Acidizing is a technique used in oil and gas extraction that is designed to lengthen the useful life of an oil well. The process of acidizing involves pumping acid into the well in order to dissolve the rocks that line the contours of the well. The acidizing process is less heavily regulated than other oil and gas extraction techniques.
What is the process of acidizing an oil well?
The process of acidizing involves pumping acid into the well in order to dissolve the rocks that line the contours of the well. Acidizing increases production rates by creating channels into the rock through which the oil and gas can flow into the reservoir.
What is acid washing in oil and gas?
Acid washing is most commonly performed with hydrochloric acid (HCl) mixtures to clean out scale (such as calcium carbonate), rust, and other debris restricting flow in the well. Matrix and fracture acidizing are both formation treatments. In matrix acidizing, the acid treatment is injected below the formation fracturing pressure.
How long has acid treatment been used to improve well productivity?
Oil and gas operators have used acid treatment (acidizing) to improve well productivity for almost 120 years. Acidizing predates all other well stimulation techniques, including hydraulic fracturing which was not developed until the late 1940s.
How is acid used in oil and gas drilling?
Acidizing involves pumping acids into the well in order to dissolve the rock, which improves production by creating channels in the rock to allow oil and natural gas to reach the well. Acids can also be used to dissolve debris found in the well.
How is hydrochloric acid used in oil production?
Oil Well Acidizing – Hydrochloric acid is used in large quantities as a bore-hole drilling agent. This fracture stimulation fluid reduces the pH of drilling fluid systems and helps dissolve rock during drilling for the Oil and Gas Industry.
What is acid used for in oil and gas?
It involves pumping acid into a drilled well or geological formation that is capable of producing oil and/or gas. This is commonly referred to as a target formation. The purpose of acidisation is to clean out the well following drilling and to improve the productivity of the well.
Why is acid used in frac?
In proppant fracturing, a propping agent is used to prop open the fracture after the treatment is completed. In acid fracturing, acid is used to “etch” channels in the rock that comprise the walls of the fracture. Thus, the rock has to be partially soluble in acid so that channels can be etched in the fracture walls.
Is hydrochloric acid used in fracking?
The answer: hydrochloric acid plays a key role in the hydraulic fracturing process. After the natural gas well's hole is bored, drillers will pump thousands of gallons of water mixed with acid down into the well.
Does acid break down oil?
Water easily dissolves other polar substances, like sodium chloride salt, but does not dissolve non-polar molecules such as oil. For the same reason, acids, which are polar molecules, generally do not dissolve oil.
Is hydrochloric acid A oil?
An acid type commonly used in oil- and gas- well stimulation, especially in carbonate formations. The reaction characteristics of hydrochloric acid enable it to be used in a wide range of treatments, often with chemical additives that enhance its performance or allow greater control of the treatment.
Why would you add acid to a well?
A matrix acid job is performed when acid is pumped into the well and into the pores of the reservoir rocks. In this form of acidization, the acids dissolve the sediments and mud solids that are inhibiting the permeability of the rock, enlarging the natural pores of the reservoir and stimulating flow of hydrocarbons.
What is injected into the ground during fracking?
What Is in Fracking Fluid? Made up of as much as 97 percent water, fracking fluid also contains chemical additives and proppants (small, solid particles used to keep the fractures in the rock formation open after the pressure from injection subsides).
What fluid is used in fracking?
waterFracking fluid is 99.5% water and sand. 0.5% is made up of safe chemical additives, most of which are found in common household products, like toothpaste and makeup remover, or in the foods you eat.
What happens to the waste water from fracking?
Contaminated water, which is fracking's largest waste product, is typically (1) treated to remove contaminants and discharged into surface waters, (2) recycled for use on other fracking projects, or (3) injected into specialized wells.
What happens to the water after it has been used fracking?
After the fracturing process, a percentage of the water returns fairly quickly to the surface as wastewater, also called “flowback.” The briny water that has long been underground and comes up during continued operation of the well, called “produced water,” can contain naturally occurring contaminants like the ...
Why is fracking so popular in the US?
Technological advancements like hydraulic fracturing and horizontal drilling further environmental progress. Fracking supports reduced air emissions, as greater equipment and engine efficiency and improved technologies mean less energy consumption – thus lower air emissions – per unit of energy produced.
What is acid treatment?
Acid Treatment. Acid treatments are accompanied by very familiar problems linked with the presence of iron in the acid that is pumped into the formations, essentially as a result of the acid dissolving the rust in the casings during pumping, and possibly the dissolving of iron-containing minerals in formation.
What temperature is dilute acid used for?
