Patent Application
20250026449
The present invention is applied in the area of offshore mooring systems and methods and, more specifically, refers to systems and methods for increasing the Load Capacity of Fixed Points (CCPF) of Offshore Mooring Systems (SAO) of a Stationary Production Unit (UEP) of hydrocarbons by artificially increasing the undrained resistance of the foundation grounds carried out through Thermal Grounds Weighting (ATS) of a foundation with characteristics of low undrained shear resistance.
The mooring of floating structures on the seabed, for drilling and oil production operations in underwater locations, can occur through different types of mooring systems. Among them, it can be mentioned, for example, anchors or drag plates, gravity structures, suction structures, driven plates or piles, drilled and filled or cemented piles.
When it is necessary to increase the mooring load capacity of a UEP, either because it is a new exploratory frontier that has foundation grounds with characteristics of low undrained resistance and/or more extreme oceanographic conditions and/or greater load capacity of deck in the UEP, it is commonly proposed, in the state of the art, to increase the number of mooring system points and/or increase the dimensions/mass/ballast of the mooring system and/or install the mooring system in ground layers of greater undrained resistance, that is, in deeper regions (greater burial of the pile in the foundation grounds).
However, such solutions generate several associated problems, such as: a) logistical problems, as the complexity and costs of transporting the pile/anchor along highways and river travel routes are increased (i.e., from where was built to the port, and from the port to the installation site); b) increased installation time; c) need for vessels with greater load capacity; d) increased handling complexity and, as a result, increased installation time and costs for mooring systems, in addition to increased risks.
Specifically, in the case of torpedo type piles, piles driven by their own weight, their load capacity is conditioned by the depth of burial of the foundation element and the undrained resistance of the foundation grounds. The greater the burial, the greater the load capacity. However, the penetration of the foundation element is conditioned by the kinetic energy imposed on the system, in this case, its own weight and the impact speed (terminal velocity) on the seabed. It is worth noting that the load capacity of a torpedo pile (traction or pulling capacity of the torpedo from the ground) is proportional to the kinetic energy that occurred (Kinetic energy=½*Mass of the pile*Speed 2).
Thus, the torpedo pile is launched vertically, from a determined height, and during its free fall it acquires enough speed so that when it hits the ground at the bottom of the sea, it has enough energy to penetrate into the ground as necessary to meet the loads of pullout.
Terminal velocity, as mentioned above, is a speed that the torpedo pile does not exceed and basically depends on the model of the torpedo pile (weight and shape) and the launch arrangement (configuration of cables and accessories). Therefore, the torpedo pile has a minimum shot height (or launch height), which is necessary for the pile to free fall towards the ground and have time to accelerate until it reaches its terminal velocity. Thus, in soft grounds, for example, the pile penetrates more, and in hard grounds, it penetrates less.
Based on the above, it is noted that the development of mooring systems that employ torpedo piles has allowed some advances in the state of the art. For example, there are torpedo piles that increase their load capacity via a mechanism that increases the contact area of the pile with the foundation grounds, with these mechanisms being installed in the front or back part of the pile. However, these systems have low effectiveness and can compromise the operation of foundations on the sea floor, either because they do not reach the ideal depth, or because they have a much lower load capacity than desired. Furthermore, as they heavily depend on strictly mechanical factors (model and design of pile improvements), the operation risk becomes greater as the probability of failure also increases.
Given the difficulties in the state of the art mentioned above, relating to increasing the load capacity of mooring floating structures on the seabed, there is a need to develop a technology capable of safely and efficiently carrying out such operations.
The search for history led to some documents that disclose subject matters within the technological field of the present invention.
Document PI 0405799-6 B1 relates to mooring equipment with vertical load of floating structures, used in the drilling and production of oil and gas wells, which uses the concept of free fall pile (called torpedo pile) basically consisting of an elongated body, a lower end that is provided with a tapered tip, while the upper end is provided with a closing disc. The pile body has vertical fins near the top. The inside of the pile body is filled with high specific weight material, distributed so that the center of gravity of the pile is located well below its center of fluctuation. The pile is installed using the potential energy generated by its free fall, from a vessel, to ensure its penetration into the seabed. However, to increase the increased gripping power (mooring) the pile uses articulated movable plates adapted to the upper part of its body, provided with flaps, and the flaps are capable of causing rotation around joints when pullout effort is exerted in the system, until at the end of the pullout effort, the plates reach contact points of stops, which is what differentiates this document from document PI 9603599-4 A, which has a more basic and general structure for torpedo piles. Therefore, document PI 0405799-6 B1 provides for the increase in load capacity via the mechanism of increasing the contact area of the pile with the foundation grounds.
