Automated scanning electron microscopy image collection from geological polished thin sections, in conjunction with autonomous stitching, can be used to construct high-resolution (micron- to submicron-resolution) image montages over areas up to several square centimeters. The technique is here applied to an oolitic limestone and a carbonate laminite to illustrate its application as a tool to study carbonate porosity and diagenesis. Montages constructed from backscattered images are ideally suited to the extraction of data on microporosity, with possibilities including the construction of contoured maps to illustrate the spatial variation in porosity; the construction of porosity logs to illustrate trends in porosity across thin sections; and stochastic construction of digital rock models, for subsequent permeability calculation. Montages taken with a gaseous secondary electron detector in low-vacuum mode can utilize charge contrast imaging (CCI) at a variety of scales and were used here in examining the evolution of carbonate cementation. One example is oolitic limestone, illustrating the formation of grain-lining and pore-occluding cements, as well as recrystallization of the depositional fabric. CCI montages commonly suffer from a variety of contrast and brightness artifacts due to variation in charge distribution across the individual scanned image tiles. Several remedies are discussed that can reduce these artifacts, making it easier to apply image analysis techniques across such montages.

Abstract Field X comprises a giant Palaeogene limestone reservoir with a long production history. An original geomodel used for history matching employed a permeability transform derived directly from core data. However, the resulting permeability model required major modifications, such as horizontal and vertical permeability multipliers, in order to match the historic data. The rationale behind these multipliers is not well understood and not based on geological constraints. Our study employs an integrated near-wellbore upscaling workflow to identify and evaluate the geological heterogeneities that enhanced reservoir permeability. Key among these heterogeneities are mechanically weak zones of solution-enhanced porosity, leached stylolites and associated tension-gashes, which were developed during late-stage diagenetic corrosion. The results of this investigation confirmed the key role of diagenetic corrosion in enhancing the permeability of the reservoir. Insights gained from the available production history, in conjunction with petrophysical data analysis, substantiated the characterization of this solution-enhanced permeability. This study provided valuable insights into the means by which a satisfactory field-level history match for a giant carbonate reservoir can be achieved. Instead of applying artificial permeability multipliers that do not necessarily capture the impacts of geological heterogeneities, our method incorporates representations of fine-scale heterogeneities. Improving the characterization of permeability distribution in the field provided an updated and geologically consistent permeability model that could contribute to the ongoing development plans to maximize incremental oil recovery.

Abstract Ancient and modern stromatolites are potentially a challenge for petrophysicists when characterizing biosediments of microbial origin. Because of the heterogeneity, sometimes very cemented and lacking porosity, sometimes highly porous, these widely differing states can be used to develop techniques that can have wider application to addressing the representative elementary volume (REV – single or multiple REVs) challenge in microbial carbonates. Effective media properties – like porosity – need to be defined on REV scales and the challenge is that this scale is often close to or significantly larger than the traditional core plugs on which properties are traditionally measured. A combination of outcrop images, image analysis techniques, micro-computed tomography (CT) and modelling have been used to capture the porosity (or in some cases, precursor porosity) architecture and provide a framework for estimating petrophysical property sensitivities in a range of situations that can be subjected to further calibration by measurements in relevant microbial reservoir rocks. This work will help guide the sampling approach along with the interpretation and use of petrophysical measurements from microbial carbonates. The bioarchitectural component, when controlling porosity in microbial carbonates, presents a significant challenge as the REV scale is often much larger than core plugs, requiring careful screening of existing data and measurement and additional geostatistical model-based approaches (with further calibration).

Abstract The author has more than 30 years of experience in addressing the aspects of the petroleum industry that continue to challenge that industry — the effective measurement, interpretation, and modeling of subsurface reservoirs for efficient petroleum reservoir development. After a 10-year industry career with Unocal, the author joined the academic institution at which he has spent the past 20 years teaching aspects of development geoscience. With that experience, he has developed a personal vision for integration — a vision gained from practical field experience and more than 50 publications and informed by a formal education across a range of geoscience and engineering subjects, including basic geology, micropaleontology, geostatistics, petroleum engineering, and geoengineering. The range of topics with which the author has experience includes aspects of geology, petrophysics, geophysics, geostatistics, and reservoir engineering. Efficient and effective integration of those topics is considered to be a subject worthy of human endeavor in its own right. Such integration has been termed geoengineering, or making practical use of the subsurface (Corbett, 1997). The present SEG/EAGE Distinguished Instructor Short Course draws from published and unpublished work and aims to further the integrated concepts that have been defined in the earlier literature. Increasing public interest in oil-production forecasts and particularly in “peak-oil” forecasts (Figure 1) will encourage industrywide development of closer integration and investment in improved oil recovery. That effort will help the industry meet projections of growing demand for petroleum liquids (Figure 2). It is suggested that traditional reservoir and/or petroleum engineers focus primarily on the specifics of a single field or small group of fields — i.e., on traditional reservoir engineering for field-development planning.

