PROCESS FOR COMPLETING OIL WELLS IN PRE-SALTY CARBONATE FORMATIONS WITH EARLY INJECTIVITY INDUCTION

Abstract

METHOD FOR COMPLETING OIL WELLS IN PRE-SALIFEROUS CARBONATE FORMATIONS WITH EARLY INJECTIVITY INDUCTION The present invention relates to a method for completing oil wells with early injectivity induction, promoting the elimination of drilling damage in a step prior to the installation of the production column and the subsea Christmas tree and without the need to use spiral tubing, by obtaining sufficient, but not excessive, initial injectivity, such that subsequent acid treatment can reach the formation without risk of fracturing, reducing the operating time and the risks associated with the use of this equipment.

Description

Title of the invention: METHOD FOR COMPLETING OIL WELLS IN PRE-SALIFEROUS CARBONATE FORMATIONS WITH EARLY INJECTIVITY INDUCTION FIELD OF INVENTION

[0001] This invention relates to the field of well drilling and completion, and concerns a process for completing oil wells in pre-salt carbonate formations with early injectivity induction. Through the proposed process, it is possible to achieve injectivity induction in most wells with an intelligent completion system in pre-salt areas without using spiral tubing, by displacing acid systems from the surface in the early stages of treatment. This, in turn, allows for the removal of filter cake from the wellbore walls in an early stage, without the need to install the production column and the underwater Christmas tree.

[0002] BACKGROUND OF THE INVENTION

[0003] The carbonate reservoirs in the pre-salt zone of the Santos Basin normally exhibit significant extensions, which prevents well-distributed stimulation over the entire range of interest, as the workflow is limited by equipment and fluid access to the formation occurs through a single point.

[0004] Thus, most pre-salt zone production development wells are equipped with intelligent completion systems, which generally do not feature decoupled bottom completion. Therefore, the formation exposed by the perforation of the production casing is only isolated after the production column and through-packings have been installed. Due to this characteristic, any massive acid stimulation operation should only be carried out after the production column has been installed, so as not to induce a level of fluid loss that would prevent the continuation of completion installation operations, since a loss exceeding a certain level can damage the mechanical annular barriers and the packing sealing hole, preventing its proper installation.Furthermore, there is an additional risk in the event of failure in the components of the production column, as it must be removed with a loss of circulation.

[0005] Typically, acidifications carried out prior to the invention, in the pre-salt zone of the Santos Basin, required the use of spiral tubes to help divert the treatment and move the initial acid front towards the bottom. This positioning is achieved with a return through the ring between the well and the column production is possible, unlike with a production column and drill string riser, as there is no circulation point between the bottom and the surface. Furthermore, spiral tubing allows the use of waterjet blasting tools, which can help introduce acid into the gap where initial injectivity is desired.

[0006] The frequent use of spiral tubing in the first few dozen wells equipped with smart completion had a significant impact on well life and cost, while there were some doubts as to the actual necessity of its use in all cases. From a safety perspective, the use of this equipment requires the mobilization of a dedicated team and a larger number of personnel on board the completion platform; it adds operational risks, as it involves high pressures, working at height with heavy equipment, and the transport of loads and assemblies. Some incidents have been recorded at various stages of the logistics and operation of this equipment. Therefore, an alternative to its use is always desirable and results in improved safety and cost savings in well construction.In order to optimize pre-salt production development projects, the completion project team sought new alternatives to implement acid carbonate treatments without resorting to the use of spiral tubing as a mandatory resource, while maintaining the same well safety standards and quality of the generated stimulation.

[0007] Therefore, optimizing well productivity depends on effective stimulation, i.e., the formation of preferential paths (wormholes) along the section to be treated. However, for the product volume to reach the formation and begin the treatment itself, it is necessary to eliminate the damage caused by drilling; thus, the inert fluid preceding the acid is injected into the formation. Therefore, before the main acidification stage, a preliminary operation is generally carried out to eliminate this damage and obtain initial injectivity, which allows the acid to reach the formation without risk of fracturing the rock. This damage elimination operation was traditionally performed using spiral tubing to induce the injectivity necessary for positioning the hydrochloric acid at the base of the lower interval.It should be noted that this operation with spiral tubes was carried out in a later stage of completion with the production column and the underwater Christmas tree already installed in order to reduce the risks of operational discontinuity in the event of a serious loss. STATE OF THE ART

[0008] Some prior art documents present solutions for the pretreatment of oil wells, for example:

[0009] Document EP0040442 A1 relates to a process for improving oil well production by preventing scale formation that can obstruct flow. It uses an aqueous solution which, when injected, initially maintains a high pH to prevent precipitation, but then slowly lowers the pH, causing the formation of a scale inhibitor precisely where it is needed. This approach is novel because it combines different chemical compounds in a controlled manner, ensuring that the solution acts effectively in the right location, improving oil extraction efficiency.

