1. WELL STIMULATION
Presented by
Hisham Usman (GU15R0255)
Azeem (GU15R0285)
B.Tech (Petroleum) 3rd year
DEPARTMENT OF PETROLEUM ENGINEERING
GLOCAL UNIVERSITY
Under the guidance of
Mr. Pankaj Mishra
(Assistant Professor)
2. CONTENTS
Introduction
Methods
Acidizing
• Matrix acidizing
• Fracture acidizing
Acid used in acidizing
Acid additives
Factors that govern the degree of acid attack on steel
Hydraulic fracturing
• Objective of hydraulic fracturing
• Hydraulic fracturing stages
• Proppant
Composition of fracture fluid
Application of hydraulic fracturing
3. Well stimulation
Some, petroleum exists in a formation but is unable to flow readily into the
well because the formation has very low permeability.
• Natural low permeability formation.
• Formation damage around the wellbore caused by invasion of
perforation fluid and charge debris.
Acidizing or fracturing is a methods used to increase the permeability near
the wellbore.
5. Acidizing
The pumping of acid into the wellbore to remove near-well formation
damage and other damaging substances.
This procedure commonly enhances production by increasing the
effective well radius
The two basic types of acidizing are characterized through injection
rates and pressures:
• Injection rates below fracture pressure are termed matrix acidizing.
• Injection rates above fracture pressure are termed fracture
acidizing.
6. Matrix acidizing
In matrix acidizing acid is pumped into the formation below the fracture
pressure.
It removes acid-soluble damage.
This method is used for both sandstone and carbonate formations.
Due to the extremely large surface area contacted by acid in a matrix
treatment, spending time is very short. Therefore, it is difficult to affect
formation more than a few feet from the wellbore
7. Fracture acidizing
In fracture acidizing acid is pumped into the wellbore, above the
fracturing pressure of reservoir rock.
It creates long and open channels.
It is usually carried out on carbonate reservoirs, which have lower
permeability than sandstone.
10. Surfactant
Surfactants should be used on all acid jobs to reduce surface and interfacial
tension, to prevent emulsions, to water-wet the formation, and to safeguard
against other associated problems.
Corrosion inhibitor
Corrosion inhibitors for acid are chemical additives that reduce the rate of
corrosion of steel by acid. There are two primary reasons for using corrosion
inhibitors:
(1) to protect the acid pumping and handling equipment
(2) (2) to protect well equipment.
11. Anti-sludge agents
Some crudes, particularly heavy asphaltic crudes, form an insoluble
sludge when contacted with acid, with greater problems experiences with
high strength acid. Dissolved fe(iii) in acid appreciably increases the
possibility of sludge.
• The primary ingredients of a sludge are usually asphaltenes.
• Sludges may also contain resins and paraffin waxes, high-molecular
weight hydrocarbons, formation fines, clays, and other materials.
12. Suspending agents
Most carbonate formations contain insoluble which can block formation
pores or fractures if fines released by acid are allowed to settle and bridge.
Suspension should be differentiated from dispersion. Dispersed particles
usually settle in a short time.
13. Factors that govern the degree of acid
attack on steel are
1. Type of steel including hardness
2. Temperature
3. Type of acid
4. Acid concentration
5. Acid contact time
14. Factors controlling the reaction rate of acid are factors
controlling the reaction rate of acid are
• Area of contact per unit volume of acid
• Formation temperature
• Pressure
• Acid concentration
• Acid type
• Physical and chemical properties of formation rock
• Flow velocity of acid
15. Hydraulic fracturing
Hydraulic fracturing is usually termed as fracking and hydrofracturing.
This stimulation method have two major steps
• Create crack in rock formation using acid
• Proppant injection
16. Objective of hydraulic fracturing
The objective of hydraulic fracturing is to increase well productivity by
creating a highly conductive path.
In hydraulic fracturing rock is fractured by a pressurized liquid, the
conductivity is maintained by propping with sand to hold the fracture
faces apart.
19. • Spearhead stage- mixing water with acid, used to clear debris and
create path way.
• Pad stage- inject fluid before proppant to break the formation.
• Proppant stage- injection of water and sand and remains in formation.
• Flush stage- at last fresh water is pumped into wellbore.
20. Proppant
• The proppant is a granular material that prevents the created fractures
from closing after the fracturing treatment.
• Types of proppant
1. Silica sand
2. Resin-coated sand
3. bauxite
4. Ceramic
22. Function of frac fluids
• Initiation of fracture
• Propagation of fracture
• To carry proppants
• Return to the wellbore after treatment
23. Application of hydraulic fracturing
1. Low permeability reservoir.
2. Damaged reservoir.
3. Naturally fractured reservoir.
4. To minimize sand production with the help of frac packing.
5. Connect height of reservoir slanted or horizontal well.
6. Minimize paraffin or aspartin deposition.
7. Increase draining area.
