Horizontal Reentry Wells in Khafji Joint Operations: From Unachievable to a Benchmark of Success

Abstract

Abstract Khafji Joint Operations (KJO) is operating a key oil-producing field. This field has been developed extensively via horizontal drilling technologies for the past two decades. With excessive time and costs required for new offshore structure installation, the utilizing of the existing wells to drill re-entry horizontal wells became imperative and economical solution for further field developing, while minimizing the cost per foot required for well delivery. Horizontal Re-entry operation in KJO has always been deemed totally undoable due to the fact that the 7 inch production liner in most of the old wells was tied back and cemented to surface. Hence, re-entry sidetrack operation would not have enough conventional casing strings options to allow the drill ahead to reservoir while having enough mechanical barriers to isolate the unstable shale zones. Also, slimming down the well design could not be a favored option as it does not accommodate the geo-steering, formation evaluation and completion requirements; which are essential for placing and producing the re-entry wells within KJO reservoirs. To enable these re-entry wells, the Khafji drilling teams have performed a comprehensive study and risk assessment to re-define the strategy for drilling these horizontal re-entry wells. The new strategy divided the targeted re-entry wells into three main categories based on the challenges and complexity underlying each well. Each category was then assigned key enabling technologies in mud, drilling systems, optimum drilling practices, and completion techniques. These strategies along with enabling technologies were successfully implemented in a new horizontal re-entry campaign in KJO and have managed to deliver eight of these challenging wells during years 2013 and 2014.