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Novel thru-tubing sand control solution: defining the operating envelope - part one

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Oilfield Technology,

In mature basins, sand issues can account for up to 10% of all shut-in wells either due to failure of the existing downhole sand control or onset of sand production caused by pressure depletion and/or water production.

While there are several remedial methodologies available to address sand management, each varies in complexity, cost, risk, longevity and effectiveness and has associated weaknesses. This can often result in reduced production or in extreme cases, loss of surface containment due to erosion.

Intervention without convention

A novel remedial solution was developed by independent advanced completions and production optimisation specialists, Tendeka, to enable compliant sand-free production to be restored effectively and efficiently and to be compatible with thru-tubing operations, including live well deployment and single trip sand clean out.

Filtrex (Figure 1) includes a new filtration mechanism using an open cell matrix polymer (OCMP) filter run compressed within a sleeve to allow passage through tight restrictions. This then decompresses to be conformant with a significantly larger inner diameter (ID) of the area requiring sand control when the sleeve is removed.

Figure 1. OCMP filter expanding out from the compression sleeve.

The high compressibility of the material means the assembly can pass through restrictions and expand into larger casing/liner configurations. The system has the added functionality of being able to clean out sand and install the OCMP filter in one trip, eliminating the need for a separate clean out trip (Figure 2).

Figure 2. Tool overview.

The system design allows the combination of multiple distinct layers with a range of pore sizes ranging from 180 – 565 micron (μm) for bespoke engineered sand retention. This ensures the design has the flexibility to be sized appropriately for the relevant formation sand to ensure effective sand retention with minimal pressure drop. The multi-layer design provides a tortuous path for sand and the outer layer dissipates any focused flow. After compression, the OCMP filter can expand in excess of 85% without affecting the ability to retain sand.

Qualification limitations

There are currently two types of laboratory sand retention test used in the industry: the slurry test or a sand pack test. Each considers two components of sand control and both are important when selecting appropriate sand control1:

  1. The screen’s ability to hold back formation sand.
  2. The screen’s susceptibility to plugging.

Both are important when selecting appropriate sand control. However, due to the high surface area and depth filtration of OCMP filter, it was not possible to use a conventional sand retention fixture to establish the sand control characteristics, it was required to be able to test in compression and at different stages of expansion.

Therefore, Tendeka developed a modified sand slurry test (Figure 3) to confirm suitability of OCMP filter with synthetic and formation sands, and to appropriately size the OCMP filter medium for sand retention. It was also used extensively to enable the layered design of the thru-tubing sand control solution to be evaluated and optimised.

Figure 3. Sand slurry test set up.

To establish a baseline and ensure that the test arrangement was giving reliable results, a 200 μm Reverse Dutch Twill Weave (RDTW) was tested in the new test fixture with a mixture of poorly sorted synthetic sands. Results were as expected, validating the procedure and fixture. As a result of the exceptionally high porosity and area open to flow of the OCMP, it was necessary to double the sand slurry concentration from 0.5 g/min to 1.0 g/min to get a high enough pressure differential to allow comparison with metal mesh and wire wrapped screens.2

Further to this, assessment of the suitability of the OCMP filter for long-term application in downhole oilfield applications required testing for chemical compatibility, mechanical strength, environmental tolerance and system deployment and retrieval, involving both laboratory and full-scale testing. Varying stages of the lifetime of the tool including manufacturing, deployment, and life in the well, were also reviewed, tested, and confirmed.

This is the first part of a two-part article. Part two is available to read here:


  1. Ballard, T. and Beare. S. 2006. Sand retention testing: the more you do, the worse it gets. Presented at the SPE International Symposium and Exhibition on formation damage control. Lafayette, LA. 15-17 February. SPE-98303-MS
  2. Ballard, T. and Beare, S. 2003. Media sizing for premium sand screens: Dutch twill weaves. Presented at the SPE European Formation Damage Conference, The Hague, The Netherlands, 13-14 May. SPE-82244-MS

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