High-Angle Well Deliverability Modeling for Openhole Gravel-Pack Completion Under Ultrahigh Gas Rate

Abstract

Abstract Open-hole Gravel packing is increasingly becoming a standard practice in the deep-water, subsea completion environment. A Chevron offshore gas reservoir will be developed with highangle near-horizontal wells with openhole gravel packs completion (OHGP) for its first phase development. The ultra high rate for individual well could be up to 320 MMSCFD and the non-Darcy effect is too significant to overlook. The objective of this investigation is to build an accurate model, to validate and quantify the non-Darcy, mechanical skins for the high-angle OHGP gas wells, and finally to develop a recommendation for the optimized design. A comprehensive semi-analytical model was developed based on modification of the horizontal well model. The additional pressure drop is added to consider the mechanical skin and non-Darcy flow in the near-wellbore zones of drilling damage, mud-cake, gravel packs, and the sand screen. This investigation indicates that the non-Darcy effect could significantly affect the production rate and the economics of the project. It was found that 80° wells have a 35% average reduction in PI due to skin and non-Darcy effect. The PI for 60° wells reduces by 62% comparing to the 80° wells due to concentrated flow to a much shorter wellbore and much larger scaled skin and non-Darcy term. Uncertainty analysis was performed on non-Darcy beta-factor, formation damage parameters, and gas effective permeability. Wellbore open-to-flow area and hydraulics affect the high rate gas well's performance significantly. The preferred design is an OHGP slanted well at 80 degrees without shunt tube (6.366" ID), which can yield much higher PI than the base design. The sound engineering design of the well completion would allow us to deliver superior value through this huge gas property.