UDC 551.24.02
D.S. Pavlov (Saint-PetersburgStateUniversity)
Software for Structural Geology: a New Generation
When doing a research in structural geology, scientists use maps, schemesandcrosssections – 3-D structure elements, projected on a plane in two dimensions. Aflatrepresentationofstructuralinformationmakesitmoredifficulttoperceivea 3-Dmodelandunderstand the nature of the given structure.
Applicationofthenewestinformation technologies allows to eliminate these drawbacks to a certain degree.Atpresent, Geographic Information Systems (GIS)areconsideredtobethemost popular software systems in geology. Thissortofsoftwareisaneffectivetoolfor processing geographically bound information.GISinheritstheconceptofdatabases and extends it by adding the possibility to visualize coordinate bound data in the form of maps, plans, schemes, etc.
The 3-D visualization provided bycontemporaryGISis only seeming. Itispossible,whenoneoftheattributesofageographicallyboundpoint is used as a third Z-coordinate.This feature helps to receive a 3-D surface by means of adding a special point altitude column in the table of its attributes. Figure 1 showsasimpleexampleofthisprocedure using ArcGis software system.Becauseanyattributecanbeusedasa Z-coordinate, thethird dimension of the resulting model is not natural.
GeographicInformationSystemsareoriginallyintendedforvisualizationandanalysisofthedata, geographicallyboundin XY coordinate system. Thus, thekeyproblem (the absence of real Z-direction) remains unsolved.
Oneofthespecificcharacteristicsofstructuralanalysisisits iterative nature in most cases.Eachiterationinvolvesrethinking, analysis, interpolationandsynthesisofnewdataon the basis of the previously obtained information.This is explained by the fact that the structural information on the target object is usually very limited.Theiterationsend, when the model of a geological structure is sufficient for the study purposes. Therefore, datagatheringconsumesmost of the researchtime.
GeographicInformation Systems are mainly intended for systematization and visualization of the data already available.Thenecessarydataselectionandpreparationof its layout is a matter of most concern. This routine work takes most time of processingin GIS.
Thus, theopportunitiesofGISapplicationinstructuralresearcharelimited, becauseGISarenotapplicabletoprocessingauthentic three-dimensional data, but is basically aimed at visualization.
However, itmustbenotedthatGISgivestheconceptualgroundforthedevelopment of the new generation of information systems, which in fact supports three dimensions.Extensiveresearchon this issue iscurrentlybeing doneby many scientific groups in differentcountries. Alsocommercial software programs are being created by a number of companies, such as Stratamodel, Inc. (USA), Technoguide (Norway), Beicip Franlab, IFP (France). These software products are oriented to the needs of petroleum industry, which is why the algorithms of such programs imply high level of exploration maturity, due to applying geological and geophysical methods. Besides, thesesystemsmaybeusedtoprocessalimitedrangeofgeologicalstructures, which results from the specifics of oil and gas industry.
Figure 1 - 3-D visualization done with ArcGis
a – a set of geographically bound points with a predetermined altitude attribute; b – attributive table with an altitude column (caption circled); c – spline interpolation of altitude values into bitmap; d - 3D-visualization of interpolation results done with ArcScene
Considering this, itseemsnecessarytocomeupwithanewsoftwareenvironment,whichmightcreateanddevelopa 3-Dgeologicalstructuremodel as well as allow to cope with the lack of scattered structural data.Itisassumedthissoftwareapplication mightbe based on the following blocks: 1) data storage block, 2) input block, 3) visualization block, 4) data synthesis block.
Thedatastorageblockprovidesgathering, storingandstructuring of the geological data.Theusageofthecentralizeddatabasealsomakesitpossibletoqueryparticularsetsofdata, using specific criteria.
Theinputblockprovidessettingtheinitial data to the data base.Theinformationsourcecanbeasfollows: geological sections, seismic sections, contour maps, etc.The main functions of this component aretounifyallthe data using XYZ-coordinates and placeit to the storage.
Thevisualizationblock is responsible for two things: visualization and preliminary interpolation. Structuralinformationundergoespreliminaryinterpolationformakingcontinuous 3-D model to be visualized.Obviously, atthebeginningofresearchthemodelwillberather rough. However, as long as more data is obtained through the data synthesis block, itwillgraduallybecomemoreprecise.
Thedatasynthesisblockis aimed at calculation of additional structural data on the basis of the initial information.Themainfeatureofthismoduleistheuseof “working plane”:theresearcherorientsthisplane in a certain manner, depending on what part of the 3-D model is of current interest, and the system automatically projects the structural information onto the “working plane” (fig. 2). Afterediting the projected data on the plane, the corrected information is stored to the data base, and the user can view the updated 3-D image.
Figure 2. “Working plane” orientation examples and projection results
a – horizontal orientation (contour map); b – vertical orientation (cross section)
The “working place” feature allows researchers to work in usual (flat) form. They can address complicated 3-D structure issues in two dimensions, which facilitates the task. Also, theresultsareimmediatelyvisualizedinthreedimensions. Therefore, the model of the geological structure becomes more detailed, as each new iteration is performed.
Thestudyofanewgenerationofinformationsystemsfor 3-Dgeomodeling seem to very promising. Suchsystemsarecurrentlyindemandandwilldefinitelybeapplicableinvariousindustrialandscientific branches, where understanding of 3-D geological structural models is necessary.