1. The following discussions contain certain “forward-looking statements” as defined by the Private Securities Litigation Reform Act of 1995 including, without limitation, estimates, expectations, plans and goals regarding Apache’s production, reserves, financings, acquisitions, exploration and exploitation prospects, energy prices, operating costs, and results of operations. Such forward-looking statements involve estimates, assumptions and uncertainties. No assurance can be given that Apache’s expectations or goals will be realized, and actual results may differ materially from those expressed in the forward-looking statements. For reconciliations of non-GAAP financial measures, see our web site www.apachecorp.com. CORPORATION Prestack Waveform Inversion: an Onshore Application in the US Gulf Coast August Lau, Chuan Yin, Mike Greenspoon, Apache Corp; Anthony Vassiliou, GeoEnergy September 2007 August Lau, Chuan Yin, Mike Greenspoon, Apache Corp; Anthony Vassiliou, GeoEnergy September 2007

2. CORPORATION Well-to-seismic tie: zero-offset synthetic and PSTM final stack. Displayed panels are (L to R): gamma-ray log, resistivity log, sonic log, bulk density log, full-stack overlaid with zero-offset synthetic, cross-correlation of the synthetic to surface seismic. Well to Seismic Tie

3. CORPORATION Post-stack Rock Properties

4. CORPORATION Pay sand has lower Vp / Vs and P- imp Sand with Pay has Lower Vp / Vs Ratio and Lower P-impedance Pre-Stack Rock Properties

5. CORPORATION Workflow

6. CORPORATION Input PSTM Gather (Left) and Modeled Gather

7. CORPORATION Starting and Final Models Density Initial Final Vp Vs

8. CORPORATION  Estimation of Vp, Vs, density, Zp, Zs and their uncertainties for fluid and lithology discrimination  Through calibration and interpretation, thickness estimation, net to gross estimation, porosity estimation  Interpretation of small-scale or localized features, such as narrow channels, slump faults, etc.  Estimation of Vp, Vs, density, Zp, Zs and their uncertainties for fluid and lithology discrimination  Through calibration and interpretation, thickness estimation, net to gross estimation, porosity estimation  Interpretation of small-scale or localized features, such as narrow channels, slump faults, etc. Applications of Pre-Stack Inversion

9. CORPORATION Full Stack Amplitude Extraction ARB LINE 2000’2000’ Well E Well C Well B Well A Well F Well D Well 3

10. CORPORATION Full Stack Main Producing Field Horizon A Horizon B WELL E WELL C WELL B WELL A WELL F Cross Section

11. CORPORATION 5-20 Angle Stack Main Producing Field Horizon A Horizon B WELL E WELL C WELL B WELL A WELL F Cross Section

12. CORPORATION Arbitrary Line-Interpreted Lithology Cube Main Producing Field Horizon A Horizon B WELL C WELL B WELL A WELL F Cross Section WELL E

13. CORPORATION Vp/Vs Volume ARB LINE 2000’2000’ Well E Well C Well B Well A Well F Well D Well 3

14. CORPORATION DZP ARB LINE 2000’2000’ Well E Well C Well B Well A Well F Well D Well 3

15. CORPORATION DZS ARB LINE 2000’2000’ Well E Well C Well B Well A Well F Well D Well 3

16. CORPORATION Major Differences between Pre-stack Waveform Inversion applied to gathers and angle-stack inversions:  Pre-stack waveform inversion is applied directly on gathers with NMO removed, preserving all amplitude, phase, offset information  Pre-stack waveform inversion is seismic data driven. Angle stack inversion commonly well log driven  Assuming long enough acquisition cable, pre-stack waveform inversion estimates directly Vp, Vs, density  Pre-stack waveform inversion is applied directly on gathers with NMO removed, preserving all amplitude, phase, offset information  Pre-stack waveform inversion is seismic data driven. Angle stack inversion commonly well log driven  Assuming long enough acquisition cable, pre-stack waveform inversion estimates directly Vp, Vs, density Inversion Technique Differences

17. CORPORATION  Pre-stack waveform inversion can work with either only primary reflections or with both primary and multiple reflections  Pre-stack waveform inversion applied directly on gathers does not have to deal with the NMO stretch effect for long cables  Pre-stack waveform inversion makes use of interval velocities.  Pre-stack waveform inversion applied on gathers is not sensitive to starting low frequency Vp / Vs / density model  Pre-stack waveform inversion can work with either only primary reflections or with both primary and multiple reflections  Pre-stack waveform inversion applied directly on gathers does not have to deal with the NMO stretch effect for long cables  Pre-stack waveform inversion makes use of interval velocities.  Pre-stack waveform inversion applied on gathers is not sensitive to starting low frequency Vp / Vs / density model Inversion Technique Differences con’t.

18. CORPORATION Conclusions  Pre Stack Inversion is a faster, cheaper, and more accurate method than traditional well-based inversion techniques  Various output volumes can be calibrated with well control for net pay estimations  Prospects can be qualified with multi-cube interpretation  A detailed geologic input model is not necessary to produce results  Pre Stack Inversion is a faster, cheaper, and more accurate method than traditional well-based inversion techniques  Various output volumes can be calibrated with well control for net pay estimations  Prospects can be qualified with multi-cube interpretation  A detailed geologic input model is not necessary to produce results

19. CORPORATION Acknowledgements  Seismic Data Courtesy of Seitel