PETRONAS embarked on a new challenge to drill and complete 5 wells with high bottom hole temperature (BHT) of 180°C and highly deviated fractured carbonate with high velocity gas producers. These wells utilized 7" big bore production tubing with new material 17CR instead of the expensive cold worked 22CR duplex stainless steel (DSS). As the first application of 17CR production tubing material in the world, a lot of risks were taken into account and mitigated via various approaches from planning engineering stage until execution. These mitigation measures included the qualification of material and connection; operational details involving parties from different disciplines to ensure smooth and efficient deployment of 17CR tubing. In addition to that, optimization opportunities were explored to further increase running efficiency and reducing flat time while ensuring tubing integrity is intact. The successful deployment of 17CR were attributed to the following: Connection modification from JFE BEAR to JFE BEAR DR-PK to minimize the risk of galling around the metal-to-metal seal area on the newly developed 17CR CRA materialTubing was racked back in double joints per stand offline during installation using offline activity cantilever (OAC) deck available on a tender assisted rig to improve running timeUtilization of side door elevator instead of single joint compensator to enable running tubing in double.Usage of Flush Mounted Slip (FMS) dressed with pre-qualified low penetration dies, to ensure sufficient gripping on the 17CR tubing OD surface without being affected by the surface scale which is known to have with high hardness valueUsage of low penetration dies instead of non-marking type hydraulic tong to reduce tubular running cost With the above mitigation measures put in place, the project was delivered with high efficiency in terms of tubular running speed achieving up to 14 joints per hour on 7" high alloy CRA tubing with extremely low number of rejection rate (0.3%) for the entire project. Utilization of 17CR as an alternative to 22CR DSS has also contributed direct cost saving of up to USD 8.2 mil to the project.
Abstracts Conductor setting depth is critical to provide structural support for next drilling sections. The shoe strength must suffice for drilling ahead and avoid any washout and unstable zone. The objective is to design and run conductor smoothly in regards to engineering and operation aspect. Multidisciplinary approach including geotechnical, drilling engineering, and structure, was implemented during planning strategy. The pre-determined conductor setting depth was defined on the maximum mud weight to be used during drilling surface hole section in accordance to the formation strength below the conductor with the purpose of not inducing losses to the formation. Lateral distance between conductor and platform jacket pile was also analyzed to secure the jacket integrity. Anti-collision analysis was performed to prevent collision due to the existence of production well in same platform. Conductor pipe size and specification with some feature was defined to withstand under anticipated load and environment. To determine the way to achieve target depth and the suitability of hammer type, drivability analysis was performed with various anticipated condition. Considering shallow refusal depth, drill and drive was required to reduce shaft friction of soil. Another environmental challenge arise during conductor operation was unable to contain fluid and cutting returns from clean-out process causing return to cover part of the production platform facility. Some of technology were planned to mitigate this challenge. By having comprehensive conductor design, the conductor pipe in all four wells drilled has been successfully installed without any problem on platform jacket integrity and subsequent drilling section. This approach also enabled to efficiency of conductor installation where the number of clean-out and driving run could be reduced. The overflow return challenge could be fully contained by utilizing selfdesigned equipment. The overall operation days of conductor has shown improvement with 1.02 saving days on the last well which equivalent to amount of cost saving around USD 203,500.
Casing-while-drilling (CWD) operations have become a well-known technology used to minimise drilling time and reduce AFE budget. PETRONAS has drilled several wells in Malaysia by using this technology, and it has proven to be a cost efficient strategy particularly in batch drilling process. Past CWD operational experiences have demonstrated stark differences when compared to conventional drilling in terms of wellbore surveying and formation evaluation. Weak and noisy signals from mud pulse telemetry were primary issues that required a significant amount of rig time when acquiring measurement-while-drilling (MWD) and logging-while-drilling (LWD) data. In fact, several significant challenges were encountered. First, the mud pulse signal which traverses from downhole (MWD) to the surface somehow dampened out. Although various types of mud pulse telemetry have been used, significant problems remain. In addition, the signal transmission worsened when seawater was used as the drilling fluid, resulting in nonproductive time due to provisioning ofchange out tools with different configurations for mitigation and trial-and-error purposes. Finally, overall drilling efficiency was reduced as a result of poor signal detection and capturing. EM-MWD used in combination with gyro-while-drilling (GWD) was identified for implementation when drilling four wells using Tesco CWD technology in the Erb West field. The mud pulse and electromagnetic telemetry systems were executed asa pair to compare captured signal strengths in the same environment, i.e., directional CWD with seawater drilling fluid. After drilling ceased, the generated results proved that EM-MWD is a viable technology that can be used to overcome signal attenuation issues in a CWD operation. It also minimise health, safety, and environment (HSE) risks as well as established a working model of EM-MWD-CWD. Most importantly, such application reduced rig time by 3.9 days which contributed to 26% of cost saving for the surface section drilling by having trouble free MWD signal detection and faster drilling operation.
