Geophysics for Petroleum Engineers (eBook)

Fred Aminzadeh, Shivaji N. Dasgupta (Autoren)

eBook Download: PDF | EPUB

2013 | 1. Auflage
344 Seiten
Elsevier Science (Verlag)
978-0-08-092961-3 (ISBN)

Infos

Geophysics for Petroleum Engineers focuses on the applications of geophysics in addressing petroleum engineering problems. It explores the complementary features of geophysical techniques in better understanding, characterizing, producing and monitoring reservoirs.This book introduces engineers to geophysical methods so that they can communicate with geophysicist colleagues and appreciate the benefits of their work. These chapters describe fundamentals of geophysical techniques, their physical bases, their applications and limitations, as well as possible pitfalls in their misuse. Case study examples illustrate the integration of geophysical data with various other data types for predicting and describing reservoir rocks and fluid properties. The examples come from all over the world, with several case histories from the fields in the Middle East. - Introduces geophysical methods to engineers - Helps understanding, characterizing, producing and monitoring of geophysical techniques - Updates the changing needs of reservoir engineering

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Summary

Chapter 1 Introduction

This book is a treatise on geoscience disciplines with a focus on geophysical application to petroleum engineering. While the book's focus is on geophysical applications, the chapters delve into other related disciplines that participate in the process. Petroleum engineers require some working knowledge of geology and geophysics during the different stages of development of oil and gas fields. Reservoir, Drilling, and Production Engineers must be able to understand the information provided by Geophysicists, Geologists, and Petrophysicists for properly utilizing it. This is particularly important because of the multidisciplinary nature of the challenges faced in oil and gas exploration and production. The need to integrate the data and the disciplines is important.

This process begins with exploration, discovery and appraisal drilling through reservoir development, production and enhanced recovery, as well as its eventual depletion and abandonment. The team efforts by geoscientists and engineers focus on maximizing economic recovery of hydrocarbons throughout the life of a field. Integration of geophysical data with geologic data, and engineering measurements improves our understanding of the reservoir, reduces uncertainties, and mitigates the risk. The improved knowledge of the reservoir impacts the life of the field, its economics, and the ultimate recoverable volume of oil and gas from the field resource base. A detailed understanding of the physical behavior of oil, water, and gas within porous rocks at reservoir pressure and temperature and their impact on the characteristics of the geophysical measurements are ascertained.

Chapter 2 Petroleum Geology

Understanding the basics of Petroleum Geology is critical for Petroleum Engineers. The chapter begins with the formation of organic matter and the origin of petroleum from burial of organic matter and the sedimentation processes. Petroleum systems are then discussed, which comprise Source Rock, Burial Depth and Temperature, Reservoir Rock, Migration Pathways, Reservoir Seals, and Traps. Different types of petroleum traps such as anticlinal, fault, salt-related, and stratigraphic traps and various types of reservoir rocks such as clastic (sandstone and shale) and carbonate rocks are enumerated. The conditions for petroleum accumulation in the reservoir are outlined. The chapter concludes with the integration of geology, geophysics, and petrophysics, in connection with reservoir geometry, volume, and assessment of reserves.

Chapter 3 Petroleum geophysics

Geophysical techniques apply the principles of physics for study of the earth. Geophysics is the study of physical responses of rocks under passive or active perturbation. Data from geophysical observations are interpreted to infer geology. Multiple geologic parameters are assessed with the same geophysical data. Geophysics measures changes of physical properties. The data interpretation has inherent ambiguity, that is, multiple interpretations. Data from geophysical tools provide coverage with spatially continuous high density of 10–25 m and vertical resolution of the order of 10–20 m. Well data like cores and well logs provide vertically high resolution of the order of 0.5 m or better at the well location; however, the distribution of wells is sparse and discontinuous. The detailed spatial coverage from geophysical data is calibrated with analysis of well logs, pressure tests, cores, geologic depositional knowledge, and other information from appraisal wells.

Geophysical data play an important role in the development of a gross reservoir model. The reservoir architecture (structure) and the reservoir properties are derived from the analysis and integration of data from various geoscience disciplines. The distributions of the reservoir and non-reservoir rock types and of the reservoir fluids determine the geometry of the model and influence the type of model to be used. Thus, the goal of geophysics is to contribute to the increment in spatial resolution for defining the building blocks of the reservoir. Geophysics contributes by either adding value or by preventing loss. The data interpretation is used for guiding business decisions. Geophysical data acquisition, processing, and interpretation are driven by established scientific principles.