[0010] US patent 8733443 B2 relates to a process for preparing a horizontal well for injecting water into a carbonate reservoir for acid treatment. First, the fluid pressure in the well is maintained above the natural reservoir pressure. Then, a valve is opened to reduce this pressure, allowing fluids from the reservoir to enter the well and expel unwanted fluids. The well is then operated in a controlled manner to remove these unwanted materials. The produced fluids are monitored until the amount of unwanted material reaches an acceptable level. After this, production is stopped and acid treatment is carried out in the well. This process helps ensure that the acid treatment is optimally effective.

[0011] Document RU2215137 Cl relates to a process for developing an oil well. First, tubing is lowered with packing, which helps control pressure. The clay solution in the well is replaced with a lighter fluid, maintaining pressure in the reservoir. Next, the packing is closed, and the device is lowered to the bottom of the wellbore. The process includes alternating pressures by using calcium chloride solutions to clean the well and allow fluids to enter the reservoir. During the process, the clay solution is progressively replaced with lighter solutions. Finally, the well is drilled to the flame, ensuring that proper pressure is maintained throughout all stages.

[0012] Document CA 1217130 A relates to a process for eliminating and preventing the Scale formation in wells that extract fluids from the subsurface. The process involves three main steps. First, an aqueous mineral acid solution is injected into the well to remove existing scale. Next, an EDTA solution is injected, which also helps remove scale. Finally, a scale inhibitor is injected into the well to prevent new scale formation.

[0013] This process is effective in maintaining well efficiency and improving fluid production.

[0014] US patent 4122896 A relates to a process for the slow acidification of carbonate materials in wells that communicate with underground formations. It involves creating an aqueous solution containing a hydrochloric acid salt and which is nearly acid-free. The solution is designed so that, at the temperature of the underground formation, the salt slowly decomposes, releasing an acid that reacts with calcium or magnesium carbonates. This results in the formation of soluble salts that can be removed. The solution is injected into the ground in a controlled manner, ensuring that the carbonate material is treated before there is enough acid to dissolve a large quantity of it. Thus, acidification occurs in a controlled and gradual manner. This process can improve the efficiency of underground resource extraction.

[0015] However, none of the documents proposes the solution described in this invention, that is, the implementation of a mild treatment before the installation of the column support, without using the spiral tube equipment and without a production column and underwater Christmas tree installed, obtaining sufficient, but not excessive, initial injectivity, so that the subsequent acid treatment can reach the formation without risk of fracturing, reducing the time of operation, as well as the risks associated with the use of this equipment.It is verified that, although the solutions proposed in these documents were developed to increase initial injectivity, eliminate and prevent scale formation, and treat the wells before the acid treatment itself, they are generally based on holistic processes. This means that an analysis is performed, starting from the origin of the specific problem and moving towards its potential impacts. From there, actions are proposed to overcome these possible problems within an existing process. In other words, the solutions obtained are proposed based on the specific reality, characteristics, and context of the situation at the time.In the present invention, the solution obtained aims to resolve most of the problems that can arise in the carbonate reservoirs of pre-salt zones which, due to their significant extent, prevent acid stimulation from being well distributed across the entire range of interest, minimizing its impacts. In contrast, in the selected prior art documents, the solutions found are geared towards a specific problem encountered, thus producing a targeted and objective result for that reality / obstacle encountered. Summary of the invention.

[0016] The present invention aims to provide a method for completing oil wells with early injectivity induction, promoting the elimination of damage caused by drilling in a step prior to the installation of the production column and the underwater Christmas tree and without the need to use spiral tubes, obtaining sufficient but not excessive initial injectivity, so that subsequent acid treatment can reach the formation without risk of fracturing, reducing the operating time and risks associated with the use of this equipment. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention relates to a method for completing oil wells in pre-salt carbonate formations with early injectivity induction, by implementing a mild treatment before column support installation, without using spiral tubing equipment and without installing a production column or subsea Christmas tree, thereby increasing initial injectivity. This method comprises the following steps:

[0018] Preparation of a volume of 100 to 300 bbl of a filter cake breaking fluid solution in an oil platform tank, which may be a solution of EDTA or acetic acid, by adding at the end a volume of saturated brine until the desired weight for the operation is reached.

