More ROV evidences of shallow faults & drilling problems- Part IIb of Root Causes.
– BK Lim
9 Oct 2010
1. Periodic gas and oil seepages through cracks in the heavily cemented seafloor.
Figures 122-1a and 1b show 2 ROV images captured from the video clip posted by rocksiphone on 18 July 2010 at http://www.youtube.com/watch?v=30WLz7eGYMY&feature=related. The seafloor appears hard with thin layers of encrusted foliation. Besides the dark patches of coloration, the focus of the camera shows a rather sharp edge foliation detached from the lower layer. In the video, blobs of oil and burst of gas can be seen seeping through the gap in the foliation. For such a foliated layer to withstand the periodic burst of gas, it must be pretty hard and resilient.
Natural deposition of clayey sediment takes a long time in quiet, low energy environment. Undisturbed natural seafloor covered with surficial soft clay has a smooth flat surface.
Why is this patch of the seafloor (40-50 ft ENE of well A) so heavily cemented? Obviously the cement must have resurfaced and hardened at the seafloor; possibly even during the October 2009 drilling period. This is a conclusive proof that BP had experienced difficulties in well A since the first time the well was spud on 7 Oct 2009. It also proved that BP continued to drill even deeper when the shallow sections of the well had not been properly sealed yet.
Figure 122-2 is the typical comment by an expert driller assuming the shallow sections of the well would have been properly tested and sealed before proceeding to drill deeper. This ROV evidence clearly shows that this was not the case.
The fact that this patch of cemented seabed and several other gas seeps (as far as 500 ft) are aligned to the “super long leaking fissure” (2), is sufficient proof that the geology here is badly fractured and faulted.
2. “Super Long leaking fissure”
ROV Video from Olympic Challenger dated 21 August : http://www.youtube.com/watch?v=IjAPRpVr-6Q showing massive gas/oil seeps that seem to hover above seabed level.
ROV Video from Skandi Neptune dated 29 August: http://www.youtube.com/user/mmimic34#p/a/u/1/EKg-GJV6d54 showing an elongated cloud that hover just above the seafloor. The video has a tag “prop wash”. This cannot be a prop wash as heavy prop-wash are generated at sea surface not at depths. Further any prop-wash bubbles would rise and dissipate fairly quickly; insufficient time for the ROV to track the “prop-wash” without seeing the vehicle generating the “prop-wash”. These are only some of the arguments against the prop-wash interpretation of these rov videos.
Basically the 2 videos confirm the existence of the WNW-ESE fault line passing through / close to Well A and offset about 50 to 70 ft N of Well B. See figure 122-3.
…. to be continued in part IIc of Root Causes.