Browsing by Subject "cutter bit"

Now showing 1 - 2 of 2

Access status: Open Access ,
Drilling large diameter intake wells with cutter bits in loose and weakly consolidated rocks
(2016) Macuda, Jan; Macuda, Małgorzata
Most of the useful aquifers in Poland occur in the Quaternary and Tertiary horizons, which are deposited at a depth of tens to hundreds of meters. Owing to the need of providing large quantities of water for municipal and industrial purposes, the aquifers are more and more frequently opened with large diameter wells of various designs. Such wells are mostly drilled with the rotary method with reverse mud circulation with the use of various bits. The Quaternary and Tertiary strata abound in loose and weakly consolidated rocks therefore cutter bits are predominantly used. They allow for high rates of drilling and shorter time of drilling of the well. This significantly influences the negative influence of drilling mud on the near screen zone of the aquifer and better hydraulic properties of the well. Drillability tests were performed with cutter bits of 0.86 and 0.67 m diameter for providing high rates of drilling of large diameter intake wells in loose and weakly consolidated rocks. The research was made for measurement sections 0.5 to 1.0 m long, and each of them was drilled at con- stant rotational velocity and axial weight on bit. Prior to the drillability tests the limitation of weight on bit and rotational velocity of bit imposed by the technical characteristic of Prakla B50 rig, strength of the string and butter bit were established. Various regression models were analyzed for the sake of finding a dependence between drilling rate and axial weight on bit and rotational velocity of bit for particular macroscopically homogeneous layers. The best results were obtained for the exponent model illustrating the influence of axial weight on bit and rotational velocity of bit on the drilling rate, which has been proved by the calculated regression coefficients and statistical parameters.
Access status: Open Access ,
Efficiency of drilling large diameter wells with cutter bits on Szczerców opencast
(2015) Macuda, Jan
Drilling of large diameter wells to be used for dewatering of lignite deposits is inefficient due to the presence of large packages of loose Quaternary and Tertiary strata. Moreover, considerable dewatering of the rock mass favors serious complications and drilling break-downs connected with the sliding of wellbore walls. Accordingly, new technical and technological solutions, which enable faster drilling, are searched for. In this way the time of operation of drilling mud on the near-wellbore zone can be shortened and the safety of drilling works increased. For the sake of obtaining higher rates of drilling in large diameter dewatering wellbores a new cutter bit 0.96 m of diameter was designed. Drillability tests in industrial conditions followed. These tests were performed in separated, loose and low-compaction, macroscopically homogeneous rocks of similar drillability. The tests were performed on selected sections 0.3 to 1.0 m long, and each of the sections was drilled at constant rotational velocity and weight on bit. Prior to these tests there were established limitations regarding weight on bit and rotational velocity of the bit, in reference to the technical characteristic of the rig, strength of the string and the cutter bit. Two different regression models were considered to find a dependence of mechanical drilling rate on weight on bit and rotational velocity of the bit for selected macroscopically homogeneous strata. The most favorable results were obtained for a power model representing impact of axial stress and rotational velocity of the bit on the drilling rate. They have been confirmed by calculated regression coefficients and statistical parameters. Industrial tests were performed to assess the efficiency of drilling large diameter dewatering wells with a cutter bit of 0.96 m diameter on the basis of the presented model of average drilling rate. The results for the average drilling rate turned out to be much higher than the ones obtained so far.