Process to produce oil or gas from a subterranean formation using a chelating agent

Abstract

A two-step process to produce oil or gas from a subterranean formation wherein in a first step the subterranean formation is treated with an aqueous composition containing a chelating agent selected from the group of glutamic acid N,N-diacetic acid or a salt thereof (GLDA), aspartic acid N,N-diacetic acid or a salt thereof (ASDA), methylglycine N,N-diacetic acid or a salt thereof (MGDA), and N-hydroxyethyl ethylenediamine N,N′,N′-triacetic acid or a salt thereof (HEDTA) and wherein, in a next step, in the outlet streams from the subterranean formation the aqueous phase is separated from the non-aqueous phase.

Claims

1. A two-step process to produce oil or gas from a subterranean formation, wherein in a first matrix acidizing and/or fracturing step the subterranean formation is treated with an aqueous composition having a pH in the range of 2-6 and containing a chelating agent selected from the group consisting of glutamic acid N,N-diacetic acid or a salt thereof (GLDA), aspartic acid N,N-diacetic acid or a salt thereof (ASDA), methylglycine N,N-diacetic acid or a salt thereof (MGDA), and N-hydroxyethyl ethylenediamine N,N′,N′-triacetic acid or a salt thereof (HEDTA) to promote the production of oil or gas from the subterranean formation as an outlet stream from said subterranean formation, the outlet stream comprising (i) an aqueous phase comprising at least some of said aqueous composition containing said chelating agent, and (ii) a non-aqueous phase comprising said produced oil or gas, and wherein, in a next step the aqueous phase of said outlet stream is separated from the non-aqueous phase.

2. Process of claim 1, wherein the outlet stream from the subterranean formation comprises an emulsion, said emulsion containing the aqueous phase and the non-aqueous phase and wherein the separation step comprises one or more steps selected from the group consisting of (i) adding a chemical demulsifier, (ii) increasing the temperature of the emulsion, (iii) applying electrostatic fields that promote coalescence, and (iv) reducing the flow velocity, which flow velocity reduction allows gravitational separation of oil or gas and water.

3. Process of claim 1, wherein the aqueous composition contains 5 to 30 wt % of chelating agent on the basis of the total weight of the composition.

4. Process of claim 1, wherein the aqueous composition chelating agent comprises GLDA.

5. Process of claim 1, wherein the composition is a foamed or viscosified composition or is one part of a kit of parts containing in addition a preflush and/or postflush part.

6. Process of claim 1, wherein the process in addition contains a step of at least partially removing a filter cake that is present in the subterranean formation.

7. Process of claim 1, wherein the subterranean formation is a carbonate formation, a sandstone formation, a shale formation, a calcium carbonate-containing sandstone formation, a calcium carbonate-containing shale formation, an illitic carbonate formation or an illitic sandstone formation.

8. Process of claim 1, wherein the composition in addition contains a corrosion inhibitor in an amount of up to 2 volume % on total composition.

9. Process of claim 8, wherein the corrosion inhibitor is selected from the group consisting of amine compounds, quaternary ammonium compounds, and sulfur compounds.

10. Process of claim 1, wherein the composition in addition contains a surfactant in an amount of up to 2 volume % on total composition.

11. Process of claim 10, wherein the surfactant is selected from the group consisting of anionic, amphoteric, nonionic, and cationic surfactants.

12. Process of claim 1, wherein the composition in addition contains a further additive selected from the group consisting of mutual solvents, anti-sludge agents, surfactants, corrosion inhibitor intensifiers, foaming agents, viscosifiers, wetting agents, diverting agents, oxygen scavengers, carrier fluids, fluid loss additives, friction reducers, stabilizers, rheology modifiers, gelling agents, scale inhibitors, breakers, salts, brines, pH control additives, particulates, crosslinkers, relative permeability modifiers, sulfide scavengers, fibres, and nanoparticles.

13. Process of claim 1, wherein the composition has a pH of between 3 and 6.

14. Process of claim 1, wherein the process involves treating the subterranean formation to increase the permeability thereof, remove particles therefrom and/or remove inorganic scale therefrom.

15. Process of claim 1, wherein the process involves cleaning of a wellbore and/or descaling of an oil/gas production well and production equipment in the production of oil and/or gas from the subterranean formation.

Description

EXAMPLES

(1) Materials Used

(2) GLDA, HEDTA, and ASDA were obtained from AkzoNobel Functional Chemicals. Oil 1 was a medium weight crude oil with an American Petroleum Institute (API) gravity of 30-31° API and Oil 2 and Oil 3 were light crude oils with an American Petroleum Institute (API) gravity of 40-50° API. HCl was obtained from Aldrich.

