FR2617900A1 - PROCESS FOR ASSISTED RECOVERY OF HYDROCARBONS IN A GEOLOGICAL FORMATION COMPRISING SILICON - Google Patents

Abstract

A process for the enhanced recovery of hydrocarbons in a geological formation containing silicon is described. According to the invention, is injected from at least one injection well to at least one production well, a solution of alkaline agents which contains at least one soluble compound containing aluminum ions under conditions such that reduces the formation of silicon in the formation. The formation is swept away by the solution and at least part of the solution and of the hydrocarbons which are separated are recovered.

Description

The invention relates to a method of assisted recovery of the

  oil in a sandstone geological formation containing hydro-

  carbides. More particularly, the method makes it possible to improve the conditions of transport and propagation of the alkaline agent solutions from the injection wells to the production wells at the time of placing.

  chemically assisted recovery methods.

  The alkaline agents employed in enhanced oil recovery may be injected alone to reduce the water-oil interfacial tension by reaction with certain heavy constituents of the crude; in admixture with polymers which provide the mobility control, to improve the recovery efficiency and to carry out the process under conditions where the retention of the polymers is reduced; in admixture with polymers and surfactants to reduce interfacial tension, control mobility and effect the process under conditions where retention of surfactants is reduced. One of the technical problems posed by the employment of agents

  alkali is to ensure their transport in the formation of the oil well.

  5 jection to the production well. In fact, the alkaline agent reacts with the constituent minerals of the sandstone rocks: quartz, silica,

  clays, feldspars, by ion exchange and dissolving processes.

  lution, which give rise to the passage in solution of chemical elements from the minerals of the reservoir. This results in a consumption of NO the alkaline agent, which opposes the spread of the pH front and reduces

the effectiveness of the alkaline agent.

  An object of the invention is therefore to reduce the consumption of

  the alkaline agent to be introduced into the hydrocarbon reservoir

  the dissolution of mineral species of the formation into the solu-

  alkali agents to sweep the formation;

  this improves the economy of the process.

  More particularly, the invention responds to the problems posed by proposing a method for enhanced hydrocarbon recovery in a

  geological formation containing silicon and containing hydrocarbons

  which is injected from at least one injection well

  to at least one production well, a solution of alkaline agents, the formation is swept away by said solution and at least a part of the solution and the hydrocarbons which are separated off are recovered. The process is characterized in that the said solution, which contains at least one soluble compound containing aluminum ions, is introduced into the formation under conditions such that the dissolution in solution is reduced.

silicon of said formation.

  The invention thus described has the advantage of reducing the consumption of the alkaline agent sweeping the formation and to render

  thus the more economical process.

  The alkaline agents thus injected, preferably in aqueous solution, may be sodium, potassium or ammonium carbonates or bicarbonates, sodium, potassium or ammonium silicates, sodium hydroxide, potassium hydroxide or potassium hydroxide. ammonia and their mixtures. Monovalent metal compounds are preferred. Preferably,

  it is sodium carbonate that will be used.

  Likewise, it will be preferred to use sodium silicate. However, depending on the geological or mineralogical environment, we can

use other alkaline cations.

  The aluminum compound may be in the form of a salt of a monovalent anion such as a halogenide and advantageously fluoride, chloride, bromide and iodide, hydroxide, nitrate, or a polyvalent anion such as monomeric or double (bimetallic) sulphate

  as aluminum sulphate and ammonium, potassium or sodium.

  Among the metal compounds of organic acids, mention may be made of monovalent anion salts such as acetate or polyvalents

like tartrate or citrate.

  It is preferable to introduce aluminum into the agent solution

  alkali in the form of sodium, potassium or ammonium aluminate

  nium, which will only slightly modify the initial pH of

the solution.

  Without being bound by any theory, it may be thought that the adsorption on the surface of the siliceous minerals of charged aluminous species exerting a repulsive force on the hydroxyl ions of the sizzling rock would thus block the mechanisms of ion exchange and of dissolution. The process would also reduce the precipitation of mineral species that could occur during prolonged contact of alkaline solutions with the siliceous geological formation and

  which could lead to permeability reductions.

