MXPA04011833A - Chemical composition for stabilizing clay minerals and process for applying the same. - Google Patents

Abstract

The present invention is related to a chemical composition for stabilizing the most hydratable clay minerals contained in oil field rocks. The addition of said chemical composition into the injection guide, for an oil secondary recovery in a field, prevents rock minerals from swelling, and pores from blocking which would reduce the fluids conduction capacity. The effectiveness of the chemical composition is based on occupying the free valences of the most problematic minerals, the composition being useful in processes where water is brought into contact with field rocks, such as: recovery of hydrocarbons by water injection, hydraulic breakage, and well perforation provided that the mud is water-based.

Description

CHEMICAL COMPOSITION STABILIZER OF CLAY MINERALS AND APPLICATION PROCEDURE DESCRIPTION TECHNICAL FIELD OF THE INVENTION The present invention relates to a stabilizing chemical composition of clay minerals and application procedure, which functions as an additive to inhibit the hydration of clays present in the rock when secondary recovery is implemented by water injection in an oil field. It also has application in processes that involve the passage of a water-based fluid through the rock, such as hydraulic fracturing and the drilling of oil wells.

BACKGROUND OF THE INVENTION After the primary recovery in the oil fields, the injection of water for the recovery of the oil of the remaining oil is one of the most used techniques worldwide due to the ease in the handling of this fluid and the economic advantages that the implementation means. The formations that have a certain content of clays present a serious problem of diminution of the permeability (capacity of conduction of fluids), when the clay minerals are hydrated and plug the pores of the rock.

For more than 70 years, the world oil industry has found in water injection, an efficient and economical method for the secondary recovery of oil oil remaining. However, when the content of clays in rocks is important, a problem of decreased permeability arises. This problem has tried to be solved by adding to the injection water different chemical substances that react with the clays, either immediately that they come in contact with them or generating in the deposit, polymers that stabilize the clays.

Among the substances that are added to water for the secondary recovery of the oil of the remaining oil are the following: KCI (Ref. 2), NaCl (Ref. 4), KOH (Ref.3), Na2C03 (Ref. 3), NaOH (Ref. 3), NH4CI (Ref. 2), AICI3 (Ref. 1, 5), zirconium oxychloride (Ref. 2), quaternary amino-polymers (Ref. 3), and salts of amines (Ref. 3) . The first seven compounds have the disadvantage of being inefficient and the remaining three are of high cost. In the case of aluminum chloride and polymeric solutions, the disadvantage is that high molecular weight compounds are formed that clog the pores and accentuate the problem they are trying to solve.

Among the documents reported in terms of the state of the art that are related to the present invention, there is US patent 5,342,530 called "Clay Stabilizer" of grant date of August 30, 1994, which focuses on the stimulation of wells and hydraulic fracturing, which involves clearing the vicinity of the well and creating fractures by dissolving the cement from the rock. Hydraulic fracturing is defined as the application of pressure by a fluid to create fractures within the rock of a reservoir. The experimentation that supports the validity of patented clay stabilizer compounds was performed using only bentonite, considered a clay mineral from the smectite and montmorillonite group, and ignores the remaining groups of clay minerals that may be present in a rock of a deposit , namely: illite, chlorite and kaolinite. In addition, bentonite in general is not present in the rocks of a deposit.

The British patent GB 2058889 called "Process for recovery of oil from subterranean reservoirs", of concession date of April 15, 1981, refers to the addition of a polymer to the injection water, which causes it to thicken and the Sweep the hydrocarbons within the reservoir more efficiently. The patent does not refer to the presence of clay minerals in the deposit.

All the above references are overcome by the stabilizing chemical composition of clay minerals of the present invention, since, in different experiments it has been shown to be a good option to stabilize clay minerals, to avoid hydration in the reaction with water molecules and that blockages occur in the pores of the rock when the secondary recovery is created by injection of water from an oilfield.

Therefore, an objective of the present invention is to obtain a stabilizing chemical composition of clay minerals that prevents the water molecules from reacting with consequent plugging in the pores of the rock, when the secondary recovery is implemented by injection of water to a Oilfield.

