The global oil market remains uncertain in terms of the potential risk factors affecting the project deliverability targets. Therefore, the operators and service providers should continuously strive to enhance operational efficiency. The Tembikai field is a marginal field in shallow waters offshore Malaysia. Meeting the operational efficiency targets was paramount to develop and make the field economically viable. To achieve the aggressive targets, a fully offline cementing operation was introduced, which resulted in an average savings of 24 hours by offline cementing alone and 14% improved operational efficiency for each well.
The five Tembikai Gas development wells were batch drilled using a jack-up rig. All wells consisted of 9 5/8 in. surface casings, 7 in. intermediate casings, and 3 1/2 in. cemented monobore completion tubing. Offline cementing for all three casing strings was planned. The offline cementing operation was performed after landing the casing at desired depth, then the rig is immediately skidded to the next well slot. While the casing is cemented offline, the rig drills the next well section, thus creating simultaneous operation efficiencies. After completing the surface section of each batch drilled well, the rig is positioned to the first well again to drill the intermediate section and the same process is repeated. Offline cementing eliminates wait on cement time (WOC) and enables the operator to perform other activities offline like running the gyro on the slickline to survey the inside of the previous casing, running cement bond logs etc.
To perform the offline cementing, a separate high-pressure cementing line was rigged up to the platform. A custom-made offline cementing assembly was used. A special compact cement head, preloaded with cement plugs, was rigged up above the wellhead compact housing. This compact cement head is 33% shorter and lighter than conventional cement heads, which helped improve the safety aspects of this operation. Providing a dependable zonal isolation barrier is key for the success of an offline cementing operation. Tailored cement slurries for each section were designed to meet well requirements and advanced three-dimensional (3D) modeling software was used to simulate hole cleaning and cement slurry placement. All risks and mitigations for offline cementing such as shallow gas hazards, losses, gas kick etc. were covered in the cementing design of service (DOS) document. As a result of detailed planning and focused execution, 24 hours were saved per well by offline cementing alone, resulting in an average of seven days per well from drilling to completion of all wells in the campaign.
The collaboration between the operator and cementing service provider for offline operations has proven to be a significant shift in operational efficiency in Malaysia, with time and cost savings achieved. These wells have achieved the lowest well cost per foot for current development wells in Malaysia.
