University

October 14, 2020

Copyright 2020-2022 Dawn Pisturino. All Rights Reserved.

References

Busby, R.L. (Ed.). (1999). Natural Gas in Nontechnical Language. Tulsa, OK: PennWell.

Natural Gas. (2013). Natural gas and the environment. Retrieved from

       http://www.naturalgas.org

Tyson Sustainability. (2019). 2019 sustainability report. Retrieved from 

https://www.tysonsustainability.com/environment/energy-emissions.

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