Nontechnical Guide to Petroleum Geology Exploration Drilling and Production

Nontechnical Guide to Petroleum Contents

• The Nature of Fuel and Oil
• The Earth’s Crust—The place We Discover It
• Identification of Widespread Rocks and Minerals
• Geological Time
• Deformation of Sedimentary Rocks
• Ocean Atmosphere and Plate Tectonics 
• Sedimentary Rock Distribution 
• Mapping 
• Supply Rocks, Era, Migration, and Accumulation of Petroleum
• Reservoir Rocks
• Petroleum Traps 
• Petroleum Exploration—Geological and Geochemical 
• Petroleum Exploration—Geophysical 
• Drilling Preliminaries 
• Drilling a Effectively—The Mechanics 
• Drilling Issues
• Drilling Strategies
• Testing a Effectively 
• Finishing a Effectively 
• Floor Remedy and Storage
• Offshore Drilling and Completion
• Workover 
• Reservoir Mechanics
• Petroleum Production 
• Reserves 
• Unconventional Oil and Fuel

Preface to Nontechnical Guide to Petroleum Geology and Production

This ebook accommodates an unlimited quantity of helpful info on the upstream petroleum business. It’s designed for simple studying, and the knowledge is instantly accessible. The introductory chapter needs to be learn first.

It is a wonderful overview that exhibits how every thing in petroleum geology, exploration, drilling, and manufacturing is interrelated. Every topic has its personal chapter that’s nicely illustrated with figures and plates. The rocks, minerals, and seismic examples are in shade.

Trade phrases are outlined within the textual content and proven in italics. All measurements are in each English and metric models. A helpful index and intensive glossary are positioned in the back of the ebook, in addition to an attention-grabbing listing of petroleum data.

Introduction to Nontechnical Guide to Petroleum Geology and Production

Each crude oil and pure fuel happen naturally in subsurface deposits. Crude oil is a black liquid that’s bought to refineries to be refined into merchandise similar to gasoline and lubricating oil. Pure fuel is a colorless, odorless fuel that’s bought to fuel pipelines to be transported and burned for its warmth content material.

There are lots of various kinds of crude oils and pure gases, some extra precious than others. Heavy crude oils are very thick and viscous and are tough or inconceivable to produce. Mild crude oils are very fluid, comparatively straightforward to produce, wealthy in gasoline, and extra precious.

Some pure gases burn with extra warmth than others and are extra precious. Some pure gases additionally include virtually pure liquid gasoline referred to as condensate that separates from the fuel when it’s produced.

Condensate is sort of as precious as crude oil. Sulfur is a nasty impurity in each pure fuel and crude oil. Bitter crude oils include sulfur, and bitter pure gases include hydrogen sulfide and are much less precious. Crude oil is measured by quantity in barrels (bbl).

Pure fuel is measured by quantity in hundreds of cubic ft (Mcf) and by warmth content material in British thermal models (Btu). To ensure that there to be a business deposit of pure fuel or crude oil, three necessary geological circumstances have to be met.

First, there have to be a supply rock within the subsurface of that space that generated the fuel or oil at a while within the geological previous. Second, there have to be a separate, subsurface reservoir rock that holds the fuel or oil.

After we drill a nicely into that reservoir rock, the fuel and oil are ready to move by means of the reservoir rock and into our nicely. Third, there have to be a entice on the reservoir rock to focus the fuel or oil into business portions.

The crust of the earth in oil- and gas-producing areas consists of sedimentary rock layers. Sedimentary rocks might be supply and reservoir rocks for fuel and oil. These rocks are referred to as sedimentary rocks as a result of they’re composed of sediments that have been previously free particles similar to sand grains, mud, and seashells or salts that precipitated out of water.

Sedimentary rocks are thousands and thousands of years previous and have been deposited when the ocean stage rose and coated the land many occasions up to now. These sediments are comparatively easy supplies similar to sands deposited alongside seashores, mud deposited on the ocean backside, and beds of seashells.

Historical sediments, piled layer upon layer, kind the sedimentary rocks that at the moment are sandstones composed of sand grains, shales composed of mud particles, and limestones composed of seashells. These are drilled to discover and produce oil and fuel.

