Patent Application
20210396100
This disclosure relates generally to a method and apparatus for injection using a dynamically positioned vessel (DPV). This disclosure relates more particularly to a method and apparatus for temporary, optionally, short-term injection into a subsea well.
The offshore Oil & Gas industry has developed subsea wells to produce oil and gas from reservoirs below the ocean or lake. Under normal conditions, the wells produce the hydrocarbons naturally due to reservoir pressure, gas cap expansion, water aquifer support, or other naturally occurring drive mechanisms. In a number of subsea reservoirs, these naturally occurring drive mechanisms need artificial drive mechanisms to increase the production rate of hydrocarbons or recover the ultimate amount of hydrocarbons after years of production (or both). The industry has used Enhanced Oil Recovery (EOR) projects to address these reservoir challenges. EOR projects are reservoir-specific and may contain a combination of gas injection wells and water injection wells. Unfortunately, EOR projects are expensive due to the subsea wells, subsea infrastructure, and the topside injection infrastructure (pumps, chemicals, etc.) required.
The effectiveness of the EOR projects is highly dependent on the reservoir characteristics, including the type of reservoir fluids and the fracture gradient, permeability, and stratigraphy of the hydrocarbon-bearing formations. Oil & Gas operators use advanced reservoir models to compute the effectiveness of an EOR project and plan the location of the injection and production wells. Sometimes, these reservoir models have considerable uncertainty. In certain cases, these wells are located in incorrect or underperforming locations, and the topside injection equipment is incorrectly specified, all based upon the reservoir analysis. Identical water or gas injection mechanical systems can have widely divergent effectiveness as driven by the reservoir response.
Ultimately, the production capacity of reservoirs can only be proven via real-world experience. Temporary injection tests have been performed before but have been performed from mobile offshore drilling units (MODUs) because a riser is required to connect the topside injection equipment to the subsea well. These tests have also typically been limited to short durations due to the cost of the MODUs. Indeed, the risers typically used are rigid in nature and require a derrick or specialized handling system to prevent damage to the subsea well. The specialized handling systems that are required limit the technically available fleet of vessels. These riser handling systems incite the Oil & Gas operators to use a MODU or other expensive vessel that is fitted with a derrick/tower system.
Therefore, there is a need in the art for a method and apparatus for injection into a subsea well that do not require a MODU. Preferably, the method and apparatus are well suited for temporary or short-term injection.
The disclosure describes a method for injecting fluid into a subsea well in which a Xmas-tree is coupled to a subsea wellhead that is located at the top of the subsea well.
The method may comprise the step of providing a dynamically positioned vessel (DPV) that includes a hoist. The hoist may include a crane, a winch, a davit, a block and tackle, or another known hoisting mechanism. The DPV may include one or more injection pumps.
The method may comprise the step of assembling a system. The system may comprise a lower riser package (LRP) that includes a bore closable with a seal capable of emergency shut down and emergency disconnect sequence. The bore of the LRP may be connectable, directly or indirectly, to the subsea wellhead. The system may comprise an emergency disconnect package (EDP) that includes a bore connected to the bore of the LRP, the bore of the EDP being closable with a fail-safe close valve. The system may comprise a tapered stress joint (TSJ) that includes a bore connected to the bore of the EDP. The system may comprise a flexible riser portion that includes a bore connected to the bore of the TSJ. The system may comprise a rigid riser portion that is connected to the flexible riser portion.
In some embodiments, the method may comprise the step of lowering the system from the hoist of the DPV onto the top of the Xmas-tree.
In some embodiments, the method may comprise the step of lowering the system from the hoist of the DPV onto the top of a subsea pile that is provided on a seafloor. The LRP may be coupled to the subsea pile.
The method may comprise the step of connecting the bore of the LRP to a bore of the Xmas-tree.
The method may comprise the step of injecting fluid at least through the system, through the Xmas-tree, and into the subsea well. Injecting the fluid may be performed using the one or more injection pumps.
The method may comprise the step of adjusting at least one of injection pressure and injection flow rate.
The method may comprise the step of measuring a reservoir response to the at least one adjusted injection pressure and injection flow rate.
The method may comprise the step of updating a reservoir model based on the measured reservoir response.
The method may comprise the step of disconnecting the system from the Xmas-tree.
In some embodiments, the method may comprise the step of connecting the system to a flow base coupled to the subsea pile. The flow base may include a flowline closable with shut-down valves and a high integrity pressure protection systems (HIPPS). The HIPPS may include a sensor of wellbore pressure or temperature, and logic electronics that is communicatively coupled to the sensor and programmed to close the shut-down valves based on measurements performed by the sensor.