Yet another objective of the present invention is to provide a method for evaluating the effectiveness of the chemical composition for stabilizing the clay minerals present in the rocks of an oil field in the range of pressures and temperatures between the atmospheric conditions and those of the reservoir.

Still further, another objective of the present invention is to use it in the stimulation of wells and hydraulic fracturing in intervals of 1 to 70% by weight of MgCl 2, 0.1 to 25% by weight of an inorganic acid (HCI and / or HF) and 2 to 95% weight of bidistilled water.

References: 1. Reed, MG: Stabilization of formation clays with hydroxy-aluminum solutions ", JPT, July, 1972. 2. Hill, DG" Clay stabilization-criteria for best performance ", SPE paper 10656, Formation damage control symposium, Lafayette, LA, March 24-25, 19823. Norman, C. A, and Smith, J. E .: Experience gained from 318 injection well KOH Clay stabilization treatments. SPE paper 60307, 2000 Rocky Mountain Regional / Low permeability Reservoirs Symposium, Denver, CO, 12-15 March 2000. 4. Gdansky, R .: "High pH clay instability rating" SPE paper 73730, 2002 International Symposium and Exhibition on formation damage control, Lafayette, LA, 20-21 February 2002. 5. Coppel, CP, Jennings Jr., HY: "Field results from wells treated with hydroxyl-aluminum" J. Pet. Tech., September 1973.

BRIEF DESCRIPTION OF THE FIGURES The figures that accompany the present invention are described below to have a better understanding of it, without limiting its scope.

Figure 1 shows the behavior of the pressure to the injection of hexane in sample 1, at pressure and laboratory temperature.

Figure 2 shows the behavior of the pressure to the injection of distilled water in sample 1, under pressure and laboratory temperature.

Figure 3 indicates the behavior of the pressure in sample 1 when the chemical composition object of this invention, called Clayst2, is injected at pressure and laboratory temperature.

Figure 4 shows the behavior of the pressure to the injection of hexane to determine the absolute permeability in sample 2, to reservoir conditions.

Figure 5 shows the behavior of the pressure to the injection of distilled water to determine the absolute permeability in sample 2, at reservoir conditions.

Figure 6 indicates the behavior of the injection pressure of the Clayst2 composition to determine the absolute permeability in sample 2, at reservoir conditions.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stabilizing chemical composition of clay minerals and application method, the chemical composition is a chemical solution which is also called as CLAYST2 stabilizer solution object of the present invention. For the preparation of the CLAYST2 solution, it requires the proper handling of certain equipment and laboratory materials such as: Scales, agitators with rpm meter (revolutions per minute), pH meters, pipettes, burettes and clock glasses.

The preparation of the chemical composition is carried out in the following manner: The amount of stabilizing composition that is required is chosen, taking as a basis for calculation one liter. The composition is prepared with distilled water as a solvent and magnesium chloride hydrated as a solute. The percentage by weight of solute suitable for the proper functioning of the composition is between 0.1 to 60% depending on the content of clay minerals present in the rock. The magnesium chloride to which this composition refers is hexahydrate, although experimentation was carried out with anhydrous magnesium chloride, obtaining results similar to those of magnesium hexahydrate.

Method of preparation of the CLAYST2 stabilizer composition: 1. The amount (between 0.1 to 60% by weight) of magnesium chloride to be added to the solvent is weighed on the analytical balance. 2. Prepare the volume of distilled water that together with the inorganic acid and magnesium chloride complete 1 liter. 3. Hydrochloric acid and / or hydrofluoric acid in a concentration between 0.1 and 20% weight is added to the water. 4. The magnesium chloride is slowly added to the solvent, then the solution is placed on a shaker at 1000 rpm for approximately 5 minutes. 5. Remove from the agitator.

The solution obtained is transparent, acid pH, between 4.5 and 6.

To test the effectiveness of the stabilizing solution of clay minerals, displacement tests were performed using rocks from oil fields whose clays content is less than 10%, as shown in table 1.