The supply of fuel and oil is the natural matter—lifeless plant and animal materials—that’s buried and preserved in some historical sedimentary rocks. The commonest, organic-rich sedimentary rock and the supply rock for many fuel and oil is black shale.

It was deposited as organic-rich mud on historical ocean bottoms. Within the subsurface, temperature and time flip natural matter into crude oil. Because the supply rock is roofed with extra sediments and buried deeper within the earth, it turns into hotter and hotter.

Crude oil begins to kind at about 150°F (65°C) at a depth of about 7,000 ft (2,130 m) under the floor of the land (fig. I–1). It’s generated from there down to a depth of about 18,000 ft (5,500 m) at about 300°F (150°C).

The reactions that change natural matter into oil are advanced and take a very long time. If the supply rock is buried deeper the place the temperatures are above 300°F (150°C), the remaining natural matter can generate pure fuel.

Fuel and oil are comparatively gentle in density in contrast to the water that additionally happens in subsurface sedimentary rocks. After oil and fuel kind, they rise due to buoyancy by means of fractures within the subsurface rocks.

The rising fuel and oil can intersect reservoir rock, which is a sedimentary rock layer that accommodates billions of tiny areas referred to as pores. A standard reservoir rock is a sandstone, composed of sand grains like these on a seashore.

Sand grains are like spheres—there isn’t any approach the grains will match collectively completely. There are pore areas between the sand grains on a seashore and in a sandstone rock.

Limestone, one other frequent reservoir rock, is usually deposited as shell beds or reefs, and there are pores between the shells and corals. As a result of limestone is soluble, there may also be answer pits within the limestone.

Porosity is the % of reservoir rock that’s pore house, and it’s generally 10 to 30%. The fuel and oil move into the pores of the reservoir rock layer.

As a result of the reservoir rock additionally accommodates water, the fuel and oil will proceed to rise by flowing from pore to pore to pore up the angle of the reservoir rock layer towards the floor. The motion of fuel and oil up the angle of the reservoir rock towards the floor known as migration.

The benefit with which the fuel and oil can move by means of the rock known as permeability. Due to migration, the fuel and oil can find yourself a substantial distance, each vertically and horizontally, from the place they have been initially shaped (fig. I–1).

Because the fuel and oil migrate up alongside the reservoir rock, it might probably encounter a entice. A entice is a excessive level within the reservoir rock the place the fuel or oil is stopped and concentrated. One kind of entice is a pure arch within the reservoir rock (fig. I–2) referred to as a dome or anticline.

Within the entice, the fluids separate in accordance to their density. The fuel is the lightest and goes to the highest of the entice to fill the pores of the reservoir rock and kind the free fuel cap. The oil goes to the center to fill the pores and kind the oil reservoir.

The saltwater, the heaviest, goes to the underside. To finish the entice, a caprock should overlie the reservoir rock. The caprock is a seal that doesn’t permit fluids to move by means of it. With no caprock, the oil and fuel would leak up to the floor.

Two frequent sedimentary rocks that may be caprocks are shale and salt. Most fuel and oil deposits are positioned in basins the place sedimentary rocks are comparatively thick. Subsurface deposits of fuel and oil are discovered by finding traps.

In some areas, the rock layers that crop out on the floor might be projected into the subsurface to uncover traps (fig. I–3). Right now, these floor rocks might be mapped utilizing images from airplanes and satellites.

Within the subsurface, the rocks in numerous wells which have already been drilled are matched by correlation to make cross-sections, and maps of the depths to the highest of subsurface reservoir rocks and their thickness are drawn.

Seismic exploration is usually used at this time to find subsurface traps. The seismic methodology makes use of a supply and detectors (fig. I–4). The supply, similar to dynamite, is positioned on or close to the floor and provides off an impulse of sound power into the subsurface.

The sound power bounces off sedimentary rock layers and returns to the floor to be recorded by the detectors. Sound echoes are used to picture the form of subsurface rock layers and discover traps.

The one approach to know for certain if a entice accommodates business quantities of fuel and oil is to drill an exploratory or wildcat nicely. Many wildcat wells are dry holes with no business quantities of fuel or oil. The nicely is drilled utilizing a rotary drilling rig (fig. I–5).

