Use of Conventional Well Logs In Selective Completion Designs for Unconventional Reservoirs

摘要

A common issue in unconventional reservoir completion and stimulation design is the selection of fracture initiation points to effectively contact producible reserves.One solution is to equally space initiation points along the entire well,with the trend being to closer spacing to increase reservoir contact.A second approach is to use some combination of logs in the lateral to selectively complete sections that appear to have better reservoir quality or producing capacity.In areas where the rock properties are relatively consistent in terms of reservoir quality,the two methods may overlap so that uniformly spaced fractures offer the best opportunity to for effective stimulation.In other cases,where sections of the lateral are out of zone,or in identifiably inferior reservoir quality,portions of the lateral may be skipped to decrease overall completion cost.This paper presents a method to use and integrate multiple well logs in both vertical and horizontal wells to identify hydrocarbon bearing intervals(storage)and highly productive zones(possibly“natural”fracture sets)for selective completion. Correlations have been found between acoustic velocity,resistivity,gamma-ray,and porosity logs and core-derived properties such as hydrocarbon saturation and TOC%.These correlations have been expanded to include mud log gas shows and ROP(rate of penetration)to differentiate between matrix and secondary fracture contributions to production.With very little core data it is possible to derive a regional model that predicts TOC%from simple log measurements that are commonly available.The analysis strongly suggests areas of a well that should be primary targets for stimulation,zones that can be bypassed with little economic downside,and sections of the well that should not be considered for zonal isolation such as packer setting points.The method has been applied in many unconventional development areas,including the Marcellus, Utica/Point Pleasant,Wolfcamp/Avalon,Duvernay,Montney,and Eagle Ford with equal success.Results have been confirmed by post-frac production logs in cases where complete data sets are available.