Rock Sample No. 1. The main petrophysical characteristics of this rock sample are the following: length, 3.23 cm; diameter, 3.83 cm; and porosity, 10.27%. Porosity is the quotient of the volume of pores between the total volume of the rock and this property is not necessarily proportional to the permeability. Permeability, as mentioned above, is the ease that a rock has to allow the passage of fluids through it and is calculated through the Darcy equation, given as follows: μL Where: q = injection expense in cm3 / s. A = area of the rock transverse to the direction of flow (cm2). Ap = pressure difference between the input and the output of the sample (atm). μ = viscosity of the fluid (centipoise). L = length of the sample (cm).

Table 1. Mineralogical composition of sample 1.

In table I it can be seen that the clay minerals of rock sample 1 is 2.8% by weight of kaolinite and 1.6% by weight of illite.

To test the effectiveness of the chemical composition developed to inhibit the effect of the "swelling" or hydration of the clays, the following experimental methodology was used: Reference permeability is established with the use of hexane and then the influence of the distilled water is compared. the Clayst2 solution on this property of the rock. This simulates in physical form what would happen if a distilled water or Clayst2 solution were injected into a reservoir to displace the remaining hydrocarbons after primary exploitation. The experimental methodology consists of the following steps: 1 . Wash the sample to eliminate the hydrocarbon residues. 2. Saturate the 100% rock sample with hexane and displace this fluid at different injection costs, which is a compound that does not hydrate the clays and that will be considered as a reference for the permeability of the rock to a liquid. 3. For each injection expense, move the necessary volume so that the pressure difference between the input and the output of the sample is constant. 4. Calculate permeability using Darcy's Law for each of the injection costs used. 5. Dry the sample in an oven at a temperature of 100 ° C to evaporate the hexane contained in the sample. At room temperature the boiling point of hexane is 69 ° C. 6. Saturate the sample 100% with distilled water and move this liquid to different injection costs to observe the influence of this polar fluid (with positive charge on one side of the molecule and negative charge on the opposite side) on the clays of the rock. 7. For each injection expense, displace the necessary volume so that the pressure difference between the input and the output of the sample is constant. 8. Calculate permeability using Darcy's Law for each of the injection costs used. 9. Dry the sample in an oven at a temperature of 100 ° C to evaporate the distilled water contained in the sample. 10. Saturate the 100% sample with the Clayst2 solution and displace this fluid at different injection costs to observe the effect of the formulation on the permeability of the sample. 1 1. For each injection expense, move the necessary volume so that the pressure difference between the inlet and the outlet of the sample is constant. 12. Calculate permeability using Darcy's Law for each of the injection costs used. 13. Compare the permeability values obtained for each of the fluids injected into the rock sample.

To show the effectiveness of the clay mineral stabilizer composition, steps 1 to 13 should be followed using low temperature and pressure (referred to as "laboratory" in this invention and then repeat all steps using reservoir pressure and temperature values.

The initial test to sample 1 was the determination of absolute permeability using hexane as fluid. The results obtained are shown in Table 2, where little variation in permeability values is observed (the milli-Darcy is one thousandth of 1 Darcy). All the tests performed in this sample were at a constant temperature of 38 ° C.

Table. 2. Determination of absolute permeability for sample 1, by displacement of hexane 3-1-h Tajin 351.

The behavior of the pressure for this test is presented in Fig. 1. The objective in each of the injection tests performed is to stabilize the pressure differential, only in these conditions is the Law of Darcy and in addition, The fact that the pressure difference between the entrance and the exit of the sample is constant indicates that there are no blockages of any kind inside the rock, that the flow is stable. As can be seen in the Fig. 1 After drying the sample to eliminate the remaining hexane in it, he was subjected to an injection of distilled water and the pressure behavior for the two expenses used (20 and 50 ml / hr) was quite acceptable, as can be seen in Fig. 2. Table 3 shows the result obtained for the permeability applying Eq. (1).

Figure 2 shows the behavior of the pressure obtained with the injection of distilled water, where it is observed that the pressure between the entry and exit of the sample was constant for the two expenses used.

Table 3. Determination of absolute permeability for sample 1, by displacement of distilled water.

After the previous tests in which the permeability of the sample with hexane and distilled water was defined, the clayst2 clay stabilizer solution was now used as the injection fluid. With this solution was also carried out the measurement of permeability using Eq. (1), the results obtained are shown in Table 4.

