HK1166342A - Organic salts for reducing rock permeabilities - Google Patents

Description

Organic salts for reducing rock permeability

The present invention relates to the use of free aromatic acids with specific characteristics for influencing a rock formation in a process for producing mineral oil or natural gas.

In the production of subterranean mineral oil and/or natural gas deposits, water is often also flushed from subterranean formations in addition to producing the desired hydrocarbon products. In general, degrees of hydration of up to 95% water content can occur. In these cases, the concomitantly withdrawn water must be separated from the fossil fraction in a complicated manner after leaving the well and then be treated or reinjected.

For the above reasons, the mineral oil and natural gas industry has understandably focused on keeping the so-called formation water flow into the production wells as low as possible. In this case, experiments were also carried out, inter alia, with the aid of polymer systems to suppress the undesirable flow of water from subterranean formations into mineral oil or natural gas production streams.

For example, US 4,617,132 describes a method of affecting the permeability of a subterranean formation bearing hydrocarbons. For this purpose, an aqueous mixture is introduced into the underground formation, which contains, in particular, water-soluble anionic polymers having a molecular weight of > 100000. The anionic polymer is then contacted with a water-soluble cationic polymer to effect stabilization. Polyvalent metal cations and a blocking anion, such as acetate, nitrilotriacetate, tetracitrate and phosphate, are used herein. After these polymer systems are forced into the rock pores, they form gels that reduce the undesirable flow of water further into the well due to the effects of temperature.

US 5,789,350 and WO 82/02052 also describe gel systems consisting of polycarboxylates and multivalent salts as crosslinkers. According to the us patent, the gel-forming composition comprises a polymer (e.g. a carboxylate-containing polymer) and-as a crosslinker component-a polyvalent metal (e.g. zirconium) in addition to a pH-lowering agent (e.g. carbon dioxide). Such compositions are made by combining the polymer with a metal compound and then introducing carbon dioxide. Also by using such compositions, it is said that the permeability of subterranean formations can be targeted through the formation of gels in areas with high water flow. Likewise, said international patent application describes water-soluble crosslinkable polymer compositions and their use in subterranean formations: wherein said crosslinkable water-soluble polymer composition comprises a polymer having at least 2 acylaminocarbonyl groups in the molecule and a compound having at least 2 formylamido groups in the molecule. The amido carbonyl group and the formylamido group react in the presence of an acid to form a bridging moiety, which results in crosslinking.

In the present case, the polymer composition is used in so-called fracture acidizing (fracturaciding), which is a pressure acidizing process. For stimulation of wells in order to increase the production of mineral oil or natural gas in subterranean rock formations, such pressure acidizing is often used in connection with carbonate rock formations, embodied, for example, as limestone, dolomite or other reservoir rock containing limestone-like materials. Typically, acidification is carried out in this way: aqueous acid is injected into the well at a specific rate and high pressure so that, in excess of the existing formation pressure in the rock, the rock bends (yield) and in this way additional fractures (fracture) occur in the formation. Furthermore, the surface of the rock fracture is attacked by the acid. The acidizing creates channels with increased oil or gas permeability so they can flow to a greater extent into the well. Typically, a thickening or gelling agent is added to the acid used to give a larger fracture volume or a larger internal width in the fracture. Furthermore, the rate of erosion of the formation surface can be controlled by the addition of such auxiliary fluids, and the viscous acids have better transport properties than other additives, such as proppants (proppantants).

However, as for stimulation of wells using acids, so-called acid diverters (acid diverters) are also used. They are said to prevent the penetration of stronger acids used for stimulation purposes into permeable formations. For example, WO 03/093641a1 discloses a thickening acid system. The system comprises an aqueous, thickened acid composition which, in addition to the acid component, contains a gel-forming agent to which, for example, ethylene glycol as solvent and at least one amidoamine oxide are added, to obtain a viscoelastic liquid. However, in addition to the thickening system, an acid-insoluble crumb capable of sealing rock formations with larger or coarse pores may also be added to the acid. Examples of this type are described in US 3,998,272. In this case, discrete solid particles of polyvinyl acetate are used as diverting agents (diverting agents) in pressure acidizing subterranean geological formations. In view of their size, the shivering solids only penetrate into and seal the relatively porous rock formation. The narrower pores remain open so that these narrower channels can be widened by acid-induced rock hydrolysis, as occurs in conventional pressure acidizing methods.

