Tishk International UniversityEngineering FacultyPetroleum and Mining Engineering Department

Enhanced Oil Recovery

Fourth Grade- Spring Semester 2020-2021

Lecture 6: Chemical Flooding

Instructor: Ms. Sheida Mostafa Sheikheh

Content:

➢ Chemical Flooding

➢ Chemical Flooding Procedure

➢ Chemical Flooding Classification

Chemical Flooding:

■ Chemical Recovery or Chemical Flooding: A general term for injection

processes that use special chemical solutions.

■ The chemical solutions are pumped through specially distributed

injection wells to mobilize oil left behind after primary or secondary

recovery.

What is Interfacial Tension?

Which condition is favorable to have more

oil recovery? High Interfacial Tension or Low

Interfacial Tension?

Chemical Flooding Procedure:

■ Preflush:

➢ In chemical flooding, a fluid stage, normally low-salinity water, pumped

ahead of the micellar or alkaline chemical solution.

➢ One of the purposes of the preflush is to displace reservoir brine containing

potassium, sodium, calcium and magnesium ions from the near-wellbore

area, avoiding adverse interactions with the chemical solution.

➢ The other purposes are to adjust reservoir salinity to favorable conditions for

the surfactant (chemical solution) and to obtain information about reservoir

flow patterns.

Chemical Flooding Procedure:

■ Additional Oil Recovery (Oil Bank):

➢ The portion of a reservoir where the oil saturation is increased because of

the application of improved oil recovery method.

➢ This is the amount of the oil which is released due to the chemicals injected

during chemical flooding.

Chemical Flooding Procedure:

■ Chemicals for Releasing Oil and Mobility Control:

➢ Polymer

➢ Surfactant

➢ Alkaline

What is Mobility Ratio?

Mobility Ratio:

𝑀 =𝜆𝑤 𝑖𝑛 𝑡ℎ𝑒 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑡𝑎𝑐𝑡𝑒𝑑 𝑝𝑜𝑟𝑡𝑖𝑜𝑛

𝜆𝑜 𝑖𝑛 𝑡ℎ𝑒 𝑜𝑖𝑙 𝑏𝑎𝑛𝑘−− −(1)

𝑀 =Τ𝑘𝑟𝑤 𝜇𝑤Τ𝑘𝑟𝑜 𝜇𝑜

Where M= mobility ratio

𝑘𝑟= relative permeability

𝜇= viscosity

𝜆= mobility =𝑘

𝜇

𝑘= permeability; o,w- subscripts denoting oil and water, respectively.

Which one is preferable?

Mobility Ratio more than one

or less than one?

Mobility Ratio:

➢ The mobility ratio of water to oil is one of the most critical factors to influence

waterflood efficiency.

➢ When mobility is greater than one, it is considered unfavorable as water is more

mobile than oil in the porous medium; injected water tends to bypass oil and early

breakthrough is experienced at the producers.

➢ At a mobility ratio of less than one, water is less mobile than oil leading to better

displacement and recovery of oil.

Chemical Flooding Classification

Polymer Flooding

Micellar-Polymer Flooding

Alkaline Flooding

Polymer Flooding:

➢ Polymer flooding is used under certain

reservoir conditions that lower the efficiency of

a regular waterflood, such as fractures or high-

permeability regions that channel or redirect

the flow of injected water, or heavy oil that is

resistant to flow.

Polymer Flooding:

➢ Adding a water-soluble polymer to the waterflood allows the water to

move through more of the reservoir rock, resulting in a larger

percentage of oil recovery.

➢ Polymer gel is also used to shut off high-permeability zones.

Micellar-polymer Flooding:

➢ Micellar-polymer flooding uses the injection of a micellar slug

containing a mixture of a surfactant, cosurfactant, alcohol, brine, and

oil.

➢ The mixture moves through the oil-bearing formation, releasing much

of the oil trapped in the rock.

➢ This method is one of the most efficient EOR methods but is also one

of the most costly to implement.

Alkaline Flooding:

➢ Alkaline flooding requires the injection of alkaline chemicals (lye or

caustic solutions such as NaOH) into a reservoir that react with

petroleum acids to form surfactants.

➢ The surfactants aid to release the oil from the rock by reducing

interfacial tension, changing the rock surface wettability, or

spontaneous emulsification.

➢ The oil can then be more easily moved through the reservoir to

production wells.

Foam for EOR:

■ Foam is defined as a dispersion of a non- wetting phase in a

continuous wetting phase.

■ The non-wetting phase is gas and the wetting phase is water that

contains surfactant at a particular concentration that is above the

critical micelle concentration.

■ Foam has been shown to reduce the gas relative permeability by

trapping a large fraction of gas.

Foam for EOR:

Nanofluids for EOR:

▪ Nanofluid flooding (also called nanoflooding) is a new chemical EOR

technique whereby nanomaterial or nanocomposite fluids are injected

into oil reservoirs to effect oil displacement or to improve injectivity.

▪ Adding certain Nanoparticles (NPs) to injection solutions can

significantly benefit enhanced oil recovery (EOR), with advantages

such as wettability alternation, changes in fluid properties, improving

the trapped oil mobility, and decreasing the interfacial tension (IFT).

Nanofluids for EOR:

Write down a short description

about Nanotechnology in EOR.

➢High surface to volume ratio, more reactive

➢Environmentally friendly

➢Easily propagating inside the reservoir due to small

size, and will not trap the pores and reduce

permeability

Advantages of Nanoparticles in EOR: