彈性波阻抗理論和實(shí)現(xiàn)方法

1、2021-12-14編輯ppt介紹介紹先回顧彈性阻抗反演的原理先回顧彈性阻抗反演的原理,然后利用然后利用Hampson-Russell 一組軟件分析彈性阻抗反演一個(gè)實(shí)際例子一組軟件分析彈性阻抗反演一個(gè)實(shí)際例子. 彈性阻抗彈性阻抗 () 是由是由BP 公司公司Patrick Connolly 提出提出.實(shí)現(xiàn)彈性阻抗反演可用實(shí)現(xiàn)彈性阻抗反演可用AVO和和STRATA軟件自然組合來(lái)完軟件自然組合來(lái)完成成. 在談?wù)搹椥宰杩狗囱葜霸谡務(wù)搹椥宰杩狗囱葜? 簡(jiǎn)單回顧反演方法在地震勘探簡(jiǎn)單回顧反演方法在地震勘探運(yùn)用的歷史運(yùn)用的歷史.2021-12-14編輯pptCDP/CRP道集迭加反演估算Z= VP地震

2、巖性估算地震巖性估算傳統(tǒng)的地震巖性估算是在地震數(shù)據(jù)疊加偏移后數(shù)據(jù)傳統(tǒng)的地震巖性估算是在地震數(shù)據(jù)疊加偏移后數(shù)據(jù)(疊后數(shù)據(jù)疊后數(shù)據(jù))道進(jìn)行道進(jìn)行反演反演. 這只能估算聲阻抗這只能估算聲阻抗, 不足于推測(cè)流體成分不足于推測(cè)流體成分.2021-12-14編輯ppt道集疊加反演AVO 分析屬性 1屬性 2估算 VP, VS, 和 估算Z= VPAVO 方法方法 同時(shí)使用多屬性估算同時(shí)使用多屬性估算VP, VS, 和和 , 可估算推測(cè)流體和可估算推測(cè)流體和巖性巖性.2021-12-14編輯pptAVO分析可能用的屬性分析可能用的屬性但是哪兩種但是哪兩種(或更多屬性或更多屬性)可用來(lái)最好地預(yù)測(cè)可用來(lái)最好地預(yù)

3、測(cè)流體和巖性流體和巖性這些參數(shù)這些參數(shù)? 目前目前AVO可提取和使用的一系列不同屬性可提取和使用的一系列不同屬性:彈性阻抗反演彈性阻抗反演截距和梯度截距和梯度提取的縱橫波反射系數(shù)提取的縱橫波反射系數(shù) RP,RS 由由 RP 和和 RS 反演到縱橫波阻抗反演到縱橫波阻抗 ZP, ZS縱橫波阻抗縱橫波阻抗 ZP, ZS 轉(zhuǎn)換轉(zhuǎn)換Lambda-Mu-Rho 分析分析本討論先使用前面兩個(gè)屬性的方法本討論先使用前面兩個(gè)屬性的方法. 后面再討論其它的屬性方法后面再討論其它的屬性方法. 2021-12-14編輯ppt范圍限制疊加范圍限制疊加道集AVO 分析近疊加遠(yuǎn)疊加以上是范圍限制疊加的簡(jiǎn)單流程以上是范圍限

4、制疊加的簡(jiǎn)單流程. 利用常偏移距或常角度的范圍疊加已經(jīng)非常利用常偏移距或常角度的范圍疊加已經(jīng)非常成熟成熟. 問(wèn)題是如何解釋其結(jié)果問(wèn)題是如何解釋其結(jié)果?2021-12-14編輯ppt(a)(b)近角度近角度 (0o-15o) 疊加疊加遠(yuǎn)角度遠(yuǎn)角度 (15o-30o)疊加疊加數(shù)據(jù)來(lái)自加拿大數(shù)據(jù)來(lái)自加拿大Colony 區(qū)區(qū)塊塊. 在在630MS有一個(gè)有一個(gè)“亮點(diǎn)亮點(diǎn)”震幅在遠(yuǎn)角度震幅在遠(yuǎn)角度 疊加上比近角疊加上比近角度疊加要強(qiáng)的多度疊加要強(qiáng)的多. 從井資料從井資料分析這是氣砂巖導(dǎo)致分析這是氣砂巖導(dǎo)致 “亮點(diǎn)亮點(diǎn)”.氣砂巖范圍限制疊加氣砂巖范圍限制疊加2021-12-14編輯ppt這是近遠(yuǎn)偏移這是近遠(yuǎn)

