| The paper is one part of Multilateral Drilling and Production Project of Sinopec, which is undertaken by Shengli Oilfield.By measuring the rheological behavior of cementing slurry especially used in the multilateral horizontal well of Shenli Oilfield the paper first make a conclusion that it is suitable for multilateral wells of Shenli Oilfield to use Binham model to describe the rheological law of this kind of slurry.Secondly, the paper theoretically analyses the forward inadequate research job, and establishes the control equation for numerical calculation of annular helical flow induced by helical casing centralizers. In turbulent flow condition, it can use Algebraic Reynolds Stress Model to close the turbulent flow control equations and give out the eccentric annular helicalflow field of the plastic cementing slurry by use of numerical method.After the numerical simulation of cementing slurry flow for the two kinds of annular structure 215.9mm × 139.7mm and 117.5mm × 88.9mm it is obtained the distribution of velocity after centralizer both in concentric annulus and in eccentric annulus and the variety of pressure drop gradient, and the result shows that the helical angle of casing centralizers has a big influence on the swirling velocity within one meter after the helical centralizers. The bigger the helical angle, the bigger the swirling velocity. The influence is dramatically lessened after the one meter; The swirling velocity decreases dramatically within one meter after the helical centralizers; The effective swirling length is about 6-8m if the helical angleis from 30°tto 6°UUnder the flow rate 1.91m3/min for the annular structure 215.mm×139.7mm, and if Q=l.lm3/min the effective swirling length is 3.4m for the annular structure 117.5mm × 88.9mm with angle 45° and it isfurther indicated that the annular size has a decisive influence on the effective swirling length; The helical angle of casing centralizers have a biginfluence on the pressure drop gradient if it is over 45°, so it isrecommended to design a casing centralizer with angle 45°.It is theoretically analyzed the interface stability of the annular flow, and established the basic equation of interface inertia stability. In order to enhance the cementing quality it should add the helical casing centralizers in right space to keep high concentricity. The analysis show that the accelerating movement of interface makes bad contributions to its stability,moreover, the unstable-developing rate is proportional to The paper also establishes the finite element method to simulate the setting space of casing centralizers. By using such a method five kinds of annular structures(244.48mm×177. 8mm, 215. 9mm × 177. 8mm, 215. 9mm×139. 7mm, 152.4mm × 101. 6mm, 152.4mm × 88. 9mm) commonly used in Shengli Oilfield are simulated, and the simulated setting space of casing centralizers in horizontal section is respectively 8. 2m, 6. 3m, 7m, 7. 5m and 5.8m, moreover, a new type of central hollow rigid casing centralizer is developed in order to enhance the concentric rate.Having established a set of practical method to judge the main factors or subordinate factors which influences cementing quality by use of the judging theory of fuzzy mathematics. After judgment the final results is that it is the cementing parameters playing big role among the three kinds of factors, then is drilling fluid parameters and well bore parameters.Finally, by using all the theoretical method mentioned in the paper in the first multilateral well(zhuangl-zhipingl) of Shengli Oilfield it shows that it is reasonable and great meaningful to make cementing , casing string design and cementing quality control.
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