In some embodiments, the method may comprise the step of assembling another system. The other system may comprise a lower riser package (LRP) that includes a bore closable with a seal capable of emergency shut down and emergency disconnect sequence. The other system may comprise an emergency disconnect package (EDP) that includes a bore connected to the bore of the LRP, the bore of the EDP being closable with a fail-safe close valve. The other system may comprise a tapered stress joint (TSJ) that includes a bore connected to the bore of the EDP. The other system may comprise a flexible riser portion that includes a bore connected to the bore of the TSJ. The other system may comprise a rigid riser portion that is connected to the flexible riser portion. The other system may be lowered from the hoist of the DPV onto the top of a subsea pile that is provided on a seafloor. The LRP of the other system may be coupled to the subsea pile. The bore of the LRP of the other system may be connected to the bore of the Xmas-tree through a jumper.
In some embodiments, the top of the Xmas-tree may further be connected to a second riser and a topside assembly capable of pumping fluid through the second riser, through the Xmas-tree, and into the subsea well. At least a portion of the topside assembly may be repaired or replaced while injecting fluid through the system. Alternatively, injecting the fluid through the system may be performed while pumping fluid through the second riser, through the Xmas-tree, and into the subsea well. At least a portion of the topside assembly may be replaced with components designed based on the measured reservoir response.
The disclosure also describes an apparatus for injecting fluid into a subsea well.
The apparatus may comprise an assembly that includes the LRP, the EDP, the TSJ, and the rigid riser portion that is connected to the flexible riser portion,
The apparatus may comprise the DPV.
The apparatus may comprise the surface tree. The surface tree may be positioned on the DPV. The one or more injection pumps may be connected to the rigid riser portion via the surface tree.
The apparatus may comprise the Xmas-tree that is provided on a seafloor.
In some embodiments, the bore of the LRP may be connected on top of the Xmas-tree.
In some embodiments, the apparatus may comprise the flow base. The flow base may be mounted on the subsea pile. The bore of the LRP may be connected on top of the flow base.
In some embodiments, the LRP is mounted on the subsea pile, and the bore of the LRP is connected to the subsea wellhead via the jumper.
For a more detailed description of the embodiments of the disclosure, reference will now be made to the accompanying drawings, wherein:
It is to be understood that the following description discloses one or more exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.
The disclosure describes a method and apparatus to facilitate a short-term or temporary injection program to allow Oil & Gas operators to prove the accuracy of the reservoir models and/or the producibility of reservoirs in actual conditions without investing all the costs to build a long-term EOR project. The method/apparatus involves a DPV that can be located above a potential injection well, inject water or other fluids temporarily or for a short period of time, adjust the injection parameters, and either continue operating for the life of the apparatus or as long as required to add permanent facilities on another platform. The method/apparatus also involves a hybrid riser system to connect the vessel to the subsea well or subsea flowline system. The hybrid riser system includes a rigid portion and a flexible portion. Introducing a flexible portion in the riser system can facilitate injection operations. Indeed, the flexible portion of the riser is used to mitigate fatigue loading and vessel heave. As such, the hybrid riser system does not require a heave compensation system, in contrast to a MODU, which has a heave compensation system. Consequently, injection operations can be performed with a DPV, which are usually more available than MODUs. Also, the cost of deploying a DPV is usually lower than the cost of deploying a MODU.
This method/apparatus would allow the Oil & Gas operators to construct a short-term or temporary injection system to connect to a subsea well and perform injection tests that can confirm or provide better estimates of a number of characteristics of the reservoir models. In turn, these confirmed or improved characteristics of the reservoir models may allow the Oil & Gas operators to better plan the long-term EOR project. In other words, this method/apparatus would allow the Oil & Gas operator to test the efficiency of a planned EOR system before sanctioning a full field EOR project. Secondarily, this method/apparatus may be used to supplement an existing EOR project. For example, this method/apparatus may also be used as a backup to an existing EOR project that may experience a mechanical failure that prevents the permanent equipment from performing as required. Another potential use for this method/apparatus is to allow the adjustment of the injection pressures and/or flowrates (or other injection parameters) to optimize the overall performance of an existing EOR project.
The apparatus can be designed such that short-term operations can be done as cost-effectively as possible but have features that allow the apparatus to be upgraded for longer-term operations. For short-term operations, subsea components similar to the subsea components typically utilized with an intervention riser can enter through the top of a Xmas-tree that is provided on top of the wellhead. For longer-term operations, reliance on the top entry does not provide an optimal level of safety, and additional features may be added to enhance the apparatus's safety. For example, the apparatus can be upgraded by installing a pile separate from the Xmas-tree and subsea components similar to the subsea components typically utilized in early production systems.
