SonicScope 675 service identifies gas reservoir using real-time compressional and shear measurements

Drill and evaluate a deepwater well in a very slow clastic formation using real-time compressional and Shear measurements to obtain accurate time-depth information, validating surface seismic and confirming reservoir fluids

SLB used SonicScope™ 675 multipole sonic-while-drilling service to obtain continuous compressional and shear measurements, using monopole Leaky-P processing for real-time pore pressure monitoring.

We monitored pore pressure in real-time using continuous compressional with Leaky-P processing in formations as slow as 220 us/ft and continuous quadrupole shear in formations as slow as 460 us/ft. We accurately tied in surface seismic data and we confirmed gas presence in the reservoir section using VP/VS crossplots.

Obtain accurate pore pressure prediction in very slow formation

When drilling a deepwater well in Southeast Asia, an operator wanted to obtain sonic-while-drilling data to reduce uncertainty in surface seismic data by monitoring real-time pore pressure and obtaining accurate time-depth information. Because of the slow, clastic formation, signal attenuation makes it difficult to acquire high-quality compressional and shear measurements using conventional sonic acquisition tools, so an advanced solution was desired.

Use SonicScope 675 sonic-while-drilling service

SLB engineers recommended using SonicScope 675 service for real-time accuracy with LWD multipole acoustics. The SonicScope service combines high-quality monopole and quadrupole measurements to deliver robust compressional and shear slownesses—along with Stoneley data—in a wide range of applications, regardless of mud slowness. Using the monopole low-frequency firing mode, compressional slowness is extracted through a leaky compressional mode (Leaky-P) that is unique to the SonicScope service.

Identified gas presence using real-time compressional and shear data

Using SonicScope 675 service, the operator was able to acquire reliable, repeatable compressional and shear data despite the very slow formation, which typically prevents high-quality measurements from being acquired using conventional sonic acquisition tools.

The multimode capabilities of the SonicScope service provided continuous compressional data with Leaky-P processing in the formation as slow as 220 us/ft and continuous quadrupole shear as slow as 460 us/ft. The compressional and quadrupole shear measurements were accurately tied in to the surface seismic, and V_P/V_S crossplots were used to identify a gas reservoir.