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 WellGamma 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