In its turn, document US 2005/0117977 A1 relates to mooring equipment that uses the same principle as document PI 0405799-B1. However, the mechanism in document US 2005/0117977 A1 is installed at the lower end of the pile. Therefore, if the mechanism is not activated (opened), the desired increase in load capacity will not occur. Furthermore, during pile installation, if the mechanism opens before the ideal moment, the pile will not reach the specified depth and the load capacity will be much lower. In other words, installation complexity increases and there is still the risk of obtaining a lower load capacity, in addition to higher costs.
The document “Centrifuge modeling of temperature effects on the pullout capacity of torpedo piles in soft clay” (GHAAOWD, I; MCCARTNEY, J. S.; SABOYA, F. Groundss and Rocks 45 (1)-2022) describes results of centrifuge modeling carried out to understand the effects of temperature changes on the vertical pullout capacity of torpedo pile models embedded in clay layers. This document describes a torpedo pile with an internal heating element of the electrical resistance heater type (thermoelectric device), and the energy supply must come from an external source. After installation of the pile, the heater can be operated (by an external electrical power source) to achieve a target temperature or power output. The document also describes the results of experiments carried out in a centrifuge to evaluate the effects of temperature changes, around a torpedo-type pile made of stainless steel and on a reduced scale (diameter=15.75 mm and length=108.6 mm) 1/50, in its vertical pullout load capacity when installed in clay layers. The study reveals a torpedo pile model equipped internally with a heating element (an electrical resistance heater) with an external electrical supply of 500 Watts (diameter=12.6 mm, length=101 mm), to provide heat and to control the temperature of the pile. It was found that the increase in grounds temperature via electrical resistance installed in the pile, followed by natural cooling, allowed the drainage of excess grounds pore pressure and, thus, resulted in an increase in the axial pullout load capacity of the pile, but without affecting pullout stiffness.
However, using the “scaling laws” for centrifuge tests, as described in the document “Thermal Improvement of the Pullout Capacity of Offshore Piles in Soft Clays”, GHAAOWD, Doctoral thesis, University of California, USA, 2018, which gave rise to the document “Centrifuge modeling of temperature effects on the pullout capacity of torpedo piles in soft clay”, it would take 12,500 hours (520.83 days) on the prototype scale (5 hours on the reduced scale model with scale factor N=1/50) to stabilize the temperature applied via electrical resistance, in addition to around 75,000 hours (3,125 days) on the prototype scale (30 hours on the reduced-scale model with scale factor N=1/50) of heating to maintain the temperature. Furthermore, for the thermal consolidation process to occur (setup), approximately 12,500 more hours (520.83 days) are required on the prototype scale (5 hours on the reduced scale model with N=1/50) to stabilize the temperature after the electrical energy supply via electrical resistance is terminated. In other words, to increase the vertical load capacity of the pile (from 19 to 58%) it would take 100,000 hours (4,166.67 days), of which 87,500 hours (3,645.83 days) would be needed to supply electrical energy (to increase from 25 to 60° C.) via floating unit electrical cable (or an installation on land, in the case of shallow water) to the pile driven into the seabed, thus, increasing the operation complexity and the costs of renting a vessel of this size with a team within 24 hours operating and supplying electrical energy, without considering energy losses due to the distance and temperature from generation to the source.
Therefore, such a procedure is inefficient and technically and economically impractical, due to high execution time and costs. Therefore, installing a new torpedo pile in the conventional way (without an internal heating element) would be faster, have a lower cost, greater load capacity and a greater probability of success than applying the method proposed in these prior art documents. Furthermore, the application of the method of the aforementioned documents would harm the implementation schedule of an offshore oil production project, thus, generating loss of profit, since generally, after installing the pile in the conventional way, in around 30 days, the pile can be connected to a UEP that starts field production. Additionally, with the generation of energy externally and over a long period (thousands of days), there is a high generation of greenhouse gases (GHG).
