Abstract

Kenkiyak sub-salt oilfield is situated in kenkiyak tectonic belt located at east edge of Caspian Sea basin in the western Kazakhstan. Challenges associated with expense and drilling efficiency in the oilfield are:

  • Salt creeping and deformation

  • Hole deviation control in the thick salt layer

  • Poor drillability of the interval from approximate 3000m to the 311.1mm section TD and of the whole of the 215.9mm section

  • Bit optimization both in 311.1mm section and 215.9mm section

  • Mud properties control when drilling with turbodrill in 215.9mm section

These challenges make the drilling environment very problematic. The relationship between rock mechanics parameters and log data were studied on cores cut from a well in kenkiyak oilfield. Then models for calculating rock mechanics parameters along depth using log data as input were built. Unconfined compressive strength and angle of internal friction of the wells were evaluated. Based on these parameters, the proper bit types and requirements of bit design for each section were recommended.

On the basis of detailed assessment of the formation characterization, operational parameters, bit performance and bottom hole assembly, we introduced vertical drilling system to drill the thick salt layer in 311.1mm section and impregnated diamond bit /turbodrill combination to drill 215.9mm section.

These advanced technologies have reduced the time taken to drill the 311.1mm section and 215.9mm section by an average of 13 days and 12 days respectively. This has resulted in an average cost saving of $450,000USD in time and materials in the 311.1mm section and 215.9mm section.

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