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Overview of Seismic Interpretation

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1 Overview of Seismic Interpretation
Lecture 9 Overview of Seismic Interpretation SLIDE 1 This slide introduces seismic interpretation It gives an outline of the next several units Courtesy of ExxonMobil L 9 – Overview Interpretation

2 From Lecture 1 Exploration’s Task Identify Opportunities Capture
Prime Areas Identify Opportunities From Lecture 1 Acquire Seismic Data Process Seismic Data Drill Wildcats Interpret Seismic Data Assess Prospects Failure Success Confirmation Well SLIDE 2 We talked about this simply flowchart for exploration in Lecture 1 We want to focus in on the box outlined in magenta – how we interpret seismic data Uneconomic Success To Development Or Production Drop Prospect Courtesy of ExxonMobil L 9 – Overview Interpretation

3 Remainder of this Course
Seismic Interpretation and Beyond … Develop a Geologic Framework Apply the Geologic Framework to Prospecting (Exploration) Given our time constraints, we will only be able to look at a subset of the concepts, procedures and tools that geologist and geophysicists use in the exploration phase of the oil & gas industry SLIDE 3 There are two major tasks in the interpretation & analysis of the seismic data First we need to develop a geologic framework As you will see, this is the identification and mapping of the main faults and the main stratigraphic horizons Once we have developed the geologic framework, in exploration we want to examine the HC system components: Where are potential reservoirs, traps, seals, mature source rocks, and HC migration pathways? Then where would we drill to make a new discovery? For development and production, we also want to develop a geologic framework (if it does not exist or does not have the level of detail that we need) Then we can consider where to drill a development well – to answer a question on the spatial distribution of fluids and reservoir rock properties Or we can consider where to drill a production well (a producer or injector) to increase HC production from the field Courtesy of ExxonMobil L 9 – Overview Interpretation

4 of these basic elements
Workflow: Overview 1. Geologic Framework We can subdivide the exploration work process from seismic interpretation forward into 4 major elements Modules provide some details on each of these basic elements 2. Data Analysis 3. Prospect Elements SLIDE 4 Here is the basic workflow for seismic interpretation & beyond First, we need to develop a geologic framework; major faults and stratigraphic packages (depositional sequences) Then we need to analyze all the key packages – where are potential reservoirs, source rocks, etc. Next we have to identify prospects – places where all the HC system elements look favorable & we are willing to propose a drill site to management Finally we have to access the prospect – what type and volume of HC do we expect & what is the chance of success or risk 4. Prospect Assessment Courtesy of ExxonMobil L 9 – Overview Interpretation

5 Geologic Framework Structural Interpretation
Using all available data (wells, seismic, outcrop, regional studies, gravity, magnetics, etc.) build a framework of present-day structure and stratigraphy Structural Interpretation Faults & Folds Subsidence & Uplift Structural Trends Structural Features Stratigraphic Interpretation Unconformities Stratal Packages Environments / Facies / Lithologies Ages SLIDE 5 A bit more about the geologic framework We want to use all the available data ………. We have to perform a structural analysis – identify & map faults …… We also need a stratigraphic interpretation – map unconformities …… Although we teach these two components separately, an experienced seismic interpreter will work structure & stratigraphy simultaneously Courtesy of ExxonMobil L 9 – Overview Interpretation

6 SLIDE 6 Module 10 focuses on structural interpretation We will look at different types of faults (extensional, compressional, strike-slip) We’ll also talk a little about diapiric structues – caused by mobile salt or shale A major product is structure maps that indicate the morphology (highs, lows, fault traces) on each of our mapped horizons

7 Applying the Framework for Prospecting
Data Analysis Present-day conditions - How things are now Basin reconstruction - How things evolved Prospect Elements Individual elements: Source, Migration, Reservoir, Trap, Seal Favorable juxtaposition of all elements Prospect Assessment Likely HC volumes in the success case Risking - How likely is the success case? SLIDE 7 The geologic framework allows us to proceed with the next steps: Analyze the data to get both present-day conditions and information on how the basin evolved Examine the prospect elements to find potential new drill locations (exploration) Assess the prospect (exploration) in terms of the type of HC, the quantity of HC, and the risk associated with the proposed well location Courtesy of ExxonMobil L 9 – Overview Interpretation

8 The Alpha and Beta Prospects
For Modules 12 through 14, we use two hypothetical leads: Alpha and Beta. Should we propose that we drill either or both? Alpha Beta Sea Water Overburden Seal Reservoir SLIDE 8 For modules 12 and beyond, we will use two hypothetical prospects: Alpha and Beta This cross-section shows a potential reservoir, source and seal with two fault-bounded anticlines The business question is whether we should drill either or both (in which order) We’ll look at how we would address this question Source Basement Courtesy of ExxonMobil L 9 – Overview Interpretation

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