Field tests evaluated the performance of three-cone insert bits using only two nozzles sized from pressure measurements made at the rig to give maximum hydraulic impact. The tests were conducted on two rigs in California and three in Texas. Test techniques entailed finding a suitable formation that required two identical bits to drill through. The first bit was operated with three nozzles while the subsequent bit was operated with two nozzles. During the test the drilling parameters (such as weight-on-bit, rotary speed, nozzle flow area, pump pressure, circulation rate, and mud weight) were kept as constant as possible. Drilling rates of the two bits were then compared and analyzed with the aid of mud-logs, electric-logs, and drilling recorder information. The depth and the relative position of the formation were also carefully compared with offset well bit records. Test results showed an average increase of 20% in drilling rate by the two-nozzle bits. One bit run showed a 3% increase and two bit runs showed 42% and 52% increases. These extreme cases were observed in Texas. The two California rigs showed 15%-19% increases. These test results together with a careful analysis of offset well bit records lead to the following conclusions: Under the conditions tested, two nozzles drilled faster than three. A moderate increase of bit loads with emphasis on weight-on-bit rather than rotary speed can significantly increase the drilling rate without shortening the length of bit run.
This paper discusses the application of MWD tools in various types of drilling operations to enhance drilling safety and efficiency. The resistivity tools from various MWD suppliers in the U.S. have been used for various applications. MWD tools can be effectively used to detect abnormal pressure zones, to select coring points, to optimize bit loading, to predict bit wear, to identify faults, and to detect influxes.There are three main types of MWD resistivity tools. Special features and limitations of each tool are presented.
The objective of this research is to analyze the characteristics of a liquid jet under different working fluid properties and flow rates. In this study, glycerol-water mixtures with different concentrations (Ω) were used as the working fluids. The properties of the working fluid were varied in terms of the main viscosity (μ), the diameter of the liquid column (dj), and the flow rate ( ) to investigate the characteristics of the breakup length (Lj) and the flow type transition between a dripping and jetting flow. From the research results, when the Ω were increased the Lj and D extended and increased, respectively. Hysteresis behavior occurred in the liquid column with a larger diameter of (≥ 1146 μm), which indicated that the critical flow rate of the transition from dripping to jetting (DJ) was different from that from jetting to dripping (JD). The range of the hysteresis increased as the Ω increased and moved to a lower We number region, especially with a larger dj. It was found that increases in Ω also caused hysteresis behavior to occur in dj that without hysteresis.
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