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.