Although various attempts have been made in the past to control or completely inhibit the flow of undesirable water into a production well, there is a need to improve upon existing methods or to provide new alternatives. In particular, it is intended to overcome the known disadvantages, such as, for example, inadequate solubility of the auxiliaries used in the hydrocarbons, in some cases the methods used and the very high costs of the auxiliaries used, inadequate reversibility of the treatment methods in the formation and inadequate selectivity of the methods, and smaller temperature limits for most known systems.

Thus, for the purposes of the present invention, the said disadvantages lead to the object of providing new chemical systems for influencing rock formations in the production of underground mineral oil and/or natural gas deposits. The new system should in particular have economic advantages, since the auxiliaries used in the production of mineral oils and natural gas are generally very important for their efficiency, but the auxiliaries themselves must only result in low procurement and application costs. Furthermore, the auxiliaries used should be substantially safe from an ecological point of view and be able to demonstrate their efficiency, in particular under conditions of high temperature and pressure and in very different rock formations.

This object is achieved by the corresponding use of free aromatic acids and/or salts thereof which contain at least two aromatic ring systems or at least two acid functions.

Surprisingly, it has been found that not only the above-mentioned disadvantages can be overcome and the stated objects achieved by using the compounds, but also the reduction of water flowing into underground mineral oil and/or natural gas deposits can be controlled in a targeted manner, in particular significantly so that no additional reactive components, such as gel formers, need to be added.

The free aromatic acid is preferably at least one member of the following series: 2-naphthoic acid, phthalic acid, isophthalic acid or terephthalic acid. By using at least one member of these four said acids or any desired mixture thereof, it is possible in particular to influence and preferably control the acid influx into the formation in a so-called acidizing treatment (pressure acidizing treatment) according to the invention. It has been found to be particularly advantageous if the acid used is insoluble in the concentrated acid of the acidification treatment.

Generally, the claimed use is independent of the specific temperature and pressure conditions; however, for influencing the acid influx into the formation during the acidizing treatment, it has proven advantageous if the temperature range is ≥ 60 ℃, the temperature ≥ 80 ℃, particularly ≥ 130 ℃ and particularly preferably ≥ 150 ℃ in comparison with the systems currently used.

Regarding the use of the invention in connection with the acidification treatment, according to the invention, the acid may be dissolved after the acidification treatment, preferably by adding an organic amine and in particular at least one member of an ethyleneamine (e.g. triethylamine, triethylenetetramine, polyethyleneimine) or an ethanolamine (e.g. triethanolamine). However, the dissolution of the acid may also be achieved by fossil materials (e.g. the crude oil itself), in particular the nitrogen-containing components present in the crude oil play a substantial role.

In addition to influencing the influx of acids, the invention also encompasses the use of free aromatic acids for reducing rock permeability and thus in particular for reducing the influx of water. Preferably, salts of said aromatic acids are suitable here, at least one member of the following series being suitable: alkali metal salts, inorganic or organic ammonium salts, and in particular compounds whose ammonium ion is part of an organic ammonium compound, for example diethylenetriamine, triethylenetetramine or tetraethylenepentamine.

