BP Oil Leak Slows, Leaking Natural Gas
[Guest post by DRJ]
The BP oil leak is reportedly slowing and possibly replaced by leaking natural gas:
“In the last few days, the spill from the broken well at the bottom of the Gulf of Mexico has begun to change. Sources tell ABC News the amount of natural gas coming out of the well is increasing, which could mean less oil spewing into the ocean. BP, trying to control the slick, confirmed the report.
When satellite images of the oil slick from May 1 are compared with the slick today, it appears smaller in size. On explanation is that it now appears that the natural gas forcing its way out of the well could be reducing the amount of oil escaping. Instead of floating on the surface, the natural gas escapes into the atmosphere.
BP confirms that it is seeing some changes in the nature of the leak, but because it is not measured, they cannot say precisely what is happening.”
Is it possible the wellbore is bridging the fluid formations?
“Bridging tendencies in ultra-deepwater blowouts. Wellbore collapse (Bridging) is the fastest, least-expensive and possibly only method of blowout control in deep water.”
On the other hand, this 2005 Offshore article almost foreshadows the BP blowout and oil spill, and it casts doubt on whether high pressure offshore wells will bridge.
— DRJ
If true, that could be due to bridging (the drillhole partly collapses) with the gas at the top of the reservoir column now exposed, preferentially compared to the lower oil column.
Good article, DRJ – The article talks more about managing risks during early production phases, but this pretty much sums it up, “Reliability data are scarce for events with low probability and high consequences.”
And in more confusion, a Berkeley Prof says the annular (betw. drillhole and casing) cement was the problem due to infiltration of gas hydrates; and Henry Waxman says it was due to leaks in the BOP.
Stay tuned for more congressional grandstanding.
MikeHu (6451eb) — 5/12/2010 @ 9:19 amMikeHu, the following is from DRJ’s excellent 2005 “Offshore” article linked above:
“Drilling/completion fluid hydrostatic pressure is the primary well control barrier for drilling and well intervention operations. When this fluid hydrostatic pressure drops below that of the formation, a kick occurs, which means that formation fluid enters the wellbore. Casing/wellhead and BOPs provide a back-up barrier to prevent a blowout when a kick occurs.”
Which pretty much sums up my take on the unfolding mechanics of the man-caused environmental disaster in the Gulf. As you know, I’m focused on the decision to withdraw the drilling fluid prior to installing a cement plug at the base of the well and allowing time for the plug to harden, about 6 hours.
This disaster wasn’t caused by “infiltration” or by “leaks in the BOP.” Those speculations are attempts to confuse the issue and distract attention from the gross error of judgment which actually allowed the blow-out to occur.
ropelight (5c7bab) — 5/12/2010 @ 10:21 amropelight – I hear you, but I’m not sure we’ve heard everything definitive about the mud exchange yet (and I’m not saying I believe anything that Henry Waxman or Berkeley professors say). I agree that it sounds like the major factor, but we’ll have to see what all the ensuing investigation turns up.
MikeHu (255b30) — 5/12/2010 @ 10:42 amAt #3, MikeHu wrote, “I’m not sure we’ve heard everything definitive about the mud exchange yet…”
Well, now, Mike, you don’t have to worry about getting any back-talk from me on that point. The decision to forgo the cement plug and begin pumping out the drilling mud prematurely is an extraordinarily weighty issue. One that could only have been made by BP in consultation with Transocean, and only with the explicit written approval of MMS.
Almost nothing, and certainly nothing related to significant drilling operations, happens spontaneously out on an off-shore oil drilling rig in the Gulf. This is a tightly controlled process, complete with on-site inspectors and highly detailed testing and reporting requirements.
The paper trail, or what’s left of it, will be closely held by MMS and the Department of the Interior. Both the EPA and Justice Departments are showing no interest or even curiosity in finding out who did what, or signed off on what, or what was or wasn’t done, and just when that might or might not have taken place.
So, I’m with you. Let’s keep our eye on the ball and wait to see the next card turned face up. Thanks to DRJ, at least we have a place to compare notes.
ropelight (5c7bab) — 5/12/2010 @ 11:36 amThanks, ropelight. I’ve been out of the upstream side of the business for nearly 25 years now. I wish I could hear what “the old-timers” on the 30th floor of OSS had to say about all this.
MikeHu (255b30) — 5/12/2010 @ 11:42 amGuys, you can’t discount what Cong.Waxman says….
AD - RtR/OS! (04f5c9) — 5/12/2010 @ 1:34 pmHe knows stuff!