5、偏移距距(角度角度)的交的交繪圖繪圖,高震幅高震幅區(qū)塊用不同顏區(qū)塊用不同顏色突出顯示色突出顯示.角度疊加進(jìn)行交繪圖角度疊加進(jìn)行交繪圖2021-12-14編輯ppt這是交繪圖中的突出區(qū)塊對(duì)應(yīng)在剖面上的位置這是交繪圖中的突出區(qū)塊對(duì)應(yīng)在剖面上的位置. 可看出氣砂巖已被很可看出氣砂巖已被很好地描繪好地描繪.2021-12-14編輯ppt(a) 近角度疊加近角度疊加 (0-15o)時(shí)間切片時(shí)間切片, (b)遠(yuǎn)角度疊加遠(yuǎn)角度疊加 (15-30o)時(shí)間切片時(shí)間切片(三維河道砂三維河道砂). 對(duì)時(shí)間切片震幅包絡(luò)求得是對(duì)時(shí)間切片震幅包絡(luò)求得是10MS窗口內(nèi)的平均值并運(yùn)用了窗口內(nèi)的平均值并運(yùn)用了Z-SCORE轉(zhuǎn)換

6、轉(zhuǎn)換. 異常異常河道砂得以清楚顯示河道砂得以清楚顯示.角度范圍疊加角度范圍疊加(a)(b)2021-12-14編輯ppt 從范圍限制疊加到彈性阻抗從范圍限制疊加到彈性阻抗范圍限制疊加使用的是常偏移距或常相位道集范圍限制疊加使用的是常偏移距或常相位道集,方法很成熟并可方法很成熟并可避免同相軸未拉平問(wèn)題避免同相軸未拉平問(wèn)題. 但它究竟有何含義但它究竟有何含義?Patrick Connolly(BP), 提出新穎的方法來(lái)解釋范圍疊加的含義提出新穎的方法來(lái)解釋范圍疊加的含義, 稱之為彈性阻抗稱之為彈性阻抗.彈性阻抗是基于彈性阻抗是基于Aki-Richards 等式等式, 下幾張圖片解釋彈性阻抗下幾張圖

7、片解釋彈性阻抗的概念和由來(lái)的概念和由來(lái).2021-12-14編輯ppt彈性阻抗理論彈性阻抗理論: 222tansinsinCBAR,21:PPVVAwhere222421PSSSPSPPVVVVVVVVB.21:PPVVCandConnolly (1999)提出提出, 類似于聲阻抗類似于聲阻抗, 我們定義彈性阻抗我們定義彈性阻抗() 為為: EIEIEIRln21212021-12-14編輯ppt假設(shè)假設(shè) 2PSVVK注意到注意到,sintantansin2222我們可以把我們可以把 :222sin41sin8tan121lnKKVVVVEISSPP假設(shè)假設(shè) K 為常數(shù)為常數(shù), 可以將上式寫為

8、可以將上式寫為:2221 4sin1 tan8sinlnlnlnlnKKPSEIVV 2221 4sin(1 tan)8sinlnKKPSVV 2021-12-14編輯ppt然后進(jìn)行積分和取冪然后進(jìn)行積分和取冪, 可得到以下彈性阻抗可得到以下彈性阻抗 : 222(1 tan)( 8sin)(1-4sin)( )KKPSEIVV2P2SVVKwhere如果如果 = 0o, 彈性阻抗就還原為聲阻抗彈性阻抗就還原為聲阻抗(), 等式為等式為: PVAIEI02021-12-14編輯ppt以上等式使用的是以上等式使用的是所有三項(xiàng)等式所有三項(xiàng)等式. 對(duì)于入射角大對(duì)于入射角大于于300, 該等式將不是線性

