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Controlled mineral cementation: the innovation in effective sand control

Producing sand is a major operational challenge for the oilfield. It’s an unwanted burden at the surface requiring separation, treatment and disposal. And sand moving at high flow rates in the well system can erode critical equipment, such as safety valves, increasing operational risks.

And it’s not just due to natural formation sand. Sand and other granular materials often pumped as proppant can also flow back into the well – a problem made more widespread by the increase in multistage fracturing.

Managing sand mechanically
Initial sand management techniques have focused mainly on mechanical systems; physical barriers such as gravel packs and screens to hold sand back and prevent it entering the well . While these solutions suited the simpler, vertical wells of the past, today’s wells are drilled at higher angles and feature longer horizontal sections. As a result, screens are harder to run in hole and must be deployed and assembled in sections – significantly increasing the risk of screens getting stuck downhole, and complicating their retrieval should they later fail.

Chemical sand consolidation
An alternative approach is chemical sand consolidation – using resins to stick grains together within the formation, or coatings designed to stabilize loose particulates. Since they can be pumped, these chemical systems provide a lower-cost alternative to installing screens.

The challenge however is that over-treatment with these super-strong ‘glues’ can clog up the flow spaces in-between grains, reducing the permeability of the formation. Removal of excess resin is difficult or impossible Generally, resins are used to treat relatively short intervals at a time, making it time consuming and therefore costly to treat longer horizontal wells.

So, what’s the alternative?

Taking cues from natural processes
It’s useful to look at the geological mechanisms at work: why is it for example that younger, shallower reservoirs are often poorly consolidated? This weakness is because they haven’t had long enough for the sandstone structure to be strengthened. And the process behind this strengthening is secondary mineralization – the natural cementation of sand grains.

Cleansorb have pioneered an innovative approach to managing sand that mirrors the natural cement deposited during the formation of rock. Our solutions use the controlled deposition of calcium carbonate and similar minerals in situ, depositing them onto existing grain surfaces. Think of it as a kind of deliberate scaling, but within the formation.

This mineral cementation enhances the natural cementation of the formation, and in a highly-controlled way.

The benefits of cementation
As you’d expect, the solution offers all the deployment benefits of a chemical system over sand screens and gravel packs. And unlike resins it is difficult to over-treat and clog up the formation. The deposited mineral scale can be easily removed if needed.

Cleansorb uses non-hazardous food-grade chemicals, making them safe for personnel to handle, and includes some listed as considered PLONOR (posing little or no risk to the environment) for North Sea use.

Saying goodbye to screens
One operator’s engineers indicated that increasing the unconfined compressive strength of sandstones by just 1 atm/15 psi would remove the need for the company to run sand screens altogether. Cleansorb’s data proves that controlled mineral cementation has been able to achieve strengthening of 100 psi.

Deployed as a single treatment, controlled mineral cementation represents a long-term, whole-life solution for sand-prone wells.

To take a stand against sand in your next well, speak to Cleansorb today.