During dilute acid treatment, dilute (mostly sulphuric) acid is sprayed onto the raw material and the mixture is held at 160-220 °C for short periods up to a few minutes. Hydrolysis of hemicellulose then occurs, releasing monomeric sugars and soluble oligomers from the cell wall matrix into the hydrolysate.
What is an alternative to inorganic acids?
As an alternative to inorganic acids, organic acids (e.g., maleic acid, fumaric acid) can also be used for dilute acid pretreatment that offers good performance in terms of recovering hemicellulose sugars, but there are also some drawbacks.
Is dioxane HCl good for O- and/or C-condensation?
Nevertheless, concentrated HCl in dioxane gives satisfactory yields in O- and/or C-condensation products when dioxane is freshly distilled on sodium and benzophenone (in order to avoid free radicals).
How does fracture acidisation work?
To enable fracture acidisation the acid is pumped in to the well at pressures above the geological formation fracturing pressure. The purpose of fracture acidisation is to enhance or create new flow paths to the well. Pumping the acid at pressure opens up new fractures and fissures and/or dissolving material in the target formation that is restricting flow to the well. This technique is generally used in lower permeability geological formations.
What is matrix acidisation?
Matrix acidisation involves pumping dilute acid into the oil and / or gas reservoir from the well. The acid is injected, or “squeezed”, in to the geological formation at a pressure that is above the geological formation pressure but below the formation fracturing pressure.
Do oil companies need environmental permits?
The Environment Agency takes any environmental risks associated with oil and gas exploration and production very seriously and are committed to ensuring that people and the environment are protected. Oil and gas companies must obtain the necessary environmental permits, unless the activity is exempt from the need of a permit, before carrying out the activities described in this document. Depending on the specific proposals and the local geology the permit may be a standard rules permit or a bespoke permit.
What is phosphonic acid?
The phosphonic acid reacts with aluminum in clays and feldspars to form a temporary protective film, which then allows a deeper and more effective acid penetration. Phosphonic/hydrochloric acid treatment has the ability to inhibit the formation of calcium carbonate scale in the well and near well bore area.
Can phosphonic acid be used to stimulate wells?
Initial tests demonstrate that phosphonic acid/hydrochloric acid blend can be used to successfully stimulate the wells and increase production. Benefits. The program design includes the use of a chemically modified hydrochloric acid combined with phosphonic acid.
What is acidizing oil?
Acidizing in the Oil and Gas Industry. Oil and gas operators have used acid treatment (acidizing) to improve well productivity for almost 120 years. Acidizing predates all other well stimulation techniques, including hydraulic fracturing which was not developed until the late 1940s.
What is the purpose of acidizing?
The purpose of any acidizing is to improve a well’s productivity or injectivity. There are three general categories of acid treatments: acid washing; matrix acidizing; fracture acidizing. In acid washing, the objective is simply tubular and wellbore cleaning. Treatment of the formation is not intended.
What is acid washing?
Acid washing is most commonly performed with hydrochloric acid (HCl) mixtures to clean out scale (such as calcium carbonate), rust, and other debris restricting flow in the well. Matrix and fracture acidizing are both formation treatments. In matrix acidizing, the acid treatment is injected below the formation fracturing pressure.
What is the simplest acid system?
Hydrochloric acid is the simplest chlorine-based acid system containing water. It consists of hydrogen chloride and water, and a variety of other chemical species, including hydronium and chloride ions. It is an important chemical reagent and industrial chemical, used primarily in the production of polyvinyl chloride for plastic.
How much water is needed to turn hydrochloric acid into gas?
Unless pressurized or cooled, hydrochloric acid will turn into a gas if there is around 60% or less of water. Hydrochloric acid is also known as muriatic acid and hydronium chloride. About 20 million tonnes of hydrochloric acid are produced worldwide annually. It also forms naturally in gastric acid and when lava boils seawater.
Why do we acidize new wells?
Acidizing is commonly performed on new wells to maximize their initial productivity and on aging wells to restore productivity and maximize the recovery of the energy resources. Acidizing involves pumping acid into a wellbore or geologic formation that is capable of producing oil and/or gas.
What is the purpose of matrix or fracture acidizing?
The purpose of matrix or fracture acidizing is to restore or improve an oil or gas well’s productivity by dissolving material in the productive formation that is restricting flow, or to dissolve formation rock itself to enhance existing, or to create new flow paths to the wellbore.
What is acid treatment?