In addition to the described use, the invention also comprises a method for influencing and in particular controlling the acid influx into a rock formation in the so-called acidizing treatment when producing underground mineral oil and/or natural gas deposits. In the method, at least one free aromatic acid containing at least two aromatic ring systems or at least two acid functions, in particular at least one of the series 2-naphthoic acid, phthalic acid, isophthalic acid or terephthalic acid, is pumped into the formation to be treated, with particular preference being given to adding viscosity-increasing additives, for example polymers or viscoelastic surfactants. Examples of suitable viscoelastic surfactants having ionic character are alkyl carboxylates, alkyl ether carboxylates, alkyl sulfates, alkyl ether sulfates, alkyl sulfonates, alkyl ether sulfonates, alkyl phosphates and alkyl ether phosphates. Cationic surfactants are alkyl amines, alkyl diamines, alkyl ether amines, alkyl quaternary ammonium, dialkyl quaternary ammonium and ester quaternary ammonium compounds. However, viscoelastic surfactants may also have zwitterionic or amphoteric properties. Mention may be made here of alkyl betaines, alkyl amido betaines, alkyl amidooxazolines, alkyl amino oxides and alkyl quaternary ammonium carboxylates.

Another use of the invention is in reducing rock permeability, particularly in reducing the flow of water through subterranean formations into wellbores during the production of subterranean mineral oil and/or natural gas deposits. Here, at least one salt, in particular an alkali metal salt, an ammonium salt and an organic ammonium salt, of an aromatic acid containing at least two aromatic ring systems or at least two acid functions is pumped into the formation to be treated, particularly preferably without addition of further reactive components. Herein, the acid is at least one of the series 2-naphthoic acid, phthalic acid, isophthalic acid or terephthalic acid.

In the method of the invention, a salt of an aromatic acid is pumped into the formation to be modified. By mixing the salt solution with the formation water, which typically contains relatively high valence cations, such as alkaline earth metal, aluminum or iron ions, the selected organic salts precipitate irreversibly and cannot re-enter the solution even by increasing the ambient temperature. In contrast to the polymer systems currently used, the systems of the present invention are suitable for blocking water flow into low permeability formations.

According to the invention, the use of the corresponding free acid is for controlling the flow of acid into a formation in an acidizing treatment. For this purpose, the salt solution is pumped into the formation to be treated, if appropriate with the addition of viscosity-increasing additives. In view of the viscosity of the treatment fluid, the salt solution preferably enters the portion of the formation having increased permeability. Subsequently, as soon as the hydrochloric acid, which is usually used in the acidification treatment, is injected and brought into contact with the salt solution present therein, the salts of the dissolved organic acids are protonated and precipitated. Thereby also reducing the permeability of the rock formation and additional acid cannot penetrate the rock.

As mentioned above, it has proved advantageous if the free acid corresponding to the salt is insoluble in the concentrated acid used in the pressure acidification treatment. Although the systems described so far in the literature and based on benzoic acid can be used at maximum formation temperatures up to 80 ℃ due to the low melting point of benzoic acid, the system of the invention is effective well above 150 ℃. To this end, free acid is added to the acidizing fluid in chip-like form to seal the coarse pore formation from the ingress of acid. These fines can be of a relatively wide range of particle sizes and can be 3 to 100 mesh. Preferably 8 to 12 mesh, especially 12 to 20 mesh, and the sizes need not be the same, but rather allow the sizes to cover the range in different fractions.

When the acid is used in the acidizing zone in accordance with the present invention, it is necessary in most cases to re-dissolve the free aromatic acid after the acid treatment in order to ensure free hydrocarbon discharge into the well. This dissolution is achieved according to the invention by the addition of an organic amine or by the nitrogen-containing component of the crude oil itself.

The following examples illustrate the advantages of the invention without limiting the invention.

Examples

Preparation examples:

1. 200g of terephthalic acid were suspended in 400ml of water. Thereafter, neutralization was carried out with about 115g of tetraethylenepentamine until a pH of 7 was reached.

2. 200g of isophthalic acid are suspended in 400ml of water and adjusted to a pH of 7 with about 135g of tetraethylenepentamine.

3. 200g of 2-naphthoic acid are suspended in 400ml of water and adjusted to pH 7 with about 56g of tetraethylenepentamine.