Table. 4. Determination of absolute permeability for sample 1 by displacing the Clayst2 solution.

As you can clearly see, in this test with sample 1 displacing the Clayst2 solution presents an increase in its permeability, ie, a positive effect of the permeability with the solution was presented.

Sample 2. This sample has the following petrophysical properties: Length :, 4.8 cm; diameter: 3.8 cm; and porosity, 10.4%. Table 5 shows the mineralogical composition of the sample, where once again, clay minerals are observed (kaolinite) Table 5. Mineralogical composition of sample 2.

Compound% Calcite 70.66 Quartz 19.78 Dolomite 4.55 Albite 3.16 Kaolinite 1.86 The initial test for this sample was the determination of absolute permeability using hexane as a fluid. All tests performed on this fragment were made at a temperature of 80 ° C and at 2700 psi confining pressure. The results obtained in the initial test for the determination of permeability to hexane are shown in Table 6.

Table. 6. Determination of absolute permeability for sample 2, by displacing hexane.

As can be seen, the permeability values obtained for the three costs of hexane injection to this sample are very similar. In the graph of the pressure behavior shown in Fig. 4, a well-defined pressure stability can be observed for the three different expenses.

After a drying process to extract the hexane by drying in an oven at 100 ° C, the sample was subjected to an injection test of distilled water. In Table 7 the results obtained for permeability are presented.

Table. 7. Determination of absolute permeability for sample 2 by displacement of distilled water.

As can be seen, the permeability values present a reduction compared to those obtained by the use of hexane. This can be attributed to the polar nature of the water molecule, which concentrates the positive charge on one end and the negative charge on the opposite end. The behavior of the pressure is shown in the graph of Fig. 5.

After drying the sample again in the oven to evaporate the water present in the pores, another injection test was carried out but now using the Clayst2 solution. The values obtained for the permeability are presented in Table 8.

Table 8. Determination of absolute permeability for sample 2 by displacing the Clayst2 solution.

As can be seen, from the test with injection of distilled water to the test with injection of the Clayst2 solution there is an increase in the permeability value, that is, as in the case of sample 1, in the injection change of distilled water to Clayst2 solution, there is an increase in permeability. The graph of Fig. 6 shows the last hours (when the pressure has stabilized) of the pressure behavior in this test. A better behavior of the pressure differential can be observed than in the case of distilled water injection.

It is considered that in achieving to maintain the permeability of a clay rock, the solution object of this invention can also be injected for the purposes of hydraulic fracturing and drilling wells (in the case that the sludge is water-based).

Claims (3)

CLAIMS Having described the present invention, it is considered as a novelty and therefore the content of the following clauses is claimed as property:

1. A stabilizing chemical composition of clay minerals, characterized in that it is constituted from 0.1 to 60% by weight of MgCl2, 0.1 to 20% by weight of an inorganic acid such as HCI and / or HF and 2 to 98% by weight of bidistilled or distilled water.

2. A chemical stabilizer composition of clay minerals, characterized in that it is used in well stimulation and hydraulic fracturing in intervals of 1 to 70% by weight of MgCl 2, 0.1 to 25% by weight of an inorganic acid, such as HCI and / or HF, and 2 to 95% weight of bidistilled or distilled water.

3. The procedure for evaluating the chemical stabilizer composition of clay minerals consists of two steps: 1) Evaluate the variation of permeability at low pressure and low temperature (laboratory conditions), 2) Evaluate the variation of the permeability to pressure and temperature of the deposit. For the case in which this patent is reported, a pressure of 2700 Ib / in2g and a temperature of 80 ° C was used. The procedure for the application of the stabilizing chemical composition of clay minerals, in accordance with clause 1 to 3, characterized in that in order to be carried out, the injection is considered in the following cases: hexane, distilled water and the Clayst2 composition. After starting the injection, wait for the pressure to stabilize with each of the fluids A stabilizing chemical composition of clay minerals and application procedure in accordance with clauses 1 to 4, characterized because it turns out to be a good option to stabilize clay minerals, prevent them from hydrating in the reaction with water molecules and clogging occurs in the pores of the rock when the secondary recovery is implemented by injection of water from an oil field.