New PDO Improved Well Design 15K Cemented Completion to Successfully Deliver Faster and Cheaper Complex Deep Gas HPHT Wells

Abstract

This paper discusses the continuous improvement in Khulud field, the most challenging field in Sultanate of Oman in terms of high pressure and high temperature. A paper (SPE-188629-MS) was published in 2017 under the title of " Achieving a Step Change in Well Duration and Cost in a HPHT Tight Gas Field" which explained many improvements in different areas including (10k cemented completion and degraded mud, operational optimization and efficiency, slim design). However, in this paper, the focus will be on 15k cemented completion, which was a challenge in that time for both designs (fat and slim). Thus, the new improvement is mainly in well design, which led to significant reduction in well delivery cost and time for 15k wells. Drilling and completing very tight HPHT deep Gas well can be very challenging. The risk of losing the well is real due to challenges related to liner hanger system failures that have been experienced several times within the field. In addition, stuck pipe risk of cleanout assembly prior to running liner top completion is another serious challenge that had led to abandoning a few wells in the past. Cemented completion for 15K well is one of the challenges mentioned in the SPE-188629-MS paper in Khulud field. Production casing is not strong enough to handle hot kill load in case completion tubing leaks and as well is not designed for full gas displacement. In addition, many failures were encountered with liner hanger system, which compromises well delivery in some cases. To overcome such challenges and reduce well delivery time and cost, PDO initiated new well designs to cater for 15k cemented completion for both fat and slim applications. Advantages and disadvantages of cemented completion for both designs will be discussed in this paper. In fat design, production casing was upgraded to higher weight and grade. 7 in casing was eliminated as the new production casing is good enough to handle hot kill load in case tubing leak happens. In slim design, ECD and high surface pressure are the main concerns. The team managed to simulate, optimize ECD for different scenarios and mitigate high surface pressure. All Risks and associated consequences were captured. A mitigation plan was developed. Future improved design has been evaluated but not approved yet which will drive cost reduction and operational efficiency.