In 2023, TCO drilled the longest well to date in Kazakhstan to confirm technical feasibility and the productivity enhancement in the lower slope of Tengiz field using newly introduced horizontal well design. The extended reach well was drilled achieving a lateral length of almost 1,900 m, making it the longest well and lateral section drilled in Kazakhstan.
An immense amount of team effort was required in the planning stage to mitigate the major subsurface challenges such as intra-salt over-pressured inclusions, undepleted pressure pockets in the upper part of the reservoir, and major fractures and karsts in the main reservoir. Simultaneously, the well had to precisely follow the complex well design and planned trajectory to penetrate the sweet spot of porosity lobes and small but effective fractures. The well design had to be modified by implementing additional string to case off over-pressured lenses in upper reservoir. An integrated analysis of seismic and offset well data allowed to delineate the drilling hazards, and detailed strategy was developed to reach the planned well TD.
The success of this well at Tengiz was bolstered by the introduction of new drilling and logging tools and technology. A dedicated logging program facilitated the use of novel logging-while-drilling tools specific to Tengiz, ensuring accurate reservoir characterization, completion design, and acid stimulation planning along the lengthy lateral section. Additionally, a new type of lower completion, featuring metal expandable packers, allowed the completion string to rotate during deployment.
Following the developed operating procedures based on real-time log correlations, geo-steering, and in-depth analysis of seismic data, the well construction stage was executed flawlessly, without any considerable issues and geological downtime. Successful delivery of horizontal well in lower slope of Tengiz field proved the feasibility of drilling complex wells with similar design in challenging geological settings and unlocked wide opportunities for potential further field development.
The paper presents a diverse array of methods employed in the planning and execution phases of this project, showcasing an outstanding use of the available geological and geophysical data. This approach enabled the safe and efficient drilling of a complex horizontal well, despite challenges posed by a naturally fractured carbonate reservoir and significant differential depletion.
