Types of Data Lecture 3 Mega-Regional Local Present Circulation Plate Reconstructions Maps showing Features SLIDE 1 This unit covers the main types of data that we use in industry The scale of the data goes from mega-regional (e.g., major lithospheric plates) to microns (e.g., pores in reservoir rocks viewed with SEMs) Outcrops Local Cores Logs Well-Seismic Ties Courtesy of ExxonMobil L 3 - Types of Data

Data Types Vary with Scale From a basin-scale analysis to a field-depletion study, we want to integrate information from all available sources Regional Analysis Basin Analysis Block Analysis Prospect Analysis Field Analysis Compartment Analysis Mega-Regional SLIDE 2 For exploration we may start with regional studies, developing an understanding of the factors influencing tectonics and sedimentation in the basin we are working As fields are discovered and we move into development and then production, we focus on studies of much finer-scale For each reservoir, how will fluids move as we produce oil & gas? Where are the flow barriers and baffles – such as thin shale layers that may segment the field vertically or small faults that might segment the field horizontally (compartments) Fine-Scale Courtesy of ExxonMobil L 3 - Types of Data

Late Jurassic to Aptian Mega-Regional Data Geologic Maps Plate Tectonics Gravity & Magnetics Regional Seismic Lines Tectonic Evolution Stratigraphic Charts Paleogeographic Maps Etc. • Maast. to Present Open marine Cen. to Maastrictian M A R I N E A N O X I C Albian to Cenomanian C A R B O N T E M A R I N E Aptian G U L F Mitchum et al., 1977b SLIDE 3 At the mega-regional scale, we would develop and use: Geologic maps Plate reconstructions Gravity & magnetic data and models Available seismic lines – typically long, regional lines A model of the tectonic evolution of the basin A stratigraphic chart that summarizes deposition and highlights potential source, reservoir and seal units Paleogeographic maps And other information that will help use understand the controls on any hydrocarbon systems Late Jurassic to Aptian R I F T AAPG©1977 reprinted with permission of the AAPG whose permission is required for further use. Courtesy of ExxonMobil L 3 - Types of Data

Mega-Regional Analysis Usually mega-regional analysis is performed to : Decide which basins hold sufficient potential Determine how much to bid for blocks Provide regional settings to help understand the characteristics of a field To guide step-out wells, i.e., those that extend beyond a known field in search of a similar HC accumulation SLIDE 4 The typical goals of mega-regional analyses are to: Decide which basins hold sufficient potential Determine how much to bid for blocks Provide regional settings to help understand the characteristics of a field Guide step-out wells, i.e., those that extend beyond a known field in search of a similar HC accumulation Courtesy of ExxonMobil L 3 - Types of Data

Outcrop Studies (age-equivalent or analogs) Local Data - Surface Surface Measurements/Observations Topographic/Bathymetric maps Surface geology (structure & stratigraphy) Nearby outcrops (or analogs) Heat flow measurements HC seeps Etc. Measured Sections 20 ft Outcrop Studies (age-equivalent or analogs) SLIDE 5 Another main type of data is what we can gather from the surface, either from field measurements and observations or from remote sensing (e.g., satelite data) These data include: Topographic/Bathymetric maps Surface geology (structure & stratigraphy) Nearby outcrops (or analogs) Heat flow measurements HC seeps Etc. Courtesy of ExxonMobil L 3 - Types of Data

Local Data - Subsurface Subsurface Measurements/Observations Data from Wells cores, cuttings, logs lithology, ages, geochem, etc Geophysical Data Seismic (2D, 3D, 4D) Gravity & Magnetics SLIDE 6 A major source of data is subsurface measurements and the resulting interpretations Subsurface Measurements/Observations Data from Wells Rock samples from cores and cuttings Measurements from subsurface rock units via logs Interpretations of lithology, ages, geochem, etc. Geophysical data, usually collected at the Earth’s surface Seismic data (2D, 3D, 4D) Gravity & Magnetics Logging a Well Vibrators – Seismic Sources Courtesy of ExxonMobil L 3 - Types of Data

Data from Wells Samples Measurements Conventional Cores Sidewall Cores Cuttings Measurements Wire-line Logs Pressure Temperature Fluid samples Flow Properties Vertical Seismic Profiles (VSP) SLIDE 7 Data from wells comes from rock samples and measurements at depth from the well bore Data from samples includes those from: Conventional Cores Sidewall Cores Cuttings Data from measurements taken in the well bore include: Wire-line Logs Pressure Temperature Fluid samples Flow Properties Vertical Seismic Profiles (VSP) Courtesy of ExxonMobil L 3 - Types of Data

