Application on Elastic seismic

(provided by Shanbei department of mine exploration)

In this project, 2D multi-coverage reflective wave methods as well as surface low speed reflection wave method were used for oil well surveying. In addition, a VSP observation well was designed.


I.Seismic wave reflection method
(1)Data collection: 12 times coverage, 48 channels,

 Schematic of reflection wave method

(2)List of Parameters
Receiver separation: 10m;Receiving channels:48;Coverage times:12;Explosion site separation:20m;Shift distance:40m;Location of explosion sites:-270, -40, 0, 40, 270
Explosion depth:  3~5m, in hard dirty, or below water layer in sand     Amount of explosives:0.8~1.4kg
P wave receiver:  target wave frequency 60Hz, every set has three receives connected in series, 1m apart, placed about 30cm underground
Data acquisition unit:  sampling rate 1000Hz, sampling interval, gain 36db, filter: all pass

DL5 lines raw data (large fluctuation of sand hill, underground water relatively deep)


(二)VSP observation well
1.Detonator and VSP observation well are 15m apart
2.Observing range 70-375m in depth, geophone location: from 70-180m, every 10m; from 180-250, every 3m; at coal layer, every 1m.
3.Explosion site: depth 1.5m, amount 100~300g
4.Receiver: target signal 60Hz, three channels
5.Data acquisition: 2000Hz, sampling time:1.024s, gain 36db, filter: all pass

Schematic of VSP observing well


Zero offset VSP: vertical component raw data

(a)Overall vertical seismic wave field                                                                         (b)Overall vertical seismic wave field

Cross section of vertical seismic wave field



Corridor wave superposition (positive, negative)   Overall superposition of waves (positive, negative)
 Superpositioned seismic wave field
 

(三)Seismic wave reflection method
1. Objective: low wave speed layer detection
2. Method: zero shift, single side explosion
3. Parameters: sampling rate 1000Hz , sampling time:1.024s, gain 36db, filter: all pass
4. Explosion: site depth 1~2m, amount of explosive 100~600g
5. Receiver: target 60Hz P wave, receiver separation 5~10m

DL6 refraction line raw data from single explosion
 

Interpretation of the seismic data

Schematic of explosion sites calibration                                               Schematic of receiver sites calibration


DL1 high precision speed profile


 DL1 horizontal superposition lines


Graphs of seismic wave at fault zones (break point on line DZ8)


ISIS constrained impedance deduced geological profile (DZ18 line cross section)


Graph of bifurcated wave group (DZ20 line)


Prediction of No.3 coal mine thickness