Successful CWD Campaign in Turnkey Project with Potential Utilisation for Well Construction Optimisation
Abstract Drilling and completion of the surface and intermediate sections in some fields is extremely challenging due to wellbore instability, especially accomplished with complete losses. Such circumstances lead to several time-consuming stuck pipe events, when existing standard ways of drilling did not lead to a permanent resolution of the problems. After exhausting the available conventional techniques without sustainable success, unorthodox solutions were required to justify the well delivery time and cost. Here comes the Casing While Drilling (CwD), being the most time and cost-effective solution to wellbore instability. CwD is introduced at full throttle aiming at the well cost reduction and well quality improvement. The implementation plan was divided in three phases. The first phase was a remedial solution to surface and intermediate sections drilling and casing off to prevent stuck pipe events and provide smooth well delivery performances. After successful implementation of CwD first phase, CwD was taken to the next level by shifting it from a mitigation to an optimization measure. Each step of CwD shoe-to-shoe operations was analysed to improve its performances: drill-out (D/O) of 18⅝-in shoe track with CwD, optimum drilling parameters per formation and CwD bit design. Implemented in 19 wells, CwD shoe-to-shoe performances have been brought up or even above standard rotary bottom hole assembly (BHA) benchmark. Planning for third phase is undergoing whereby CwD is aiming to optimize a well construction to reduce well delivery time, by combining surface and intermediate sections thus eliminating one casing string. Numerous challenges are being worked on including open hole (OH) isolation packer which conform to and seal with the borehole uneven surface. Special "for purpose built" expandable steel packer and stage tool have been manufactured and qualified for the specific application. A candidate well has been chosen and agreed for first trial. The key areas of improvement include, drilling and casing off the surface and intermediate sections while competing with standard rotary BHA performances and slimming down the well profile towards tremendous time and costs savings. This paper encompasses details of constructions of various wells with sufficient contingencies to combat any expected hole problems without compromising the well quality while keeping the well within budget and planned time. It also provides an analysis of the well trials that were executed during the implementation of first and second phases of CwD implementation and the captured lessons learnt which are being carried forward to the next phase. This paper provides the technique on how CwD can be used to help with three aspects of drilling, successfully mitigating holes problems by reducing OH exposure time and to eliminate drill string tripping and modifying conventional casing design to reduce well time and cost by eliminating one casing string.