Understanding Formation Damage in a Stevens Reservoir at Elk Hills California

摘要

As reservoirs mature, understanding the source andrnreversibility of any formation damage is particularly criticalrnfor sustaining production. The 26R Reservoir at Elk Hillsrncontains a substantial oil column. Gravity drainage is thernprimary recovery process of this remaining oil in place.rnRecently, two horizontal wells were successfully drilledrnthrough the bottom of the oil column to enhance gravityrndrainage. Subsequent testing revealed drilling fluids leak offrnwill create a wellbore skin; reducing permeability andrnproduction potential by over 90%.rnThis paper will review analytical calculations and assumptionsrnused to determine well production potential and discussesrnextensive core description and core flow work completed.rnThe core work has validated production potential assumptions.rnThe extensive core description work and core flow tests hasrngenerated a better understanding of rock and mineralogicalrnproperties, at a pore level. Cores were exposed to variousrndrilling and workover fluids and stimulation procedures.rnTreatment effects were then measured via return permeabilityrntests and then further evaluated by preparing contaminatedrncore thin sections and using a scanning electron microscope.rnWorkover fluids are now more carefully applied during wellrnremedial operations. In addition, the core work has modifiedrnacidizing and perforating procedures. Follow-up wellrntreatments have shown promise by reducing observed skin,rnand increasing production