Examining the Effects of Stress Dependent Reservoir Permeability on Stimulated Horizontal Montney Gas Wells

摘要

The Montney gas play in NE British Columbia and NW Alberta is undergoing intense development utilizing multi-stage fracturing of horizontal wells.Problems persist in determining an optimal development strategy for each area within the Montney.For the Groundbirch area,operators are in the early stages of development.As a consequence they have invested significantly in well monitoring including microseismic,pressure build-ups,real time rate and pressure measurements and offsetting pressure observation wells.Conventional core analysis indicates that reservoir rocks have permeability in the micro-Darcy range.Lab experiments indicate permeability is also a function of the changing effective stress.Effective stress increases and permeability decreases as production occurs.A coupled geomechanical/reservoir study was performed after 1 year of production history in order to match behavior and determine the sensitivity of conventional production forecasts to the changing stresses within the reservoir.This study developed a unified description of the study well,successfully matching an early build-up test distorted by cleanup effects along with the long term production behavior.The sensitivity to geomechanical induced stress effects was quantified.Accurate techniques were developed that eliminated the need to perform the time consuming geomechanical calculations.This allows the use of conventional reservoir models with pressure dependent permeability functions of a special form to be used in day to day analysis.Additionally the power of an old plot,dm/q versus superposition linear time,is illustrated.This gives significant insight into well behavior,and is superior to the traditional dm/q versus square-root(time)plot traditionally used in the industry.