METHOD FOR REMOVING FOULING USING CARBONIC ACID

Abstract

The present invention refers to a method for removing fouling in carbonate reservoirs and/or depleted reservoirs by adding carbon dioxide to industrial or desulphated water to produce carbonic acid, in producing well stimulation operations, to be used as a weak acid for removing fouling in remote operation aiming at keeping the productivity of producing wells and lessening the need for remote operations with stimulation vessel, and therefore reducing operating costs.

Claims

1. METHOD FOR REMOVING FOULING USING CARBONIC ACID, characterized in that it comprises the following steps of: (1) aligning the carbon dioxide with the atomizer to prepare the carbonic acid solution; (2) aligning the water with the atomizer to prepare the carbonic acid solution; (3) adding the fouling inhibitor to the carbonic acid produced by mixing carbon dioxide with water; (4) pumping the carbon dioxide solution with fouling inhibitor through lines aligned with the service or gas-lift line to be injected into the well string to the reservoir; wherein the injection of a volume of water into the production string is followed by water and diesel plug for displacement and injection into the formation.

2. METHOD, according to claim 1, characterized in that the water used is industrial or desulphated water.

3. METHOD, according to claim 1, characterized in that the volume of water injected is 1.5 times the volume of the production string.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be described in more detail below, by referring to the attached figure which represents, in a schematic way and not limiting the inventive scope, an example of its embodiment. The drawing contemplates the following:

[0015] FIG. 1 illustrates a schematic of the process for removing fouling using carbonic acid, in which are represented: [0016] (1) Oil-Gas Separator; [0017] (2) CO.sub.2-Gas Separation System; [0018] (3) System CO.sub.2 Compressor; [0019] (4) Pressure reducing valve; [0020] (5) Tank for water additivation with hydrate inhibitor and corrosion inhibitor; [0021] (6) Additive industrial water pump; [0022] (7) Water CO.sub.2 Atomizer; [0023] (8) Well Gas-Lift Line; [0024] (9) Well Production Line; [0025] (10) Well Wet Christmas Tree; [0026] (11) Mudline [0027] (12) Well Annular; [0028] (13) Production String; [0029] (14) Gas-Lift Valve, [0030] (15) Perforations; [0031] (16) Reservoir.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The method for removing fouling using carbonic acid according to the present invention and illustrated in FIG. 1 comprises the following steps of: [0033] (1) aligning the carbon dioxide with the atomizer, in which it is used to mix CO.sub.2 in industrial or desulphated water to produce the carbonic acid; [0034] (2) aligning industrial or desulphated water with the atomizer to prepare the carbonic acid solution; [0035] (3) adding the fouling inhibitor to carbonic acid produced by the above mixture; [0036] (4) pumping the carbonic acid solution with fouling inhibitor through lines aligned with the service or gas-lift line to be injected into the well string to the reservoir; [0037] wherein the injection of a volume of water is 1.5 times the volume of the production string, followed by water and diesel plug for displacement and injection into the formation.

[0038] By mixing the carbon dioxide (CO.sub.2) with water, the production of carbonic acid (H.sub.2CO.sub.3) occurs, which, despite being a weak acid, can be used to remove calcium carbonate fouling. For stationary units in which the carbon dioxide is produced, it can be separately applied to produce carbonic acid in the SPU and applied to fouling removal operations for removing soluble inorganic deposits (calcium carbonate) from the production string and subsequently improving the solution by chemical additives with fouling inhibitors. The field of application will be in the carbonate reservoirs at high temperature with fluid produced with low gas-to-water ratio, and also can be applied to depleted reservoirs at high temperature with fluid produced with high gas-to-water ratio. This solution meets the requirement for calcium carbonate fouling removal stimulation, aiming at keeping the productivity of producing wells and increasing, through a process of adding the carbon dioxide, the industrial or desulphated water in producing well stimulation operations.

[0039] The present invention can be fully applied by the Lifting, Flow and Reservoirs areas, in the pre-salt producing fields having carbon dioxide separation, being addressed to the Reservoirs area in the reservoir management for managing the increase or maintenance of well production by controlling losses and ensuring the flow. It can be applied as a well intervention technology in the productivity restoration phase, through injection operations of carbonic acid into the string and the reservoir to remove calcium carbonate fouling. It can also be used in the application of fouling inhibitor associated with the carbonic acid in operations that can be classified as mixed (removal and inhibition) and, therefore, the application of this technology facilitates the fouling management for producing wells.

EXAMPLES

[0040] The following examples are provided in order to illustrate more completely the nature of the present invention and how to embody the same, without, however, being considered as limiting its contents.

[0041] The mixture of carbon dioxide produced with industrial and/or desulphated water in a pre-salt SPU to produce carbonic acid to be used as a weak acid for removing fouling in remote operation, is deemed as an innovation. However, this reaction of water with CO.sub.2 to ptoduce carbonic acid, is already described in the literature by means of inorganic chemistry books. However, the result obtained by the invention, at first, can be measured using thermodynamic simulation. For example, studies performed on ARXIM geochemical simulator have demonstrated the dissolution of calcium carbonate by the mixture of water and carbon dioxide in different proportions and at different pH ranges.

[0042] It should be noted that, although the present invention has been described with respect to the attached drawings, amendments and adaptations can be performed by a person skilled in the art, depending on the specific situation, and provided that it is within the inventive scope defined herein.