Second EAGE Borehole Geology Workshop
The programme includes three training courses:
1. Borehole Geology Clastic Environment Structural Interpretation
Date: Tuesday, 10 October 2017
Time: 15:45 - 16:45 hrs
Instructor: G. Aplin (Task Fronterra Geoscience)
Application of borehole image logs in the sedimentological interpretation of clastic reservoirs.
Borehole image logs provide high resolution geological data that may be used for the detailed reservoir characterization. The aim of this 1 hour training course is to provide participants with an understanding and workflow for the interpretation of borehole image log data from clastic reservoirs using modern sedimentological techniques.
Structural interpretation (10 minutes): A structural interpretation of the borehole images is a prerequisite for detailed sedimentological analysis. Approaches to dip analysis and examples of dip type schemes applicable to different depositonal systems will be discussed. Methodologies for deriving bulk structural zonations and populating with representative structural dips using dip trend analysis, stereonets, azimuth vector plots and curvature analysis techniques will be demonstrated.
Sedimentological interpretation (10 minutes): This will begin with an assessment of the type of sedimentary features that may be observed in borehole images. Examples will be shows of how sedimentary fabrics and dip data derived from the borehole image can be used in conjunction with openhole logs and other supporting data to determine image-based facies and facies associations from different sedimentary environments.
Sediment dispersal analysis (10 minutes): Sediment dispersal is assessed from dip data after it is returned to its depositional attitude through removal of structural dip. The types of sedimentary structures that that provide sediment dispersal information such as cross-bedding, bounding surfaces, slumps and rotated blocks will be discussed. Examples of how rotated dip data can be used in palaeotransport and palaeoslope analysis and sand body architecture in different sedimentary settings will be shown.
Clastic depositonal environments (20 minutes): Examples will be shown of borehole images from a number of clastic environments, namely aeolian, fluvial, shallow marine, deltaic and deep water systems. The key features that may be seen in borehole images and key interpretive challenges such as assessing structural dip from a dune sequence or palaeoslope orientation from a slumped deep marine system will be discussed.
Thin bed analysis in clastic reservoirs (10 minutes): High resolution borehole image logs allow thin beds below the resolution of standard logs to be determined. Techniques for analysis of thin beds from on borehole images to generate an earth model will be presented.
2. Natural or not? Borehole image artifacts & geomechanical features
Date: Wednesday, 11 October 2017
Time: 08:30- 9:30 hrs
Instructors: Johanne Paludan, Morgane Bizeray, Anne Bartetzko, Ingelinn Aarnes (BHGE)
Features that are not related to the geology of the formation are known as borehole image artifacts and are familiar to all image analysts. Artifacts are derived from a number of sources, including tool mechanics, acquisition parameters and borehole wall shape. An important subcategory of the latter is stress-induced artifacts, borehole breakout and drilling-induced fractures, which provide important geomechanical information. Separating drilling-induced from natural fractures is essential for accurate reservoir characterization but can be a very difficult task when both types of fractures are present.
This short course will discuss some of the accepted criteria for distinguishing between geological features and artefacts, with special focus on geomechanical features. Real log examples will be presented, both typical “text book” and some more unusual or ambiguous examples, of which the interpretation is not straight forward. Along with the presentation of our interpretation the audience will be invited to participate in discussion of the validity of the criteria used and to present their own experience and opinions.
3. Borehole Geology Carbonate Environment Facies Textural Analysis
Date: Wednesday, 11 October 2017
Time: 15:45 - 16:45 hrs
Instructor: N. Bize-Forest (Schlumberger)
This 1 hour training course covers an integrated workflow for formation evaluation using the last image log technology available in Techlogy for facies textural analysis interpreted on electrical and ultra-sonic images logged in WBM or OBM. Through a combination of lectures and discussions the class will learn the principles of PoroSpect, PoroTex or VugDensity Analysis and their main quantitative outputs that measure the secondary porosity: Pore size, pore typing and pore connection.
PoroSpect: Porosity Spectrum Analysis. The method provides porosity distribution and vug fraction quantification from Wireline and LWD electrical images logged in WBM. We will discuss about the principle of the method based on Archie’s equation and its main parameters, and the choice of the best thresholds that discriminate the secondary porosity and the outputs signification.
PoroTex Analysis: Full Porosity-Textural Facies analysis, using Wireline and LWD electrical images logged in WBM. PoroTex Analysis aims to obtain quantitative measures of secondary porosity including geometric information like size and proportion of vugs. We will discuss how to set up the parameters for vug quantification or connectedness and how to compute the pore type’s contribution to the total porosity.
VugDensity Analysis: The method provides the vug fraction quantification from ultra-sonic borehole images logged in WBM or OBM. We will discuss about the principle of the method its main parameters and outputs.
An example of a complete facies analysis workflow integrating borehole image textural interpretation, open hole logs and a combination of statistical and clustering techniques will be presented at the end of the class with the objective to develop a more complete understanding of the quality of the facies in the reservoir.