The document “Centrifuge modeling methodology for energy pile pullout from saturated soft clay” (GHAAOWD, I; MCCARTNEY. Geotechnical Testing Journal, 45 (2)-2022) describes a test configuration and methodology for carrying out pullout centrifuge tests of a reduced scale cylindrical pile (diameter=25 mm and length=255 mm) installed in organic white clay (kaolin), with the aim of understanding how heating the pile improves the shear resistance of the grounds/pile interface through thermal consolidation (thermal weighting). In the test carried out in this document, an externally powered electrical resistance heater (diameter=12 mm, length=200 mm) with 500 Watts of power was used inside the aluminum pile to heat the grounds-pile interface to a controlled target temperature, with the annular space pile/heater filled with dense sand to standardize the temperature. Thermocouples and pressure transducers installed in the clay layers were also used to monitor the coupled heat transfer and water flow processes. When the scaled-down pile was tested at a 50 g acceleration, heated from 20 to 65° C. and then cooled, the increase in vertical load capacity of the pile was 1.43 times greater than that of the unheated pile. And, after the pile pullout test, tests were carried out with a T-bar penetrometer on the clay layers to correlate the increase in the undrained shear strength of the clay layers with the increase in the load capacity of the pile.
Again, using the “scaling laws” for centrifuge tests, in relation to the variable “time relative to diffusion parameters”, where the scale is 1/N2, with N being the scale factor, where in the aforementioned document N=1/50 was used, it would take 12,500 hours (520.83 days) on the prototype scale (5 hours on the reduced scale model with scale factor N=1/50) to stabilize the applied temperature via electrical resistance, in addition of approximately 75,000 hours (3,125 days) on the prototype scale (30 hours on the reduced scale model with N=1/50) of heating to maintain the temperature and, for the thermal consolidation process to occur (setup), it is necessary plus approximately 15,000 hours (625 days) on the prototype scale (6 hours on the reduced scale model with N=1/50) to stabilize the temperature after the electrical energy supply via electrical resistance is terminated. In other words, to increase the vertical load capacity of the pile by 1.43 times, 102,500 hours (4,270.83 days) would be required, of which 87,500 hours (3,645.83 days) would be necessary to electrical energy supply (for an increase of 20 to 65° C.) via floating unit cable (or from an installation on land in the case of shallow water depth) to the pile driven into the seabed, thus, increasing the complexity of operation and the costs of renting a vessel of this size with a 24-hour team operating and supplying electrical energy, without considering energy losses due to the distance and temperature from generation to the source.
Therefore, even changing the dimensions, the pile material (in the study conducted by the aforementioned document, the dimensions were doubled and a material with a higher thermal conductivity coefficient was used) and the heating source (in the study conducted by the aforementioned document dimensions were doubled) and temperature, such a procedure is inefficient and technically and economically impractical, due to high execution time and costs, as previously mentioned. Therefore, installing a new torpedo pile in the conventional way (without an internal heating element) would be faster, would have lower cost, greater load capacity and greater probability of success than applying the method proposed in this document. And, as already mentioned, using the method in this document from the state of the art would harm the implementation schedule of an offshore oil production project, thus, generating loss of profit, as generally, after installing the pile in the conventional way, in about 30 days it can be connected to a UEP that starts field production. Furthermore, with the generation of energy externally and over a long period (thousands of days), there is a high generation of greenhouse gases (GHG).
Therefore, given the difficulties in the state of the art mentioned above, relating to increasing the load capacity of mooring floating structures on the seabed, there is a need to develop a technology capable of carrying out safely and efficiently such operations and with a lower carbon footprint. Therefore, the current state of the art mentioned above does not have the unique characteristics that will be shown in detail below.
The present invention is applied in the area of offshore mooring systems and methods and, more specifically, relates to a method and system that increases the load capacity of mooring systems by artificially increasing the undrained resistance of the foundation grounds carried out through thermal foundation grounds weighting (ATS).
The system of the present invention and, therefore, its method, works autonomously, automatically and simultaneously with the crimping process, without the need for external energy supply, with a lower carbon footprint and without compromising the implementation schedule of an offshore oil production venture, not causing loss of profit.
In summary, the system and method of the present invention promote the heating of the grounds around the pile through an exothermic physical-chemical-nuclear process, which works autonomously, automatically and simultaneously with the process of driving the pile into the seabed, without the need for external energy supply, thus, constituting a unique system for increasing the load capacity of fixed points (CCPF) of offshore mooring systems (SAO) of a stationary production unit (UEP).
Specifically, the present invention provides an improvement in the undrained resistance of a clayey grounds, which should be understood as the shear resistance offered by the grounds when requested quickly, without the condition of drainage of interstitial water, which will occur through grounds consolidation applying a physical-chemical-nuclear process (exothermic type) that leads to a decrease in the original void index, that is: increase in pore pressure→dissipation of excess pore pressure→plastic volume variation→increase in effective stress→increase in grounds shear strength→increase in mooring load capacity.