There might be hundreds of ft of metal drill pipe with a bit on the top, referred to as the drill string, suspended within the nicely. By rotating the drill string from the floor, the bit on the underside is turned and cuts the outlet.

Because the nicely is drilled deeper, each 30 ft (9.1 m) drilling is stopped and one other part of drill pipe is screwed on the drill string to make it longer. The ability to the rig is provided by diesel engines. A metal tower above the nicely the derrick or mast together with a hoisting line and pulley system is used to elevate and decrease tools within the nicely.

An necessary system on the rig is the circulating mud system. Drilling mud, often manufactured from clay and water, is pumped down the within of the drill pipe the place it jets out of nozzles on the bit and returns up the skin of the drill pipe to the floor (fig. I–6).

The drilling mud removes the rock chips made by the bit, referred to as nicely cuttings, from the underside of the outlet and prevents them from clogging up the underside of the nicely. The nicely is at all times saved stuffed to the highest with the heavy drilling mud as it’s being drilled.

The stress of the drilling mud prevents any fluids similar to water, fuel, and oil from flowing out of the subsurface rocks and into the nicely. If fuel and oil flowed up onto the ground of the drilling rig, they might catch fireplace, inflicting a blowout.

Even when solely water flowed out of the encircling rock into the nicely, the edges of the nicely may collapse, and the nicely might be misplaced. Because the nicely is being drilled, it may be drilled straight down, out at an angle as a deviated nicely, or out horizontally as a horizontal nicely by means of the oil and fuel reservoir (fig. I–7).

Horizontal wells sometimes produce oil and fuel at a higher fee than vertical wells. Offshore wells are drilled into sedimentary rocks on the ocean backside the identical approach as on land.

For offshore exploratory wells, the rig is mounted on a barge, floating platform, or ship that may be moved. As soon as an offshore subject is positioned by drilling, a manufacturing platform is put in to drill the remainder of the wells and produce the fuel and oil.

The manufacturing platform might be fastened with legs that sit on the ocean backside or floating with anchors and cables to maintain it in place.

As a result of drilling mud retains fuel and oil within the rocks, a subsurface deposit of fuel or oil might be drilled with none indication of the fuel or oil. To judge the nicely after it has been drilled, it have to be logged, and nicely logs have to be created.

A very good log is a document of the rocks and their fluids within the nicely. A mudlogger is a service firm that makes a mud log because the nicely is being drilled. The mudlogger rigorously analyzes each the drilling mud and nicely cuttings for traces of crude oil and pure fuel.

One other service firm drives a logging truck out to the nicely after the nicely is drilled to make a wireline nicely log. A protracted cylinder containing devices referred to as a logging software is unloaded from the truck and run down the nicely on a wireline (fig. I–8).

Because the logging software is introduced again up the nicely, the devices remotely sense {the electrical}, sonic, and radioactive properties of the encircling rocks and their fluids. These measurements are recorded on an extended strip of paper referred to as a wireline nicely log (fig. I–9) within the logging truck and are additionally digitized, encoded, and despatched by radio telemetry to an information heart.

Effectively, logs are used to decide the composition of every rock layer, whether or not the rock layer has pores and how a lot is pore house, and what fluid (water, fuel, or oil) is within the pores. Relying on the take a look at outcomes, the nicely might be plugged and deserted as a dry gap or accomplished as a producer.

To finish the nicely, many sections of large-diameter metal pipe referred to as casing are screwed collectively to kind an extended size of pipe referred to as a casing string that’s lowered down the outlet. Moist cement is then pumped between the casing and nicely partitions and allowed to set (fig. I–10) throughout a cement job.

This stabilizes the outlet. The casing is completed in phases referred to as a casing program, throughout which the nicely is drilled, cased, drilled deeper, cased once more, drilled deeper, and cased once more (fig. 1–11). To ensure that the fuel or oil to move into the nicely, the nicely is both accomplished open-hole or with perforated casing.

In an open-hole completion (fig. I-11a), the casing string is cemented down to the highest of the reservoir rock and the underside left open. In perforated casing completion (fig. I-11b), the casing is cemented by means of the reservoir rock and the casing is shot with explosives to kind holes referred to as perforations.