  The efficiency of the process according to the invention is a function of

  0 operating conditions and more particularly pH, temperature and

  ture and aluminum concentration in the alkaline solution. For example, the mixture of said solution and a metal compound having a pH of at least about 10 is injected into the silicon-containing formation which is at a temperature of about 20 ° C. to 100 ° C. The best results are obtained when the temperature is between about 20 and 50 ° C and preferably between about 25 and 45 ° C, and when the pH of the alkaline solution is between about 10 and 14 and preferably between about

11 and 12.

  The aluminum compound introduced into the injected alkaline solution is generally at a concentration of about

  ppm (5 x 10-6) and 5% by weight expressed as aluminum metal and

  Preferably, the concentration of the alkaline agent in the solution is usually from about 0.1 to 10% by weight and preferably from 0.2 to 10% by weight.

2% by weight

  According to a first mode of use of the method similar to the so-called alkaline agent injection (caustic flooding) technique, it is possible to inject into the formation the alkaline agent solution with the compound

  of metal then sweep the formation with said solution.

  According to another mode of use, it is possible to inject into the geological formation the above mixture, incorporated in a solution of

  surfactant, co-surfactant and / or polymer and then sweep away the

  by the new mixture thus obtained.

  According to another mode of use, it is also possible to inject a mixture of the alkaline agent solution with the metal compound into the formation according to a preflush technique and to sweep said formation with a solution of surfactant, co-surfactant

and / or polymer.

  In all the described modes of use, the injected fluids

  will be pushed into the formation by water containing or not a poly-

  mother following the usual techniques of oil recovery.

  The surfactants, co-surfactants and / or injected polymers are for example described in U.S. Pat. Nos. 3, 202, 711 and 3,

811, 505.

  For these various modes of use, the volume injected into the formation of each solution whose composition is defined above, for example the mixture of the solution of alkaline agent and of aluminum compound or said mixture with the surfactant solution. active, co-surfactant and / or polymer, is generally between 0.1 and 1 pore volume and preferably between 0.2 and 0.5 pore volume. This volume is obviously a function of the mineralogy, the

  tank temperature, the pH of the water in place and the concentration

  introduced metallic species, as well as the concentration of

  surfactant, co-surfactant and / or polymer.

  As a general rule, at the end of the sweep, at least one production well, a solution comprising at least part of the introduced agents and hydrocarbons which are separated by the

  techniques known to those skilled in the art.

  The following examples illustrate the process according to the invention.

Example 1

  A natural sand of Entraigues (France) containing 98.7% by weight of silica and having a particle size of between approximately 50 and 150 microns is contacted at 30 ° C. in a closed system with an aqueous solution of sodium carbonate (1% by weight). ) in a solid-liquid mass ratio of about 1.2. The pH is adjusted by adding iN sodium hydroxide. Depending on the pH value and the time, the influence of the added aluminum content is studied on the consumption of alkaline agent, which is measured by the determination of the solubilized mineral concentration, for example silicon, present initially in

rocky rock.

  Aluminum sulphate is then introduced into the sodium carbonate solution and the pH is adjusted to the desired value (pH = 11.5 measured at 20 ° C.) by additional addition of sodium hydroxide.

  The results are shown in Table 1 below.

Table 1

  Solubilized Silicum (ppm) Time pH 11.5 pH 12.9 days A1 - 0 A1 - A1 - A1 A1 - A1 = ppm 100 ppm 50 ppm 100 tpe

1 33.6 6.4 4.8 39.4 21.9 17.1

3 62.9 11.1 8.3 83.2 41 34.9

15 124 14.5 8.2 210.5 111 90

  The dissolution of silicon is less and therefore the consumption of alkaline agent lower, when operating in the presence of an initial concentration of aluminum in the alkaline agent solution and the effect is even stronger than the concentration of

aluminum is high.

Example 2

  Example 2 is carried out under the same conditions as those of Example 1, except that the sodium carbonate is replaced by sodium hydroxide (0.5% by weight). After addition of aluminum sulphate, one adjusts

  the pH is about 12.9 by additional addition of sodium hydroxide.

  The results are shown in Table 1.

Example 3

  We want to show the influence of aluminum concentration on

  the dissolution of another mineral such as kaolinite.

