A Novel Autonomous Inflow Control Device Design: Improvements to Hybrid ICD
Authors: Zeng Quanshu , Wang Zhiming , Wang Xiaoqiu , Li Yiwei , Zou Weilin , Xiao Jingnan , Chen Tian , Yang Gang , Zhang Quan 
Published: March 2015

Abstract
In long horizontal wells, early water or gas may breakthrough into the wellbore due to the imbalanced production profile caused by the heel-toe effect, reservoir anisotropic, reservoir heterogeneity or fracture-existing. Once coning occurs, oil production may severely decrease due to the limited flow contribution from the non-coning regions. Inflow control devices (ICD) are installed to maintain the flow across production zones uniformly by creating an additional pressure differential which cancels out the imbalanced production profile. This will lower startup production, however, unwanted fluids from breaking through are significant delayed, and total oil production is maximized. Unfortunately, once water/gas does break through, they will take over the well, significantly reducing oil production.
In this paper, a novel autonomous inflow control device (AICD) design is proposed on the combination of hybrid ICD and water swelling rubber (WSR). The WSR installed in the slot will swell once water breakthrough occurs, and the swell increment will be adjusted automatically according to the water content, thus changing the minimum flow area and the flow resistance rating (FRR). This autonomous function enables the well to produce oil while restrict water. To highlight the excellent performance of the novel design, four other designs (nozzle-based, helical channel, tube-type, and hybrid) with a same FRR were compared, with structural parameter optimization, and fluid property sensitivities researched. The results show that the novel design has good performances during every phase of a well's life: high plugging resistance at startup, high erosion-resistant during peak production, continuous inflow control and low viscosity sensitivity during declining, and significantly flow resistance increase at eventual water onset.

1. Introduction
In long horizontal wells, early water or gas may breakthrough into the wellbore due to the imbalanced production profile caused by the heel-toe effect[1–2], reservoir anisotropic[3], reservoir heterogeneity[4] or fracture-existing[5]. Once coning occurs, water/gas fast track will be generated, and then oil production may severely decrease due to the limited flow contribution from the non-coning regions. To eliminate these issues, inflow control devices (ICD) are downhole tools which are placed in every screen joint to balance the production inflow profile across the entire lateral length and to compensate for permeability variations.
Currently, various ICDs have been developed in the industry. These ICDs can be divided into passive inflow control devices (PICD) and autonomous inflow control devices (AICD) according to whether their flow resistance ratings (FRR) are constant. The PICDs are usually installed to maintain the flow across production zones uniformly by generating an additional pressure drop. They use restriction mechanism (the nozzle-based type[6], and the orifice type[7]), friction mechanism (the labyrinth type[8], and the helical channel type[9]) or cooperating both the mechanisms (the hybrid type[10–11], and the tube type[12]) to generate the similar pressure drop. Their FRRs are fixed, and unfortunately, once water/gas does breakthrough, the low viscosity water/gas will take over the well, thus rendering the PICD useless and significantly decreasing the oil production.