New Exploration Methods for Oil and Gas
In the unrelenting search for more oil and gas, innovation plays an unquestionable role. As large oil and gas fields become increasingly difficult to find, geologists, geophysicists and engineers employ new technologies, such as seismic, to uncover resources that just 10 years ago were unimaginable. Seismic is a technology that bounces sound waves off rock formations deep below the surface of the Earth to provide explorers with a picture of the subsurface, often revealing locations where oil and gas may be trapped. The technology of finding oil has even incorporated 3D visualization tools from Microsoft’s Xbox game console! The system will help geoscientists examine and interact with 3D models of the Earth.
In order to process the massive amounts of information collected from seismic surveys, mathematicians, physicists and other scientists are constantly developing new computer algorithms to find complex patterns that enhance our understanding of the land beneath us. If we are to continue finding new fields hidden deep inside the Earth, breakthroughs in computer processing power and data management are necessary.
The oil and natural gas we use today have been trapped deep inside the Earth for millions of years. Although it is tempting to think of oil and gas reservoirs as large pools and wells with giant straws that suck the fluid to the surface, oil and gas is actually locked inside the rocks like water in a sponge. Just like the small holes in a sponge that collect and hold water, there are tiny spaces or pores in rocks that fill with oil and gas. For the past 100 years, oil and gas was extracted from rocks with small pores that were still big enough that the fluids flowed easily. If you were a tiny molecule of oil, flowing through these rocks would be like driving on a highway in the express lane. During this time period, geologists and engineers knew about other large quantities of hydrocarbons trapped in rocks with even smaller and more complex pores, but were unable to harness the resource—the oil and gas flowed too slowly or not at all from these rocks. Instead of driving on a large and fast highway, flowing through these rocks would be like driving on a small two-lane road with many stoplights and intersections. Conventional gas wells drilled into these formations were considered uneconomic since the gas locked in the rock would flow out of the tiny pores in the rock at such low rates. This picture changed, and changed in a big way, with the advent of stimulated horizontal wells.
Before the technology advances of the past few decades, the best place to put a well was directly above the anticipated location of the oil or gas reservoir. The well would then be drilled vertically to the targeted oil or gas formation. Technology now allows the industry to drill directionally from a site up to 5 miles (8 km) away from the target area. Engineers can even target an area the size of a small room more than a mile underground! This directional drilling technology means that the industry can avoid placing wells in environmentally sensitive areas or other inaccessible locations yet still access the oil or gas that lies under those areas.
In simplified terms, the drilling process uses a motor, either at the surface or downhole, to turn a string of pipe with a drill bit connected to the end. The drill bit has special “teeth” to help it crush or break up the rock it encounters to make a hole in the ground. While the well is being drilled, a fluid, called drilling mud, circulates down the inside of the drill pipe, passes through holes in the drill bit and travels back up the wellbore to the surface. The drilling mud has two purposes:
· To carry the small bits of rock, or cuttings, from the drilling process to the surface so they can be removed.
· To fill the wellbore with fluid to equalize pressure and prevent water or other fluids in underground formations from flowing into the wellbore during drilling.
Water-based drilling mud is composed primarily of clay, water and small amounts of chemical additives to address particular subsurface conditions that may be encountered. In deep wells, oil-based drilling mud is used because water-based mud cannot stand up to the higher temperatures and conditions encountered. The petroleum industry has developed technologies to minimize the environmental effects of the drilling fluids it uses, recycling as much as possible. The development of environmentally friendly fluids and additives is an important area of research of the oil and gas industry.
Even with the best technology, drilling a well does not always mean that oil or gas will be found. If oil or gas is not found in commercial quantities, the well is called a dry hole. Sometimes, the well encounters oil or gas, but the reservoir is determined to be unlikely to produce in commercial quantities.
Technology has increased the success rate of finding commercial oil or gas deposits with less waste and a smaller impact on the surface. While conventional oil and gas wells are typically vertical, contacting only a limited amount of the target reservoir rock, horizontal wells look like a large “L.” The long horizontal wellbore, sometimes more than 4,000 feet long, contacts a large portion of the productive reservoir. The surrounding rock formation is then hydraulically fractured to release the oil or gas trapped inside. In hydraulic fracturing, massive trucks pump thousands of gallons of fluid into the rock at very high pressures in order to force the rock to crack. These cracks are then propped open with sand to allow a highly conductive passage through which the oil or gas can flow.
In shale fields, as many as 15 major fractures are placed along the horizontal wellbore, serving to connect all those small two-lane roads to wide boulevards and even larger, faster highways. Currently, the limits of this technology are being pushed back every day in order to unleash giant gas resources. In the future, this technology will have to go even farther to allow more fractures and longer horizontal wells. Advances in this area will undoubtedly transform our energy landscape.
For more information on shale gas and horizontal drilling, see Modern Shale Gas: A Primer from the U.S. Department of Energy.
Once a company identifies where the oil or gas may be located, it then begins planning to drill an exploratory well. Drilling a well is expensive: Shallow offshore wells or deep onshore wells can cost more than $15 million each to drill!
Locating a suitable site for drilling is just the first step in extracting oil. Before drilling can begin, companies must make sure that they have the legal right to drill, and that the impact of drilling on the environment is acceptable. This can take years. Once they finally have the go ahead, drilling begins. The exact procedure varies, but the idea is first to drill down to just above where the oil is located. Then they insert a casing of concrete into the newly drilled hole to make it stronger. Next, they make little holes in the casing near the bottom, which will let oil in, and top the well with a special assembly of control and safety valves called a “Christmas tree.” Finally, they may send down acid or pressurized sand to break through the last layer of rock and start the oil flowing into the well. (Source: Oil and Natural Gas, Society of Petroleum Engineers, Richardson, TX.)
