Burintekh Extends the Area of PDC Bit Application

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Traditionally, companies of the oil industry summarize the results of their work in the previous twelve months on the eve of the Oilman’s Day. Burintekh is not an exception.

A successful application of new PDC bit designs in the carbonate sections of the fields in Eastern Siberia, Orenburg Region and Komi Republic is one of the main events of 2008.
Geological sections of the fields in these regions are traditionally considered to be complex. Dense dolomite and limestone occur here; interbedding of various rocks of 4 to 7 hardness category is quite frequent, and intervals of soft and medium-hard rock include plenty of various resistant (hard-to-drill) interlayers. The first tests of PDC tools proved possibility of achieving higher rate of penetration compared to that of three-cone drill bits. However, low meterage limited by the early wear of the bit cutting structure made application of the available PDC bits economically inefficient. However, cooperation of Burintekh’s Center for Drilling Tools Design with the world leading manufacturers of PDC bit inserts, made it possible to equip the bits with exclusive inserts of the latest generation.
Certain requirements to the final characteristics of these inserts were introduced at the design stage.
The new bit designs proposed for the carbonate section drilling did more than just equalled the engineering and economical performance of the traditionally used three-cone drill bits – they exceeded it. Table 1 provides examples of use of the drill bits offered by Burintekh. We have every reason to expect that application of the PDC technologies will become a common thing for certain regions in the nearest future. However, we cannot definitely predict the application results at the new fields without performing preliminary tests of the particular PDC bits.
As our experience shows, preliminary information on the geological characteristics of this or that field appears to be not true in many cases. As it is expected that one PDC bit can drill at least 1,000 meters, the bit cutting structure must fit the properties of all the rocks composing the interval to be drilled. However, in real practice, availability of even small interlayers of increased hardness and abrasivity in the section can result in early wear of the bit cutting structure and consequent drilling rate drop. In addition, use of the imperfect solids control equipment results in the sharp increase of abrasive wear of PDC bit body caused by the circulating drilling mud. That is why the final conclusion on the compliance of the offered drill bit with the particular drilling conditions can be made only after analysis of results received in the course of the tool operation. 
Capabilities of PDC core bits should be mentioned separately. Core drill bits of Burintekh have been successfully used at the fields of Eastern Siberia for a long time. Surgutneftegaz uses these core bits at the fields of Yakutia for coring in the intervals composed by dolomite and limestone of various densities, and also in the intervals of terrigenous deposits composed by interbedding of rocks of various hardness categories (4 to 7). Total meterage drilled by one core bit varies from 58 to 116 meters depending on the bit diameter and intervals of coring, at the average rate of penetration 0.52-0.95 m/hr.
In spring of 2008, jointly with the Drilling Department of Surgutneftegaz, we evaluated performance of the core bits used in the Republic of Sakha (Yakutia) and determined ways for improvement of their engineering and economical performance. Consequently, in May of 2008, a new design of the core bit was tested, which was intended for drilling in the given formations with higher rate of penetration. The tests were successful. At the average meterage of 50.3 m, average rate of penetration 1.38 m/hr was achieved.
Summing up all the above, we can say that at the present time, the use of PDC bits in the carbonate sections comes from the tests stage to the stage of selecting appropriate modifications for the particular field conditions, thus repeating the route of the PDC technology introduction at the fields of Western Siberia.

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