The placement of cement plugs in extended-reach drilling (ERD) wells is a challenging task. Poor hole cleaning, insufficient mud displacement, incomplete centralization, and tight ECD management are some of the more common risks. Mud displacement efficiency and accurate cement placement is notably more complicated in ERD wells due high deviation angles and asymmetrical fluid velocities; problems which are compounded in presence of Synthetic Based Mud (SBM). In fact, the industry standard for setting and successfully testing cement plugs in highly deviated wells is 2.4x per successful attempt. For deepwater projects, these risks must be mitigated to ensure timely operations as the financial implications of failed cement plugs are vast. Adopting best cementing practices in job planning and execution are beneficial elements to overcome the challenges; however even with excellent operational guidelines cement plug failures are common. A properly designed job should consider appropriate selection of equipment and materials, tailored properties of slurry and spacer systems, accurate down-hole pressure and temperature simulation, extensive laboratory testing, and identification and management of key risks. This paper will discuss the various operational, engineering, and unique design techniques for setting horizontal cement plugs in a SBM environment on a project in deep waters offshore Indonesia. To date, four kick off plugs have been set successfully in the first attempt on four consecutive ERD wells. Conservative cost savings for achieving first attempt kick-off is 1.2 MM USD, applying 12 hours per well (48 hours total) with a daily rig rate of 600K USD. The achievement is owing to application of best cementing practices in job design and execution, along with use of a unique cement system and innovative spacer. Techniques used in placing challenging kick off plugs are discussed followed by discussion on how the trouble-free operation has created value for both the client and service provider. Multiple case histories will be presented, along with specifics of the unique slurry and spacer system.
The requirement of drilling in very close proximity to adjacent wells in surface hole section has been common as field become more crowded. This is true especially in offshore mature field where the last wells are drilled on a dense platform. In Santan Field, East Kalimantan, conductor pipes were driven between the existing wells since sidetrack or platform extension options were not available at the time while there are still opportunity for infill and step out wells. This situation introduces challenges on well construction in term of collision avoidance since the spacing between the wells are tight from surface point. The distance between slots is as low 1 meter from center-to-center, and 0.64 meter between wall-to-wall. Directional works was also required at shallow depth to kick of the well as per trajectory requirement. The risk of unplanned intersections with adjacent well can lead to financial loss, personnel safety as well as environmental issue. A comprehensive risk assessment were conducted during the planning phase as the safety of drilling operation has been one of the main concerns. Mitigations plan were then formulated with the objectives to manage the negative consequences to acceptable level. During the planning phase, detail anti-collision procedure was executed to evaluate the collision risk. On the field, several activities were carried out on adjacent wells prior to rig move in as mitigations measure: 1) Rig less resurvey, 2) Well integrity inspection, and 3) Well barrier placement. While drilling, following strategies were performed: 1) GWD utilization, 2) Monitoring on subject and adjacent wells, and 3) Collision-tolerant drilling bit application The all-surface hole were drilled safely without any HSE or reliability issue. No major indications of well collision were observed. However, the drilling time took bit longer than usual performance due to drilling controlled manner for anti-collision precautions. This paper explain how well collision mitigations was implemented in Santan Field, East Kalimantan, which can be a reference for further drilling as a successful case of top-hole drilling on a dense fixed platform. The method is expected to gain economic value, which is notably beneficial in mature field.
Santan is a mature gas field in East Kalimantan, Indonesia, where infill wells are being drilled to increase production rates. A crowded offshore platform in the Santan Field increases well trajectory complexity and presents a heightened risk of wellbore collision issues. The high number of wells on this directional pad in the shallow water drilling environment results in densely populated existing conductor pipe. Thorough drilling assessments and anti-collision directional drilling mitigation practices are key to successfully executing safe and reliable drilling operations. To further mitigate the likelihood of a well control situation resulting from a collision with a neighboring conductor or casing, a 17.5 in. IADC Classification 115 Steel Tooth (ST) rolling cone bit with special heel technology was utilized in the Santan field. This is the first time this technology has been applied in Asia Pacific. The ST bit employs continuous disk shaped heel rows on all three cones rather than conventional ST chisel shaped heel row teeth which have multiple sharp cutting edges. The special disk heel rows are designed to deflect off casing in the event of a collision in order to minimize damage to conductor or casing. The use of the special disk heel technology bit has yielded positive results to date. The bits have successfully and safely drilled in a critical zone where the center-to-center distance between slots was as low as 1m. The drilling performance and well trajectory targets were achieved. Reduced drilling parameters were used as per anti-collision and lost circulation practices, however, the overall rate of penetration (ROP) and directional behavior with the special disk heel bit was similar to conventional ST bits used in offset wells without collision risks. Turn and build rates of up to 4.8°/100 ft were achieved on a bent motor bottomhole assembly, while the average distance to the plan at the end of the section was only 10.59 ft. A series of laboratory casing collision tests was conducted during the development of the special disk heel bit which demonstrated a 75-80% reduction in casing collision damage as compared to a conventional IADC 115 ST bit. Overall, this technology minimizes the detrimental effects should a collision occur, without sacrificing ROP or steerability performance. The special disk heel ST bit has proven to cause significantly less damage to casing from a collision event than any other bit type – ST, tungsten carbide insert (TCI), or PDC bits, while still providing excellent ROP and steerability in soft formation, shallow water applications. This technology allows operators to more confidently place additional wellbores in crowded offshore template environments for greater field development from a single platform.
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