Use examples

1. Rock permeability is reduced by multivalent cations to control water entry into the well:

formation water ((4.26% CaCl) for Gildehaus sandstone, having a porosity of 20.3%, a gas permeability of 2285mD and an initial water permeability of 2043mD₂1.05% MgCl₂110ppm NaHCO₃270ppm of NaSO₄380ppm NaBO₂xH₂O) impregnation. Thereafter, the sandstone sample was treated in a Hasser cell with a 10% strength sodium terephthalate solution at a flow rate of 1 ml/h. A volume of 4ml (38% of the pore volume) was pumped in. The temperature was 50 ℃. Thereafter, the sample was treated with 2.5ml/h of formation water, the system was allowed to stand for 15 hours, and then treated with 1ml/h of formation water. Thereafter, formation water was injected alternately with saline solution at a flow rate of 1ml/h and then treated with 1 pore volume of the saline solution described in preparative example 1. The water permeability of the rock is reduced by 78%.

2. Precipitation by addition of acid to control acid influx into the formation during acidizing:

the concentrated hydrochloric acid solution was added to the salt solutions prepared according to preparation examples 1 to 3. Thereby precipitating all three compounds. The suspension was heated to 90 ℃ to determine whether the precipitated organic acid entered the solution again. No significant dissolution of the free acid at this temperature could be observed.

3. Dissolution of the free acid by washing with organic amine:

40g of concentrated hydrochloric acid were added to 20g of the amine salt obtained according to preparation example 2. The precipitated free acid was washed with water and then suspended in 100ml of water. 20g of tetraethylenepentamine are added and then stirred for 20 minutes at 60 ℃. The precipitate was completely dissolved.

Claims (11)

1. Use of a free aromatic acid and/or salts thereof containing at least two aromatic ring systems or at least two acid functions for influencing a rock formation in the production of underground mineral oil and/or natural gas deposits.

2. Use according to claim 1, characterized in that the free acid is at least one of the series 2-naphthoic acid, phthalic acid, isophthalic acid or terephthalic acid.

3. Use according to claim 2 for influencing and especially controlling the acid influx into a formation in a so-called acidizing treatment.

4. Use according to claim 3, characterized in that the acid is insoluble in the concentrated acid used for the acidification treatment.

5. Use according to any one of claims 3 and 4, in a temperature range of 60 ℃ or more, preferably 80 ℃ or more, in particular 130 ℃ or more and particularly preferably 150 ℃ or more.

6. Use according to any of claims 3 to 5, characterized in that the acid is dissolved after the acid treatment, preferably by adding an organic amine and in particular at least one of an ethylene amine such as triethylamine, triethylene tetramine, triethylene pentamine, polyethylene imine or an ethanolamine such as triethanolamine.

7. Use according to claim 1 for reducing the permeability of rock and in particular for reducing the inflow of water.

8. Use according to any one of claims 1 and 7, characterized in that said salt is at least one member of the following series: alkali metal salts, inorganic or organic ammonium salts, and in particular compounds whose ammonium ion is part of an organic ammonium compound, for example diethylenetriamine, triethylenetetramine or tetraethylenepentamine.

9. Method for influencing and in particular controlling the acid influx into a rock formation in a so-called acidizing treatment when producing underground mineral oil and/or natural gas deposits, characterized in that at least one free aromatic acid containing at least two aromatic ring systems or at least two acid functions, in particular at least one of 2-naphthoic acid, phthalic acid, isophthalic acid or terephthalic acid, is pumped into the rock formation to be treated, particularly preferably with the addition of viscosity-increasing additives, such as polymers or viscoelastic surfactants.

10. Method for reducing rock permeability and in particular for reducing water influx into subterranean formations during the production of subterranean mineral oil and/or natural gas deposits, characterized in that at least one salt, in particular an alkali metal, ammonium or organic ammonium salt, of an aromatic acid containing at least two aromatic ring systems or at least two acid functions is pumped into the formation to be treated, particularly preferably without addition of further reactive components.

11. A process according to claim 10, characterized in that the acid is at least one of the series 2-naphthoic acid, phthalic acid, isophthalic acid or terephthalic acid.