Fall Meet., San Antonio, Tex., Oct 8– Google Scholar. Williams, et al., Williams, B.B., Gidley, J.L. and Schechter, R.S., Acidizing Fundamentals. Matrix acidizing refers to one of two stimulation processes in which acid is injected into the well penetrating the rock pores at pressures below. Stimulation by acidizing is an old production enhancement technique dating as far . B.B. Williams, J.L. Gidley, and R.S. Schecter, “Acidizing Fundamentals”.
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It can be used to either remove formation damage or stimulate undamaged formations to produce conductive channels within the fracture where oil and gas can migrate. In radial flow, wormholes form a dendritic pattern, like acidizihg roots of a tree.
Migration of these particles fines into the pores of the near-wellbore area can reduce production and they will not dissolve in strong acids such as hydrochloric acid, but will dissolve in hydrofluoric acid HF.
Carbonate matrix acid stimulation is also useful acidiznig treat carbonate cemented sandstones and formation damage from acid soluble species such as calcium carbonate CaCO 3 or sulfide scales, lost circulation materials, etc. The successful acid placement in matrix treatments of open-hole horizontal wells is even more difficult due to the length of zone and potential variation of the formation properties.
The maximum rate allowed is a function of the carbonate permeability. In high temperature applications, HCl does not produce acceptable stimulation results due to its fast reaction that leads to lack of penetration. Basically, there are two types of acid treatments that are related to injection rates and pressures.
Help to improve this page What’s this? By posting, you agree to be identified by your IP address. We were unable to find this edition in any bookshop we are able to search. In the absence of damage, the large volume of acid that is required to improve the formation permeability in the vicinity of the wellbore may not justify the small incremental increase in production, especially in sandstone.
Matrix acidizing –
In carbonate rock, hydrochloric acid enlarges the wellbore or tends to bypass damage by forming wormholes. There are several other ways that acidizing, both for sandstone and carbonate reservoirs, can lead to formation damage if not carried out correctly.
In sandstone matrix acidizing, the primary purpose is to remove acid-soluble damage in the well and near wellbore area. Set up My libraries How do I set up “My libraries”? Lists What are lists? Injection rates resulting in pressures below fracture pressure are termed “matrix acidizing,” while those above fracture pressure are termed ” fracture acidizing. Fracture acid stimulation is usually carried out on carbonate reservoirs, which have lower permeability than sandstone reservoirs. May not be open to the public ; BROC Treatment design and planning are often performed to ensure that the acid is placed across the entire interval.
Acid stimulation refers to using a stimulation fluid containing reactive acids to increase permeability both in production and injector wells, carbonate or sandstone, by dissolving various acid-soluble solids naturally present in the rock matrix or as formation damage.
Author Williams, Bert B.
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J Pet Technol 45 3: Later injected fracturing fluid tend to leak off into the wormholes rather than lengthening the desired fracture. Jennings, “A contemporary approach to matrix acidizing” SPE Contact Us Subscribe to newsletter How to contribute? In addition, the acid stimulation fluid follows the paths of least resistance and create typically long-branched passageways leading away from the fracture interface, which are called “wormholes”.
Advances in Matrix Stimulation Technology. Matrix acidizing is used primarily for damage removal, while fracture acidizing is used to enlarge the effective wellbore by creating an acid-etched fracture deep into the wellbore for relatively low-permeability formations to improve well productivity several-fold. Fracture acidizing is to pump the acid treatment above the fracturing pressure of the reservoir rock, which create long, open channels from the wellbore penetrating deep into the formation.
Although the acid systems used in sandstone and carbonate differ, the same practices apply to both.
Acidizing Fundamentals – Bert B. Williams, John L. Gidley, Robert Samuel Schechter – Google Books
None of your libraries hold this item. Matrix acidizing refers to one of two stimulation processes in which acid is injected into the well penetrating the rock pores at pressures below fracture pressure.
During matrix acidizing the acids dissolve the sediments and mud solids within the pores that are inhibiting the permeability of the rock. Evaluation of acid treatments. Although highly corrosive, HF is classified as a weak acid due to its low ionization in water and it is very toxic. Skip to content Skip to search. View online Borrow Buy Freely available Show 0 more links Treating fundamentalx undamaged sandstone well with matrix acids does not usually lead stimulation unless the reservoir is naturally fractured.
The effect of damage on well productivity and flow is illustrated in Figs.
Wormholes are small, continuous channels formed by acid preferentially enlarging pores in carbonate, usually around 2 to 5 mm in diameter.