A thesis submitted to the Faculty and Board of Trustees of the Colorado School of Mines in partial fulfillment of the requirements for the degree of Master of Science (Geophysics).
ABSTRACT
A baseline, multicomponent 4-D surface seismic dataset from Vacuum Field, Lea County, New Mexico was interpreted to characterize the Grayburg-San Andres reservoir.
At Vacuum Field, multicomponent seismic methods, when integrated with borehole data, delineate lithology, porosity, and permeability in the interwell space. Multicomponent seismology enables a more complete reservoir characterization than is available from wireline log and conventional seismic data alone.
Compressional to shear wave velocity ratio (Vp/Vs) measurements computed over the San Andres reservoir interval indicate porosity at Vacuum Field. Correlation of Vp/Vs values with neutron porosity log values indicates two trends. In the northern portion of the study area, a correlation between increased Vp/Vs ratios and increased porosity is indicated. To the south, anhydrite alters pore structures, and results in decreased Vp/Vs ratios. Anhydrite filling along fault and fracture planes may provide buffers to fluid flow. The ability to seismically image anhydrite-rich zones will aid in the identification of banked hydrocarbons and bypassed pay.
Shear wave anisotropy measurements define areas of aligned fractures within the Grayburg-San Andres reservoir interval. Comparison of anisotropy trends with total fluid production data indicates a link between seismic anisotropy and permeability. This relationship allows for the identification of preferential fluid flow pathways within the reservoir. Establishment of these trends provides an estimation of reservoir areas likely to change over time-lapse analysis, and indicates bypassed pay potential in relatively unfractured zones.
Detailed static description of complex reservoirs is critical for meaningful time-lapse seismic analysis. Multicomponent seismic methods provide enhanced baseline characterization of reservoir properties that control fluid flow. This improved static description provides a framework in which dynamic reservoir changes can be analyzed. Characterization of porosity and fracture permeability trends at Vacuum Field suggest the applicability of multicomponent seismic techniques to the characterization of other carbonate reservoirs.
ABSTRACT
1.1 Vacuum Field
1.2 Geologic Setting
1.3 Characterization Methods.
1.3.1 Compressional over Shear Velocity (Vp/Vs) Measurements .......... 7
1.3.2 Shear Wave Anisotropy Measurements........................................... 10
1.4 Available Data.......................................................................................... 13
2.1 Introduction
2.2 Compressional Seismic Correlation
2.3 Shear Wave Correlation
2.4 Calibration Review
3.1 P-Wave Interpretation
3.1.1 P-Wave Resolution............................. ................................. 36
3.1.2 Stratigraphic Interpretation............................................................. 39
3.1.3 Structural Interpretation.................................................................. 44
3.1.4 P-Wave Amplitude Analysis............................................................ 61
3.1.5 Significance of P-Wave Interpetation.............................................. 64
3.2 Shear Wave Interpretation
3.2.1 Shear Wave Resolution................................................................... 67
3.2.2 Shear Wave Amplitude Analysis..... 67
3.3 Integrated, Multicomponent Interpretation...
3.3.1 Vp/Vs Measurements...................................................................... 75
3.3.2 Shear Wave Anisotropy Measurements........................................... 95
3.4 Summary of Interpetive Results...................................................... 109
4. CONCLUSIONS AND RECOMMENDATIONS
1.1 Vacuum Field location map.................................................................................... 2
1.2 Generalized stratigraphic column, Permian interval................................................. 3
1.3 Shear wave birefringence model............................................................................ 11
1.4 RCP survey location map...................................................................................... 14
1.5 Study area map with borehole data indicated......................................................... 15
2.1 Map of study area showing sonic-logged wells...................................................... 17
2.2 CVU 203 P-wave synthetic................................................................................... 18
2.3 WS 2-26 P-wave synthetic.................................................................................... 20
2.4 P-wave surface seismic VSP tie......................................................................... 21
2.5 CVU 200 S-wave synthetic................................................................................... 22
2.6 Phase VII S1 VSP gather, VGWU 127................................................................. 24
2.7 Phase VI S1 VSP gather, CVU 200...................................................................... 26
2.8 S1 surface seismic VSP tie................................................................................. 27
2.9 S1 surface seismic VSP tie................................................................................. 28
2.10 P and S1 surface seismic comparison, Yates horizon........................................... 30
2.11 P and S1 corridor stack comparison, Yates horizon............................................. 31
3.1 P-wave seismic profile, Maljamar 3D survey......................................................... 34
3.2 RCP surface seismic basemap............................................................................... 35
3.3 P-wave seismic profile, RCP Phase VII survey...................................................... 37
3.4 P-wave spectral analysis, reservoir interval............................................................ 38
3.5 Well log cross section, flow units indicated........................................................... 40
3.6 CVU 203 P-wave synthetic, flow units indicated................................................... 41
