METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS

Abstract

The invention proposes a tool for flow uniformization in stimulation operations that uses a washing string with divergent perforation, provides a better direction of stimulation and, therefore, a better management of the reservoir.

The technology can be applied entirely through the wells area, being addressed to the reservoirs area in the management of reservoirs; wells stimulated in a homogeneous way will have fewer problems of premature cones of water and/or gas, and in the lift and flow area will contribute to improving the guarantee of flow of production from the wells. It can be applied as a technology in the intervention of wells in the phase of restoration of productivity, through operations of injection of acid in the reservoir as well as operations of squeeze of scale inhibitor. In this way, the application of the technology creates ease for the management of scaling for producing wells, and it can also be applied in injecting wells to improve the efficiency of sweeping in the reservoir and in the recovery of the injectivity index.

Claims

1- A METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS, characterized in that it: uses information from the horizontal well, such as: length and diameter, viscosity and API grade of oil; uses information from the reservoir, such as: static pressure and flow pressure; uses the wash pipe tool to stimulate the reservoir; performs reservoir stimulation with the wash pipe tool with divergent perforation during the well completion.

2- THE METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS according to claim 1, characterized in that it calculates the length of the string of wash pipes as a function of the length and diameter of the well.

3- THE METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS according to claim 1, characterized in that, from the static pressure and flow pressure, it calculates, in the simulator, the pressure drop distribution that will be applied to generate the flow uniformization during the acid injection.

4- THE METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS according to claim 2, characterized in that the wash pipe tool is a perforated pipe, capable of promoting a uniform flow along the horizontal length of the well.

5- THE METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS according to claim 1, characterized in that it uses acids, solvents or scale removers to stimulate the oil well.

6- THE METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS according to claims 1 and 5, characterized in that it uses hydrochloric acid or acetic acid or formic acid or mixtures thereof for acid stimulation.

7- THE METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS according to claims 1 and 5, characterized in that it uses diesel or xylene or butyl-glycol or mixtures thereof as solvents.

8- THE METHOD FOR UNIFORMIZATION OF FLOW FOR STIMULATION OPERATIONS according to claims 1 and 5, characterized in that it uses DTPA (ethylene triaminopentacetic acid) or EDTA (ethylenediamine tetraacetic acid) as scale removers.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] The present invention will be described in more detail below, with reference to the attached figures which, in a schematic way and not limiting the inventive scope, represent examples of its embodiment. In the drawings, there are:

[0024] FIG. 1 illustrates the effect of permeability;

[0025] FIG. 2 illustrates the effect of flow on the flow profile;

[0026] FIG. 3 illustrates a schematic of the distribution profile of the sweeping in the injection well at the beginning of the injection, injecting (bottom) and producing (top) pair;

[0027] FIG. 4 illustrates an overlap profile of the distribution of the sweeping in injection well on the production of the producing well, injecting (bottom) and producing (top) pair, RF is the field recovery factor that increases proportionally with the increase in sweeping efficiency;

[0028] FIG. 5 illustrates the distribution of homogeneous flow between the sweeping of the injecting well and drainage of the producing well, injecting (bottom) and producing (top) pair, RF is the field recovery factor that increases proportionally with the increase in sweeping efficiency;

[0029] FIG. 6 illustrates the uniform steam flow scheme;

[0030] FIG. 7 illustrates a graph of a well's peak production history;

[0031] FIG. 8 illustrates the first stage of acidification, the string removed and measuring until the upper seals were inside the Swell Packer, the acidification of the first stage carried out with closed BOP;

[0032] FIG. 9 illustrates the second acidification stage, the lower 4.75″ (12.07 cm) seals positioned on the lower Swell Packer and the upper 4.75″ (12.07 cm) seals positioned on the upper Swell Packer, the second acidification stage carried out;

[0033] FIG. 10 illustrates the third stage of acidification, the lower 4.75″ (12.07 cm) seals positioned in the upper Swell Packer, the pipe ram closed and the third stage of acidification carried out.

DETAILED DESCRIPTION OF THE INVENTION

[0034] There follows below a detailed description of a preferred embodiment of the present invention, by way of example and in no way limiting. Nevertheless, it will be clear to a technician skilled on the subject, from reading this description, possible further embodiments of the present invention still comprised by the essential and optional features below.

