In the name of

GODthe compassion the merciful

Well stimulation

Teacher:Dr.Ghavidel

Sedighe ZanganehMahdi shahbazi

95.8.24

A treatment performed to restore or enhance the productivity of a well.

Stimulation treatments

hydraulic fracturing

matrix treatments

are performed above the fracture pressure of the reservoir formation and create a highly conductive flow path between the reservoir and the wellbore.

Fracturing treatments

are performed below the reservoir fracture pressure and generally are designed to restore the natural permeability of the reservoir following damage to the near-wellbore area.

Matrix treatments

Stimulation in shale gas reservoirs typically takes the form of hydraulic fracturing treatments.

We can use hydraulic fracturing and matrix stimulation treatments to restore or enhance well productivity in all types of formations and reservoir environments.

Increase productivity

Maximize your reservoir production by creating highly conductive reservoir flow paths—selecting the appropriate treatment for each environment is critical to well economics.

Treatment by environment

The natural energy of a reservoir can be used to move oil and gas toward the wellbore. Used in such a fashion, these sources of energy are called drive mechanisms

Drive mechanisms and recovery

Early determination and characterization of the drive mechanism(s) present within a reservoir may allow a greater ultimate recovery of hydrocarbons.

Drive mechanisms

• the analysis of historical production data

• primarily reservoir pressure data

• fluid production ratios.

The three primary oil reservoir drive mechanisms

water drive

gas cap drive

solution gas

drive

Water drive A strong water drive provides very good pressure support from the aquifer

(100% voidage replacement) with minimal pressure drop at the wellbore. The aquifer water expands slightly, displacing the oil or gas from the reservoir toward the borehole as pressure drops around the borehole. This mechanism exists only where the aquifer is of equal or better quality than the reservoir and has a much larger volume than the reservoir (about 10 times) or is in communication with surface recharge. A strong water drive is more effective in oil reservoirs than in gas reservoirs. On a semi-log plot of production decline, the curve tends to be flat.

In fields where the aquifer is smaller and/or has lower quality, there is limited expansion of water into the reservoir as oil or gas is withdrawn. This is a partial water drive.

Gas cap drive(gas expansion)

In reservoir systems with little or no water drive, gas expansion often provides the energy necessary to move hydrocarbons to the wellbore. Free gas in a gas reservoir or in the gas cap of an oil reservoir expands to replace produced hydrocarbons. In an oil system, this expansion slows the rate of fluid pressure drop in the reservoir and supports hydrocarbon production. Pressure drops in proportion to the volume of hydrocarbon removed from the reservoir and the quality of the reservoir. Reservoirs with gas expansion drives have, at most, a limited aquifer.

Solution gas drive

Crude oil under high pressure can contain large amounts of dissolved gas. The more gas there is in solution, the more compressible the oil. In oil reservoirs with little or no water drive, reservoir energy to drive the oil toward the wellbore can be supplied by expansion of the oil due to gas expanding in solution. This is a solution gas (or dissolved gas or depletion) drive. When pressure drops below the bubble point in the reservoir, small, disconnected gas bubbles form in pores, also pushing the oil toward the wellbore. At about 5–10% free gas in the reservoir, the bubbles coalesce and the gas moves toward the wellbore as a separate flowing phase. When this happens, oil production drops and gas production increases rapidly because of the increased relative permeability to gas.

Reservoir pressure trends and producing gas-oil ratio trends of these three drive mechanisms

two or more of the primary drive mechanisms are present in the same reservoir.

Combination drive

A combination drive may also occur when one or more of the

primary drive mechanisms areassisted by gravity

drainage.

Combination drive

Most oil reservoirs produce under the influence of two or more reservoir drive mechanisms, referred to collectively as a combination drive. A common example is an oil reservoir with an initial gas cap and an active water drive