The Alaska Oil and Gas Conservation Commission has concluded an evaluation of allegations by Chuck Hamel that unreported North Slope well blowouts occurred in December 2004 and July 2003, and has concluded that there were no unreported blowouts.
In a Feb. 11 letter, AOGCC Chairman John Norman told Hamel that it is continuing to investigate claims of falsification of equipment test report and drilling records, but has concluded evaluation of well blowout and spill allegations.
Norman said the commission’s investigation determined that “Nabors Rig 9ES experienced well bore breathing” over the period of Dec. 4-11 while drilling the Shublik formation in well PBU L-02A. “Well bore breathing is a non-routine phenomenon which can occur while drilling naturally fractured strata such as the Shublik,” he said. “Near-well bore pore spaces within naturally fractured strata can become charged by relatively higher well bore fluid pressure while mud is being pumped in the well.” When the mud pump is turned off, “the pressure-charged naturally fractured strata can release some drilling mud and formation fluids back into the well bore, mimicking the effects of a well kick.”
In the December occurrence, Norman said, pressurized gas and drilling mud were “forcefully ejected upward from the well bore, as gas was being circulated to the surface.”
PBU L-02A is a sidetrack, and well bore breathing occurred when the PBU L-02 well was drilled, so BP Exploration (Alaska) had developed an engineered approach to mitigate the well bore breathing.
Norman said the commission learned that there was disagreement between BP and Nabors personnel on how best to handle the situation, but, he said, the commission believes the BP approach “is within the range of good oil field engineering practices…”
The drilling crew never lost control of the well during the event, and the commission does not consider the event a blowout.
BP personnel reported the event “at least three times,” Norman said, by telephone or e-mail to the commission’s North Slope office or its Anchorage office. No reporting requirements for use of blow out prevention equipment existed in July 2003 at the time of the other allegation, when the commission found Nabors Rig 9ES “encountered subsurface gas hydrates” while drilling well PBU V-111. Norman said the commission found no evidence indicating that there was a loss of well control during the incident.
Editor’s note: See full story in Feb. 20 issue of Petroleum News.