In the petroleum industry, production is the phase of operation that deals with bringing well fluids to the surface and preparing them for their trip to the refinery or processing plant. Production begins after drilling is finished.
The first step is to complete the well – that is, to perform whatever operations are necessary to start the well fluids flowing to the surface. Routine maintenance operations, such as replacing worn or malfunctioning equipment – known as servicing – are standard during the well’s producing life. Later in the life of the well, more extensive repairs – known as workovers – may also be necessary to maintain the flow of oil and gas. The fluids from a well are usually a mixture of oil, gas, and water, which must be separated after coming to the surface. Production also includes disposing of the water and installing equipment to treat, measure, and test the oil and gas before they are transported away from the well site.
So production is a combination of operations: bringing fluids to the surface; doing whatever is necessary to keep the well producing; and taking fluids through a series of steps to purify, measure, and test them. (Source: Fundamentals of Petroleum, Petroleum Extension Service, The University of Texas at Austin, Austin TX)
A major obstacle to producing tomorrow’s oil and gas resources is operation in ultra-deep water. The frontier of oil exploration continues to be offshore, over 10,000 feet/3,048 meters below sea level. Operating in this environment requires billions of dollars and boundless technical expertise. Safely and economically bringing oil to the surface requires experts in everything from underwater vehicles that install subsea equipment to structural engineers that make sure the huge floating platforms can withstand large waves. Operators must be able to hit a seemingly tiny target that they cannot see over 30,000 feet/9,144 meters under the surface—all while floating on waves. To put this in perspective, it is a bit like a quarterback trying to throw a football to his wide receiver more than 100 football fields away! Innovation will continue to drive this frontier into new territory.
We depend on oil and gas for a host of products we use in our everyday lives, and we will continue to depend on them for years to come. And while oil and gas production may contribute to the greenhouse effect on the environment, the industry is doing its part to offset those effects while still meeting the world’s petroleum demands.
Already great strides have been made to ensure that oil and gas producers make as little impact as possible on the natural environments in which they operate. This includes drilling multiple wells from a single location or pad to minimize damages to the surface, employing environmentally sound chemicals to stimulate well production, and ensuring a seamless transition from the wellhead to the consumer. While conventional oil and gas operations have been streamlined to maximize human safety and environmental protection, development of unconventional resources like Canada’s oil sands and Colorado’s oil shale will require major technological innovations.
Exploitation of these resources will be important in meeting tomorrow’s energy demand, but current methods consume large quantities of water and depend on expansive surface operations. How can the vast potential locked in these resources be tapped in a more efficient, environmentally sound manner? Research today focuses on inserting heaters into rock formations below the surface to convert the heavy hydrocarbons into liquid that can then be drained and produced by more conventional oil wells. Such a process would dramatically reduce the impact of these unconventional sources on the surface. However, the next generation of engineers and scientists must further refine this technology or generate new ideas in order to tackle these problems.
· Saudi Arabia
· Canada
· Iran
· Iraq
· Kuwait
· United Arab Emirates
· Venezuela
· Russia
· Libya
· Nigeria
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No one can know for certain how much oil and gas remains to be discovered. But geologists sometimes make educated guesses.
The total amount of oil or gas in the reservoir is called original oil, or gas. For a specific reservoir, engineers estimate this amount using information about the size of the reservoir trap and properties of the rock. Some of the original oil and gas deposited millions of years ago has been discovered, while some remains undiscovered—the target of future exploration.
Discovered (or known) resources can be divided into proved reserves and prospective or unproved (probable and possible) resources.
· Proved reserves are the quantities of oil or gas from known reservoirs that are expected to be recoverable with current technology and at current economic conditions.
·
Prospective resources are those that may be recoverable in the
future with advanced technologies or under different economic conditions.
The Oil & Gas Journal (OGJ) estimates that at the beginning of 2009,
worldwide reserves were 1.34 trillion barrels of oil and 6,254 trillion cubic
feet (Tcf) of natural gas. The oil estimate is 16 billion barrels of oil higher
than in 2007, reflecting additional discoveries, improving technology and
changing economics.
Continental North America and much of continental Europe have already been explored heavily, and any new discoveries are likely to be small. But many areas of the globe are largely unexplored, and large new deposits are waiting to be found. Global hot spots that may house significant new oil and gas reservoirs include:
· Offshore Brazil
· The Gulf of Mexico
· Alaska
· Offshore western Africa
· Russia
· Areas across Asia and the Pacific.
These are just a few of the current areas of growth. Most observers agree that significant deposits of oil and gas remain undiscovered in the Middle East.
The largest reserves of natural gas are found in Russia, Iran, Qatar, Saudi Arabia, the United Arab Emirates, the United States, Algeria, Nigeria, Venezuela and Iraq.
At current consumption levels, the remaining reserves represent 44.6 years of oil and 66.2 years of natural gas. Does this mean that the world will be out of fossil fuels in 50 years or so? That theory has been around since the 1970s. In fact, the figures for years of remaining reserves have remained relatively constant during the past few decades as the industry has balanced consumption with newly discovered oil and gas deposits.