Case Study: Integrated BHA Optimizes Hole Enlargement While Drilling for Total in Brunei

Engineered drilling system acquires high-quality LWD data while enlarging a challenging deepwater section in one run

Challenge: Obtain optimal LWD data while drilling and enlarging a challenging section in an offshore exploration well where there was a high risk of downhole vibration.

Solution: Use the IDEAS integrated drillbit design platform and i-DRILL engineered drilling system design to customize an integrated BHA that includes the PowerDrive X5 rotary steerable system (RSS), an MDi616 PDC drill bit, and a combination of LWD services to acquire real-time measurements.


  • Drilled and enlarged an 8 1/2-in pilot hole in a 12 1/4-in section with moderate stick/slip and low lateral vibrations in one run.
  • Acquired high-quality LWD data.

Drill and enlarge a deepwater well 

Total was drilling three deepwater exploration wells in Brunei. To acquire the high-quality data it needed, the company required an integrated BHA that would reduce the risk of downhole vibration and maintain good directional control during a hole-enlargementwhile-drilling (HEWD) operation. The primary objective was to drill and enlarge a challenging section in one of the wells in one run, while acquiring high-quality LWD data in real time. 

Engineer a drilling system for optimal hole enlargement 

Taking a multidisciplinary approach, a team of Schlumberger drilling experts customized a drilling system to reduce the risk of detrimental downhole shock and vibrations that can result in a potential lost-in-hole BHA. 

The IDEAS platform and i-DRILL drilling system design were critical in modeling and predicting the drillstring dynamics of the BHA, directional tendency, and recommended surface drilling parameters and to select the bit, staged hole opener, and the related cutting structures. Four BHA models were analyzed to determine the most stable drilling system configuration. 

The engineered drilling system included the PowerDrive X5 rotary steerable system (RSS) with an MDi616 PDC drill bit provided by Smith Bits, a Schlumberger company. A combination of LWD services comprising TeleScope high-speed telemetry while drilling, EcoScope 675 multifunction logging while drilling, and StethoScope 675 formation pressure while drilling were used for directional control and to obtain pore pressure measurements. 

A concentric HEWD solution was incorporated into the BHA design consisting of a Smith Bits 10 1/2-in staged hole opener and a 12 1/4-in Rhino XS hydraulically expandable reamer. 

The dual reamer configuration BHA enabled the LWD tools to acquire data in the 8 1/2-in pilot hole, while enlarging the hole to 12 1/4 in for a larger diameter casing string to be run at a later time. The HEWD solution also provided dynamic stability over an eccentric reamer, allowing for the acquisition of high-quality data. 

Acquire high-quality data, reduce vibration, and deliver quality hole 

The integrated drilling system reduced vibration and provided better hole quality. In one run, the 8 1/2-in pilot hole was drilled in the 20° tangent section of the deepwater well from 2,409 m to 2,912 m MD. The hole was then enlarged to 12 1/4 in with moderate stick/slip and low lateral vibrations. 

Due to this low level of vibrations, the triple combination of LWD services was able to deliver high-quality measurements. As predicted by the IDEAS platform, only minor directional corrections were necessary.

Download: Integrated BHA Optimizes Hole Enlargement While Drilling for Total in Brunei (1.43 MB PDF)

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