Sampling While-Drilling Goes Where Wireline Can’t: Case Studies Illustrating Wireline Quality Measurements in Challenging Borehole Environments

In the early 2000s, formation pressure while-drilling tools were introduced that can obtain formation pressure data, even in highly deviated wells and extended-reach drilling. In the past two years this LWD technology has evolved with the addition of downhole fluid sampling and fluid analysis. LWD Sampling and Testing can now be performed in challenging environments that cannot be performed with wireline tools such as horizontal or highly deviated wells. The limitations of wireline deployment in these wells are due to the cumulative frictional resistance of the wireline, the toolstring components and the borehole where it is run. Although several technologies exist to mitigate the risks, such as fly wheels, wireline tractors or pipe-conveyed options, operators prefer to eliminate the risks and costs associated with them by utilizing LWD technology. The first part of this paper describes the new sampling and testing service that was designed for the LWD environment. This service has several closed-loop control systems for pressure testing, mobility determination and for pumping during the sampling and cleanup operations. In-situ fluid analysis is achieved with the use of sensors that measure optical refractive index, sound speed, density and viscosity. Downhole fluid samples are retrieved with the use of single-phase tank technology. The second part of this paper details case studies of field tests that were performed for a major operator in Trinidad and for an IOC in the Netherlands. In Trinidad the service successfully performed pressure testing, real time fluid analysis and recovered three single phase samples while drilling a 300ft section at 70° deviation. On a dedicated logging run in the Netherlands the service first accurately took 25 formation pressure points and clearly identified three distinct gradients. The customer targeted four zones of interest and acquired 11 samples, six single phase samples in the oil zone, three single phase samples in the water zone and finally three single phase samples in the gas zone. This pressure testing and sampling operation was all executed in a 1307 m tangent section at 73° inclination. The service was utilized to determine the presence of moveable fluids in the reservoir for a horizontal development well for a customer in Norway. The tool was positioned at a sampling station with a mobility of 1.8 mD/cP and after almost 5 hours of pumpout at that station, it successfully acquired the first sample, after another 4 hours of pumpout at the same station the tool acquired the second sample. In both cases the LWD sampling and testing service was chosen over wireline to mitigate the risks of sticking during the sampling and pressure testing operation. These field tests demonstrated that the LWD service is capable of taking wirelinequality measurements in extremely challenging borehole environments.