The grounds consolidation process described above occurs through the use of equipment installed inside the pile, which generates heat and, thus, increases the temperature of the grounds and promotes its weighting and, as a consequence, increases the mooring load capacity. Therefore, the system and method of the present invention can be applied to different types of foundation elements, such as gravity piles, suction piles, driven piles, drilled and filled piles.
In this way, the method and system developed in the present invention make it possible to reduce the number of fixed points of mooring systems compared to the state of the art. Using the method and system of the present invention, the deck load on the UEP can also be increased, or the UEP can be installed in more extreme oceanographic conditions, maintaining the number of mooring points due to the increase in mooring capacity promoted by the present invention.
Additionally, the method and system described in the present invention have advantages that surpass the state of the art in that they can reduce the number of mooring points, facilitate the underwater arrangement of other equipment (ducts, riser, lines, PLET, PLEN, BOP, ANM, etc.) and reduce mooring system time and costs. There is also an advantage associated with enabling the use of stationary production units (UEP) that require greater mooring load capacity. Thus, enabling better results in relation to what is described in the prior art, in addition to the solution shown by the present invention being less risky and more effective.
Therefore, the advantages and objectives of the present invention are achieved by providing a system for increasing the load capacity of fixed points of mooring systems that comprises: a mooring connected to a pile and a connector; the pile comprising: —a lower portion internally containing ballast material; and —an upper portion filled with reagents containing a chemical reagent of composition A in a first compartment and a chemical reagent of composition B in a second compartment; wherein the compartment containing chemical reagent A and the compartment containing chemical reagent B are separated by a rupture diaphragm that ruptures autonomously and automatically when the pile is driven into seabed, generating products C and D and releasing energy in the form of heat due to the exothermic reaction between reagents A and B, without flame generation.
Furthermore, according to an embodiment of the present invention, a method of increasing the load capacity of fixed points of mooring systems is also provided, comprising the following steps: driving a pile into seabed; breaking the rupture diaphragm autonomously and automatically when driving the pile into the seabed; and generating products C and D, releasing energy in the form of heat, to increase the undrained resistance of the foundation grounds through thermal weighting in a region surrounding the pile.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
The brief description above, as well as the detailed description below, of the preferred embodiments of the invention in question, will be better understood when read in conjunction with the attached drawings. It must be understood, however, that the invention in question is not limited only to the precise arrangements and instruments shown.
Therefore, the present invention will be described below with reference to its typical embodiments and also with reference to the attached drawings.
In the following, reference is made in detail to the preferred embodiments of the present invention illustrated in the attached drawings. Whenever possible, the same or similar reference numbers will be used throughout the drawings to refer to the same or similar features. It should be noted that the drawings are in simplified form and are not represented to a precise scale, so slight variations are anticipated.
The present invention relates to a method and a system for increasing the load capacity of fixed points (CCPF) of offshore mooring systems (SAO) of a stationary production unit (UEP) of hydrocarbons by thermal weighting of foundation grounds (ATS) with characteristics of low undrained shear strength. More particularly, the method and system provided by the present invention promote the heating of the grounds around the pile through an exothermic nuclear physicochemical process autonomously, automatically and simultaneously with the pile driving process.
In particular, chemical reagents of different compositions are inserted inside the pile itself, and separated by a mechanical seal, which breaks during driving, thus, allowing the reaction and the release of energy in the form of heat. Alternatively, the chemical elements can be replaced by a generation 3+ nuclear reactor, with its activation also occurring autonomously and simultaneously with the pile driving process. Therefore, according to the configurations proposed by the present invention, there is no need for an external connection via an umbilical cable starting from the pile, nor for a support boat to generate and supply energy to heat the pile/grounds, nor for an increase in the interval time between the pile driving and its service start time (setup), nor the generation of greenhouse gases (GHG).
It should be noted that the new hydrocarbon exploration frontiers have foundation grounds with characteristics of low undrained resistance, in addition to more extreme oceanographic conditions, which lead to the need for a greater mooring load for stationary production units (UEP).
In this sense, reference is made to
In the configuration shown in
Below is a detailed description of a preferred embodiment of the present invention, which is exemplary and in no way limiting. Nevertheless, it will be clear to one skilled in the art, from reading this description, possible additional embodiments of the present invention still comprised by the essential and optional features below.
Thus,
Furthermore, the first compartment containing the chemical reagent of composition A is separated from the compartment containing the chemical reagent of composition B by a rupture diaphragm 17 (seal or mechanical disc) arranged inside the upper portion filled with reagents 18 and designed or configured to break when the pile 02 impacts the ground during the gravity driving process.
