Exercises
Interpret the poorly imaged zone on this structure as a steep fold limb using the method described on the previous page. Does the predicted fold limb properly "connect" seismic horizons on each side of the poorly imaged zone?
Part A1: Folds
Seismic Exercise: Permian basin, Texas, USA
Solution Instructions
Step 1: Jump correlatereflections across the poorly imaged zone. Step 2: Pinpoint truncations of reflections as they enter the poorly imaged zone. Step 2: Pinpoint truncations of reflections as they enter the poorly imaged zone. Step 4: Define the dip of beds in the kink band by making γ2 equal to γ1.
γ=61°
5 km
58°
Step 5: Compare interpolated horizons with your initial jump correlation. What can be done toimprove the match?
7
Post-stack time migration displayed in depth (V.E. = 1:1).
Data courtesy of Texaco, Inc.
Exercise A2-1: Interpreting thrust ramps on seismic sections
Part A2: Faults
Interpret the thrust ramps using the three fault recognition criteria. S e is mic Exe rc is e : Pe ruvian Ande s
2
1
dipping over horizontal reflections
1
1 1
3
dipping overhorizontal reflections
2
3
1
VE of 1:1.
fro m S ha w e t a l., 1998; Da ta co urte s y o f PERUPETRO.
inte rpre te d fa ults
VE is 1:1.
5 km
This section images structures that involve two large thrust faults, which can be interpreted using the fault recognition criteria. The section is interpreted using: Cutoffs (1), kink band terminations (2), and fault-plane reflections (3).Note how a series of cutoffs and kink-band terminations can corroborate, and be used to extrapolate beyond, the fault-plane reflections. (2D seismic data, reprinted from S haw et al., 1998, and published courtesy of Perupetro).
S olution
Exercise A2-2: Interpreting detachment levels
Part A2: Faults
Interpret the prominent detachment and associated thrust ramps using the faultrecognition criteria.
S e is mic Exe rc is e : S ic huan bas in, China
back thrust
1 km
E
0
we dge
upper detachment wedge tip
forethrust
5km
fro m S ha w e t a l., 1995, Da ta c o urte s y o f CNPC
Exercise B1-1: Synclinal fault-bend fold
Interpret the synclinal fault-bend fold using the graphs provided on the previous pages. θ and γ can be readily determined from the seismicimage, and used to calculate φ and β.
Part B1: Fault-bend folds
Seismic Exercise: Argentina
0.5 km
2
3
θ = 15º γ = 82º φ = 15º
γ γ = 82°
β = 14° θ = 15° φ = 15°
β = 14º 4
Data courtesy of BHP
5km
Exercise B1-2: Anticlinal fault-bend fold
Interpret the anticlinal fault-bend fold using the graphs provided on the previous pages. θ and γ can be readily determined fromthe seismic image, and used to calculate φ and β. Seismic Exercise: Niger Delta
Part B1: Fault-bend folds
0.5 km
2
β = 28°
S1
γ = 80° θ = 24°
θ = 24º 3 γ = 80º φ = 16º
φ = 16°
S0
4
β = 28º
Data courtesy of VERITAS
Exercise B1-3: Composite fault-bend fold
Complete the structural interpretation using fault-bend fold theory. Does the fault sole to a basaldetachment?
Part B1: Fault-bend folds
Seismic Exercise: Permian basin
1 km
2
Instructions Step 1: Interpret the upper detachment and forelimb axial surfaces. Step 2: Measure the forelimb cut-off (β) and the forelimb interlimb angle (γ). Step 3: Use the anticlinal fault-bend folding graph to determine the dip of the ramp (based on φ) and the initial cut-off angle (θ). Determine R. 3 Step 4:Interpret backlimb axial surfaces (note: use slip on upper detachment and R value to define backlimb width). Step 5: Measure the backlimb cut-off (β) and interlimb angle (γ). Step 6: Use the synclinal fault-bend folding graph to determine the change in dip of the ramp (φ) and the initial cut-off angle (θ). Step 7: Interpret the geometry of a few key horizons based on your fault-bend fold...
Regístrate para leer el documento completo.