Changes

The technology is essentially the same for offshore wells, accomplished with boats and equipment modules that can be placed on the drill ship or offshore platform.  

The technology is essentially the same for offshore wells, accomplished with boats and equipment modules that can be placed on the drill ship or offshore platform.  

A hydraulic stimulation project must have all of this equipment linked together to be able to push a slurry of water and sand down a narrow pipe to a depth of one to two miles – and then along a lateral pipe to a distance of possibly more than a mile and a half. The pumps must overcome not only the friction of the water in the pipe, but also the natural pressure of the geologic formation at depth. Thus, many pumps working together are necessary to both overcome friction and squeeze the water and sand mixture into the fractures.  

A hydraulic stimulation project must have all of this equipment linked together to be able to push a slurry of water and sand down a narrow pipe to a depth of one to two miles – and then along a [[lateral]] pipe to a distance of possibly more than a mile and a half. The pumps must overcome not only the friction of the water in the pipe, but also the natural pressure of the geologic formation at depth. Thus, many pumps working together are necessary to both overcome friction and squeeze the water and sand mixture into the fractures.  

The horizontal part of the well is stimulated in multiple sections. The stimulation of each section takes a few hours and the entire hydraulic fracturing operation will be spread over two to five days.

The horizontal part of the well is stimulated in multiple sections. The stimulation of each section takes a few hours and the entire hydraulic fracturing operation will be spread over two to five days.

Different types of rocks have different physical properties and contain different fluids: oil, natural gas and water. The location, size and design of the rock’s existing fractures, density and variations in subsurface pressures also affect the hydraulic fracturing operation, so all of these factors must be considered for every type of rock that will be hydraulically stimulated.

Different types of rocks have different physical properties and contain different fluids: oil, natural gas and water. The location, size and design of the rock’s existing fractures, density and variations in subsurface pressures also affect the hydraulic fracturing operation, so all of these factors must be considered for every type of rock that will be hydraulically stimulated.

   

   

For most oil and gas wells, the force of gravity on the rock generally determines the vertical pressure at any depth. Vertical pressure on the rock increases as you go deeper, just as water pressure increases as you go deeper in the ocean.

For most oil and gas wells, the force of [[gravity]] on the rock generally determines the vertical pressure at any depth. Vertical pressure on the rock increases as you go deeper, just as water pressure increases as you go deeper in the ocean.

   

   

An additional complication is that rocks are deposited in basins and are not all horizontal – and they are pushed as the continents shift. The vertical pressure always generates the largest stress on a rock; the horizontal stresses on a rock will control the lateral spreading of the hydraulic fractures. Fractures tend to form in the direction of the least stress, which is generally horizontal.  

An additional complication is that rocks are deposited in basins and are not all horizontal – and they are pushed as the continents shift. The vertical pressure always generates the largest stress on a rock; the horizontal stresses on a rock will control the lateral spreading of the hydraulic fractures. Fractures tend to form in the direction of the least stress, which is generally horizontal.  

In some cases – the Marcellus Shale, for example – the distance between the gas/oil-bearing strata and the deepest fresh water aquifer is more than 5,000 feet. In others, as in the San Joaquin Valley, this distance can be more than 25,000 feet.

In some cases – the Marcellus Shale, for example – the distance between the gas/oil-bearing strata and the deepest fresh water aquifer is more than 5,000 feet. In others, as in the San Joaquin Valley, this distance can be more than 25,000 feet.

The location and magnitude of created fractures typically are monitored using microseismic and tiltmeter technology, geophysical methods that measure very small seismic events and motion caused by breaks in the rock as it is fractured. The sensors used to measure these events, described as the equivalent to jumping one foot in the air and landing, allows operators to have a better understanding of the volume of rock that they are fracturing and where the cracks are forming.

The location and magnitude of created fractures typically are monitored using microseismic and tiltmeter technology, [[geophysical methods]] that measure very small seismic events and motion caused by breaks in the rock as it is fractured. The sensors used to measure these events, described as the equivalent to jumping one foot in the air and landing, allows operators to have a better understanding of the volume of rock that they are fracturing and where the cracks are forming.

These monitoring programs show that the hydraulically formed fractures are located far from aquifers.  

These monitoring programs show that the hydraulically formed fractures are located far from aquifers.  

Global demand for oil and natural gas continues to grow, and will for decades to come.  Meeting the needs of the developed and developing world alike will require the petroleum industry to find and produce new oil and natural gas resources.  Hydraulic fracturing will help make this possible.

Global demand for oil and natural gas continues to grow, and will for decades to come.  Meeting the needs of the developed and developing world alike will require the petroleum industry to find and produce new oil and natural gas resources.  Hydraulic fracturing will help make this possible.