Lessons learned from evaluation of frac-pack flow performance before and after full clean-up for subsea wells in high-permeability gas reservoirs

The objectives of this paper are: 1) to evaluate clean-up flow effects on High Rate Water Pack (HRWP) and Cased Hole Frac Pack (CHFP) completions and 2) to develop predictive models to quantify clean-up effects on well inflow performance in these types of sand control completions. Analysis methods include: data acquisition and well test design for reservoir property estimation, multirate test and non-Darcy skin factor analysis, and perforation tunnel permeability factor (Kpt/Kr) analysis to evaluate gravel pack flow performance. Eight zones from five gas wells have been investigated using this procedure. All pressure data were obtained by intelligent well systems' (IWS) permanent downhole pressure gauges located at reservoir depth. The study results show a two-fold improvement in the average perforation tunnel permeability after clean-up flow. Based upon the study findings, two empirical correlations that can predict postclean-up well inflow performance are developed. For planning purposes, Kpt/Kr improvement factors can be estimated based on formation permeability while for wells tested using short-term clean-up flows Kpt/Kr improvement factors and stabilized well flow potential can be calculated from Water/Gas Ratio (WGR) data collected during the clean-up flow period. These predictive models are expected to help engineers assess future well performance for high-rate water pack and frac-pack completions in high permeability reservoirs. A thorough review and comparative well performance analysis of a series of HRWP and CHFP wells has been conducted using high quality downhole pressure data. The perforation tunnel permeability (Kpt/Kr) database and correlations presented in this work can be used for predicting both initial and long-term well flow performance of gravel and frac-packed wells, which can be very useful information for optimizing future completion designs and field development plans.