[0019] After preparation, the solution is pumped into the well, displacing it with water-based completion fluid until it is positioned over the entire interval of interest (drilled or open well). This pumping is carried out before the installation of the riser support, by circulating through the production string via intelligent completion valves with an annular return between the production string and the casing, and between the drill string riser and the drill string riser.

[0020] The process uses a cushion that works by complexing metallic ions, in this case calcium from carbonate rock, but with low corrosive potential, an essential condition for this application. This product is positioned by circulation at the bottom of the wellbore immediately before the installation of the column support, and an increase or onset of fluid loss to the formation from its contact with the drilled interval is generally observed. It is progressively injected into the formation by the wellbore feed process itself during subsequent operations.

[0021] Since the treatment may remain in contact with the completion equipment for several hours until it is completely injected, particularly in case of difficulties in the operation, it is essential that it does not generate a corrosive process or damage to the elastomers.

[0022] As previously observed, the treatment is positioned before confirmation that all the equipment comprising the production column is Operationally, this can pose a critical problem because the well will be stimulated, but several operations will still be performed, such as testing the equipment that makes up the completion assembly. In case of failure, it may be necessary to remove the production column to correct the problem. Under these conditions, a controlled and slow treatment response is essential, as uncontrolled fluid loss to the formation is undesirable. This could make it difficult, or even impossible, to feed the well due to the lengthy duration of subsequent operations. Furthermore, inducing a significant loss through excessive treatment can damage the mechanical annular barriers and the packing hole seal, preventing their proper installation.

[0023] An early injectivity induction, distributed throughout the upper and intermediate perforated interval (if applicable), not only allows the main subsequent injection treatments to be moved to the bottom, but also helps to distribute the treatment in these intervals, as it allows the initial damage to be reduced in a more homogeneous way, given that less contrast is generated between the areas already treated and those that have not yet been reached by the filter cake breaking fluid, and that the contact time with the formation before all the fluid is injected is increased.

[0024] EXAMPLE OF THE INVENTION

[0025] In pre-salt carbonate wells equipped with intelligent completion, the mechanical step of hydrochloric acid jetting using spiral tubes for injectivity induction has been advanced and replaced by a mild chemical treatment step involving the positioning of a filter cake breaking fluid cushion. This pumping takes place through intelligent completion valves with an annular return between production and the casing and between the drill string riser and the riser. This displacement is performed immediately before the casing support is installed, at the last opportunity when fluid can flow through the casing.This solution contributes significantly to reducing the overall completion intervention time, either by eliminating spiral tube operations or by enabling injectivity induction before the installation of the production column and the underwater Christmas tree.

[0026] From an economic standpoint, the use of spiral tubes entails higher costs in acid treatment, given that the historical average operating time of this equipment is approximately 3 days on an oil platform. There is also the possibility of additional time due to availability, delays in assembly, use, and disassembly caused by conditions. adverse weather conditions, thus adding several days to the duration of the operation with a consequent increase in costs.

[0027] Furthermore, with the early injectivity induction operation, better performance is expected in the distribution of the treatment over the entire interval of interest, because the incorporation of weaker products increases the probability of a slower and more evenly distributed treatment, resulting in a potential gain in productivity and hydrocarbon recovery.

[0028] It is estimated that a reduction of more than 10 days of oil platform per well from said invention, in combination with other actions and techniques, is one of the initiatives with the greatest impact in campaigns for the construction of pre-salt wells in the Santos Basin.

[0029] APPLICATION OF THE INVENTION

[0030] In wells equipped with intelligent completion, the conventional stimulation strategy adopted in the vast majority of wells up to mid-2015 included an initial treatment step to increase initial injectivity and the creation of a preferential flow zone, generally called a loss zone, at the base of the lower interval perforations, using spiral tubing equipment. However, following the first successful applications of the early injectivity induction completion methodology, without using spiral tubing equipment and without a subsea production column and Christmas tree installed, this operation began to incorporate the set of best practices used in Petrobras well completion with a similar configuration.

[0031] One of the impacts of the acidification strategy using spiral tubes is the need to perform this operation after the installation of the production column and the underwater Christmas tree. For this reason, in all cases where spiral tubes were used, the installation of the underwater Christmas tree was carried out with the probe itself, which significantly added time to the duration of the interventions.