9、的擬合該等式將不是線性的擬合. 對(duì)于大角度對(duì)于大角度 (大偏移距大偏移距), 如果只用等式的前兩如果只用等式的前兩項(xiàng)項(xiàng),等式可寫為等式可寫為: 222(1 sin)( 8sin)(1 4sin)( )KKPSEIVV2PSVVKwhere當(dāng)當(dāng) = 0o, 得到得到: PVAIEI02021-12-14編輯ppt將聲阻抗將聲阻抗(AI)轉(zhuǎn)換入射角為轉(zhuǎn)換入射角為30 的彈性阻抗通常曲線類似但阻抗絕對(duì)值變低的彈性阻抗通常曲線類似但阻抗絕對(duì)值變低. 角度增加其視聲波阻抗降低角度增加其視聲波阻抗降低. 油砂巖比頁(yè)巖視聲波阻抗降低幅度更大油砂巖比頁(yè)巖視聲波阻抗降低幅度更大.如下圖如下圖Connolly 1

10、999 彈性阻抗彈性阻抗 油飽和度的影響油飽和度的影響2021-12-14編輯ppt彈性阻抗彈性阻抗 實(shí)例實(shí)例下圖下圖 顯示聲阻抗和彈性阻抗顯示聲阻抗和彈性阻抗(30度角度角)的曲線比較的曲線比較:2021-12-14編輯ppt重疊顯示更好地區(qū)分彈性阻抗和聲阻抗在含油砂巖處的差別重疊顯示更好地區(qū)分彈性阻抗和聲阻抗在含油砂巖處的差別:2021-12-14編輯pptEI 反演步驟反演步驟道集AVO 分析近角度疊加1遠(yuǎn)角度疊加2反演彈性阻抗 EI(1)反演彈性阻抗 EI(2)2021-12-14編輯ppt2021-12-14編輯pptApplying Elastic Impedance to the

11、 Colony DataIn this exercise, we will start with the 2D Colony dataset which we analyzed earlier and apply the Elastic Impedance analysis to it.First re-open the avo_class database in GEOVIEW. On the GEOVIEW window, click on Database / Open. Select avo_class.wdb from the pullDown list, as shown, and

12、 click on OK:2021-12-14編輯pptOn the GEOVIEW main window, click on the AVO / AVO button to restart the AVO program:Select the option to Open Previous Project and choose the colony.prj project:2021-12-14編輯pptBefore analyzing the data, we will create the elastic impedance logs in the modeling window. If

13、 it is not visible, click on the Modeling / Single Well button on a seismic window and select AVO_WELL on the Open Well menu to get the following window :2021-12-14編輯pptNext, click on the Logs / Transforms button as shown on the left, and select the Elastic Impedance option from the Transforms menu

14、shown below:2021-12-14編輯pptClick Next on the Transforms menu and select the correct well (AVO_WELL) for the P-and S-wave logs and for storing the Elastic Impedance log, as shown below.2021-12-14編輯pptOn the next menu, make sure the FRM edited logs are used for the calculation of the elastic impedance

15、 and call the result EI_Near as shown.2021-12-14編輯pptClick on Next and fill in the next menu as shown, choosing Constant Angle and filling in an angle of 7.5 degrees.2021-12-14編輯pptWhen the EI_Near log has been created, select the Logs / Transforms option again, and fill in the menus as shown previo

16、usly except for the last two menus shown here. On these menus, create a new log called EI_Far (making sure that the FRM edited logs are used in the calculation) at a constant angle of 22.5 degrees.2021-12-14編輯pptTo display the two elastic impedance traces together, click on the “eyeball” icon to bri

17、ng up the Parameter menu. Under the Layout tab, turn off the Display Only Active Logs button to see all of the logs, and put the EI_Near and the EI_Far logs on the same track, as shown.2021-12-14編輯pptClick on Ok and you will see the display below. Notice that the EI_Far log plots to the left in the

18、gas zone and to the right in the rest of the log. Now, lets crossplot these two logs.2021-12-14編輯pptClick on Crossplot and fill out the menu as shown below, selecting the Elastic Impedance log type as well as and . Then, click on Next .On this menu, select the well, and click on Next . 2021-12-14編輯p

19、ptOn this menu, select Elastic Impedance for both the X and Y axes, and change the Plot Title as shown below. (Note that we will select a different elastic impedance log for each axis on the next menu). Click on Next .2021-12-14編輯pptOn this menu, select EI_Near for the X axis and EI_Far for the Y ax

20、is, as shown. Click on Next .On this menu, select Time as the domain, with start and end values of 600 and 675. Click on Ok to get the crossplot.2021-12-14編輯pptNotice that the axes of the plot are both labeled the same. To change the annotation, click on Edit / Annotations and change the menu as sho

