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The article focuses on the design, testing, installation, and performance of the first fully completed well by use of an intelligent inner completion inside an uncemented liner for the selective high-rate carbonate matrix acidization. It mentions the technical challenges associated with completing cemented laterals in the wells of Ekofisk waterflood. It also mentions that the strategic placement of both mechanical openhole and inner-string packers based on caliper and drilling log.

The article reports on a study of perforation skin-factor model for perforated horizontal wells. It develops a comprehensive skin-factor model through combining analytical calculations and 3D finite-element simulation. It finds out that a perforated well may have lower productivity due to the convergence and blockage of flow to the perforations and to the wellbore. Its results show that the azimuth of a perforation has an impact on the performance of perforated completions in anisotropic reservoirs. It also demonstrated that perforations will develop horizontal well flow if they are normal to the maximum permeability direction.

A well completion is a critical interface between the productive formation and the wellbore. An effective completion must maintain the mechanical integrity of the borehole without creating any significant restrictions on the flow capacity of the well. In this paper, a process is outlined to design optimal completions for horizontal wells by applying comprehensive skin-factor models that include damage and turbulence effects for all common types of completions. Slotted or perforated liner, cased, perforated, or gravel-pack completions have been used in horizontal wells for borehole stability and sand-control purposes. However, these completions may have lower productivity (as characterized by a positive skin) relative to an equivalent openhole completion, because the convergent flow to perforations or slots increases fluid velocity in the near-well vicinity. In addition, any reduced permeability zones (formation damage caused by drilling, completion, or other processes) magnify the convergent flow effects and therefore may result in substantially increased skin factors. Compound effects of formation damage around the well completion, a crushed zone because of perforating, plugging of slots, and turbulent flow, as well as interactions among these effects, are included in the model. This paper illustrates how to use skin factor models to screen the available completion types for cased/perforated and slotted liner completions. This screening approach considers reservoir permeability, permeability anisotropy, fluid properties, formation damage effects, and rock mechanical characteristics as the key parameters. The types of completion that yield the most productive well performance for this matrix of properties are presented. A more detailed completion design is then illustrated by showing how the skin-factor models were used to redesign the slot configuration of liner completions for viscous oil reservoirs on the North Slope of Alaska. Application of the slotted or perforated liner models to the readily available liners showed that the completion skin factor can vary by as much as 40%, depending on the detailed characteristics of the slots or perforations in the liner (slot or perforation size, density, and distribution). The example showed that optimizing the performance of the completion can increase well productivity at little or no cost and with no loss in liner mechanical strength. [ABSTRACT FROM AUTHOR]

Presents a reply by K. Furui et al to a discussion of their study by Turhan Yildiz on the rigorous formation damage skin factor and reservoir inflow model for a horizontal well. Discussion on productivity and heterogeneous skin models.