Improving liner cementing has been a constant objective of the industry. Recent developments in rotating liner hanger technology have made this cetnenting technique applicable to more wells than before.Presented here is an analysis of 45 jobs done during i '/2 years. The study examined mechanical success ratios as a function of liner size, depth, length, method of rotation, setting tool types, deviation, casing hardware ! (centralizers, scratchers, etc.), and bearing load. The results give the drilling and completion engineer a better understanding of the chances of a mechanically successful job.
Tubing movement, forces, and fiber stresses in single completions have been discussed thoroughly by Lubinski et al. Subsequent papers have expanded this discussion to combination tubing strings and fixed intermediate packers. This paper presents the theory and solution of tubing movement, forces, and fiber stresses for dual- flow assembly installations-that is, situations in which the intermediate packer is free to move within a seal bore. Introduction Shortly after the introduction of the polished or packer bore receptacle (PBR), dual-PBR completion methods were designed and field tested. Fig. 1 is a schematic of a typical dual-flow assembly completion. Since then, dual-PBR completions have been used extensively in the industry. Early applications used large-OD tubing strings with heavy walls, small casing-to-tubing clearances, and high slack-off weights. The balanced piston effect kept the effective area below the dual-flow assembly small so that the pressure force tending to lift the assembly during stimulation was negligible. Because of these particular circumstances, certain simplifying assumptions were made concerning tubing movement that resulted in reasonable solutions and yielded good field success. Since these early completions, the trend has been away from large-OD tubing strings and toward smaller tubing and fewer tieback practices. This, in turn, leads to larger tubing-to-casing clearances that result in greater tubing movement and higher bending stresses during stimulation. Additionally, the use of dual-flow assemblies with permanent packers for the lower zone, rather than PBR's, eliminates the balanced piston advantages of earlier completions. Under these circumstances, reliance on previous design methods may lead to tubular failure. A more rigorous solution is needed that can predict dual-flow assembly movement and the resulting fiber stresses in each string of a multiple completion. Using the methods presented in the paper, we may predict the movement of a dual-flow assembly under any well condition. Tubing forces and fiber stresses in individual strings can be calculated. Furthermore, techniques presented here can be applied directly to dual packers to evaluate tubing buckling and induced forces. The Problem Consider the well depicted in Fig. 2. The following sequence of events will illustrate the problem. Replacing the lower packer with a PBR will not jeopardize the results. 1. Stimulating the lower zone will develop an upward force against the lower seal assembly. This force is transmitted to the bottom of the dual-flow assembly by String 3 and, along with buckling, ballooning, and temperature effects, will tend to make String 1 shorten. How much it shortens is not only a function of its reaction to these effects but also dependent on the reaction of String 2 to the rising dual-flow assembly. 2. Stimulating the upper zone will cause String 2 to contract. However, the pressure differential across the dual-flow assembly may cause String 1 to contract also. In this case, both strings may resist the dual-flow assembly movement. On the other hand, if String 2 shortens sufficiently that it no longer contracts the dual- flow assembly, only String 1 may be effective in resisting the dual-flow assembly motion. As in Event 1, the reaction of one string is dependent on the state of the other. SPEJ P. 866^
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