Industry standards are critical to safety achievement. They represent best practices as determined by leading experts in the many disciplines that support oil and gas exploration and development. Another plus for standards is that, unlike regulations, they can be developed in a timely manner, particularly where there is an immediate need. However, industry mergers and streamlining have reduced the diversity of input, and some companies either do not participate or participate primarily to promote or protect their particular interest. The need for a consensus can also result in “lowest common denominator” outcomes that lack the necessary rigor.
Minerals Management Service (MMS) reviews indicated that cementing issues were the leading contributing factor to well control incidents between 1992 and 1996 (see chart below). On August 16, 2000, MMS challenged a new API cementing work group to improve zonal isolation, reduce the occurrence of sustained casing pressure, and prevent annular flow incidents before, during, and after cementing operations. Unfortunately, the standard was long delayed because of internal disagreements within the work group. Feedback indicated that some participants preferred a watered down, less rigorous version.
It is undisputed that the primary cement at Macondo failed to isolate hydrocarbons in the formation from the wellbore—that is, it did not accomplish zonal isolation. If the cement had set properly in its intended location, the cement would have prevented hydrocarbons from flowing out of the formation and into the well. The cement would have been a stand-alone barrier that would have prevented a blowout even in the absence of any other barriers (such as closed blowout preventer rams, drilling mud, and cement plugs).
Chief Counsel’s Report, National Commission on the BP Deepwater Horizon Oil Spill
API Standard 65-2, Isolating Potential Flow Zones During Well Construction, if completed in a timely manner and complied with would likely have prevented not only the Macondo disaster, but also the 2009 Montara blowout in Australia. (The Montara investigation hearings were covered extensively on this blog in 2010.) This important standard was ultimately finalized in a reactive manner after the Macondo well blew out.
Standard 65-2 focuses on the prevention of flow through or past barriers that are installed during well construction. A few key elements that are pertinent from a Macondo perspective:
- Companies are required to perform a risk assessment prior to utilizing foamed cement and make sure that the results of this assessment are incorporated in the cementing plan. In setting the production casing on the Macondo well, foamed cement was used in an oil-based mud environment, destablizing the cement and contributing to the failure to isolate the highly productive oil reservoir.
- The standard specifies float valve and cement requirements for the shoe track at the base of the casing, the Macondo failure point. (Weatherford float equipment failures were a common element to both the Montara and Macondo blowouts. Weatherford’s $75 million settlement with BP seems rather modest when one considers the magnitude of the damage costs.)
- The framework in Annex D of the standard does a good job of outlining the questions that should be asked in conducting a cementing risk assessment. These issues identified in the Chief Counsel’s report, which includes an outstanding review of the technical and management issues associated with the cementing/zonal isolation of the Macondo reservoirs, should have been addressed by BP and their contractors before initiating the well suspension program:
- narrow pore pressure/fracture gradient;
- use of nitrogen foamed cement;
- use of long string casing design;
- short shoe track;
- limited number of centralizers;
- uncertainty regarding float conversion;
- limited pre-cementing mud circulation;
- decision not to spot heavy mud in rathole;
- low cement volume;
- low cement flow rate;
- no cement evaluation log before temporary abandonment; and
- temporary abandonment procedures that would severely underbalance the well and place greater stress than normal on the cement job.
Unfortunately, such an assessment was not conducted and critical operational decisions were made in a rash manner with the objective of saving time. We know the outcome – 11 lives lost, massive pollution, and enormous social costs
Despite making multiple changes over the last nine days before the blowout, the Macondo team did not formally analyze the risks that its temporary abandonment procedures created. The Macondo team never asked BP experts such as subsea wells team leader Merrick Kelley about the wisdom of setting a surface cement plug 3,000 feet below the mudline to accommodate setting the lockdown sleeve or displacing 8,300 feet of mud with seawater without first installing additional physical barriers. It never provided rig personnel a list of potential risks associated with the plan or instructions for mitigating those risks.
Almost every decision the Chief Counsel’s team identified as having potentially contributed to the blowout occurred during the execution phase.
Chief Counsel’s Report
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Bud's Offshore Energy (BOE) 