In 2016 PETRONAS embarked on the challenge of drilling and completing high temperature, highly deviated fractured carbonate development wells using Pressurized Mud Cap Drilling (PMCD) techniques. With equivalent formation pressure gradients of 13ppg, H2S levels of 140ppm and formations with potential for massive losses, but also very high gas productivity, severe challenges were presented to the drilling engineering and operations teams and to the logistical infrastructure; these challenges were successfully overcome, ensuring that the wells were delivered safely using the planned Tender Assisted Drilling Rig. Maintaining well control integrity throughout all drilling and completion operations is always crucial to ensuring safe well delivery. In wells with total losses, drilled through highly productive carbonate formations, there is a high risk that any loss of the primary drilling fluid barrier may result in the well flipping out to gas very rapidly. This risk is highest during trips out of the hole, when the Rotating Control Device (RCD) pressure seal must be removed to retrieve the drilling BHA and run the lower completion. For wells with total losses, options to control the well during trips have traditionally involved a combination of methods including setting gunk plugs, setting composite bridge plugs, or using a preinstalled Downhole Isolation Valve. The purpose of this paper is to present a fourth option, the top-kill method using a dual-density fluid system. During the 2015-2016 PETRONAS development drilling campaign, following thorough risk assessments and detailed planning and logistical evaluation, this method was proven to be a reliable and safe means of controlling the well during trips. A total of five (5) wells were drilled from the development platform, using a surface BOP stack and an RCD. Top kill operations were engineered by pumping two types of fluid into the annulus at surface; a slightly underbalanced Light Annular Mud and a heavier density Kill Mud. By combining these fluids, the well was put into an engineered overbalanced state, with the loss rate controlled via a pre-determined pumping rate. Once the RCD seal element was re-installed, the well reverted back to pumping Light Annular Mud into the annulus as per normal PMCD procedures. This paper highlights the meticulous planning, execution, training and continuous learning that was evident in these challenging operations. This paper also discusses critical HSE concerns and makes recommendations for future PMCD projects.
With the far-reaching reservoir target coupled with other surface constraint including fix well slot coordinate and pre-determined conductor size, the longest well with 2.5 ERD Index in Offshore East Java was pioneered. The team has big task in hand to ensure all aspect of ERD well engineering and construction are being addressed properly within the fast-paced time frame given. One of the approaches strategized by the team is to split the high angle big hole size long interval of middle section into two casing string which was not the common architecture applied in the other offset wells. The objective was to ensure that the middle section of the well will not be compromised and avoid complication in the deeper section of the well. Worth to mention that the middle section consists combination of challenging lithology that deserve the right solution to avoid unwanted problem. There are highly kartsitified carbonate formation, shale and sand interbedded formation, and thick time dependent shale formation. To mitigate the challenges previously mentioned, intermediate section which is normally drilled and isolated with 17-1/2" hole × 13-3/8" casing in previous wells, now separated into two sections which require enlargement: 17-1/2" to 20" and 14-3/4" to 17-1/2". This paper focuses on 14-3/4" × 17-1/2" which is the most challenging underreaming operation in this well and the first of its kind in this field application. Adding to the fact that the inclination reach 75 degree in this section, SOBM and RSS BHA are deployed to mitigate the torque and drag issue. State of the art modelling tool is also used by team to define effectively match BHA and drilling parameter with minimal lateral vibration and stick slip for this section Apart from drilling stage, the enlarged hole size requires a condition to have uncommon casing size and specification, 16" intermediate semi flush liner connection and 13-3/8" full flush intermediate casing connection to ensure sufficient annular area and less restriction during running to bottom. The relentless effort to secure one the most critical ERD well construction phase has really paid off by allowing the next phase of operation to be executed as per plan thus assuring the overall well objective is met.
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