Microseismic Event Analysis From the Earnest Stocker 4H & 5H Wells Seismic Analysis Group January 2011

Topics Background for the Earnest Stocker Project Objectives Experiment setup Summarize a Few Results from Microseismic Events Look at relationship of Estimated Stimulated Volume to geology Stimulation modeling New processing in progress Outline the Way Forward

The Earnest Stocker Experiment 4D seismic differences are capable of detecting very small changes in timing and amplitude caused by production at Ekofisk, can it help us see the propped portion of the frac’s? What can be learned about microseismic monitoring by comparing these various geophysical measurements? How do they compare to treatment-derived estimates of the frac’s? Vert. Monitor wells Shallow wells Earnest Stocker #4 & 5H wells 4D Active Surface Seismic 4D Active VSP (2 vertical wells) 4D Shallow monitor wells (four) Borehole microseismic monitoring 17 stages, 80 levels total Surface microseismic monitoring 17 stages, about 4000 receivers

Time Line Equipment Deployment 16 Nov – start surface geophone deployment 17 Nov – start down hole phone deployment Baseline Survey (750 shots) 21 Nov – start 3D surface shooting 24 Nov – Base survey finished Frac First Stage – MS monitoring 25 Nov – First frac stage complete Monitor 1 Survey (169 shots) 28 Nov – Acquire limited repeat survey Frac 2-18 stages – MS Monitoring 29 Nov – Dec 7 Remaining frac stages completed Monitor 2 Survey (750 shots) 9-12 Dec – Acquire repeat survey Cleanup & Flowback Wells Production Logs Run 18 Jan & Mid March Monitor 3 Survey (750 shots) Late April 3D/4D Timeline

Context: All MEQ Events Marble Falls & Viola Ls Horizons Omni-Frasier Well Log Schiflett Family #1 Well Gamma Ray Sonic Density, Red

60% of Full Volume from Top 3 Stages of 17

Geology in the Nearby Vertical Wells The carbonates seen in the ES#3 have been variously called the Stocker Fan, the Lime Wash, or F-carbonate. Wavelet Classification w. Coherency. Anastasia Mironova

Geologic Setting Upper surface is Top Marble Falls; lower is Viola Ls. 4H stage4 (orange) and 4H stage6 (blue) MS events and perf’s along the treatment wellbore near a geologic boundary as shown by the wavelet classification from 3D seismic mapped onto the Viola surface. Gamma ray logs from vertical wells show more carbonate layers (i.e., frac barriers) lying above the perforated interval on the left side of the image.

Frac Development 90% of full size in 42 minutes 90% of full size in 26 minutes Frac height (pink curve) grows in spurts & plateaus. Frac height here grows more uniformly ( and more quickly). Prism Dimensions from MS Events

Stress Indicator: Aspect Ratio of MEQ Prisms From 5H Well

Comparing Reprocessed Results 4H stage 3 events from HiPoint (left) sized by “amplitude”, and from Magnitude’s migrated event set (right) colored by time and sized by moment magnitude. Rose diagram of the two versions (far right).

MS Focus for 2011 Understanding uncertainty and how to deal with less than perfect event sets. Compare acquisition and location methods: One well vs. two wells 8 phones vs. 40 phones Migration vs. grid search Surface monitoring vs. downhole Reconcile microseismic results with: 4D anomalies Stimulation models Geomechanics / stresses Petrophysical, Pressure, Treatment, and Production data Provide Guidance to Business Units regarding use of MS monitoring: Best practices QC measures Recommendations for dealing with uncertainty