Hydraulic fracturing
hydraulic fracturing
has been and will remain, one of the primary engineering tools for improving well productivity. This is achieved by
placing a conductive channel through near wellbore
damage, bypassing this crucial zone
extending the channel to a significant depth into
the reservoir to further increase productivity
placing the channel such that fluid flow in the reservoir is altered
Proper treatment design is thus tied to several disciplines
production engineering
rock mechanics
fluid mechanics
selection of optimum materials
operations.
what is fracturing
If fluid is pumped into a well faster than the fluid
can escape into the formation , inevitably pressure rises,
and at some point something breaks.
Injecting fluid into formation at pressure higher than the fracturing pressure of the formation creates fractures which propagate as more fluid is injected
Methods of hydraulic fractures
Acid fracturing
Proppant fracturing
Basic reasons for hydraulic fracturing
1- increase the rate or productivity
2- improve ultimate recovery
Fracture orientation
Fracture either horizontal or vertical
pressure behavior for fracturing formation
break down pressure: the pressure required to break the formation and initiate fracture.
Propagation pressure: the pressure required to continually enlarge the fracture.
Instantaneous shut in pressure: the pressure required to hold the fracture opened.
Idealized pressure behavior during fracturing
Oil well stimulation plays a vital role in production operations. With oil prices at all-time highs, it is imperative from an oil company's perspective and the consumer's perspective that as much production as possible be safely extracted from the reservior .
why do wells need oil well stimulation?
Hydraulic fracturing and acid fracturing in practically all types of formations and oil gravities, when done correctly, have been shown to increase well productivity above that projected in both new and old wells. From an economic standpoint, oil produced today is more valuable than oil produced in the future. Fracturing candidates may not necessarily "need" oil well stimulation, but the economics may show that such a treatment would pay=off.
To understand why remedial stimulation (matrix acidization) is necessary, you have to consider the conditions at work, deep down inside the reservoir...
Before the well is ever drilled, the untapped hydrocarbons sit in the uppermost portions of the reservoir (atop any present water) inside the tiny pore spaces, and in equilibrium at pressures and temperatures considerably different from surface conditions.
Once penetrated by a well, the original equilibrium condition (pressure, temperature, and chemistry) is permanently changed with the introduction of water or oil-based drilling fluids loaded with suspended clays, and the circulation of cement slurries. The interaction of the introduced fluids with those originally present within the reservoir, coupled with pressure and temperature changes can cause a variety of effects which, in turn, can plug the numerous odd-shaped pores causing formation damage. Some of the types of damage include: scale formation, clay swelling, fines migration, and organic deposition.
Petroleum engineers refer to the level of formation damage around the wellbore as skin effect. A numerical value is used to relate the level of formation damage. A positive skin factor reflects damage/impedance to normal well productivity, while a negative value reflects productivity enhancement.
Formation damage, however, is not limited to initial production operations. Remedial operations of all kinds from well killing to well stimulation itself, can cause formation damage. Nor is fines and scale generation limited to the reservoir. They can also develop in the wellbore in casing and tubulars, and be introduced from surface flowlines and incompatible injection fluids. These fines and precipitates can plug pores and pipe throughout an entire oil field.
In short, any operation throughout a well's life can cause formation damage and impede productivity.
types of Stimulation:-
1- Hydraulic fracturing
2- Acid fracturing