(3) 4 solutions were prepared: 1) 20 wt % GLDA in water having a pH of about 3.8, 2) 20 wt % HEDTA in water having a pH of about 3.8, 3) 20 wt % ASDA in water having a pH of about 3.8, and 4) 15 wt % HCl in water. These solutions were used as such (non-neutralized) or as neutralized with CaCO.sub.3 solutions in the tests below.

(4) The neutralized solutions were prepared by adding CaCO.sub.3 to mimic spent acid solutions as obtained after a subterranean formation treatment. To neutralize the solutions, 2.35 grams of CaCO.sub.3 were used (purity >99.9%). This quantity was determined as “X” for the tests described in Example 2 and Example 4.

Example 1

Oil 1 and Non-Neutralized Solutions at Room Temperature

(5) 75 ml of oil 1 were added to a plastic beaker and then 75 ml of the GLDA, HCl or HEDTA solutions were added on top. The sample was then stirred using an UltraTurrax at 10,000 rpm for 5 minutes at 70° F. (20° C.). Immediately after stirring, the sample was poured on a 100 ml graduated cylinder and data was acquired over time measuring the volume of the aqueous phase separated from the emulsion at 70° F. (20° C.). Full (100%) separation would result in an aqueous layer of 50 ml. The remaining emulsion was kept in a closed vessel.

(6) Data was acquired at 10, 20, 30, 60, 120, 180 minutes and after 72 hours.

(7) The results are summarized in Table 1 and FIG. 1 and show that the GLDA-based solution separates from the oil phase within 20 minutes, whereas 15% HCl shows no sign of separation within the time frame of the experiment. Additionally, the GLDA-based solution separates more completely from the oil phase than HEDTA, 78% separation for GLDA and 14% separation for HEDTA.

(8) TABLE-US-00001 TABLE 1 Results obtained for the separation of crude oil 1 and the non-neutralized solutions HCl GLDA HEDTA 15 wt % 20 wt % 20 wt % Time ml ml ml (min) aqueous phase aqueous phase aqueous phase 0 0 0 0 10 0 12 5 20 0 38 7 30 0 39 7 60 0 39 7 120 0 39 7 180 0 39 7 4,320 2 39 7

Example 2

Oil 1 and Neutralized Solutions at Room Temperature

(9) For this series of experiments, the aqueous phases used were: GLDA 20 wt %, neutralized with “X” grams of CaCO.sub.3 HCl 15 wt %, neutralized with “X” grams of CaCO.sub.3 HEDTA 20 wt %, neutralized with “X” grams of CaCO.sub.3

(10) 75 ml of oil 1 were added to a plastic beaker and then 75 ml of the neutralized aqueous phase were added on top. The sample was then stirred using an UltraTurrax at 10,000 rpm for 5 minutes at 70° F. (20° C.). Immediately after stirring, the sample was poured on a 100 ml graduated cylinder and data was acquired over time measuring the volume of the aqueous phase separated from the emulsion at 70° F. (20° C.). The remaining emulsion was kept in a closed vessel. The results are summarized in Table 2 and shown in FIG. 2. Also in the case of the neutralized solutions the GLDA-based solution separated within 10 minutes after stirring was stopped, resulting in a 46% separation. The state of the art 15% HCl solution did not separate during the first 2 to 3 hours.

(11) TABLE-US-00002 TABLE 2 Results obtained for the separation of oil 1 and the neutralized solutions Time HCl Neutralized X g CaCO.sub.3 GLDA Neutralized X g CaCO.sub.3 (min) ml aqueous phase ml aqueous phase 0 0 0 10 0 22 20 0 23 30 0 23 60 0 23 120 0 23 180 1 23

Example 3

Oil 1 and Non-Neutralized Solutions at High Temperature

(12) 75 ml of oil 1 were added to a plastic beaker and then 75 ml of the GLDA, HCl or HEDTA solutions were added on top. The plastic beakers with the samples were placed in a water thermic bath at a temperature of 140° F. (60° C.) until temperature of the mix was stable. The samples were then stirred using an UltraTurrax at 10,000 rpm for 5 minutes. Immediately after stirring, the sample was poured on a 100 ml graduated cylinder and data was acquired over time measuring the volume of the aqueous phase separated from the emulsion at 140° F. (60° C.). The remaining emulsion was kept in a closed vessel.

(13) Data was acquired at 10, 20, 30, 60, 120, 180 minutes and after 72 hours.

(14) The results are summarized in Table 3 and FIG. 3 and show that the GLDA-based solution separates from the oil phase within 10 minutes, whereas 15% HCl shows the maximum grade of separation after 2 hours of starting the experiment.

(15) Additionally, the GLDA-based solution separates more completely from the oil phase than HEDTA, 88% separation for GLDA and 86% separation for HEDTA.