Well Samples: Conventional Cores Coring apparatus positioned at the bottom of the drill stem Often gets intact samples of 1 meter or more Good for analyzing lithology, sedimentary features, porosity, permeability, paleontology (ages, environments) Interval is cored ‘blind,’ i.e., before the interval is logged Expensive (2 round trips for the drill stem = lots of rig time) SLIDE 8 Our best subsurface data comes from conventional cores The coring apparatus is positioned at the bottom of the drill stem We often get intact cores of 1 meter or more Cores are good for analyzing lithology, sedimentary features, porosity, permeability, paleontology (ages, environments) One drawback is that we have to core ‘blindly,’ i.e., we have to decide where to take a core before the interval is drilled and logged Another drawback is that cores are very expensive To take a core, we have to pull out the drill stem Attach the coring device and lower the drill stem (1 round trip) Obtain the core and pull the drill stem again Detached the coring device and send the drill stem down again (a second round trip) All of this takes a lot of time, which is expensive (about $1 million per day) Courtesy of ExxonMobil L 3 - Types of Data

Well Samples: Sidewall Cores Small samples (1 x 2.5 inches) 30 samples per run Sampling based on logs Step 1: Gun in position Step 2: Shot fired Stabilizer Gun Body Core Barrels SLIDE 9 This slide explains what a sidewall core is The tool (pictured on the left) is part of the drill stem It has about 30 casings that can be fired into the formation The casing captures a small sample of rock The samples are retrieved at the end of a logging run This does not require very much extra rig time – so is relatively inexpensive The drawback is that the sample is small – we get the rock type but nothing about vertical variability, sedimentary structures, etc. Step 3: Core retrieved Courtesy of ExxonMobil L 3 - Types of Data

Well Samples: Cuttings The ‘rubble’ that comes up the sides of the well bore with the circulating fluid Can provide samples for certain kinds of analysis – e.g., lithology, paleo Not suitable for porosity, permeability, sedimentary structures (pulverized) Very inexpensive – no lost rig time PROBLEM – no control on the depth from which the samples came from – any zone not cased SLIDE 10 Cuttings are the ‘rubble’ that comes up the well bore and reaches the surface Think of drilling into a block of wood Shavings of wood come up as you drill down In general, the shavings indicate the property of the wood being drilled – with a built in delay The delay relates to the time it takes for a shaving cut at the drill tip to move up to the surface Cuttings are the rock ‘shavings’ There is a delay related to the time it takes for ‘shavings’ cut at a certain time (say high noon) to reach the surface – a distance that can be several thousand feet Another problem is that cuttings do not all come from the bottom of the hole As drilling proceeds, material can break free anywhere along the well bore and get mixed in with the ‘bottom of the hole’ cuttings So the drilling operations are not delayed at all (~ no cost) BUT there is a lot of uncertainty about the depth from which the material came from The material is also pulverized, so we can not get rock properties such as sedimentary structures, porosity and permeability Courtesy of ExxonMobil L 3 - Types of Data

Well Measurements: Wire-line Logs A well log is a record of one or more physical measurements as a function of depth in a borehole Gamma Ray Resistivity Density Depth SLIDE 11 There are many ‘tools’ that can be lowered into a well bore to take measurements Usually a section is drilled, a string of tools is lowered to the (current) bottom, and measurements are recorded as the tools are slowly pulled up the well bore Some tools work only before the well bore is lined with steel casing – called open-hole logs Other tools can work in cased holes In the old days, the measurements were recorded on a strip of paper that was registered by the depth of the toll as the measurements were made – a log (right image) Now everything is captured digitally, but the data are still displayed as ‘logs’ Photo on left some the wire-line on a drum The tools are attacked to the end of the wire-line and lowered into the well bore The wire-line is pulled back and measurements are recorded. The rotation of the drum is calibrated to translate into the depth of each tool as measurements come in The white/blue building houses the recording equipment and the operator Courtesy of ExxonMobil L 3 - Types of Data

Examples of Logging Tools SLIDE 12 This photo show SOME of the tools that can be used to take measurements We will discuss several of these tools and what they measure in Unit 4 Courtesy of ExxonMobil L 3 - Types of Data

Property What Logs Measure Lithology/Mineralogy Porosity Fluid Type Fluid Saturation Permeability Stratigraphy Downhole Pressure Density Acoustic Velocity SLIDE 13 As a preview of Unit 4, here is a list of some of the rock and fluid properties that we can measure/interpret in a typical logging run The recorded data often have to be processed and then interpreted to get the rock and fluid properties In many cases, several logs are analyzed jointly to get information Log analysis is a complex procedure, larger companies have experts that spent their entire career analyzing well logs Courtesy of ExxonMobil L 3 - Types of Data

