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Case Study: Saturn 9-in Probe Samples Near-Saturation Hydrocarbon in an Unconsolidated Laminated GOM Reservoir

Ultralow-contamination single-phase samples acquired in one-fifth the time compared with conventional single-probe sampling

Challenge: Efficiently collect ultralow-contamination samples of near-saturation hydrocarbon and test the connectivity of a high-mobility reservoir comprising unconsolidated laminated sands where conventional probes perform poorly even at costly extended station times.

Solution: Deploy the 9-in Saturn 3D radial probe with the industry’s largest surface flow area of nearly 80 in2 for inducing and sustaining flow across a wide permeability range while its reliable self-sealing technology provides circumferential support in unconsolidated formations.

Result:

  • Successfully collected clean single-phase hydrocarbon samples—with only 1.2-wt% contamination measured by downhole fluid analysis (DFA) and confirmed by laboratory analysis— in only 2.5 h for cleanup and sampling.
  • Quantified connectivity across the laminated sands.

The challenges of sampling an unconsolidated laminated reservoir

An operator needed to acquire fluid samples from a 12.25-in wellbore in a high-permeability, highly laminated deepwater reservoir in the Gulf of Mexico. A previous attempt to sample a similar unconsolidated laminated sand in a nearby well by using a conventional single probe had not been successful. Only one out of the five stations could be sampled, and that operation took more than 12 h to obtain the sample because the seal could not be maintained, which also adversely affected sample quality. Such extended time on station at expensive deepwater rig rates greatly increased the cost of the evaluation and also the operational risk.

Self-sealing radial probe with the industry’s largest surface flow area

Available in 7- and 9-in diameters, the Saturn 3D radial probe readily creates and maintains circumferential flow around the borehole at four elliptical ports, which have the industry’s largest surface flow area of 79.44 in2. Because the ports self-seal to the borehole wall, the drainage assembly helps support unconsolidated formations, and the large flow area reduces drawdown while providing high flow rates for efficient sampling that maintains single phase. Unlike conventional sampling with a probe and straddle packer, the Saturn probe does not require isolating a large interval, which minimizes storage volume effects for quicker fluid cleanup times and the efficient acquisition of high-quality pressure measurements.

Successful ultralow-contamination sampling and connectivity evaluation

The large circumferential inlet area of the 9-in Saturn 3D radial probe deployed in the 12 1/4-in open hole made it straightforward to locate a high-mobility (200-mD/cP) layer for sampling. The Saturn probe reliably maintained the seal with no failures while providing mechanical support to the unconsolidated formation to prevent collapse. The pressure differential from the formation pressure was only 35 psi, which kept the near-saturation hydrocarbon in single phase and further avoided failure of the formation.

In only 2.5 h for cleanup and sampling—one-fifth the time required by the conventional probe—the Saturn probe collected single-phase samples with only 1.2-wt% contamination measured by DFA, which was subsequently confirmed by laboratory analysis.

To evaluate the connectivity across the highly laminated reservoir, transient testing and vertical interference testing were performed with a probe set at a 4-ft interval above the Saturn radial probe. These tests quantified the vertical communication across the sands.


Download: Saturn 9-in Probe Samples Near-Saturation Hydrocarbon in an Unconsolidated Laminated GOM Reservoir (1.47 MB PDF)

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Fluid Flow and Pressure Data Where Not Previously Possible

Saturn 3D Radial Probe
The self-sealing Saturn 3D radial probe flows fluid circumferentially from the reservoir to extend formation testing to low permeabilities, heavy oil, unconsolidated reservoirs, near-critical fluids, and rugose boreholes.
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