21、wn on the right:Click on Ok and the plot will appear as shown on the left. Notice the clear separation of the points on the lower left of the plot.2021-12-14編輯pptLet us now perform zone analysis to see if the anomaly seen on the crossplot really is the gas sand. To do this, first display the well lo

22、g curves by clicking on the Cross-Section button.After using the Zoom option, you should see a plot similar to this:2021-12-14編輯pptNow, click on the Zones / Add option and create the elliptical grey background trend as shown on the right.2021-12-14編輯pptNow define the elliptical yellow gas trend as s

23、hown.2021-12-14編輯pptNote that the plot of the well logs has been updated with the colors, and the anomalous points do indeed correspond to the gas sand zone.2021-12-14編輯pptNow go to the window containing the original CDP gathers. Click on Process / Stack / Range Limited Stack:2021-12-14編輯pptUse the

24、defaults on the first menu as shown on the right, and click on Next .Then, fill in the second menu as shown on the left. Notice that we are creating 2 angle stacks from 0 to 30 degrees.2021-12-14編輯pptThe two angle stacks are created as shown here, where range_limit_stack is the near angle stack, and

25、 range_limit_stack2 is the far angle stack.2021-12-14編輯pptSelect the file called range_limit_stack.vol from the menu and click on Open. Next, click on the STRATA button on the GEOVIEW main window. We will continue using the colony project, as indicated in the menu on the right.Click on Ok to bring u

26、p the STRATA main window, and then click on Data Manager / Import Data / Open Seismic / Open From Project.2021-12-14編輯pptFill out the Well to Seismic Map menu as shown and click Ok.The STRATA window now looks like this:2021-12-14編輯pptClick on Horizon / Pick Horizons and pick a second event, as shown

27、. Horizon 1 is the trough at the top of the gas sand.2021-12-14編輯pptFinally, pick a third event, as shown here. Then click Ok to finish the picking.2021-12-14編輯pptNext, click on Model / Build/Rebuild a Model. Fill in the first page as shown on the right, changing the option to: Typical setup of Elas

28、tic Impedance for far-offset stack inversion. Click on Next .On the third page, select the well AVO_WELL and click Next .2021-12-14編輯pptOn the next page, we must select the Elastic Impedance log which corresponds to the Near Angle stack. Since this stack covers an angle range of 0 to 15 degrees, cho

29、ose EI_Near, calculated for the angle of 7.5 degrees.Now click on Next twice and OK to build the model.Then, click on Invert / Model Based as shown:On the first page, change the output file name to near_inversion. Click on Next twice.On the third page, change the Average Block Size to 4.Click OK to

30、run the inversion.2021-12-14編輯pptThe inversion result will look like this:2021-12-14編輯pptNext, click on Window / New Window to create an emptySTRATA window. In this new window, click on Data Manager / Import Data / Open Seismic / Open From Project and select range_limit_stack2.vol, as shown on the r

31、ight. Click on Open to get the result shown below. Notice that the existing picks are annotated.2021-12-14編輯pptNext, click on Model / Build/Rebuild a Model and select the option Typical setup of Elastic Impedance for far-offset stack inversion on the first page, as done previously. Select AVO_WELL o

32、n the third page and choose the EI_Far log (22.5 degrees) on the fourth, as shown. The new model will look like this (you may need to update the color key):2021-12-14編輯pptNext, click on Invert / Model Based and change the name of the output volume on the inversion menu as shown below. On the third p

33、age, change the Average Block Size to 4 and click on OK to start the inversion process:2021-12-14編輯pptWe now have two inversion results. Note that we have had to use two different color scales, since the impedance values are scaled differently.Near_inversionFar_inversion2021-12-14編輯pptNow let us com

34、pare the near-angle inversion with the far-angle inversion by cross-plotting the two volumes.On either of the two inversion results, click on Process / Cross Plot:On the first menu page, select the CDP range from 300 to 360 and the two volumes as shown:Click Next until you reach the fourth page. Spe

35、cify a Constant Time of 630 ms as shown:2021-12-14編輯pptIf there were no AVO effects, we would expect the far and near impedances to be related by a straight line. In other words, there would be a single cluster. Lets add some zones to the crossplot and view the cross-section to see where these zones lie.Click on Zones / Add:2021-12-14編輯pptMake the first zone using