Analysis And Application Of Drilling Fluid Centrifuge In Ultra - Deep Well

In the oil industry, the horizontal spiral sedimentation centrifuge has been used to process drilling fluid for nearly seventy years so far. With the development of modern drilling technology, deep well and ultra deep well drilling has been very common. When drilling in the operating conditions, the down-hole problems become more complex, and it put forward higher requirements on drilling fluid properties. The drilling fluid centrifuge is an important link of solids control system, especially plays a very important role in the processing and recovery process of the weighted drilling fluid in the ultra deep well. It’s the fact that experimental study ahead of theory research for the study of drilling fluid centrifuge at present. Because of the complexity of the drilling fluid properties, the various operating parameters and impact parameters of working condition of the centrifuges, it has been exist many difficulties and problems in the reasonable use of centrifuge. Besides, the advanced foreign design theories and research methods are shrouded in secrecy so that we are unable to use for reference. These are the difficulty all need to solve in the process of research. So, this paper was conducted research and analysis work based on the basic theory, research methods, and field experiments to further study the influence factors of centrifuge in ultra deep well drilling. This will provide valuable references for design and site operation of drilling fluid centrifuge, and lead the centrifuge better services in the oil field operation.The research work of this paper is mainly embodied in the following respects:(1) Through access to retrieve the literature at home and abroad, the characteristics of common weighted drilling fluid in the ultra deep well, the distribution of common used weighting material-barite particles, and the structural parameters of horizontal spiral sedimentation centrifuge were studied in this paper. The type and parameters of the analyzed drilling fluid centrifuge were determined. The basic assumptions and basic flow theories of centrifuge separation flow were studied. Based on size of the separation particle, the barite separation efficiency calculation formula of the drilling fluid in the centrifuge was deduced. Refined the centrifuge capacity formula put forward by the predecessors, combined with the equipment parameters of centrifuge and the deduced barite separation efficiency calculation formula, more detailed and Realistic capacity calculation formula was deduced theoretically.(2) Aimed at the complex flow of drilling fluid centrifuge, flow geometry model with screw of centrifuge was established. Based on the k-ε model, the flow characteristics of three phase flow of liquid-solid-solid were simulated. Set in boundary conditions according with field conditions and conducted numerical simulation analysis by computational fluid software CFX, and then obtained the intuitive accurate conclusions. Contrasted of the simulation results in multiple sets of condition, the laws of velocity field and solid phase distribution were obtained.(3) With the orthogonal experiment design method, the orthogonal experiment scheme of the five factors and five levels which influence the separation recycling efficiency of solids in the drilling fluid centrifuge was reasonably determined. With the help of scientific orthogonal experiment on multi-factor experiment, the primary and secondary order of the five significantly reduced influence factors which were drum rotational speed-capacity-viscosity-density-separation particle size was obtained. Through the analytical methods of range analysis, variance analysis, interaction analysis between factors, effect curve analysis etc, the influences of solids recovery efficiency by above mentioned factors and between each other were analyzed deeply, and the relevant conclusions were reached.(4) Through the field experiments, conducted the curve fitting of data, comparatively analyzed the field experiment results with the numerical simulation orthogonal experiment results. The influence change rules of above mentioned factors on barite recovery efficiency were perfected. And for the analytic LW550centrifuge, a series of optimal parameter combinations to ensure the barite recovery efficiency were put forward. This provides a useful reference for the similar type of centrifuge.