The demand for oil and gas continues to grow but the new hydrocarbon reserves, which have to be put into production, are located much deeper compared to already developed reservoirs and are defined by more complicated mining and geologic aspects. Given the situation, the increase of drilled footage and improvement of drilling’s cost-performance ratios have become topical issues. One way to accomplich these tasks is to use more efficient rock destruction tools. As a rule, subsurface hard rock of the 6th category and over are drilled by cone rock bits with press-fitted hard-alloy cutters.
Burintekh successfully developed PDC bits to drill soft rock and soft rock with inclusions of medium-hardness rock, and worked intensively to design PDC bits to drill wells in hard rock of the 6th and 7th categories.
Field testing in the European part of Russia and in East Siberia proved that application of PDC bits increased drilling rates. However, rapid wear of cutters and the resulting reduction in total footage per bit make it inexpedient to use PDC bits for drilling hard rocks of the 6th and 7th categories. Based on analysis, rapid wear of cutters is the result of vibrations, which cause a significant dynamic stress on PDC bit cutters. Strong vibrations may be caused by unbalanced forces, which affect cutters while drilling.
Burintekh has developed a new bit design of BIT 215,9 V 613 UE.30, with a complex cutting structure designed specifically for drilling hard rock of the 6th and 7th categories.
In August 2007, this bit was successfully tested in the area of RN-Bureniye’s operations (the East Rogozinskoye field), within an interval of 3,431-3,753 m which was composed of interbedded limestone, anhydrite and dolomite. With regard to this interval, the penetration rate by the BIT 215,9 V 613 UE.30 model using the DRU-176 and DRU-195 screw downhole motors was 4.3 m/h, which is higher than the average rates for cone rock bits in these intervals.
Thanks to the use of the BIT 215,9 V 613 UE.30 bit, well construction period has been reduced as the penetration rate was increased and the time required for round-trip operations was shortened.
