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陸 上 震 測 資 料 處 理 陳 建 文 台灣中油公司探採事業部國資處震測資料處理組 2011/11/04. 陸上震測資料處理. 1. 陸上震測資料特性. 2. 靜態修正 (statics correction). 3. 剩餘靜態修正 (residual statics correction). 4. 地滾波 (ground-roll) 消除. 1. 陸上震測資料特性.
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陸 上 震 測 資 料 處 理陳 建 文台灣中油公司探採事業部國資處震測資料處理組2011/11/04
陸上震測資料處理 1.陸上震測資料特性 2.靜態修正(statics correction) 3.剩餘靜態修正(residual statics correction) 4.地滾波(ground-roll)消除
1.陸上震測資料特性 • Onshore seismic acquisition requires an energy input from a “thumper” truck. Geophones arrayed in a line behind the truck record the returning seismic signal. Vibrator (source) Geophones (receivers)
V=940 m/sec f=11Hz λ=85m V=470 m/sec f=10Hz λ=47m
2.靜態修正(statics correction):修正因地表地形起伏與近地表低速層分布不 均勻所產生之時間偏移(Time shift)量;使 炸點與接受器位於同一基準面(Datum)上。
Uphole time • Tuh : Uphole time • TD = -(Ts+Tr) (Total static correctoin ) • Ts= (Es-Ed-Ds) / Vb (Shot statics) • Tr = (Er-Ed-Dr)/Vb + Tuh (Reciever statics) (Yilmaz 1987)
折射靜態修正 (Refraction statics) (Yilmaz 1987)
Generalized Reciprocal Method (GRM)(Plus-minus method) (Yilmaz 1987)
(Plus-minus method) (Plus term) t+= tABCD + tDEFG – tABFG = 2 * tDelay =2*ZD*cos(ic )/ VW ZD = (t+*VW ) / cos(ic ) * 1 /2 (Minus term)d t_/ d x = 1 / V b
3.剩 餘 靜 態 修 正(Residual statics) :以自動計算方式修正因靜態修正誤差產生的 時間偏移量。 • Surface consistent residual statics: • 1.Travel time picking method • 2.Maximum stack power method • B.Non-surface consistent residual statics : • cdp statics (trim statics)
Corrections that solely depend on source or receiver locations at the surface , not on raypaths in the subsurface.
Travel time picking method (Yilmaz 1987)
CMP Gathers with field statics applied 1. Velocity analysis Apply Residual statics NMO-Correction Compute Residual statics 2. Velocity analysis NMO-Correction with new Velocities Stacking Residual statics
4.地滾波(Ground roll)消除方法: • Coherence noise • 野外震源及接受器排列設計 • 資料處理方法(f-k filter 等)
受波器群組(Digital Group Forming)應用描線間距37.5m 單受波器震測記錄受波器間距6.25m
Signal velocity region V1 VL f2 noise velocity region 1.0 rejection due to pattern n * L L L (n-1) / n * s V2 k 0 fL pattern rejection band k