A protracted size of narrow-diameter metal pipe referred to as a tubing string is then suspended down the middle of the nicely. The produced fluids (water, fuel, and oil) are introduced up the tubing string to the floor to forestall them from touching and corroding the casing string that’s tougher to restore.

An expandable rubber gadget referred to as a tubing packer on the underside of the tubing string retains the tubing string central within the nicely and prevents the fluids from flowing up the skin of the tubing (fig. 1–11).

The tubing string is comparatively straightforward to restore throughout a workover. In all fuel wells, fuel flows to the floor by itself. There are some oil wells, often solely early within the improvement of the oil subject, wherein the oil has sufficient stress to move up to the floor.

Fuel wells and flowing oil wells are accomplished on the floor with a vertical construction of pipes, fittings, gauges, and valves referred to as a Christmas tree, which is used to management the move (fig. I–12a).

Most oil wells, nonetheless, don’t have sufficient stress for the oil to move to the floor, and the oil will fill the underside of the nicely solely up to a sure stage.

A sucker-rod pump or beam-pumping unit (fig. I–12b) is usually used to carry the oil and water up the tubing string to the floor. A downhole pump on the underside of the tubing string is pushed by the floor beam-pumping unit.

A motor causes a beam on a pivot, referred to as the strolling beam, to pivot up and down. The strolling beam is related to a downhole pump by an extended, slender, sucker-rod string that runs down the middle of the tubing string (fig. 1–12b).

The pump lifts the oil and water up the tubing string to the floor. On the floor, fuel is ready for supply to a fuel pipeline by gas-conditioning tools that removes impurities similar to water vapor and corrosive gases.

Precious pure fuel liquids, similar to condensate, are faraway from the fuel in a pure fuel processing plant and bought individually. The fuel can then be bought to a fuel pipeline. For oil, alongside vertical or horizontal metal tank referred to as a separator is used to separate pure fuel that bubbles out of the oil and the saltwater that settles to the underside (plate I–1).

The oil is then saved in metal inventory tanks till it’s bought to a refinery. The manufacturing fee from wells might be elevated by acid and frac jobs. Acid is pumped down a nicely to dissolve a number of the reservoir rock adjacents to the wellbore throughout an acid job.

Throughout a frac job, the reservoir rock is hydraulically fractured with a liquid pumped below excessive stress down the nicely. Propping brokers similar to sand grains are pumped down the nicely with the frac fluid to maintain the fractures open and permit the oil and fuel to readily move into the nicely.

Periodically, manufacturing from the nicely have to be interrupted for repairs or to clear out the nicely throughout a workover. A service firm drives out to the nicely with a manufacturing unit to do the workover.

As fluids are produced from the subsurface reservoir, stress on the remaining fluids drops. The manufacturing fee of oil and fuel wells and the entire subject decreases with time on a decline curve. Final restoration of fuel from a fuel reservoir is usually about 80% of the fuel within the reservoir.

Oil reservoirs, nonetheless, are much more variable and much less environment friendly. They vary from 5 to 80% restoration however common solely 35% of the oil within the reservoir. This leaves 65% of the oil remaining within the pressure-depleted reservoir.

After the reservoir stress has been depleted in an oil subject, waterflood and enhanced oil restoration might be tried to produce a number of the remaining oil.

Throughout a waterflood, water is pumped below stress down injection wells into the depleted reservoir to drive a number of the remaining oil by means of the reservoir rock towards producing wells (fig. I–13).

Enhanced oil restoration includes pumping fluids similar to carbon dioxide, nitrogen, or steam down injection wells to receive extra manufacturing. Just lately, an unlimited quantity of pure fuel has been produced from shales with a particular method.

Shale is a really fine-grained rock. Although many shales include fuel, shale has no permeability and the fuel can not move by means of the shale right into a nicely.

Horizontal wells drilled into these shales, nonetheless, are used for a particular frac job referred to as a slickwater frac, which permits the fuel to move by means of the shale and into the nicely. After the nicely has been depleted, it’s required by regulation to be correctly plugged and deserted to forestall air pollution.

The cement have to be poured down the nicely to seal the depleted reservoir and to defend any subsurface freshwater reservoirs. A metal plate is then welded to the highest of the nicely and the nicely is roofed with soil.

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