Drilling the Severnaya Truba Field in Aktobe, Kazahkstan, has proved to be a costly and time consuming challenge for operators trying to maximize profits. The formation is typically drilled with roller cone bits that take multiple runs to complete an interval. To increase effectiveness and drilling efficiency, a hydraulically powered percussion drilling system along with a fixed cutter PDC bit were added.In place of a conventional drilling system, a new energy distribution system was introduced that would induce axial oscillations and percussion impacts while applying the same weight and torsional energy to the bit. In combination with a drilling fluid powered percussion hammer (FPPH), a fit for application polycrystalline diamond compact (PDC) bit with depth of cut (DOC) control features was used to minimize the exposure of the cutting structure and prevent breakage.The system combines the torsional power of a conventional positive displacement motor with a high frequency axial pulse created with each rotation. The torque is transferred directly to the bit and 100% of the hydraulic flow is utilized by the bit nozzles to maintain hole cleaning and keep PDC cutters cool. The mechanical lifting and falling action creates a rapid variation in weight on bit (WOB), allowing the bit's depth of cut to fluctuate while overcoming different stresses. These variations, along with the percussion pulse created with each stroke, lead to increased rates of penetration.This system has been used throughout the world on a variety of formations, using both PDC and roller cone insert bits. This paper will focus on an 8½ in interval drilling operation in the Severnaya Truva field, located 60 km from Zhanazhol field in Kazakhstan. The formations consisted of soft to medium siltstone, red/grey clays, sandstone, hard cemented dolomite, limestone, and very dense clay stone. This new technology proved to increase both ROP and interval drilled, saving seven days of drilling compared to offset wells.

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.

Drilling the Severnaya Truba Field in Aktobe, Kazahkstan, has proved to be a costly and time consuming challenge for operators trying to maximize profits. The formation is typically drilled with roller cone bits that take multiple runs to complete an interval. To increase effectiveness and drilling efficiency, a hydraulically powered percussion drilling system along with a fixed cutter PDC bit were added. In place of a conventional drilling system, a new energy distribution system was introduced that would induce axial oscillations and percussion impacts while applying the same weight and torsional energy to the bit. In combination with a drilling fluid powered percussion hammer (FPPH), a fit for application polycrystalline diamond compact (PDC) bit with depth of cut (DOC) control features was used to minimize the exposure of the cutting structure and prevent breakage. The system combines the torsional power of a conventional positive displacement motor with a high frequency axial pulse created with each rotation. The torque is transferred directly to the bit and 100% of the hydraulic flow is utilized by the bit nozzles to maintain hole cleaning and keep PDC cutters cool. The mechanical lifting and falling action creates a rapid variation in weight on bit (WOB), allowing the bit's depth of cut to fluctuate while overcoming different stresses. These variations, along with the percussion pulse created with each stroke, lead to increased rates of penetration. This system has been used throughout the world on a variety of formations, using both PDC and roller cone insert bits. This paper will focus on an 8½ in interval drilling operation in the Severnaya Truva field, located 60 km from Zhanazhol field in Kazakhstan. The formations consisted of soft to medium siltstone, red/grey clays, sandstone, hard cemented dolomite, limestone, and very dense clay stone. This new technology proved to increase both ROP and interval drilled, saving seven days of drilling compared to offset wells.