  A Charentes kaolin containing 86.2% kaolinite, 6.5% muscovite and 3% quartz is contacted in a closed system with a solution of sodium carbonate (0.5% by weight), the temperature of which is adjusted. pH with IN sodium hydroxide at 11.4. The solid / liquid mass ratio is

0.1.

  This solution contains or does not initially contain aluminum in the form of aluminum sulphate. The pH is in all cases adjusted to 11.4 with iN sodium hydroxide. The solubilized silicon concentration after 24 hours of contact time at a temperature of 30 C is given in

Table 2 below.

Table 2

  Al concentration Initial Si concentration (ppm) in solution (ppm)

0O 10.8

43 2.6

109 0.8

Example 4

  at). EXPERIMENT: An alkaline solution comprising 1% sodium carbonate was circulated in a clayey porous rock containing 5% of kaolin until the steady state was reached. The temperature is approximately 45 ° C. The pH is fixed at a value of 11.5 (measured at 20 ° C.) by controlling the content of

  sodium carbonate introduced into the solution.

  At the outlet of the rock, the concentration of solubilized silicon in a stationary state is followed by the alkaline solution.

  silicon concentration is about 31 ppm.

  b). Experiment b A second experiment identical to the previous one is carried out except that 100 ppm of aluminum introduced in the form of sodium aluminate is added to the sodium carbonate solution. The pH remains substantially unchanged. The silicon concentration solubilized when

  the steady state is reached is equal to about 12 ppm.

  EXAMPLE 5 Example 5 is carried out under the same conditions as in Example 1, except that the sodium carbonate is replaced by

  sodium silicate. Under the same pH conditions, we obtain sensi-

  the same results as those presented in Table 1.

Example 6

  Example 6 is carried out under the same conditions as in Example 1, except that the aluminum sulphate is replaced by aluminum tartrate. The results obtained at substantially identical pH

  are substantially the same as those of Example 1.

Claims (8)

claims   1- Process for the enhanced recovery of hydrocarbons in a geological formation containing silicon and containing hydrocarbons, in which at least one injection well is injected   to at least one production well, a solution of alkaline agents   In this way, the formation is swept away by said solution and at least a part of the solution and the hydrocarbons which are separated off are recovered, characterized in that the said solution, which contains at least one soluble compound containing aluminum ions in such conditions that   reduces the dissolution of the silicon of said formation.   2 - Process according to claim 1 wherein the aluminum compound   is chosen from halides, hydroxide, nitrate, monometallic or bimetallic sulphates, acetate,   mono- or bimetallic citrate, mono- or bimetallic tartrate.   3 - Process according to claim 1 wherein the aluminum compound is a sodium aluminate.   4 -Procédé according to one of claims 1 to 3 wherein the agents   alkalis are selected from sodium, potassium and ammonium carbonates or bicarbonates, sodium, potassium and ammonium silicates, sodium hydroxide, ammonia, and mixtures thereof.   - Method according to one of claims 1 to 4 in which one injects   said solution in the formation which is at a temperature between about 20 and 100 C. 2617900-   6 - Process according to claim 5 wherein the temperature of the formation is between about 20 and 50 C, preferably   between 25 and 45 C, and the pH of the alkaline solution   line is between about 10 and 14 and preferably between about 11 and 12.   7 - Process according to one of claims 1 to 6 wherein the compound   aluminum is at a concentration of between about 5 ppm and% by weight expressed as metal.   8 - Process according to one of claims 1 to 7 wherein the agent   alkali is at a concentration of about 0.1 to 10% by weight in said solution.   9 - Process according to one of claims 1 to 8 in which one injects   in the formation of said solution of alkaline agent and metal alone and said formation is scanned with said solution, either   said solution with a solution of surfactant, co-surfactant   active, and / or polymer and said formation is scanned with said solution and the solution of surfactant, co-surfactant and / or polymer, either said solution alone (preflush) and one   sweeps said formation with a solution of surfactant, co- surfactant and / or polymer.   - Method according to one of claims 1 to 9 wherein is injected   in the formation a volume of said solution corresponding to 0.1   at 1 pore volume of said formation.