Terrigenous intervals usually consist of interbedded sandstone, siltstone, clay and claystone. These intervals can be also difficult to drill even though rocks have low strength. Sticky and plastic rocks are the cause of rate of penetration (ROP) decreasing without drill bit cutting structure wear. A new hyperbolic diamond element (HDE) bit has been developed to improve drilling efficiency in such conditions. HDE has a standard cylindrical carbide substrate as conventional PDC cutter. The main difference is shape of diamond layer, it has hyperbolic profile. HDE has positive rake which helps to improve performance in soft formations: the cutter penetrates deeper in rock under the same loadings. Hyperbolic diamond element also helps to avoid ribbons generation while drilling in soft and plastic formations.
HDE technology was implemented on different oilfields in Russia. Naulskoe oilfield is one of them. It is in the Timano-Pechora oil basin. Development section interval consists of terrigenous rocks: sandstone, clay and claystone. New bit design with HDE cutters was specially developed for oilfield geology. The same well profile, bottom hole assembly (BHA) and drilling parameters (flow rate, weight on bit and drill pipe rotation) were used in bit tests. HDE bits set a new field ROP record which is 70% higher than average result on the drilling pad and 17% higher than the best previous result. This achievement proved HDE technology efficient.
HDE bits were used also on another oilfield which is located in the South part of Russia. Low rate of penetration is observed while drilling soft and plastic clay there even with no bit dull. There were several different tries to optimize drilling process with no success. It was decided to test hyperbolic elements technology on the oilfield. Average ROP increased in 90% as a result after HDE bit implementation. It allowed to reduce well construction time.
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