New Technologies to Enhance Performance of Section Milling Operations that Reduces Rig Time for P&A Campaign in Norway

Abstract

In 2008, ConocoPhillips completed the plug and abandonment (P&A) of two of eight water injection wells at the 2/4 W Platform in the Norwegian sector of the North Sea. The average performance was 65 days per well. One of the most challenging aspects of the 2008 P&A campaign was deep section milling of the casing to install the secondary reservoir barrier where multiple section mill runs were necessary. In mid-2009 ConocoPhillips resumed operations to P&A the remaining 6 wells. The scope to P&A the remaining 6 wells was increased to include a second barrier across the Miocene which called for more section milling than the first campaign. ConocoPhillips management challenged the rig team to significantly improve performance on the second campaign. Performance on the final six wells improved dramatically to an average of 46 days. P&A requirements called for section milling 165 feet of 9 7/8" casing at depths ranging from 8,585 ft to 10,896 ft. A joint ConocoPhillips and Baker Hughes team was formed to seek a method to significantly reduce the time required to mill the casing for the second campaign. The team set an aggressive goal of milling the section in one run. In addition a plan would be needed for additional section milling to achieve the second Miocene plug as well as potential for 13-3/8" milling to achieve adequate isolation.Two new technologies were implemented to improve the performance of section milling operations during the P&A campaign. A new cutter technology that had shown significant impact resistance and longer life than previous cutter technology was installed on the section mill blades which demonstrated increased resistance to wear and improved chip breaking ability. In addition, a new downhole optimization sub was included in the BHA that gathered information at the section mill and sent the data back to surface in real-time for on-site evaluation by engineers.These two technologies significantly reduced rig time due to the longer lasting cutters as well as the real-time data transmitted back to surface from the downhole optimization sub. The information from the optimization sub was evaluated onshore during the entire P&A campaign and operational improvements were made as each successive well was completed.

Acid Treatment as a Way to Reduce Shale Rock Mechanical Strength and to Create a Material Prone to the Formation of Permanent Well Barrier

“…Under such circumstances the casing needs to be milled, swarf has to be removed and the remaining casing pulled. These procedures are very time consuming and thus very expensive [2]. Data from ConocoPhillips [2] indicate that pipe removal is one of the most time-consuming P&A operations, taking on average 65 days [2].…”

“…These procedures are very time consuming and thus very expensive [2]. Data from ConocoPhillips [2] indicate that pipe removal is one of the most time-consuming P&A operations, taking on average 65 days [2]. Assuming a daily rig day of USD 0.47 million [3] pipe removal from only one well can cost on average USD 38 million.…”