New approaches for performance evaluation and design of well completions in horizontal wells

Abstract

The design of the well completion is one of the important steps in field development planning with strong effect on the production profile and thereby the economics. This is a crucial decision that should be taken prior to the start of production and it should include the phenomena happening throughout the production time. The advanced wells and hydraulically fractured horizontal wells are the two most complicated completions. Although the industry is very successful in installing these completions, very little work has been done on the horizontal well completion design optimisation. This study focuses on evaluation of the well lifetime performances of these completions and aims at developing advanced methodologies for delivering the optimum design of these wells. The first part of this study focuses on the advanced well completion design in particular (autonomous) inflow control devices ((A)ICD) and how to integrate them with Annular Flow Isolations (AFIs). The observed mutual dependency between ICD design and AFI location has led to the development of integrated advanced well completion workflows that simultaneously optimises the ICD device strength and the numbers and placement of AFIs. New developed approaches for AFI design include impacts of the well-reservoir interactions, the strength of ICDs, the placement and numbers of AFIs and reservoir uncertainties while considering the economical and practical limits. The second part of the study concentrates on multiple fractured horizontal wells (MFHWs) in tight reservoirs. Various analytical and statistical approaches have been adopted to evaluate the well lifetime performances of these wells. Initially, a new equation for the well productivity calculation of MFHWs in tight reservoirs flowing under pseudo-steady-state conditions has been developed. The expression is general, reliable and simple for prediction purposes because it benefits from limited, appropriate dimensionless numbers and is not limited to the fracture characterisations. In addition, using statistical analysis, the applicability of the analytical PI model for designing optimum MFHWs for the whole production period has been proven even though the transient flow regimes may last relatively long. Based on these findings, a new workflow that optimises MFHWs design while considering the economics and practical limits has been developed. Following these and by identifying the practical flow regimes around MFHWs, a new analytical methodology has also been developed to predict the well lifetime performance under both unsteady state and boundary dominated flow conditions. The proposed simple and practical approach covers the early linear flow, compound formation linear flow, pseudo-steady-state boundary dominated and the long transitions in between. The application of the developed workflows are illustrated using some case studies. Moreover, a general, fit for purpose set of guidelines, suitable for an improved well design are proposed.