3.7 P-wave isochron, Upper San Andres-Glorieta....................................................... 43
3.8 P-wave isochron, Yates-Queen............................................................................. 45
3.9 P-wave isochron, Queen-Upper San Andres.......................................................... 46
3.10 Isopach, Grayburg-Upper San Andres................................................................. 47
3.11 P-wave coherency attribute map, Lower San Andres interval.............................. 48
3.12 P-wave seismic profile, RCP Phase VII survey, reservoir interval........................ 49
3.13 P-wave time structure map, Lower San Andres................................................... 51
3.14 P-wave RMS amplitude map, Lower San Andres interval.................................... 52
3.15 P-wave synthetic cross section, CVU 196 CVU 203........................................ 53
3.16 Depth structure map, Lower San Andres............................................................ 54
3.17 P-wave time structure map, Glorieta................................................................... 56
3.18 P-wave spectral analyses, upper and lower reservoir intervals .......................... 57
3.19 P-wave isochron, Upper San Andres-Lower San Andres..................................... 59
3.20 Isopach, Upper San Andres-Lower San Andres.......... ..................................... 60
3.21 P-wave RMS amplitude map, Grayburg-Cycle1 . 62
3.22 Crossplot, mean porosity vs. P-wave amplitudes, Grayburg-Cycle1 . 63
3.23 S1 seismic profile, RCP Phase VII survey........................................................... 66
3.24 S1 spectral analysis, reservoir interval................................................................. 68
3.25 CVU 200 S-wave synthetic, flow units indicated............. ................................. 69
3.26 S1 RMS amplitude map, Grayburg-Cycle1 70
3.27 Crossplot, mean porosity vs. S1 amplitudes, Grayburg-Cycle1 . 71
3.28 S2 RMS amplitude map, Grayburg-Cycle1 72
3.29 Crossplot, mean porosity vs. S2 amplitudes, Grayburg-Cycle1 . 73
3.30 Vp/Vs1 map, Grayburg-Cycle1........................................................................... 76
3.31 Vp/Vs2 map, Grayburg-Cycle1........................................................................... 77
3.32 Crossplot, CVU 200 sonic log Vp/Vs vs. porosity............................................... 78
3.33 Crossplot, Vp/Vs1 vs. porosity........................................................................... 80
3.34 Vp/Vs1 map, Grayburg-Cycle1, crossplot trends indicated.................................. 81
3.35 Crossplot, Vp/Vs1 vs. porosity, Trend1.............................................................. 82
3.36 Crossplot, Vp/Vs1 vs. porosity, Trend2.............................................................. 84
3.37 r maa-Umaa crossplots, CVU 196 and CVU 203....... ............ .................. 85
3.38 r maa-Umaa anhydrite distribution map........... ..................... .................... 86
3.39 Crossplot, percent r maa-Umaa anhydrite vs. Vp/Vs1 88
3.40 Reservoir model extraction with anhydrite trends................................................ 89
3.41 GOR map, reservoir interval ............................................................................ 92
3.42 Oil production map, reservoir interval ...................................................... 93
3.43 Mean Porosity map, Grayburg-Cycle1................................................................ 94
3.44 Anisotropy map, Grayburg-Glorieta.................................................................... 96
3.45 Anisotropy histogram......................................................................................... 97
3.46 Anisotropy map, Tansill-Grayburg...................................................................... 98
3.47 Anisotropy map, Rustler-Tansill........................................................................ 100
3.48 Anisotropy map, Grayburg-Cycle1, total fluid production contours............. .. 101
3.49 Crossplot, Anisotropy vs. total fluid production, all wells................................. 103
3.50 Crossplot, Anisotropy vs. total fluid production, selected wells......................... 104
3.51 Neural net permeability map, Grayburg-Cycle1................................................. 106
3.52 Comparison of Vp/Vs1 and anisotropy maps..................................................... 111
3.53 Compiled interpreted zone map......................................................................... 112
1.1 Seismic velocity relationships for major minerals..................................................... 9
1.2 Vp/Vs ratio ranges for common lithologies............................................................. 9
3.1 Summary of multicomponent responses............................................................... 114
Reflecting upon my graduate career, I am aware that there are a great many faculty, students, family members and friends deserving of my gratitude. Unfortunately I do not have the space here to thank them all. A few, however, have provided extraordinary guidance and support; this work is a reflection of their efforts as much as my own.
I thank my advisor, Dr. Thomas L. Davis, for the opportunity to work with the Reservoir Characterization Project. His knowledge, support, and friendship have made my work possible and enjoyable. I would also like to thank my committee, Dr. Robert Benson, Dr. John Warme, and Professor Max Peeters, for their guidance and interest in my research.
I cannot fully express my gratitude to the student researchers of the Reservoir Characterization Project. Luca Duranti, Barbra Maher, Raúl Cabrera-Garzón, Matt Pranter, Gwenola Michaud, Robert Lorenzen, and Miguel Galarraga not only contributed substantially to my research, but made my tenure at Colorado School of Mines infinitely more enjoyable with exceptional grace and good humor.
I would like to express my gratitude to Dawson Geophysical in Midland, Texas, for encouraging me to pursue my education and providing financial support while I was here.
Finally, I would like to thank my parents, Steve and Mary Ann Blaylock, for 26 years of support, guidance, and perspective.