Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. That type of environment is where organisms capable of forming calcium carbonate shells and easily extracted into the ocean water. Limestones formed from this type of sediment are biological sedimentary rocks
It is a calcium magnesium carbonate with a chemical composition of CaMg(CO3)2. It is the primary component of the sedimentary rock known as dolostoneand the metamorphic rock known as dolomitic marble. Dolomite is rarely found in modern sedimentary environments but dolostones aregeographically extensive and hundreds to thousands of feet thick.
the design process is a systematic approach to estimating and calculating injection pressure and rate, volumes, and concentrations. Like HF and HCL acid usually penetrates only about 6 to 12 in. into the sandstone before spending. If acid can easily reach nearby plugging solids, small volumes of 25 to 50 gal/ft of HF and HCL type acid can dissolve this damage; however, with more severe damage, more time and volume are needed to reach the plugging solids. Effective acid diversion reduces acid volumes needed.
Carbonate Acidizing & design 142
Carbonate Acidizing & Design
Carbonate rocks are a class
of sedimentary rocks.
Composed primarily of two major types
of carbonate minerals.
2.Dolostone or Dolomite
Composed of skeletal
fragments of marine
organisms such as
coral or foraminifera.
Acidizing & Designing
Acidizing involves pumping acid into a
wellbore or geologic formation that is
capable of producing oil and/or gas.
Purpose of any acidizing is to improve a
well’s productivity or injectivity.
Acidizing designing in which we selecte the
appropriate acids, after that ready to
design the treatment.
Two types of acids are most
1.Hydrochloric acid in all formation types.
2.Hydrofluoric acid in sandstones and
Other types of acids, such as organic
acids, may also be used in specialized
Three general categories of
acid treatments are
Mostly used in carbonate formations
Objective is simply tubular and wellbore
Most commonly performed with
hydrochloric acid (HCl) mixtures to clean
out scale (such as calcium carbonate),
rust, and other debris restricting flow in the
Mostly used in sandstone formations
Acid is injected into the well penetrating rock
pores at pressures below fracture pressure.
Used to either stimulate a well to improve flow
or to remove damage.
During this process the acids dissolve the
sediments and mud solids within the pores
that are inhibiting the permeability of the rock.
Mostly used in carbonate formations
Involves pumping highly pressurized
acid into the well,
physically fracturing the reservoir rock
and dissolving the permeability inhibitive
Purpose is to restore or improve an oil
or gas well’s productivity
Acidizing Refers to
Well stimulation is a well intervention
performed on an oil or gas well
To increase production by improving the
flow of hydrocarbons from the drainage
area into the well bore.
After an acid job is performed,
used acid and sediments removed from
the reservoir are washed out of the well
in a process called Backflush.
fields challenging to produce
Carbonates can exhibit highly varying properties
(e.g., porosity, permeability, flow mechanisms)
within small sections of the reservoir,
making them difficult to characterize.
This involves detailed understanding of the fluids
reservoir rock type,
and natural fracture systems at different scales.
It is estimated that more than 60% of the
world's oil and 40% of the world's gas
reserves are held in carbonate
The Middle East, is dominated by
carbonate fields, with around 70% of oil
and 90% of gas reserves held within
Most carbonate reservoir are present in
Pakistan ( Northern areas) in which 90% of
gas and 60% of oil are produces to fulfill
the demand of oil/gas for our country.
But many reserves are remaining to
extract or evaluate the hydrocarbon,
because this reserve has an ability to fulfill
the demand of the energy in Pakistan.
Every nation depend on economy and
economy stable by profitable business,
Oil & gas sector is more profitable business
in the whole world.
More exploration get more profit and stable
the economy of any country.
Government interest required in exploration.
Carbonate acidizing and design is required
to produce well efficiently & economically.