Reentry drilling operations have been one of the most popular means for field development over the past decade. Many of the wells in mature fields tend to suffer from low productivity which would require reentry operations to increase reservoir contact and extend the life of the well. This has been preferable, in many cases, to drilling a completely new well from surface with all the associated costs and risks present in crowded old fields.Reentry drilling operations would normally require slimming down of the well design or the use of newly introduced expandable technologies to maintain similar hole sizes. The use of expandable technologies requires hole enlargement before running the liner. Running and expanding a liner string requires a smooth wellbore with minimal doglegs and tortuosity. A bad quality wellbore will lead to challenges that may result in not being able to run the expandable string to bottom, getting stuck or not fully expanding the liner. Past experiences have shown that utilizing a conventional motor and bent sub assembly to drill the 6 1/8-in. hole, and then run a 7-in. or 7 3/8-in. hole opening assembly has proven to be time consuming and may require under-reaming the same section more than once. The result is a borehole with an inconstant hole diameter, excessive doglegs and high tortuosity due to shifting between sliding and rotary mode. This phenomenon is significantly reduced when using a rotary steerable system (RSS) due to the continuous rotation of the string during directional drilling.In an effort to optimize the reentry operations, Saudi Aramco and the service company utilized a highly sophisticated drilling assembly combining hole-opening technology, high-build-rate RSS and measurements-/logging-while-drilling (MWD/LWD) tools. This was the first time such an assembly has been utilized for this particular application worldwide. The goal was to sidetrack, drill, and enlarge the section in one run, producing a well geometry suitable for landing and expanding the solid expandable tubular. The first application drilled and underreamed the 6 1/8-in. X 7 3/8-in. hole from the kick off point to total depth using Schlumberger's high-dogleg RSS system. As a result, the 5 1/2-in. expandable liner was run to bottom, cemented, and expanded successfully.So far, this system has been successfully run twice in Saudi Aramco reentry operations. In both cases, utilizing the combined drilling system has proven to improve wellbore quality and reduce the well delivery time by an average of 4 operating days.

The objective of drilling a well is to accommodate the completion string designed to optimize reservoir production. Streamlining a completion design for a mature field maximizes the chances of achieving the well objective with minimal drilling challenges. Therefore, introducing a new completion technology requires reevaluating the drilling procedures and practices to accommodate for the modified completion, and this is more true when running new completion designs into the open hole as opposed to cased hole completions. The Saudi Aramco drilling team were faced with the challenge of executing a multi-lateral well plan that will allow for running three open hole completions that will segment the open hole laterals and provide active control and monitoring capabilities for each segment. Such a completion requires a complex power and telemetry system that can energize all the segmented lateral completions including the ones that are deployed through the windows. The open hole laterals must be conditioned properly to successfully run the completion components in the open hole without restriction, and land the completions at the pre-planned target depths. The main power supply and telemetry conduit between the upper completion and the open hole completions is a cable cemented behind the 7 in. liner. This presented several challenges such as running and cementing the liner and milling the windows without intersecting the cable, which would jeopardize the success of the entire completion. The team addressed the challenges by developing procedures to properly execute the mentioned operations while maintaining the integrity of the power system and land the completions at depth. This was confirmed by conducting tests at various stages throughout the implementation process. An integrated project such as this requires focused collaboration between the drilling and completion teams because the traditional practice is to drill to total depth then complete the well, although this unique completion design requires a drill-complete-drill-complete sequence as the well progresses. In addition to highlighting the key factors in managing and implementing such a well construction project where various disciplines are interdependent and require continuous coordination, the paper will summarize the modifications applied to the drilling procedures to achieve the objective of the subject well. The emphasis will mainly be on three operations: Under-reaming while drilling the 8-1/2 x 9 in. hole section, hole preparation prior to running the open hole completion, and the implementation of a unique cable avoidance procedure during conventional window milling operations.