The Alaska Oil and Gas Conservation Commission has concluded an evaluation of allegations by Chuck Hamel of Alexandria, Va., 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 the commission is continuing to investigate claims of falsification of equipment test report and drilling records, but has concluded evaluation of well blowout and spill allegations.
Hamel told the commission in January that there were unreported North Slope well blowouts and liquid spills during drilling operations on Nabors Alaska Drilling Inc. Rig 9ES, and falsification of equipment test reports and drilling records.
Norman said the commission used information from a number of sources in its evaluation. It interviewed BP Exploration (Alaska) and Nabors personnel and evaluated information from Nabors Rig 9ES International Association of Drilling Contractors reports; BP’s drilling information management system records; Nabors Rig 9ES automatic rig data recording system records; Nabors Rig 9ES blowout prevention equipment test reports; commission regulations; and American Petroleum Institute recommended practice.
Allegation of December blowout
The first allegation, Norman said, was that Nabors Rig 9ES “experienced a gas kick/blowout” Dec. 6 while drilling on the L Pad in the Prudhoe Bay unit. “Gas and liquids were blown 70 feet upward and onto the ground,” according to the allegation and Nabors and BP managers “were rushing to restart drilling and disregarded known unresolved down-hole problems.”
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; well bore breathing occurred when the original PBU L-02 well was drilled. BP anticipated that well bore breathing might occur on the sidetrack and BP personnel had developed an engineered approach to mitigate the well bore breathing.
Some disagreement on handling of 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…”
“While contrary to conventional strategies taught in well control schools (i.e., increase mud weight after a well bore influx), BPXA has developed an engineered approach to mitigate well bore breathing that incorporates BPXA’s localized historical knowledge of the phenomenon,” Norman said.
The drilling crew never lost control of the well during the event, he said, and the commission does not consider the event a blowout.
The commission found, Norman said, that BP “drilling personnel accurately and in a timely manner diagnosed the phenomenon experienced by Nabors Rig 9ES … (and) that actions taken by BPXA and Nabors personnel to mitigate well bore breathing were appropriate and consistent with good oilfield engineering practices.”
The commission also found there was “no reportable spill” during this event, with ejected liquids substantially contained by the rig structure with “relatively small volumes of drilling mud” reaching the well pad outside the rig. The Alaska Department of Environmental Conservation is independently investigating the spill allegation, Norman said.
Non-essential personnel were cleared from the rig floor during the event, “while potentially flammable gas was being circulated to surface and was escaping the well bore.” Norman told Hamel this is “routine practice during critical operations” and “not necessarily indicative of an event as potentially serious as you alleged in your letter.”
Essential personnel were working on the rig floor during the incident, he said.
No well control loss in July
Hamel also alleged that Nabors Rig 9ES experienced a blowout in the first week of July 2003, but, Norman said, the commission “finds no evidence indicating that Nabors Rig 9ES experienced loss of well control during the first week of July 2003.”
While drilling the PBU V-111 well July 30-July 31, 2003, “Nabors Rig 9ES encountered subsurface gas hydrates,” Norman said.
Gas hydrates occur naturally and when “exposed to certain pressures and temperatures, gas hydrates can sublimate; that is, gas hydrates can change phase directly from solid to gaseous.” During drilling through strata containing gas hydrates, “the drilling mud becomes permeated with many solid pieces of gas hydrate. As these solids circulate toward the surface, the gas hydrates’ confining pressure decreases, and the solids can suddenly change to expanding gas in the well bore.”
The gas then needs to be “circulated out of the well bore, which was being done by Nabors Rig 9ES” at the time of the second alleged well blowout. “This phenomenon resulted in pressurized gas and drilling mud being forcefully ejected upward from the well bore.”
Norman said no commission regulations were violated in the event. The Nabors blowout prevention equipment “functioned properly during this event, and at no time did the Nabors Rig 9ES crew lose well control.”
Norman said the commission “believes it is inappropriate” to characterize these events as a blowout.
Ejected liquids were “substantially contained by the drilling rig structure and mud system during this event,” and the Department of Environmental Conservation is independently investigating spill allegations.
Norman said the commission found BP “drilling personnel accurately and in a timely manner diagnosed the phenomenon experienced by Nabors Rig 9ES …” in July 2003 and “… further finds that actions taken by BPXA and Nabors personnel to mitigate the event were appropriate and consistent with good oilfield engineering practices.”
December event reported
BP personnel reported the December 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 blowout prevention equipment existed in July 2003 at the time of the other allegation.
While the commission did not receive specific notice of fluid release during the July allegation, Norman said the commission believes that if there was a fluid release in the July 2003 incident, the fluid volumes involved were not large enough to meet its reporting requirements.
The Department of Environmental Conservation is independently investigating the spill allegations.
Hamel also alleged that Nabors and BP concealed “two reportable blowouts/spills,” but Norman said the December events “are recorded in the Nabors Rig 9ES IADC (International Association of Drilling Contractors) report, in BPXA’s well L-02A DIMS (drilling information management system) records and in the Nabors Rig 9ES automatic rig data recording system.” The events of the July 2003 incident “are recorded in the Nabors Rig 9ES IADC report.”
BP personnel also notified the commission of the December events.
Norman told Hamel the commission “is continuing to investigate your allegations of drilling records falsifications.” He said the commission has further personnel interviews scheduled and is reviewing multiple information sources.
“At this time we cannot predict how long it will take to resolve the drilling records falsification phase of the investigation but we assure you we will vigorously pursue this phase of our investigation until satisfied we have an overall understanding of exactly what may have occurred.”