(16) TABLE-US-00003 TABLE 3 Results obtained for the separation of oil 1 and the solutions HCl GLDA HEDTA 15 wt % 20 wt % 20 wt % Time ml ml ml (min) aqueous phase aqueous phase aqueous phase 0 2 8 7 10 30 44 41 20 32 44 43 30 32 44 43 60 32 44 43 120 38 44 43 180 38 44 43 4,320 38 44 43

Example 4

Oil 1 and Neutralized Solutions at High Temperature

(17) GLDA 20 wt %, neutralized with “X” grams of CaCO.sub.3 HCl 15 wt %, neutralized with “X” grams of CaCO.sub.3 HEDTA 20 wt %, neutralized with “X” grams of CaCO.sub.3

(18) 75 ml of oil 1 were added to a plastic beaker and then 75 ml of the GLDA, HCl or HEDTA solutions were added on top. The plastic beakers with the samples were placed in a water thermic bath at a temperature of 140° F. (60° C.) until the temperature of the mix was stable. The samples were then stirred using an UltraTurrax at 10,000 rpm for 5 minutes. Immediately after stirring, the sample was poured on a 100 ml graduated cylinder and data was acquired over time measuring the volume of the aqueous phase separated from the emulsion at 140° F. (60° C.).

(19) The remaining emulsion was kept in a closed vessel.

(20) Data was acquired at 10, 20, 30, 60, 120, 180 minutes and after 72 hours.

(21) The results are summarized in Table 4 and FIG. 4 and show that the GLDA-based solution separates from the oil phase within 10 to 20 minutes, whereas 15% HCl shows a very slow separation rate after 72 hours of starting the experiment.

(22) Additionally, the GLDA-based solution separates more completely from the oil phase than HEDTA, 88% separation for GLDA and 84% separation for HEDTA.

(23) TABLE-US-00004 TABLE 4 Results obtained for the separation of oil 1 and the neutralized solutions at high temperature HCl Neutralized GLDA Neutralized HEDTA Neutralized X g CaCO.sub.3 X g CaCO.sub.3 X g CaCO.sub.3 Time ml ml ml (min) aqueous phase aqueous phase aqueous phase 0 2 5 5 10 8 43 38 20 8 44 38 30 8 44 38 60 10 44 38 120 11 44 41 180 11 44 42 4,320 23 44 42

Example 5

Oil 2 and Neutralized Solutions at Room Temperature

(24) For this series of experiments, the aqueous phases used were: GLDA 20 wt %, neutralized with “X” grams of CaCO.sub.3 GLDA 20 wt %, neutralized with “½X” grams of CaCO.sub.3 HCl 15 wt %, neutralized with “X” grams of CaCO.sub.3 HEDTA 20 wt %, neutralized with “X” grams of CaCO.sub.3 ASDA 20 wt %, neutralized with “X” grams of CaCO.sub.3

(25) 75 ml of oil 2 were added to a plastic beaker and then 75 ml of the neutralized aqueous phase were added on top. The sample was then stirred using an UltraTurrax at 10,000 rpm for 5 minutes at 70° F. (20° C.). Immediately after stirring, the sample was poured on a 100 ml graduated cylinder and data was acquired over time measuring the volume of the aqueous phase separated from the emulsion at 70° F. (20° C.). The remaining emulsion was kept in a closed vessel.

(26) The results are summarized in Table 5 and shown in FIG. 5. The result indicate that the treatment fluids of the invention all separate faster and more completely from the oil layer than state of the art HCl, even if they have not fully reacted.

(27) TABLE-US-00005 TABLE 5 Results obtained for the separation of oil 2 and the neutralized solutions HCl GLDA GLDA ASDA HEDTA Neutralized Neutralized Neutralized Neutralized Neutralized X g CaCO.sub.3 X g CaCO.sub.3 ½ X g CaCO.sub.3 X g CaCO.sub.3 X g CaCO.sub.3 ml ml ml ml ml aqueous aqueous aqueous aqueous aqueous Time (min) phase phase phase phase phase 0 2 5 1 2 5 10 15 40 2 5 10 20 20 40 5 35 36 30 25 42 25 37 36 60 28 42 47 37 36 120 35 42 47 37 36 180 35 42 47 37 36 4,320 42 42 47 37 36

Example 6

Oil 3 and Non-Neutralized Solutions at Room Temperature

(28) 75 ml of oil 3 were added to a wide glass beaker and then 75 ml of the GLDA and HCl solutions were added on top. The glass beakers were then shaken vigorously by hand for 3 minutes. Immediately after stirring, the beaker was placed on a steady surface to visually check for phase separation, colour changes, formation of emulsions or precipitates.

(29) While the solution containing GLDA separated completely in less than 10 minutes and showed no signs of emulsion formation, precipitates or colour change; the solution containing HCl did not separate after 24 hours, and the aqueous phase developed a dark yellow colour, in contrast to the initial transparent fluid.