METHOD FOR REMOVING SCALE FROM A SUBSEA MANIFOLD

Abstract

During meeting for planning operations for scale removal and scale inhibitor squeeze treatment in wells, the possibility of the manifold being partially incrusted with scale raised considering the more critical mixture of water produced. The proposed solution is a method of treatment for removing scale from a manifold. Said method uses the geothermal heating of the exploration reservoir to heat a chemical removal solution (50). Heating is required to ensure the temperature is in a range that is also suitable for conducting the removal reaction, since the distance that the solution travels to the manifold (20) e the low temperature of the underwater environment make the reaction occur inefficiently, as in the case of pre-salt.

Claims

1. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, characterized by comprising the following steps: a. removing scale from the production string (31); b. cleaning the production string (31) following the pumping of the entire treatment solution into the reservoir (40) for the treatment of scale; c. positioning the treatment solution in the reservoir (40) where a scale removal solution (50) will be injected into reservoir (40); d. using geothermal heating of the reservoir (40) to heat the scale removal solution (50); e. displacing the removal solution (50) to the manifold after reaching stabilization and balance of temperature; f. positioning the removal solution (50) within the manifold (20).

2. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 1, characterized by pumping the scale inhibitor to the pre-flush with organic solvent from the cleaning step of production string (31).

3. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 1, characterized by the step of cleaning the production string (31) having treatment with the chelant and ovetflush.

4. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 1, characterized by pumping after overflush 1, the overflush 2 (which corresponds to a volume equivalent to the sum of the volume of the production string (3) plus the volume of the line of the wet Christmas tree (ANM) (30) to the manifold (20)).

5. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 1, characterized by overflush 1 and overflush 2 using diesel.

6. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 1, characterized by pumping the scale removal solution (50) into the manifold (20).

7. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 1, characterized in that the scale removal solution (50) is completely pumped into the reservoir rock (40) for geothermal hibernation.

8. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 7, characterized by waiting for the removal solution (50) to reach equilibrium with the temperature of the reservoir (40).

9. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 1, characterized by closing the other wells that produce to the manifold (20).

10. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 1, characterized by closing the valve in ANM (30) of the gas line (1) of the ANM itself (30), opening the well (60) to produce the removal solution (50) that is in the reservoir (40) by the production string (31) that continues through the segment of production line 1 (21) until filling the manifold (20).

11. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claim 10, characterized by aligning one of the wells to produce to the manifold (20) the equivalent volume of the scale removal solution (50) plus overflush 2 plus the volume of manifold (20), in order to position the removal solution (50) inside manifold (20) at a temperature of 62.5° C.

12. METHOD FOR REMOVING SCALE FROM SUBSEA MANIFOLD, according to claims 10 and 11, characterized by waiting for the temperature drop to values less than 40° C. for the completion of the complexation reaction and repeating this operation twice more and or until the entire volume of removal (50) that is in the reservoir is produced by the manifold (20).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The present invention will be described in more detail hereinafter with reference to the accompanying figures which, in a schematic and non-limiting form of the inventive scope, represent exemplary embodiments thereof. In the drawings, there is provided:

[0050] FIG. 1 illustrates the mechanism of scale forming;

[0051] FIG. 2 illustrates the chemical structure of the metal-EDTA complex;

[0052] FIG. 3 illustrates a dissolution test of barite in DTPA, EDTA, CDTA, and DOTH with 0.18 M at 40° C. in a system with stirring;

[0053] FIG. 4 illustrates the chemical structures of the chelating agents;

[0054] FIG. 5 illustrates the connection between UEP, manifold and the ANM of the well;

[0055] FIG. 6 illustrates the connection between UEP, manifold and the ANM of the well when scaling occurs in the production string;

[0056] FIG. 7 illustrates the connection between UEP, manifold and the well when scaling occurs in the production string and or in the manifold;

[0057] FIG. 8 illustrates the connection between UEP, manifold and the well for removing scaling from the interior of the production line and or manifold;

[0058] FIG. 9 illustrates the connection between UEP, manifold and the ANM of the well when the removal of scale is completed.

DETAILED DESCRIPTION OF THE INVENTION

[0059] in order to improve the efficiency of the reaction of the scale removal treatment in the manifold (20), therefore eliminating obstruction of the flow through pumping of the treatment with a suitable temperature for the efficiency of the complexation reaction. It has been devised for wells that have the occurrence of scale in the string, a procedure with the following sequence:

[0060] a removing scale from the production string (31);

[0061] b cleaning the production string (31) followed by pumping the entire treatment solution (pre-flush, scavenger solution and overflush) into the reservoir (40) for the treatment of scales;

[0062] c positioning the treatment solution in the reservoir (40) where a scale removal solution (50) will be injected into the reservoir (40);

[0063] d using geothermal heating of the reservoir (40) to heat the scale removal solution (50);

[0064] e after reaching stabilization and temperature balancing, performing the opening of the well (60) for production to ensure displacement of the removal solution (50) to the manifold (20), which is at a certain distance from the well (60), where its temperature will be around 62.5° C.;

[0065] f positioning the removal solution (50) inside the manifold (20).

[0066] Thus the removal solution may reach the manifold (20) at a temperature well near the ideal and thus promote the complexation reaction of the cations of the scale. Increasing the temperature alters the kinetics of the reaction that finally removes the scales in a more efficient manner, thus optimizing the treatment time as well as increasing the efficiency of the treatment. The innovation can generate time reduction of the treatment and the rig time, which improves the economy (net present value) and the production curve of the field, and therefore increases the productivity of the wells.

[0067] The entire treatment solution (Preflush, removal solution (50) and overflush) is injected directly into the well (60). The mixture takes place with the well fluids (60). However, Preflush is a pre-flush of the rock, acts by removing some of these fluids, allowing greater interaction with the removal solution (50) to ensure the effectiveness of the treatment. The ovetflush is a displacement solution.

