Toe Valve Considerations

After a horizontal well has been cased and cemented, operators need to create a flow path to pump down either balls for a sleeve completion or plugs for a Plug & Perf completion. Toe Valves have become the standard method for creating flow path in the well for pumping the first plug down to start the completion operation. Originally toe valves were used in sleeve completions because the graduated ball seats used to open each sleeve eliminated the ability to push TCP guns to the bottom, so a hydraulically actuated toe valve was employed. As this method became more accepted operators that utilized Plug & Perf looked to eliminate the need for TCP on location, saving time and money, by switching to toe valves as well. The goal of a toe valve is to not interfere with getting the casing string to depth, provide a bore that can easily be wiped of cement, and to reliably open as expected. So, when selecting a toe valve for your completion there are three things you need to consider; dimensions, geometry, and reliability. 

Dimensions

With all oilfield tools the two forces that are most important, especially for pressure actuated tools, are burst and collapse. Fundamentally for a tubular part, increasing the thickness of the part also increases the it’s ability to withstand burst and collapse. And, as the inner diameter (ID) gets larger, the thickness of the tube will have to increase to maintain the same burst and collapse values. This fact drives the decisions the toe valve dimensions. If you need a larger ID, then the outside diameter (OD) will have to increase. Or, if you want a smaller OD then the ID will have to shrink as well. Many operators would like to have a toe valve that has an internal diameter equal to that of the casing, this would allow them to use an industry standard cement wiper plug. However, to achieve this and maintain the same pressure ratings the outside diameter will have to increase as well. This increase in OD could be restrictive for getting your casing to the bottom of your well. If so, an ID smaller than that of the casing will have to be used which will require the use of a special wiper plug designed to effectively wipe the ID of the casing as well as through the restricted ID of the tool. These dimensions all must be considered when choosing the right tool for your completion.

Geometry

The second goal of a toe valve is to ensure that the selected wiper plug can effectively be pumped through the valve without damage. The interior geometry plays an important role in this. If the fins of the wiper plug pass through any abrupt shoulders or slots in the valve it could damage the plug. Damage to the fins on the plug could cause cement to remain in the ID of the valve and the casing below the valve. This remaining cement could affect the valve's ability to open when necessary. It’s important for the ID of the sleeve to be as smooth as possible to reduce the chances of damage to the wiper plug. 

Also, if the design of the tool is such that internal and external ports must be aligned to have full flow area to the reservoir make sure that they’re mechanically aligned during assembly. If the inner and outer ports aren’t held mechanically in alignment the two sleeves could shift during installation, significantly reducing the flow area through the ports. This reduction could result in the tool being clogged or not providing the required flow for an efficient pump down operation.

Reliability

Finally, the most important consideration for selecting a toe valve is reliability. The benefits of using a toe valve over TCP is time savings, less services on location, and overall reduction of risk. If the toe valve is unreliable it increases more risk to the operation because there will be a rush to mitigate the problem. While the two considerations above play a role, the design and functionality of the tool determine the long-term reliability of the product. All cemented toe sleeve on the market utilize an atmospheric chamber that is pinned open by a shear or burst mechanism. Once the hydrostatic and applied pressure on the well exceeds the shear mechanism, the pressure on the well acts against the chamber shifting the sleeve open. The main key to reliability is protecting this atmospheric chamber throughout the life of the valve prior to opening. Designing the tool with robust seals that protect a simple chamber design. Valves with complex geometries that require additional sealing tend to see higher probability of issues. When choosing the right toe valve, understanding how the valve protects its atmospheric chamber will be the best predictor for reliability.

HydraSTART STV - Single Open Toe Valve

All three of the aspects described above have been taken into account with the design of the Rubicon HydraSTART Toe valve. The HydraSTART STV provides a balanced OD and ID combination, shown in the table below. The result is a larger ID with a moderated OD to provide no issues running in hole and sufficient ID for use with any industry standard plug. The geometry of the ID has smooth transitions without any requirement of sleeve alignment for maximum flow area, significantly reducing the risk of damage to the plug. Finally, the HydraSTART STV Toe Valve has a design that contains only three metal parts. The simple design reduces the number of seals required to maintain the performance of the tool. This reduction in complexity also reduces the risk associated with opening the tool. HydraSTART has proven this through over 100 successful installations in North America.

How can I help you? If you’d like to know more about completions, toe valves, or specificially about any of Rubicon Oilfield International’s downhole product portfolio I'd love to help! Please contact me at matthew.crump@rubicion-oilfield.com.