[0032] The proposed completion method made it possible to break up the well's filter cake without spiral tubing and, consequently, without the prior installation of the production column and the subsea Christmas tree, a solution known as "early injectivity induction." In this case, operations are carried out with the shear riser joint and the tubing support installation tool connected to the riser support, and the intervention with the oil platform is completed after the blowout preventer is removed, without the installation of the subsea Christmas tree. Measures to mitigate risks, increase efficiency, and address other operational contingencies also contributed to consolidating this new completion sequence. The installation of the subsea Christmas tree was entrusted to a vessel specialized, which offers superior performance at a significantly reduced cost compared to the same operation carried out with the oil platform.

[0033] Using this new completion sequence, it is estimated that drilling rig time will be reduced by more than 10 days per well. Between 2016 and mid-2019, 50 smart completion rig interventions were carried out using the above technique, generating savings in oil platform demand of approximately 500 days. Individually, the development and application of this methodology is one of the initiatives with the greatest impact on well-building campaigns in these regions.

[0034] ADVANTAGES OF THE INVENTION

[0035] Economy / productivity

[0036] - Possibility of performing early injectivity induction before tree installation of underwater Christmas. This important practice represents one of the most important advances, as it allows the installation of the underwater Christmas tree with specialized vessels instead of using an oil platform, which represents a saving of about 10 days of oil platform per well and has accumulated to around 500 days of oil platform, counting between 2016 and 2019;

[0037] - Reduction of chemical costs by using basic products for preparation of filter cake breaking fluid took place in systems registered by service companies;

[0038] - Since it does not require the use of spiral tubes, reductions Up to three days of operation with the oil platform were reduced, and a potential gain in processing allocation was observed, positively impacting the oil recovery factor. Not using spiral tubing also eliminates the possibility of additional time due to waiting for equipment availability, delays in assembly, use, and disassembly caused by adverse weather conditions, which can add several days to the operation time and consequently increase costs.

[0039] - In addition to the economic and safety advantages associated with non-use By using spiral tubing, this methodology has the potential to promote increased well productivity and improved hydrocarbon recovery, as it increases the homogeneity of the treatment over the entire exposed interval.

[0040] - Reduction in resource demand for platform operations oil by enabling the transfer of the underwater Christmas tree installation operations to the specialized vessel.

[0041] - Reduction of the probability of anomalies during the installation of the Christmas tree submarine, given the greater expertise of the ship specializing in the same operation with an oil platform. In addition, in the event of anomalies, the impact with this vessel is much less significant due to the greater flexibility of its equipment and its higher maneuvering speed, as they are lowered by cable and not by column.

[0042] Health / Safety

[0043] - From a safety point of view, the use of spiral tube equipment This requires the mobilization of a dedicated team and a larger number of personnel on board the oil completion platform. This adds operational risks, as it involves high pressures, working at heights with heavy equipment, and the transport of loads and assemblies. Incidents have been recorded at various stages of the logistics and operation of this equipment, so finding an alternative to its use is always desirable and undoubtedly leads to greater safety in well construction.

[0044] - The absence of corrosivity of the treatment, which allows it to remain in contact during several hours with the completion equipment until it is completely injected, especially in cases where difficulties in the operation may arise, in which it is essential that it does not cause a corrosive process or damage to the elastomers.

[0045] Thus, in general, the key to the success of said completion process was to find an alternative to induce well injectivity that would create conditions for moving the acid treatment to be carried out to a later stage, but which, at the same time, would not be aggressive to the equipment, could even remain in the well for long periods, and, more importantly, would not cause significant losses so as not to damage the annular mechanical barriers and the packing sealing hole, and which would also not present an additional well safety risk in the event that it became necessary to remove the completion for repair after its placement.

Claims

Demands

1. A process for completing oil wells in pre-salt carbonate formations with early injectivity induction, characterized in that it includes the implementation of a mild treatment prior to the installation of a column support, without using spiral tube equipment and without a production column and underwater Christmas tree, increasing the initial injectivity, in which said mild treatment includes the following steps: preparing a volume of 100 to 300 barrels of a filter cake breaking fluid solution in a tank located on an oil platform, by adding a volume of saturated brine;after preparation, pumping of the filter cake breaking fluid solution supplemented with saturated brine into the well, displacing it with water-based completion fluid until it is positioned over the entire interval of interest, principally a drilled and open well, in which said pumping is carried out prior to the installation of the column support.

2. A method according to claim 1, characterized in that the filter cake breaking fluid solution is a solution of EDTA or acetic acid.

3. Method, according to claim 2, characterized in that a low corrosive potential metal ion complexing cushion is positioned by circulation at the bottom of the well immediately before the installation of the column support.