A unique inflow control system for any application
The DAR Assembly
In order to fully exploit the ability to control inflow of undesired fluids along a reservoir section – having permeability contrasts, faults and different pressure regimes – inflow control needs to be supported by an unperforated base pipe and annular flow restrictions. This compartmentalization together with the expected well production determines the number of DAR assemblies required to properly control the sweep and undesired breakthrough of water and/or gas.
Each DAR assembly is a separate load-carrying tool in the lower completion, which provides flow interfaces to adjacent sand/debris screens and accommodates fluid control modules of choice. A description of individual fluid control modules, like the Water Control Module (WCM) and Gas Control Module (GCM), is given below.
An important functionality of the DAR assembly is that it provides a large bypass for efficient removal of well construction fluids. If combined with a Cleanup Control Module (CCM), efficient cleanup is ensured all the way to the toe. Other options include e.g. a functionality for washpipe-free installation.
DAR fluid control modules
A DAR system is designed to control any undesired fluid, at any volume fraction and pressure differential. This functionality is provided for by individual fluid control modules, giving maximum flexibility and the ability to meet even the most demanding inflow control requirements.
The Water Control Module (WCM) controls undesired water production. It is insensitive to fluid viscosities, flow rates and Reynolds numbers and only requires a density difference between oil and water of at least 50 kg/m³. The WCM is designed to meet the following operator specifications:
The WCM closes and re-opens automatically on-the-fly during production. The in-situ water fractions (WF) for closing and re-opening are completely insensitive to flow rate and can take any value from 5% to 95% with extreme accuracy. It is recommended that the re-opening WF is about 5 – 10% lower than the closing WF.
The Gas Control Module (GCM) controls undesired gas production. It is insensitive to fluid viscosities, flow rates and Reynolds numbers and only requires a density difference between oil and gas of at least 50 kg/m³. The GCM is designed to meet the following operator specifications:
The GCM closes and re-opens automatically on-the-fly during production. The in-situ gas fractions (GF) for closing and re-opening are completely insensitive to flow rate and can take any value from 5% to 95% with extreme accuracy. It is recommended that the re-opening GF is about 5 – 10% lower than the closing GF.
The 3-phase control module (3CM) combines WCM and GCM and controls water and gas production. It is insensitive to fluid viscosities, flow rates and Reynolds numbers and only requires a density difference of at least 50 kg/m³ between the different fluids. The 3CM is designed to meet the following operator specifications:
The additional information provided under WCM and GCM is also applicable to 3CM.
Like the other modules, the Cleanup Control Module (CCM) is based on the patented ERV© technology that makes use of flotation elements. It provides a functionality that resolves one of the major challenges associated with long horizontal wells: how to ensure proper cleanup of the well, such that all reservoir zones contribute to the production. The CCM ensures that mud is cleaned out all the way to the toe, thereby avoiding an inactive mud-filled toe section that never contributes to production or requires significant reservoir depletion before it suddenly becomes activated.
The optional CCM works together with the mandatory Mud Control Module (MCM), where the latter module ensures that during cleanup, all fluids heavier that formation water are allowed to flow directly into the base-pipe, thereby bypassing the WCM, GCM or 3CM.
If the CCM is included, mud will still flow unrestrictedly into the basepipe, but the CCM will automatically cause the system to close once oil enters from the reservoir. The purpose of temporarily closing is to avoid a situation where a well section that is already clean, still contributes to the total well flow and thereby occupies hydraulic capacity that uncleaned sections could have benefited from. By automatically closing clean sections and maintaining the same total flow rate by opening the topside choke more, lower pressure and larger drawdown will be imposed on those sections that are still open and in the process of being cleaned up.
When the clean-up process is completed and the well is temporarily shut in, the system will automatically reset itself to production mode, where all fluids are forced through the WCM, GCM or 3CM.
The Mud Control Module (MCM) is mandatory and ensures that all well construction fluids heavier than formation water are allowed to enter directly into the basepipe, thereby bypassing the other fluid control modules.
The beauty of the DAR technology is its flexibility that allows it to be configured for different types of fields with different needs. For example, the DAR technology can easily be configured for gas-condensate fields using the Liquid Control Module (LCM) such that gas is allowed to enter the well, but liquid is not. Alternatively, water can be stopped, but not condensate.
Use of DAR technology for WAG wells has also been patented by Innowell. By applying different degrees of flow restriction for water and gas, the injection profile and reservoir sweep can be optimized. This can be achieved by the Alternating Control Module (ACM).
The Orientation Control Module (OCM) is mandatory for all DAR installations as this ensures that the orientation of all modules relying on flotation elements is automatically aligned with the gravity vector. Misalignments up to ±30º can be tolerated. Forced orientation is possible as a backup mechanism.
Various combinations of temporary and permanent check valves can be incorporated into the DAR assembly to prevent backflow during mud displacement and water flooding of the reservoir during shutdowns, but at the same time allow bullheading and scale squeeze operations.
A fail-safe module can also be included, which can be designed to let reservoir fluids bypass some or all of the other modules. This also enables conversion from oil to gas producer later in the well’s life.