Erosive and abrasive wear effect of water-based drilling fluid (WBM) on down-hole tools may reduce the service life of down-hole tools, and its magnetic contamination on Measurement-While-Drilling (MWD) directional tools may cause azimuth errors and reduce the wellbore trajectory accuracy. The erosive and magnetic effects would be worse when a high density WBM densified with a high content weighting agent was employed. One of the main reasons of the erosive and magnetic effect is related to the weighting agent used. To reduce the erosive effect and magnetic interference of weighting agent, a micronized barite as a new weighting material was prepared in this paper, and then characterized by scanning electron microscope (SEM) and laser particle size analyzer.In our experiments, two conventionally weighting agents, barite and hematite were chosen as the comparing samples. The erosive effects, magnetic contaminate tests, lubricity and rheological properties of high density WBM weighting with micronized barite, barite and hematite were evaluated on erosion instrument, a fluxgate magnetometer, an EP lubricity tester and a rotational viscosimeter, respectively. It was found that the high density WBM weighted with micronized barite showed less erosion, lower magnetic susceptibility, better rheological properties, and smaller lubricating coefficient than that weighted with hematite or barite.Comparing with hematite or barite, the micronized barite could effectively reduce erosive wear on down-hole tools, reduce magnetic contamination on MWD directional tools, and control the rheological property of high density WBM, which would significantly contribute to the service life of down-hole tools, the wellbore position accuracy and the safety of drilling operations.The prepared micronized barite, as a new weighting agent of high density WBM, has a great promise of application in reducing the drag, erosion and magnetic interference along the horizontal section of large extended-reach wells and horizontal wells. It can also be used in high pressure high temperature (HPHT) wells and coiled tubing drilling technology.
Signal attenuates while Measurement-While-Drilling (MWD) mud pulse is transmited in drill string during high temperature deep well drilling. In this work, an analytical model for the propagation of mud pulse was presented. The model consists of continuity, momentum, and state equations with analytical solutions based on the linear perturbation analysis. The model can predict the wave speed and attenuation coefficient of mud pulse. The calculated results were compared with the experimental data showing a good agreement. Effects of the angular frequency, static velocity, mud viscosity, and mud density behavior on speed and attenuation coefficients were included in this paper. Simulated results indicate that the effects of angular frequency, static velocity, and mud viscosity are important, and lower frequency, viscosity, and static velocity benefit the transmission of mud pulse. Influenced by density behavior, the speed and attenuation coefficients in drill string are seen to have different values with respect to well depth. For different circulation times, the profiles of speed and attenuation coefficients behave distinctly different especially in lower section. In general, the effects of variables above on speed are seen to be small in comparison.
The ultra-deep reservoir is characterized by huge reserves and high productivity with high temperature and pressure, which has broad exploration and development prospects. In recent years, sand production often occurs in this kind of reservoirs such as Nanyuan oilfield, Dina gas reservoir, and Tarim Basin in China (Figure 1). Sanding onset has caused serious safety
Aerated underbalanced horizontal drilling technology has become the focus of the drilling industry at home and abroad, and one of the engineering core issues is the horizontal borehole cleaning. Therefore, calculating the minimum injection volume of gas and liquid accurately is essential for the construction in aerated underbalanced horizontal drilling. This paper establishes a physical model of carrying cuttings and borehole cleaning in wellbore of horizontal well and a critical transport mathematical model according to gas-liquid-solid flow mechanism and large plane dunes particle transport theory.
Aimed at studying the casing wear in the highly deviated well drilling, the experimental study on the casing wear was carried out in the first place. According to the test data and the linear wear model based on the energy dissipation proposed by White and Dawson, the tool joint-casing wear coefficient was obtained. The finite element model for casing wear mechanism research was established using ABAQUS. The nodal movement of the contact surface was employed to simulate the evolution of the wear depth, exploiting the Umeshmotion user subroutine. In addition, the timedependent geometry of the contact surfaces between the tool joint and casing was being updated continuously. Consequently, the contact area and contact pressure were changed continuously during the casing wear process, which gives a more realistic simulation. Based on the shapes of worn casing, the numerical simulation research was carried out to determine the remaining collapse strength. Then the change curve of the maximum casing wear depth with time was obtained. Besides, the relationship between the maximum wear depth and remaining collapse strength was established to predict the maximum wear depth and the remaining strength of the casing after a period of accumulative wear, providing a theoretical basis for the safety assessment of worn casing.
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