Acid treatment, i.e. addition of inorganic or organic acids, is used both for forage and cereal grains and results in a rapid decrease in pH , which efficiently prevents the growth of most microorganisms. Acid treatment inactivates the sprout and interferes with the baking process, and thus is not appropriate for storage of grain intended for baking or malting (Jonsson 1997 ). Acid application is a delicate process and needs to be monitored accurately as addition of the correct concentrations of acid depends on the water content of the crop ( Lacey and Magan 1991 ). Uneven distribution of acid over the kernel surface may permit mould growth during storage as inaccurate dosage of formic acid has, for example, been shown to increase the risk of aflatoxin production ( Clevstroöm et al. 1989 ). Low concentrations of propionate may also stimulate the production of aflatoxins ( Al-Hilli and Smith 1979 ).
What is acid treated starch?
In this method, a concentrated starch slurry is heated in 1 to 3% HCl at about 50°C for 12–14 hours, leading to partial acid hydrolysis of the glucosidic bonds in the amorphous portion of the starch. The crystalline areas are not freely accessible to the acid and remain intact. After neutralization and recovery by filtration, the modified starch, with a lower molecular weight but with its crystalline structure intact, displays different characteristics on heating it in water. The granules fragment more and swell less, and the temperature range of gelatinization increases and, on gelatinization, the starch becomes soluble. The resulting paste is less viscous and the gels are more rigid. Acid-modified starches are used in jelly beans and other gum confectioneries.
Does acid treatment cause DNA to turn red?
Acid treatment, even if mild, brings about at least partial apurinization of DNA and thus changes its stainability by AO. As a result, AO forms dimers at depurinized regions, thus causing the DNA red fluorescence. This makes it necessary to avoid the presence of acids in fixatives used for AO conventional fluorescence microscopy of nucleic acids. At the same time it opens up important possibilities for the investigation of the DNA state in situ.
What is acidizing oil?
What Is Acidizing? In the oil and gas extraction industry, acidizing is a technique used to extend the useful life of an oil and gas well. The process of acidizing involves pumping acid into the well in order to dissolve the rocks that line the contours of the well.
Why is acidizing used in oil wells?
Indeed, because it is a relatively expensive process to employ , acidizing will only be used once simpler methods, such as primary recovery techniques, have been fully utilized.
What is the process of acidizing a well?
The process of acidizing involves pumping acid into the well in order to dissolve the rocks that line the contours of the well . The acidizing process is less heavily regulated than other oil and gas extraction techniques.
How does acidizing a well help?
An additional benefit of acidizing a well is that it can help dissolve any loose debris found in the well .
How long has acidizing been used?
According to the American Petroleum Institute, the basic practice of acidizing has been widespread for nearly 120 years. In the 1930s, its popularity waned as a result of the damage it could do to the steel linings of the wells.
Is acidizing more effective than hydraulic fracturing?
Acidizing may be more useful than hydraulic fracturing in some situations. Hydraulic fracturing–also called fracking–is a process that creates channels in underground rock formations by injecting a mixture of water and fracking chemicals into the well at very high pressures.
Is acidizing a chemical process?
The types and concentrations of acids used in the acidizing process are often not disclosed by the companies that manufacture them , although hydrochloric and hydrofluoric acids have been known to be used. Because of this ambiguity, it can be difficult to accurately assess the safety and environmental risks associated with the practice.
Injection-rate control and monitoring
The main acid job should be circulated in place with HCl acid placed across the formation before the packer is set or before the bypass valve is closed. All perforations should be covered by acid before injection starts. Injection should start at a predetermined injection rate and the pressure observed to determine the condition of the wellbore.
Pressure behavior during acid injection
Two pressure responses are often observed during acid treatment. Fig. 1 shows one response. In this well, when acid hit the formation, pressure dropped immediately. As the pressure dropped, the rate was increased; then the pressure began to rise. The rate was reduced, and then the well was shut in while another batch of acid was mixed on site.
On-site evaluation of acid treatment effectiveness
The pressure and rate chart of the acid treatment show the effect of acid volume on the formation as the acid treatment proceeds. The papers of McLeod and Coulter, Paccaloni et al., and Prouvost and Economides are significant to the on-site evaluation of acidizing treatments.
Spent acid production control
The well should be produced first at the same rate before acidizing. As soon as the well has cleaned up and all spent acid has been recovered or reduced to zero water cut, the producing rate may be increased. In formations with moveable fines, the rate should be increased once each week to finally reach the optimum producing rate for that well.
Produced fluid sampling
Spent acid samples should be collected at the surface to properly analyze the response of the well to the acid treatment. These samples should be analyzed for pH immediately and kept in airtight containers for chemical analysis.
Noteworthy papers in OnePetro
Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read
External links
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro
