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2. Cement Job Returns

During the cementing operation for the production casing, rig personnel
continuously monitored fluids being pumped into and flowing out of the well.
The rig crew calculated the quantity of fluids pumped into the well using the
pump’s piston volume output and efficiency. Piston volume is calculated using
the pump’s liner inside diameter and stroke length efficiency. Sensors on the
pump measure how fast the pump is moving instead of directly measuring the
volume of fluid being pumped. Flow out of the Macondo well could be
measured several ways, including by monitoring pit volumes, monitoring
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Transocean’s flow paddles, or monitoring the sonic and radar sensors (flow‐
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out meters) located in the return flow line. Monitoring the return flow line
138
would provide the most accurate measure of fluid volumes out of the well. The
flow‐out meter has a 10 percent margin of error and must be based on properly
calibrated devices. Recalibration of the flow‐out meter is frequently necessary
due to rig movement, ballasting, crane operations, sea movement, and other
factors.

The rig crew observed that cement displacement occurred at a rate of
approximately 4 bpm, and they believed that full returns were achieved while
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circulating. Dr. John Smith, an expert retained by the Panel, calculated that
both the main pit volume record and the calculated cumulative flow‐out versus
flow‐in indicated that about 2.3 bbls of mud was lost during the cement job. John
Gisclair of Sperry‐Sun performed a post‐job review of the flow‐in and flow‐out
data and agreed with Dr. Smith’s report that if the sensors and paddles had been
properly calibrated, the accuracy of the flow‐out volumes should have been
within 5 to 10 percent of the recorded data. In testimony, however, Gisclair
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cautioned that “flow‐out is never intended to be an actual measurement of
volume. If you want to see the volume, the actual amounts of a gain or a loss,

136 Pit volume refers to the amount of mud in any of the rig’s mud pits at a given time.
137 Transocean’s “Hitec” monitoring system on the rig had paddle‐type sensors. As fluid rushed
past, the fluid pushed and lifted the paddle. The system calculated flow rate based on how much
the paddle moved.
138 The return flow line was the conduit within the pit system.
139 BP‐HZN‐MBI137370.
140 Testimony of John Gisclair, Joint Investigation Hearing, October 8, 2010, at 100.

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