Saturn 3D Radial Probe Samples Fluids from Tight Formations, Gulf of Thailand

Published: 07/30/2013

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Permeability too low for conventional single-probe formation testers

Mubadala Petroleum's development of low-permeability deep reservoirs in the Gulf of Thailand was presenting numerous challenges for measuring formation pressures and collecting reservoir fluid samples. Conventional single-probe formation testers often either cannot properly seal or lose the seal as a result of delayed mudcake formation. When the seal does hold, the probe usually cannot retrieve fluid despite extended pumpout times from the tight clastic and carbonate formations.

Long station times are a concern because they raise exposure to sticking risk. This concern also applies to the alternative approach of deploying formation testers with dual packers. The relatively larger interval volume isolated between the packers also increases station times.

Circumferential fluid flow for quick fluid extraction and cleanup

The Saturn 3D radial probe acquires formation fluid by deploying four self-sealing elliptical ports that have the industry's largest surface flow area, totaling more than 79 in2. Even in tight formations, flow is quickly established and maintained from the entire circumference of the wellbore instead of funneling fluid from the reservoir to a single-probe access point. The Saturn design also minimizes storage volume effects. The result is quicker cleanup times and the efficient performance of pressure measurements, especially in low-mobility formations where conventional probes cannot function.

Pressure measurements and fluid sampling at 0.03-mD/cP mobility

The Saturn radial probe was deployed in a Gulf of Thailand well, where at all six stations it successfully self-sealed to the tight formations. Inflation pressure was as low as 35 psi, and inflation and deflation times were less than 10 min, which is half the time required by a dual-packer testing configuration for the same operation.

Although mobilities were calculated from the pretests to be between 0.3 and 17 mD/cP, pumping through the large, circumferential surface flow area of the Saturn radial probe produced reservoir fluid from the formations in a few minutes. Cleanup time was minimal, with total time per station between 45 and 114 min.

Image: Saturn 3D Radial Probe Samples Fluids from Tight Formations, Gulf of Thailand
The Saturn drain assembly positions the four self-sealing probes at 90° intervals against the borehole wall to pull fluid circumferentially from the reservoir.
Graph: Saturn 3D Radial Probe Samples Fluids from Tight Formations, Gulf of Thailand
Good pressure transient data was quickly obtained in the tight Gulf of Thailand formations by using the Saturn 3D radial probe. Total time at this sampling station was only 72 min.
Thailand, Asia, Offshore

Challenge: Collect high-purity fluid samples from low-permeability formations where delayed mudcake development prevents conventional probe-type formation testers from successfully sealing

Solution: Deploy the Saturn 3D radial probe with its large surface flow area of multiple elliptical ports that self-seal with high differential pressure capability to establish circumferential flow and acquire representative reservoir fluid

Results: Conducted six sampling stations by successfully sealing the Saturn radial probe to measure good pressure transient data and collect clean fluid samples in formation mobilities between 0.3 and 17 mD/cP

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