Report

New Decline Curve Tool for GOM3/GOMsmart & “Forgotten Oil & Gas Study” 2012 GOM3 User Conference at Anadarko John D. Grace, Ph.D. Earth Science Associates New Tool Objectives • Provide a robust tool for forecasting production & estimating remaining resources by completion/completion interval • Introduce optional new method for refining decline curve analysis accounting for “breaks in regime” • Internally, use tool in batch mode to identify opportunities for further production Decline Curves • Use regression analysis to forecast a production series beyond the last observation • With forecast “integrate under the curve” for remaining resources ≥ abandonment level • Use confidence intervals on regression to estimate confidence intervals on remaining • Use analysis of breaks in time series to improve on “naïve” regression models Stereotypical Decline Curve Oil Production Barrels per day 400 300 200 100 1 2 3 Years on Production 4 Fitting a Decline Curve • Classical functional forms of decline curves – Exponential (rate vs. time) – Hyperbolic (rate vs. time) – Linear (rate vs. cumulative production) – P/Z vs. cumulative production (gas only) • Where does the estimable decline start? – Global maximum production rate? – At the last significant structural break in regime? Exponential Decline Model y aebx Hyperbolic Decline Model q q0 (1 kb0t ) 1 k Linear Decline Model y a bx (P/Z) Linear Model y a bx Improving & Choosing Model • Statistical measures of “goodness of fit” – R2 and “predicted R2” – Statistics on estimated parameter of decline – Still under research (e.g., retrospective forecast) • Actuarial approach (cum. prob. den. function) • Optimal choice of structural break – Last break – problem of shutting down well – Compare candidate breaks (& forms) against cdfs – Allow user to chose break point Actuarial Approach to EUR Cumulative Prob. Oil Gas 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 0 2 4 Million bbls 6 0 10 20 30 BCF 40 50 Conditioning Variables: Drilling date, perf thickness, geologic age, reservoir volume, reservoir permeability, GOR, oil viscosity, gas specific gravity, reservoir drive mechanism, operator (?) Exploiting Structural Break in Regime Global Max Default: We find break Option: You set break Terminal Regime Break Adding Water to Analysis Tool Interface (in GOMsmart) Tool looks the same in GOM3 & the GOMsmart Map but is called from the Hot Link Tool Tool Output Charts Reports Excel Download “Forgotten Oil & Gas Study” • Motivated by running Decline Curve Tool in batch mode – ~60,000 completions/ completion intervals – Sensitivities to abandonment rate