عرض مشاركة واحدة
قديم 08-02-2012, 10:48 PM
  #103
ابوبقعة
 
La spécialité: Télécommunications
اخرى ( جامعة عربية او اجنبية )
تاريخ التسجيل: 08-02-2012
المشاركات: 1
ابوبقعة عضو يستحق التميز
افتراضي رد: انا مهندس جيولوجيا من يريد المساعدة انا مستعد

السلام عليكم ورحمة الله وبركاته
انا ياجماعة مهندس اتصالات ودارس الامواج وكل حاجة عنها .
seismic شاءت الاقدار انى اشتغل فى شركة تعمل فى مجال
seismic processing steps وانا الحقيقة هذه الايام ابحث على الانترنت على معلومات تخص
ووجد الكثير منها وهي فعلا هذه الخطوات التى نعمل عيها هنا ولكنى اريد شرحها بالعربى من احد الاعضاء الكرام الذين درسوا هذا المجال .
انا عارف انى هتعبكم معايا بس انا حاليا بقرأ كثير وفهمت كتير بس محتاج معلوماتى تتاكد بالعربى لانى عمرى ما درست الحاجات دى انا هكتب اللى اعرفه وانتوا صلحوا وضيفولى وياريت ياريت لو احد الاعضاء لو يتكرم وياخد اميلى ونتكلمم مع بعض شوية كل لما يكون فاضى بحيث اقله اللى انا مش عارفه يبقى جزاه الله خيرا وهذا اميلى
eng.hassangazal على الياهو


انا تعلمت الاتى :
عرفت ان موضوع الجيوفيزيك فيه
seismic , resistivity , ....
وحاجات تانية كمان اللى يهمنى هو الطريقة الزلزالية
تعلمت ان هناك مكان يتم وضع فيه المستقبلات بحيث انها تسجل الموجات المنعكسة من باطن الارض وعرفت ما هو تركيب
geophones
وتعلمت ايضا ان البيانات تمر من خلال هذه المسجلات الى محطة اسمها
recorder
يتم فيه تحويل الداتا الى صورة ديجيتال , ثم بعد ذلك تاتى لنا هنا فى القسم على
tapes
نقوم بعد ذلك بتطبيق عليها بعض الخطوات وهى الاتى والتى لم افهمها كلها بشكل جيد , مع العلم ان المشكلة ان معى مصريين ولكنهم لا يريدون اخبارى اى شىء وهذه هى الخطوات والتى اريد شرحها بالعربى خطوة خطوة :

. Demultiplexing: orders seismic data by seismic trace instead of being ordered by time. Multiplexed recording is still found in older data or in current data shots with old recording instruments.
1-b. Reformatting: puts the data in a format that is understandable by computers (e.g. SEG-Y format, SEG-D format, etc.).
1-c. Editing: examines seismic data for bad, noisy, and\or monofrequency traces, and deletes them, and also spots any traces with incorrect polarities and corrects them.
1-d. Geometrical spreading correction: It is also called amplitude correction. Because the signal becomes weaker as it moves away from its source (i.e. its amplitude decreases with time), amplitude correction is needed to count for this lose, and to make amplitudes stronger.
1-e. Set up of field geometry: incorporates field geometry with seismic data processing. Coordinates, shot\ receiver locations and spacing must be entered to the system carefully and precisely because processes like CMP sorting, for example, highly depend on this.
1-f. Application of field statics: This is needed for land data collected on non-flat areas. It reduces the travel times into a common datum level. The datum could be the sea level or any other local datum.

2- Deconvolution and trace balancing: Deconvolution makes the signal look better by increasing the temporal resolution and removing echoes. Trace balancing makes the amplitude uniform.

3- CMP sorting: sorts the data into CMP gathers, so it can be corrected for the NMO and stacked after that (see step 7).

4- Velocity analysis: gives info about velocities in the subsurface layers. It finds the stacking velocity (very close in value to the RMS velocity) that best fits our data (This step may be delayed after step 5).

5- Residual statics: counts for near-surface velocity variations that causes some static and dynamic distortion problems.

6- Velocity analysis: (see step 4). If we have residual statics problems, we do velocity analysis after we count for them.

7- NMO correction: counts for the increase in travel time with increasing offset distance. This increase makes flat reflectors look dipping, and makes dipping reflectors look even more dipping. The amount of correction needed decreases with depth, so that shallower reflectors get more “stretched” than do the deeper ones.
7-a. Muting: It is just a fancy word for deleting a part of a trace. Muting a whole trace is called “killing”.
7-b. Stacking: After sorting the data into CMP gathers and applying the NMO correction, reflectors line up nicely and hence their stacking gives a stronger signal. Multiples\ random noises do not line up. Stacking increases S/N ratio by decreasing multiples\ random noise from the data which enhances the overall quality. It also reduces the seismic data volume to the plane of the seismic section.

8- Time- variant band-pass filtering: filters unwanted “signals” based on their frequencies. For example, ground roll has a lower frequency (and higher amplitude) compared to the rest of the section, so we can filter it out based on that fact.

9- Migration: So far, each trace is plotted under its CMP location which puts reflectors in the wrong subsurface location. Migration process moves those reflectors into their true subsurface locations, and that improves lateral resolution. Migration also collapses diffractions into identifiable points on the seismic section.

10- Gain recovery: Seismic energy gets lost in many different ways (e.g. scattering, frication, etc.). Gain is the inverse function of energy loss. It is very hard to predict the attenuation function because primary reflections, multiple reflections, and random noise have different decay functions. Instead, we examine (test) different gain values, and see which value gives a better looking data.

ولدى بعض الاسئلة الاخرى ما هو الفرق التفصيلى بين
CDP , NMO , DMO , MIG
انا اعلم ان اسئلتى كثيرة بس معلش انا فى وضع صعب جد




نا متأسف يا جماعة معلش كمان مرة , ياريت لو ترتيب الخطوات دى مش صح حد يقولى انا عارف الخطوات دى ولكن مش بالصورة الكاملة فارجوا التوضيح باللغة العربية وياريت لو فى بعض الرسومات
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