The power of polymer
The main factors considered during testing are the amount of sand passing through the OCMP filter, and the pressure profile generated.
The results of the commissioning tests demonstrated that the OCMP filter behaves as a depth filter. Single layer sand screens are designed to retain the sand grains on the surface of the filter medium. However, the OCMP filter requires some sand invasion into the filter matrix and partial filling of the pores, especially if the sand size is smaller than the pore sizes. Doubling the sand slurry concentration during testing stabilised the flow behaviour and produced repeatable results. As sand initially penetrated the pores, the pressure remained steady, but as more sand flowed, pressure began to increase and the amount of sand passing through became constant.
It was found that the OCMP filter demonstrates retention behaviour similar to both gravel pack and metal mesh screen industry data. Since the OCMP filter in this test assembly acts as a depth filter, it is unlikely that the results can be evaluated in the same way that wire wrapped screens (WWS) or RDTW are evaluated. Therefore, during the commissioning testing and the first round of qualification testing, new acceptance criteria were developed.
However, further sand retention analysis is needed to determine definitive retention criteria for each available OCMP filter. A testing program has been developed to obtain the data to better understand the operating envelope and be able to optimise OCMP filter selection. From the initial use of outcrop sands, the future program will be extended to include formation sands as well as expanding the size range of outcrop sand testing.
Additional OCMP filter testing was performed in the laboratory and with a full-scale tool. This firstly assessed compression to evaluate if the OCMP filter would return to its original dimensions post compression. Adhesion trails were also performed in order to select a suitable bonding system to attach the OCMP filter to both metal and itself that can withstand anticipated temperatures and various fluid environments.
Fluid compatibility and temperature testing were also undertaken to create a database of compatible fluids and define a range of acceptable operating temperatures. Further testing is ongoing to establish the impact of other commonly encountered oilfield fluids at temperature. In addition, a full program of testing to investigate the impact of Hydrochloric Acid (HCl) on OCMP is being conducted.
Deployment qualification testing
A deployment method was developed to set the tool and remove the compression sleeve exposing the filter media. A high expansion anchor system was engineered to function hydraulically, locking the tool in place and enabling deployment through tight restrictions (Figure 4). Once the tool has been set and anchored in place, the compression sleeve attached to the running tool is pulled off to expose the OCMP filter. Testing indicated that it was necessary to apply 2000-3000 lbs/metres of filter to pull off the sleeve.
Figure 4. Top: Anchor non-engaged; Bottom: Anchor set in casing.
Findings demonstrated that the Filtrex tool can be run in hole where the OCMP filter is compressed by the compression sleeve and the anchors un-extended until it reaches the required depth. When the tool reaches the top of the ingress of sand, the jetting nozzles can be activated enabling sand clean out whilst running to setting depth and setting the anchor – this can withstand 16,000 lbf (12T) in tension and compression.
After clean out is complete, the anchor is activated hydraulically locking the tool in place. Once the anchor is set, the running tool and compression sleeve can be removed and the OCMP filter can expand and conform to the ID of the casing or failed screen. The filling of the annular gap prevents further ingress of formation solids whilst still allowing passage of liquids or gases.
It can be deployed in a live well and enables sand clean-out and chemical treatments to be performed as a single trip process, detailed in Figure 5.
Figure 5. Deployment sequence.
While continuous sand production of small quantities can sometimes be viable, it can lead to production being significantly impaired, wells shut in or surface equipment becoming damaged and disabled. The environmental and financial impact of disposing of large quantities of sand being produced to surface should be considered when assessing completion methods for sand producing wells.
In determining a qualification method for Filtrex, Tendeka concluded that the standard methodology for sand retention testing for RDTW and WWS is not applicable to OCMP filters. The designed test apparatus and method provides a representative comparison to RDTW samples. Further testing is required to establish operating parameters of the OCMP using formation sands.
This is the second part of a two-part article. The first part is available to read here: https://www.oilfieldtechnology.com/special-reports/06012021/novel-thru-tubing-sand-control-solution-defining-the-operating-envelope/
Read the article online at: https://www.oilfieldtechnology.com/special-reports/07012021/novel-thru-tubing-sand-control-solution-defining-the-operating-envelope--part-two/