The objective of geophysical techniques is to minimize risk and maximize value. Exploration risk changes throughout the life of a venture. Geophysics contributes to reservoir characterization, reservoir monitoring, and its management by adding maximum value to improving production plan and by minimizing risk (risk of dry hole, risk of blow out, risk of inefficient recovery process, among others). Geophysics is a risk reduction tool; it reduces exposure to loss.

For optimum application of geophysical data for petroleum engineers, integration of many disciplines is essential. Geophysicists calibrate the measured geophysical attributes with rock properties near the wellbores. They use well logs, core data, and borehole seismic information that are available in order to test the correlation of reservoir data with geophysical measurements. Other reservoir properties that can affect geophysical measurements are density, oil viscosity, stresses, and fractures. Detailed understanding of reservoir rock and fluid properties and their influence on production and injection efficiency is imperative for optimum asset management. As the primary production from a reservoir begins, the development requirement is to position new wells at optimal locations that would maximize hydrocarbon recovery. During secondary recovery and then enhanced recovery process, the engineer's objective is to maximize the volume of hydrocarbon contacted by injected fluids. This is to achieve maximum volumetric sweep efficiency for fluid production. To minimize cost and risk, engineers attempt to predict reservoir performance—for both planning and evaluation of hydrocarbon recovery projects. Reservoir description in terms of reservoir architecture, flow paths, and fluid-flow parameters is the key to reservoir engineering. Accurate prediction of reservoir production performance is predicated primarily on how well the reservoir heterogeneities are understood and have been modeled and applied for fluid-flow simulation.

Ambiguity in seismic interpretation-- lateral changes in amplitude can be caused by changes in one or more properties and are therefore inherently ambiguous. Structural features apparent on seismic data could be due to local anomalies unrelated to the structure.

Geophysical methods use high-precision sensors (e.g., geophone, hydrophone, magnetometer, and gravity meter) that measure the physical properties on the surface, in oceans, in wells, and from air. Rather than the overall magnitudes of these properties, the small differences in physical properties that exist among various rock bodies are what we need. These differences in physical properties must be measured accurately. Accuracy of measurements and their analysis rely heavily on the technological development. Geophysical tools are deployed from ground surface, at sea, in boreholes, and in air. There are also measurements from satellites.

Chapter 4 Petrophysics

Petrophysical analysis of well logs and core provides information about formation rocks and fluids in the borehole. Various types of well logs measure different properties in the well. Logs that describe lithology changes include gamma ray logs, photoelectrical logs, and spontaneous potential (SP) logs. Such logs are very effective in discriminating sandstone versus shale in the subsurface. Logs sensitive to the porosity of reservoir rocks include bulk density, neutron, nuclear magnetic resonance (NMR), and acoustic (sonic) logs. Well logs sensitive to reservoir fluids include NMR and resistivity logs.

Analysis of the data determines the volume of hydrocarbons present in a reservoir and its potential to flow through the reservoir rock into the wellbore. This helps us to understand and optimize the producibility of a reservoir. When oil and gas wells are drilled, physical property measurements are taken from specialized geophysical instrument packages: either attached as drill collars, behind the drill bit Measurements While Drilling (MWD) or Logging While Drilling (LWD), or suspended on wireline cables (Wireline Logs) after the drill pipe has been removed from the borehole. Initially, these measurements were designed to provide detailed stratigraphic and structural correlation of geologic horizons between wells. In time, however, the measurements, themselves, and their application have much more complex, to the point that the future of wells and fields hinge on the interpretation of these measurements.

We cannot measure Porosity and saturation directly; we measure formation electrical galvanic or induction Resistivity (R), mud filtrate/connate water salinity contrast (Spontaneous Potential, or SP), formation radioactivity (Gamma Ray, GR), inverse acoustic velocity (Interval Transit Time or Δt), formation electron density Density Log (RhoB) and Photoelectric Effect (PEF or Z), formation hydrogen ion density (Neutron Log, HI), and Nuclear Magnetic Resonance (NMR Log).

Chapter 5 Geostatistics

A reservoir is intrinsically deterministic. In reservoir description process, we are dealing with limited and incomplete data. We are constantly trying to extrapolate information from sparse measurements (e.g., limited well data and core data on the one hand and large volumes of seismic data with limited spatial resolution on the other). We resort...

Produkt-Details

• Erscheint lt. Verlag: 9.12.2013
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geophysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie
• Themenwelt: Technik ► Elektrotechnik / Energietechnik
• ISBN-10: 0-08-092961-3 / 0080929613
• ISBN-13: 978-0-08-092961-3 / 9780080929613