According to an embodiment of the present invention, the chemical reagent of composition A used is one or more of: calcium oxide, copper sulfate, magnesium, iron oxide, copper oxide, or combinations thereof. In relation to the chemical reagent of composition B, one or more of: water, carbon dioxide, zinc, aluminum, or a combination thereof are used. It should be noted that NaCl can be added to reagents to speed up reactions.
From the reaction between reagents A and B, when diaphragm 17 is ruptured, products C and D are generated, through an exothermic reaction. Product C is one or more of: calcium hydroxide, zinc sulfate, magnesium hydroxide, aluminum oxide, or a combination thereof; while product D is one or more of: copper, hydrogen, or a combination thereof. It is also noted that the exothermic reaction releases energy in the form of heat.
Shown below, by way of example, are chemical equations that represent the processes previously described, involving reagents A and B that give rise to products C and D through an exothermic reaction:
CaO(s)+H2O(l)→Ca(OH)2(s)+Heat [Equation 1];
CaO(s)+CO2(g)→CaCO3(s)+Heat [Equation 2];
CuSO4(s)+Zn(s)→ZnSO4(s)+Cu(s)+Heat [Equation 3];
Mg+2H2O→Mg(OH)2+H2+Heat [Equation 4];
Fe2O3+2Al→2Fe+Al2O3+Heat [Equation 5];
3CuO+2Al→3Cu+Al2O3+Heat [Equation 6].
Due to the finite volume of reagents, their reaction rate and heat dissipation in the ground, in an interval of less than 30 days the process is terminated, with this, the UEP 09 mooring procedure which consists of connecting the tie 05 of the pile 02 to the other components up to UEP 09 can occur in a conventional way to start field production, as illustrated in
Knowing that enthalpy is the thermal energy involved in different types of chemical reactions, the change in enthalpy (ΔH) can be calculated by subtracting the enthalpy value of the products (Hp) by the enthalpy value of the reagents (Hr), as shown in
ΔH=Hp−Hr [Equation 7].
Thus, the result of the enthalpy change calculation will determine the amount of heat released, as shown in
According to an alternative embodiment of the present invention, the chemical reagents A, B in the upper portion of the pile 02 can be replaced by a nuclear reactor of generation 3+ of power below 1 MW (not illustrated), with its activation also occurring autonomously and simultaneously with the pile 02 driving process. Therefore, there is also no need for external connection via umbilical cable starting from the pile 02, nor for a support boat to generate and supply energy to heat the pile/grounds, nor the increase in the time interval between the pile driving and its start-up time (setup), nor the generation of greenhouse gases (GHG).
To conclude,
Reference is made to
Based on the foregoing, the present invention relates to a method and system that increases the load capacity of mooring systems by artificially increasing the undrained resistance of the foundation grounds carried out through thermal weighting (ats) of foundation grounds through an exothermic physical-chemical-nuclear process autonomously, automatically and simultaneously with the pile driving process, without external energy supply and without changing the schedule of an offshore oil production project. The present invention can be applied to gravity piles (torpedo piles), suction piles, driving piles, drilled and filled piles.
Therefore, the method and system developed by the present invention make it possible to reduce the number of fixed points of mooring systems compared to the prior art. Or, the deck load on the UEP can be increased, or the UEP can be installed in more extreme oceanographic conditions, maintaining the number of mooring points due to the increase in mooring capacity by the present invention.
Furthermore, the method and system described by the present invention show a condition that surpasses the state of the art by being able to reduce the number of mooring points, simplify (facilitate) the underwater arrangement of other equipment (ducts, riser, lines, PLET, PLEN, BOP, ANM, etc.) and reduce the time and costs of the mooring system. Furthermore, the present invention makes it possible to use stationary production units (UEP) that require greater mooring load capacity. Therefore, the present invention enables better results than the means described in the state of the art, in addition to the present invention providing a solution with less risk, greater effectiveness and lower carbon footprint.
Although the present invention has been primarily described in terms of the constituent elements of the system, a person skilled in the art will readily understand that the system can be associated with a method of increasing the load capacity of fixed points of mooring systems comprising the following steps: driving a pile 02 into seabed 20; breaking the rupture diaphragm 17 autonomously and automatically when driving pile 02 into the seabed 20; and generating products C and D, releasing energy in the form of heat 22, to increase the undrained resistance of the foundation grounds through thermal weighting in a region surrounding the pile 23.
Those skilled in the art will value the knowledge shown here and will be able to reproduce the invention in the embodiments shown and in other variants, covered within the scope of the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| BR 1020230147380 | Jul 2023 | BR | national |
