Summary
In this paper we study the flow in a perforated pipe where fluid enters the pipe through the perforations. The focus of the paper is to describe and understand the evolution of the pressure field inside the pipe as a result of the radially inflowing fluid. Details of extensive single-phase experimental measurements are reported. A first-generation model which describes trends observed in the experiments is presented.
Introduction
While oil production by means of horizontal wells has many advantages over conventional oil recovery techniques, there are many specific complications in applying horizontal-well technology to produce oil. One of the main complications is related to the length of the well. Although the perforated pipe section may be up to a few kilometres long, the pressure drop in the pipe can severely limit the actual production length of the pipe. Namely, it will be clear that frictional effects will lead to a significant drop in the pressure between the heel and the toe of the well. The result is that the pressure difference between the well and the reservoir may reduce significantly as one moves from the heel toward the toe of the well. This leads to a corresponding reduction in the oil production per unit length of the well. It is clear that for high permeability reservoirs where the drawdown is small, one of the central questions in horizontal-well production technology concerns the pressure drop in a well liner.
The prediction of the pressure drop is complicated for various reasons. First of all, the horizontal-well problem is not one which deals with a fully developed turbulent pipe flow. It is, in fact, quite the opposite. Liquid (and/or gas) enters the well bore through perforations along the length of the well so that the volume flux inside the perforated pipe increases toward the heel of the well. It follows that a fully developed flow is unlikely to exist in any section of significant length. Furthermore, the distortion of the pipe flow as a result of many thousands of radial inflow points is highly nontrivial, and the pressure drop in such perforated pipes is not readily calculated. Additional complications occur because, for a variety of reasons not only oil, but also gas, water, or sand may enter the pipe. Furthermore, the name "horizontal well" is misleading because the well bore is, in fact, unlikely to be truly horizontal along most of its length. The result of this is that the horizontal-well problem is one in which we have to deal with the problem of multiphase flow through inclined, perforated pipes. A detailed outline of difficulties that may be encountered in horizontal-well operations is given by Tehrani and Peden.
In this paper results are presented from experiments in which the pressure loss in single-phase pipe flow is studied when radial inflow occurs. Experiments have been carried out with pipes which have different perforation geometries so as to be able to investigate the effect of perforation geometry on the pressure loss. Data analysis of these experiments, as well as analysis of experiments carried out by other groups, yields a pressure loss model which accurately describes pressure losses in single-phase pipe flow with radial inflow through perforations in the pipe wall. The experimental data is subsequently used to establish a numerical value of a parameter which is used in a model description. This leads to the formulation of an effective friction factor for pipe flow with radial inflow.
In this paper, results are presented from an experimental comparison between a light hydrocarbon system from the North Sea and a model oil system in pipe flow. The experiments were carried out in order to compare similar fluid systems (density, viscosity, oil-water interfacial tension) with respect to pressure drop and flow pattern for horizontal flow. The results show significant deviations with respect to pressure drop and flow patterns for two and three-phase flow. This may contribute to the explanation of the discrepancies often revealed between multiphase models and measurements on multiphase flowlines in the oil and gas industry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.