Objective: Analogy: Geophysical Data Take measurements at the surface that give us an image of the subsurface Analogy: A sonogram SLIDE 14 Geophysical methods provide us with a wealth of data about the subsurface Well data is more direct and detailed than the data we get from geophysics The problem with well data is that it gives us information at or close to the well bore – what about locations not near a well? The biggest advantage of geophysical data is that we can obtain data over very large areas The objective:of geophysical data is to take measurements at the Earth’s surface that will give us an image of the subsurface As a analogy, think of a sonogram We may want to get an image of a baby in a womb The technology for this has many parallels to imaging the subsurface: Sound waves are used to get the image Sound travels down through the mother’s tummy Some of the sound waves are reflected (bounce off) the baby’s surface Data processing ‘focuses’ the sound waves bouncing off the baby to give us an image Unit 5 goes into more detail on how we use sound waves (acoustic energy) to image the subsurface Courtesy of ExxonMobil L 3 - Types of Data

 Seismic Data .3 s .1 s .5 s 0 s .2 s .4 s .6 s .7 s .8 s 0 s Energy Some Energy is Reflected Most Energy is Transmitted Energy Source .1 s .5 s Some Energy is Reflected Most Energy is Transmitted  An Explosion! 0 s .2 s .4 s Listening Devices .6 s .7 s .8 s 0 s SLIDE 15 As a preview of Unit 5 We use an energy source at the surface – such as a dynamite explosion Sound waves propagate in a radial fashion down through the Earth At major rock boundaries (more detail in Unit 5) a small part of the acoustic energy is reflected – most is transmitted (continues downward) We have “listening” devices at the surface In this simple cartoon, the left device “hears” acoustic energy that bounces off the top of the orange layer at 0.4 seconds The right device “hears” acoustic energy that bounces off the top of the brown layer at 0.8 seconds Courtesy of ExxonMobil L 3 - Types of Data

Raw Seismic Data For the explosion we just considered ... Device #1 Device #2 For the explosion we just considered ... Time 0.0 0.1 0.2 0.3 0.4 Listening device #1 records a reflection starting at 0.4 seconds Listening device #2 records a reflection starting at 0.8 seconds 0.5 0.6 0.7 0.8 SLIDE 16 This shows the raw data recorded by the two “listening” devices on the previous slide The acoustic wave is recorded at device #1 at 0.4 seconds The acoustic wave is recorded at device #2 at 0.8 seconds To image the subsurface, we use hundreds of shots (explosions) and millions of receivers (listening devices) arranged in lines either on land or offshore To Image the Subsurface, We Use Many Shots (explosions) and Many Receivers (listening devices) Arranged in Lines either on Land or Offshore Courtesy of ExxonMobil L 3 - Types of Data

From Raw Data to an Image Field Record (marine) Data Processing Stream Offset Time SLIDE 17 This first image shows what the raw seismic data for one “explosion” recorded at about 50 “listening” devices looks like The raw seismic data is sent to a data processing center Here specialists in signal analysis, data analysis, imaging, math, computer science, etc. transform the raw data into an image of the subsurface Again at large companies, there are many experts in data processing that can spend an entire career processing seismic data Seismic imaging is an area that remains a focus of R&D – obtain better images faster and cheaper We cover some basics of data processing in Unit 5 Once the data are processed and we have an image of the subsurface, the next step is to interpret the data – turn images such as the one in the lower right into a model of the subsurface rocks and fluids Several Units focus on sesimic interpretation and data anlysis http://www.ig.utexas.edu/people/staff/mrinal/Results/carlos_nn1_files/image006.jpg Subsurface ‘Image’ Courtesy of ExxonMobil L 3 - Types of Data

Gravity & Magnetic Data Instruments measure the local gravity and magnetic field Data are processed to highlight local anomalies (residual maps) Bodies with anomalous density or magnetic susceptibility are modeled/interpreted SLIDE 18 Seismic data accounts for 90%+ of geophysical data collection dollars each year There are other geophysical data types The other two main geophysical data types are gravity data and magnetic data Gravity data is used to interpret the density structure within sedimentary basins and the underlying lithosphere Magnetic data gives us information on magnetic susceptibility within sedimentary basins and the underlying lithosphere G&M data is often used to map “basement” and thus get the total sediment thickness for an area G&M data can also help locate bodies with anomalous densities or magnetic susceptibilities An example of a body with an anomalous density is a salt dome An example of a body with an anomalous magnetic susceptibility is a volcanic sill Courtesy of ExxonMobil L 3 - Types of Data