Optimal Scheduling of Well Treatment in Commingled Formations Undergoing a Near Wellbore Damage

Abstract

Abstract Methodology and theoretical considerations are presented for scientifically guided optimal scheduling of well treatment in reservoir formations involving commingled pay zones of different properties. Introduction Maintaining the productivity of wells completed in reservoirs involving multiple thin pay zones is a particularly challenging petroleum engineering problem requiring scientifically guided development of optimal strategies. The formation capacity (permeability-thickness product) of the various pay zones determines the contribution of these zones to the overall well production. Because of the differences in the formation characteristics, different zones may experience different types, time scales, and orders of formation damage. This implies that the productivity of the various pay zones may become non-economic at different times requiring maintenance treatment measures applied at different times. Further, the wellbore fluid hydraulics may affect the relative contributions of the commingled zones to the overall production. Managing productivity in wells completed through many thin zones requires an accurate characterization of the formation damage potential of these zones and careful monitoring of the production from each zone. This requires a model-assisted analysis of the well production conditions and the pay zone production response over the producing time. A formation damage and production response model can help interpret the various data gathered over the producing time. In addition, the formation characteristics data obtained during drilling and laboratory core tests can be used to understand the prevailing formation damage mechanisms and infer for the characteristic time scales affecting the rate of permeability impairment in each zone. Numerous studies have been carried out over the past years in an effort toward understanding of the processes reducing the productivity and for development of optimal strategies by designing and scheduling effective maintenance treatments. This is critical for economic management of productivity in commingled zones. However, a proven methodology and approach required to alleviate this problem is still not available for generalized applications. The well performance essentially depends on the pressure loss during production that is caused by the combined effects of the completion and formation damages. Separating the contributions of the completion and formation damages to the loss of well performance is not a trivial task. A review of the available approaches reveals that the estimation and remediation of the completion and formation damages requires complicated detection, evaluation, and analysis techniques (Civan, 2007). In the present paper, the attention is devoted to formation damage and a simplified approach is developed.