Directionally drilling of 16-in hole section in a deep gas field had been always a challenging task to the Operator. This is mainly due to the lithology, consisting of very hard limestone with thin bed of shale where the kickoff would generally start around 11,200 ft. The operator attempted to kick off the 16-in hole using both roller cone TCI bit and PDC bit technology and utilizing a mud motor as the drive mechanism. This method provided an unacceptable low rate of penetration. In addition, there were difficulties in achieving the directional control, and multiple bit trips were required to finish the required directional work. The operator determined that a new bottomhole assembly (BHA) would be needed to efficiently drill this section to the desired inclination and azimuth in one run, while meeting the performance requirement. Multi-function teams were organized to aggressively look for new BHA configuration that could consistently drill this interval in one run with a good rate of penetration. Historically the sliding ROP in the curve section consumes the maximum time (as low as 2-3 ft/hr) with PDC bits and Motor Kick off due to tool face control. To mitigate this, Motorized Rotary Steerable System was selected for this section. The section was kicked off very successfully achieving the required build rates with double the ROP compared to previous wells. The team collaborated to custom design a new bit and BHA with new drive system that would achieve the operator's objectives. The collaborative effort resulted in achieving new records in drilling, with the fastest ROP, 50 - 100% higher than previous attempts on the fastest offset wells ever drilled in a 16-in hole and precisely drilling to the planned trajectory. The application of this new technology proved to customer that what was not previously possible could be done now more efficiently and cost effectively.
KOC have been drilling deep HP/HT wells for over thirty years during which time the well prospects have become more challenging, aiming for new frontier areas with increased depth and formation difficulty. The rig designs employed have therefore been developed over the years with new technologies being incorporated to meet these challenges, and to improve safety and operational performance. In 2011 KOC looked into the enhancement of the equipment specifications for deep drilling rigs to integrate ‘State-of-the-Art’ technologies in the new contract terms. UPDC-776 was the first of the existing fleet rigs to be upgraded and this work was handled as an integrated project by the rig contractor working in close cooperation with the field operator. With regard to the rig design, major changes were made to enhance safety, capacity and automation of the drilling functions. These modifications included; re-design of sub-structure to incorporate full 15K BOP stack rig-up, upgrade of TDS, 2200HP mud pumps and associated 7500 psi discharge pipework, new power train and SCR system, upgraded drawworks with semi-automated control system, iron roughneck and power slips, increased capacity mud system with latest design solids control equipment. The actual rig modifications were carried out within the scheduled time and performance has been improved with less downtime than comparative new build start-ups. This paper will describe the ‘Upgrading Project’ including the re-engineering and design, rig modifications and construction phase, commissioning / break-in operations on the first well. The case study will make particular reference to the planning, logistics, and teamwork employed during this process and conclude with lessons learnt plus recommendations for future rig modification projects.
Well integrity assurance and zonal isolation, are the main pillars for any oil and gas well, it was a practice in the past to evaluate cement behind casings for casings smaller than 13 3/8 inch, however with the increase in drilling deeper and more challenging wells, the need for evaluating cement behind larger and thicker casings became a necessity. Different logging companies have invested in their existing cement evaluation services and upgraded their tool designs, specifications, and increased tool operating range to address the larger and thicker casing requirements. By mid-2016, the upgraded tool measurements range was extended to evaluate up to 22-inch. KOC in South-East asset started developing their Marrat deep reservoir back in 2018, these wells are designed with large surface casings ranging between (18 5/8-inch and 24-inch) across their main reservoirs (Burgan) and the shallow water and gas bearing formations (Dammam, Radhuma, Tayarat, and Mishrif). Dammam, Radhuma, Tayarat, and Mishrif formations, feature a highly fractured carbonate reservoir and comprise corrosive water and trapped gas pockets. The corrosive water and the trapped gas pockets pose future potential well integrity risks in the field, which implies the need for proper zonal isolation throughout the well and the field lifespan. These formations also comprise a low formation frac gradient, that raises the requirement for low-density cement ranging from 8.5 to 10.5 PPG to overcome the shallow loss zone. The newly developed extended range for the ultrasonic cement evaluation tools can cover up to 18 5/8 inch surface casings for KOC, however, some additional tests, work, and modifications were required to accommodate the 24-inch casing, which will be discussed later in this paper.
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