[0035] Before the invention, the wells were completed with conventional equipment, which did not have a flow uniformization design in the production string along the horizontal length of the wells, and were stimulated with conventional tools that did not promote flow uniformization. Normally, depending on the tool, a string was used and, at the end, there was a flow system between two types of wash cups that treated the horizontal length of the well in small intervals and thus continued until the entire horizontal length of the well was completed. There were risks associated with the occurrence of acid flowback during maneuvers on the rotary table in the rig, the rig time to perform the treatment was very long, which made the operation more expensive in financial terms due to the use of critical resources.

[0036] The stimulation method using the wash string is described below: [0037] use of information from the horizontal well, such as: length and diameter, viscosity and API grade of oil; [0038] use of information from the reservoir, such as: static pressure and flow pressure; [0039] use of the wash pipe tool to stimulate the reservoir; [0040] performance of the stimulation of the reservoir with the wash pipe tool with divergent perforation during the stage of completion of the oil or natural gas well. Stimulation can be acidic, with solvents or scale inhibitors.

[0041] Acids can be organic or inorganic, such as hydrochloric acid, acetic acid, and formic acid, for example. Solvents to be used are, for example: diesel, xylene, butyl glycol. Inhibitors can be DTPA (ethylene triaminopentacetic acid) and EDTA (ethylenediamine tetraacetic acid). That is, chemicals and solvents usually used in well stimulation.

[0042] FIGS. 3 and 4 represent the generic flow profiles, expected for wells without equalization. It can be seen that, without flow uniformization, the expectation of recovery leads to a lower NPV due to the tendency towards premature breakthrought.

[0043] FIG. 5, in turn, represents the expected gain from the equalization of the production-injection system, with the following improvements: [0044] Increase in the useful life of the well; [0045] Improvement of the recovery factor; [0046] Increase in the efficiency of the water injection process; [0047] Obtaining an NPV closer to the foreseen.

[0048] Even so, it is important that there is prior knowledge of the flow distribution in the horizontal well to: [0049] Check if there is a need for uniformization; [0050] Design the appropriate uniformization system.

[0051] Although FIG. 5 is an optimistic representation, intermediate and even so quite attractive results can be obtained, improving the management of the fields.

Examples

[0052] At one operational unit, flow uniformization was employed to improve steam distribution in the wells. Wash pipes with divergent perforation were used in the cyclic injection of steam in a single horizontal producing well, in the range of 919.5 to 1318 m. FIGS. 6 and 7 illustrate the use of wash pipes and the flow distribution curves obtained. The graph records the production of the well without steam injection, followed by three cycles of steam injection and oil production, and the steam injection using the technology of divergent wash pipes was carried out in the fifth cycle. It was evaluated that the production was close to what was expected for the conventional injection, thus indicating that the test should be carried out in the first cycle of a well to obtain a better measurement of the result in relation to the conventional one.

[0053] In this way, the wells were equipped with conventional perforated wash pipes and the treatment was carried out in stages of a 500-m interval, using the wash pipes instead of the liner (production string), without any restrictions on production of the wells being noted.

[0054] Its application in the well provided production flow rates of about 6900 m.sup.3/day in a carbonate formation. The other wells in this field were treated using the same technique, also obtaining the same treatment efficiency.

[0055] The application of the technique resulted in a time gain of 60 h in the stimulation operation compared with acidification via flexitube. FIGS. 8 to 10 show the treatment with wash pipes performed after the liner was run in. At the end of the treatment, the wash pipes were removed from the well to run in the production string.

[0056] The invention is formed by the use of information from the horizontal well, such as: length and diameter, to be used to calculate the length of the wash pipe string; viscosity; the API grade. From the reservoir, there is used information, such as: static pressure and flow pressure, to be used to calculate in the simulator the pressure drop distribution that will be applied to generate flow uniformization during the acid injection.

[0057] The solution achieved by the use of the tool (wash string) promotes homogeneous stimulation, with a distribution of the injection flow of acid, solvent or scale removers evenly along the horizontal length of the wells. This solution meets the need for stimulation with homogeneous flow for horizontal wells, aiming at increasing productivity for producing wells and increasing sweep efficiency for injection wells, through a flow uniformization process in the stimulation of horizontal wells and/or vertical wells or directional with large net pays lengths between producing intervals. In the case of horizontal producing and injecting wells, these normally produce or inject with greater flow rate in the section closest to the beginning of the horizontal length of the well, normally the shoe of the last liner.