What make me think in this problem is this (having to perform groundwater flow modeling):
If for example I have two lithological categories with very different spatial structures ( different anisotropy, different variogram ecc..) but with the same Hydrogeologic parameters, does grouping these two lithologic categories together make sense?(for me not too much!)
But, and I'm sorry for my English, what I was asking in my mail was not in which way I can find the "right" categories. But in which way, once I have my categories along the boreholes, I can geometrically discretize the boreholes in data to use in simulation or estimation.
For example I divided a borehole of 10m in punctual values spaced every 25cm....but probably it is not the best approach.
Sincerely Sebastiano Trevisani
--------------------------------------------------------------------------------------------------- past mails (in geological order!!!!)
Sebastiano
The way we do it is to 'composite' samples with the same lithology, to a reasonably consistent length. Then we do semi-variogram analysis either on each lithology separately or at least not pairing samples between lithologies. This is an excellent way of finding out whether your lithologies have different continuity of values or not. Sometimes you can then group similar units together.
Depending on how that stage goes, you can then krige within lithologies or in proper 3d.
Isobel http://geoecosse.bizland.com/BYOGeostats.htm
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Sebastiano,
This is a much debated, classic problem reservoir engineers have in the oil industry. To deal with it, I would recommend you first focus on what you want your model to do for you. If you plan to build a flow simulation model, you need to decide how the different rock types affect flow and how they can be grouped to capture different depletion schemes. Rock types generally can be grouped together if they have similar properties like porosity, permeability, and residual saturations. Another way to identify flow units is to plot (by well) cum well permeability vs. depth or cum well permeability vs. cum porosity (also called a Lorenz plot), where changes in the slope of the plot identify breaks between flow units. If these breaks can be correlated across the reservoir, they make nice boundaries for geostatistical data points.
Regards,
Paul Taylor Sr. Reservoir Engineer BP
----- Original Message ----- From: "sebastiano trevisani" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, November 20, 2003 3:21 PM Subject: AI-GEOSTATS:
--------------------------------------------------------------------------------------------------------------------- > Hi list members!!! > Another question for you! > > I have to perform geostatistical geological modeling using some boreholes. > The litology in these boreholes is described according to geotechnical > classification. My question essentially is this: which is the best way to > transform boreholes in data to use in geostatical modeling? The litological > vertical variability is very high, for example I can have layers > with thickness of only 10cm. If I discretize the boreholes with a coarse > grid (say a step of 50cm) I lose these details (that in the case of a clay > layer could be very important from the hydraulic point of view) and if I > use a too dense grid I have too many data. For example I tried to > discretize borehole data with a grid, along the borehole, of 10 cm, > obtaining about 9.000 data. I'm wondering if it could be an idea try to > discretize in an "intelligent way", for example trying to adapt the step of > the grid in relation to the thickness of the level (and why not to the > category?) encountered. Or if there is another approach... > I have read some books in geostatistical reservoir modeling...but they > don't deal with this problem. > If some has some idea where to look thank you for your help! > > Sebastiano Trevisani > > > > -- > * To post a message to the list, send it to [EMAIL PROTECTED] > * As a general service to the users, please remember to post a summary of any useful responses to your questions. > * To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list > * Support to the list is provided at http://www.ai-geostats.org
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