[0068] For operation of pumping scale inhibitor, the pre-flush steps of the entire productive system (reservoir, column, riser and production lines) will be followed with organic solvent (generally a mixture of diesel, butylglycol and xylene) for cleaning the reservoir rock, treatment with the selected product and overflush 1 with diesel.

[0069] The adaptation consists of pumping after overflush 1, a second overflush that will be called overflush 2 (which corresponds to the volume equivalent to the sum of the volume of the string plus the volume of the line of the wet Christmas tree (ANM) (30) to the manifold (20), followed by pumping of the scale removal solution (50) to the manifold (20) that will be fully injected into the reservoir rock for geophysical hibernation.

[0070] After the completion of geothermal hibernation, when the temperature of the solution (50) for removing scale from manifold (20) is in equilibrium with the reservoir temperature (40), the other wells that produce to the manifold (20) will be closed, from this time one of the wells will be aligned to produce to the manifold (20) the volume equivalent to the scale scavenger plus overflush 2 plus the volume of manifold (20), in order to position the removal solution (50) inside the manifold (20) with a temperature around 62.55° C. and wait for the treatment solution to cool below 40° C. to complete the complexation reaction.

[0071] In order to maintain the operating conditions of manifold (20) (free of scaling) this operation can be repeated every time one is to perform the injection of scale inhibitor through some wells that produce through the same manifold (20).

[0072] FIG. 5 shows, in a schematic way, a layout of UEP (10) connected to the manifold (20) through the production line, which in turn is connected to ANM (30) of oil well (60) through a production line and a connected gas line from UEP to ANM (30) of the well (60). The production of the well (60) passes through section 1 (21) of the line that goes from ANM (30) to manifold (20) and from manifold (20) by section 2 (22) from the production line to UEP (10). In a manifold (20) more than a well, sometimes, depending on the production development project, can reach up to 5 wells.

[0073] in the production system, the wells that produce to UEP (10), through the manifold (20) have scaling potential, the scale formation will occur first in the production string (31) inside the well (60), then in the production line section 1 (21) and then the occurrence will be in the manifold (20).

[0074] FIG. 6 shows schematically, when scaling occurs in the string, the removal procedure is to pump the removal solution (chelants) (50) through the gas line (11) from UEP (10) to ANM (30) and from this to the production column (31) where the removal solution (50) is positioned for a period of up to 24 hours. After this period, the well (60) is aligned and opened to UEP (10) thus producing by the production line section 1 (21), manifold (20) and production line section 2 (22) to UEP (10).

[0075] FIG. 7 shows in a schematic way, when scaling occurs in the production string (31) and or in the production manifold (20), the removal procedure is to pump the removal solution (50) through the gas line (11) from UEP (10) to ANM (30), following to the production string (31) and reaching the reservoir (40) where the removal solution (50) is positioned for a sufficient period of time for geothermal heating the removal solution (50) (as a function of depth of well (60) inside the rock layers). After this period, well (60) is aligned and opened for UEP (10), thus producing by production section 1 (21), manifold (20) and production line section 2 (22) to UEP (10).

[0076] FIG. 8 shows in a schematic way the removal of scale from the inside of the production string (31) and or inside the production manifold (20). The removal procedure is to close the valve in the ANM (30) of the gas line (11) of the ANM itself (30), open the well (60) to produce the removal solution (50) that is in the reservoir (40) by the production string (31), which follows the production line section 1 (21) until filling the manifold (20). Then wait for the time required for the manifold temperature (20) to reach the stabilization value with the seabed temperature, displace a new volume of removal solution (50) into the manifold (20) and wait for stabilization with the seabed temperature, repeat this operation for two more times and or until the entire volume of removal solution (50) that is in the reservoir (40) is fully produced to the manifold (20).

[0077] Finally, as can be seen in FIG. 9, after completing the step of scale removal in the manifold (20), the well (60) is aligned and opened to UEP (10), thus producing by the production line section 1 (21), manifold (20) and by the production line section 2 (22) to the UEP (10).

[0078] The Sizing of Treatments for Well Damage Removal CRT-24 was used. Which was prepared by CENPES/PDEP/TEE scale group on August 2007. The sizing was performed based on results obtained from tests of dissolution efficiency of barium sulfates and removal of damage caused by dissolution and reprecipitation of calcium and iron compounds in porous medium.

[0079] Data of well production:

TABLE-US-00002 Data Well CRT-24 Water flow rate (m.sup.3/d) 545 - previous Producing area (m) 15.03

[0080] Sizing of Damage Removal Operation

[0081] Product Chelating Agents—Volume of Fluids/Pumping Flow Rate

TABLE-US-00003 Pads Volume (bbl) Pre-flush (mixture of diesel and butylglycol) 100 Treatment (removal solution) 300 Overflush (displacement fluid being diesel or Displacement up even aqueous fluid) to formation Shut-in (h) (residence time of treatment 5 solution in reservoir rock) Pumping flow rate bbl/min 2.66

[0082] Fluid composition:

[0083] Pre-flush—Butyiglycol and diesel p Treatment—BAD 40% MA

[0084] Overflush—Diesel

[0085] Sizing of Scale Damage Removal Operation:

[0086] Product Chelating Agent—Volume of Fluids/Pumping Flow Rate

TABLE-US-00004 Pads Volume (bbl) Pre-flush 100 Treatment 300 Overflush Displacement up to formation Shut-in (h) 12 Q pumping bbl/min 2.66

[0087] Fluid composition:

[0088] Pre-flush—Butylglycol, diesel and xylene

[0089] Treatment—Chelating Agent—Trilon PP3—PH=8.0

[0090] Overflush—Diesel