System 10 comprises a lower riser package (LRP) 104. The LRP 104 includes bore isolation valves to shut off and isolate the subsea well during normal operations and during emergency operations. These valves would typically be considered primary well control barriers. The LRP 104 may also include a control panel for a remotely operated vehicle (ROV) to manually operate the valves. Additionally, the LRP 104 may include chemical injection ports to facilitate well operations. As such, the LRP 104 includes a bore closable with a seal and/or a shear ram 120 (shown in
In the example of
Preferably, system 10 has a bore thru the riser system (i.e., the rigid riser portion 12 and the flexible riser portion 102), the TSJ 114, the EDP 118, and the LRP 104 having a diameter sufficient to allow passage of tools and wellbore components (e.g., wireline plugs). The shape of the flexible riser portion 102 can be modified to facilitate the passage of these tools and wellbore components by properly positioning the DPV 14 above the subsea wellhead 122.
The LRP 104 and EDP 118 may be operated from the DPV 14, be automated, or be operated with the ROV.
The surface tree 50 further includes one or more valves 22 capable of sealing off the rigid riser portion 12. The surface tree 50 also includes a pressure and/or flow rate sensor 24 capable of measuring pressure and/or flow rate of the fluid flowing into (or out of) the flexible hose 110, the rigid riser portion 12, the flexible riser portion 102, and the TSJ 114. As shown in
The injection pumps 30 are preferably capable of adjusting injection pressure and/or injection flow rate. As such, a reservoir response to the injection pressure or injection flow rate can be measured. For example, the reservoir response can be characterized by parameters such as injection flow rate (measured by the sensor 24) when the injection pressure is adjusted, injection pressure (measured by sensor 24) when the injection pressure is adjusted, hydrocarbon production flow rate out of another well, water production flow rate out of another well, pressure in another well, or other reservoir parameters. A reservoir model can be updated based on the measured reservoir response. The updated reservoir model can be used to design the equipment for a long-term EOR project.
In other embodiments, the injection pumps 30 may be included on a vessel other than the DPV 14.
The flow base 108 is coupled to a subsea pile 130 that is anchored into the seafloor near the subsea wellhead 122. The flow base 108 includes a flowline closable with one or more shut-down valves of high integrity pressure protection systems (HIPPS) 128. The HIPPS 128 also includes one or more sensors of wellbore pressure or temperature (not shown), one or more accumulator supply bottles (not shown) capable of actuating the shut-down valves, and logic electronics (not shown) that is communicatively coupled to the sensor and programmed to close the shut-down valves based on measurements performed by the sensor. Compared to
The injection pumps 30 (in
In some embodiments, the apparatus useable for short-term or temporary injection can be initially assembled without the flow base 108, as shown in
In other embodiments, the apparatus useable for short-term or temporary injection can be initially assembled with the flow base 108, as shown in
Optionally, a top of the Xmas-tree 124 is further connected to a second riser (not shown) and a topside assembly (not shown) capable of pumping fluid through the second riser, through the Xmas-tree 124, and into the subsea well. In some cases, the apparatus can be used to replace the injection normally occurring through the second riser while the topside assembly coupled to the second riser (not shown) is being repaired or replaced by another topside assembly. In other cases, the apparatus can be used to supplement the injection normally occurring through the second riser. In such cases, the apparatus may provide enhanced operational flexibility for adjusting injection pressure and/or injection flow rate into the subsea well. As such, a reservoir response to the adjusted injection pressure or injection flow rate can be measured, and a reservoir model can be updated based on the measured reservoir response. The updated reservoir model can be used to redesign the equipment for a long-term EOR project, for example, redesign the topside assembly coupled to the second riser.
While the LRP 104, the EDP 118, and the HIPPS 128 have been described as being actuated by accumulator supply bottles, other actuators known in the art can be used instead of, or in addition to, accumulator supply bottles.
In alternative embodiments to the one shown in
Regardless of whether the flow base 108 is provided or not, coupling the LRP 104 directly or indirectly to a subsea pile 130 avoids transmitting loads to the wellhead 122. These loads may be caused by vibrations of the LRP 104, the EDP 118, the TSJ 114, the flexible riser portion 102, and the rigid riser portion 12, or by the movement of the DPV 14. Compared to
This application claims the benefit of priority to U.S. provisional application Ser. No. 63/040,728 filed on Jun. 18, 2020, which is incorporated herein by reference for all and/or any purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63040728 | Jun 2020 | US | |
| 63040736 | Jun 2020 | US | |
| 63040739 | Jun 2020 | US |