Abstract It has been recognized for many years that “the best way to identify and quantify rock-framework and pore-space variations is through the deliberate and integrated use of engineering and earth-science technology” ( Harris and Hewitt, 1977 , p. 761, published at the start of this author’s career). Fred Aminzadeh, a former Unocal colleague of the author and 2007-2008 SEG president, later called for integration “of disciplines, not results” and used the term geoengineer in the sense of being a possible “torchbearer” ( Aminzadeh, 1996 ). The industry’s management teams in the 1990s shared several concerns. There were general moves toward open-plan offices; it was felt that the absence of walls would encourage integration. Management always had struggled to measure and reward integration effectively. There were reports of one company poaching high-performing teams from another when the market arose for integrated teams. Finally, many people were concerned that the provision of greater breadth conflicted with the development of greater depth. Indeed, perhaps the development of breadth — the petroleum-geoengineering model — conflicts with preservation of deep expertise and remains a major challenge for the industry today. This concern certainly can foster a resistance that needs to be overcome if geoengineering is to become adopted more widely. Geoengineering in itself might one day come to be considered an expertise. Individuals also have had concerns. The 1990s were a period of sustained low oil prices. An individual had to weigh development of team skills against development of greater depth while keeping job security in mind.

Abstract Until a few years ago, no formal definition of petroleum geoengineering existed ( Corbett, 2006 ), nor does the term geoengineering itself appear to have a formal definition, although it has reasonably wide usage. Indeed, inserting “define:geoengineering” into a search engine on the Web fails to produce a definition, in contrast to “define:engineer-ing,” which produces many diverse definitions, as might be expected. A search of the Internet in the late 1990s revealed several civil-engineering geoengineering projects that involve fluids and subsurface exploitation — including salt-cavern excavation and hazardous-waste disposal. There also were calls at that time for chartered-geoengineer (CGeoEng) status for those working at the geotechnical interface of mining engineering and geology ( Rhoden, 1997 ). A geoengineer is in that respect a natural outgrowth of the engineering geologist or geologic engineer ( Fookes, 1998 ). An April 2004 Web search on geoengineering produced nearly 18,000 hits; a search in May 2008 produced 222,000 hits. Clearly, the term is in increasingly common usage. The expression is used in a variety of contexts, as we see in examples from the 2004 survey: The Department of Civil and Environmental Engineering at the University of California, Berkeley, offers a program in geoengineering ( http://www.ce.berkeley.edu/geo/index.php ) that replaces the traditional geotechnical program because of expansion in scope and coverage. This program covers petroleum engineering, rock mechanics, and reservoir engineering. “Geoengineering is the intentional large-scale manipulation of the global environment,” states D. W. Keith in an article in the Encyclopedia of Global Change ( Keith, 2002 , p. 420), in which he also identifies a paper by C. Marchetti, “On geoengineering and the CO2 problem,” as being the first published occurrence of the term geoengineering ( Marchetti, 1977 ). Keith goes on to say that sequestration (capture and storage) of CO2 is classified rightly as a novel geoengineering endeavor — rather than as conventional pollution mitigation — because it fails to compensate for emissions after they occur on a global scale ( Keith, 2001 ). Keith emphasizes that scale and intent are central to the common meaning of geoengineering. In Keith’s sense, scale means at the largest planetary scale.

Abstract What is it about geologic media that makes them so challenging to engineers? Engineering models of the subsurface usually are based on estimation of some effective property, whether the models are analytic or are cellular based (in the latter case, the properties are thought to be effective at the scale of a single cell). Therefore, a systematic approach to measuring, interpreting, and modeling the subsurface needs to consider the scale at which the measurement has been made, the interpretation model used to analyze the data, and the modeling technique used to simulate the data. The response to any engineering process in the subsurface will be predicted most effectively by an analytic model or a simulation model. Geologic media are essentially hierarchical, with multiple-length scales reflecting the depositional process (it is assumed in this book that most reservoirs are in sedimentary rocks, but those concepts can be extended to metamorphic and igneous rocks). All measurements taken in a rock will have to consider the scale of measurement relative to the geologic-length scale, the method used to interpret the measurements, and the scales that must be incorporated into the effective media. This book is concerned primarily with permeability because it relates directly to oil recovery. Effective permeability is defined as the single equivalent property of a homogeneous volume upscaled from all the heterogeneous point measurements at smaller volume scales. Measurement and scaling of effective permeability are major challenges in petroleum-development projects. The effective-medium concept was proposed by Bear and Bachmat (1990) as the fundamental property that governs flow in a porous medium (Figure 1 ).

Abstract Addressing the challenge of working with the wide range of petrophysical properties that occurs over the multiple-length scales of geologic media requires a broad background that extends across geoscience and engineering. The core skills of a petroleum geoengineer are found in the disciplines of geology, geophysics, geostatistics, petrophysics, engineering, and management. Those skills provide each of the bases that a petroleum geoengineer must visit in the course of a reservoir-description and reservoir-modeling project. Having one person with specialist-level knowledge in each of those areas brings the advantage that at an early stage, an initial model can be built to consider management options before a more detailed petrophysical characterization and/or geologic modeling is commissioned. This ensures that workers can use the available data to identify appropriate questions for modeling to address, and that ultimately leads to more useful predictions and improved recovery. Rocks are deposited with certain geometries that are determined by the environment of deposition, and this knowledge is fundamental to our understanding of stratigraphy. An example is found in a progradational parasequence set from a typical high-stand systems tract (Figure 1 ). The geologic architecture is controlled by relative sea level and sediment supply. Knowledge of such systems is important for correlating reservoir flow units and detecting intrareservoir seals. Sequence-stratigraphic concepts can be extrapolated to other environments. Models for fluvial systems can explain the stacking patterns of fluvial channels (Figure 2 ). As sea level rises, incised valleys are filled with a high net-to-gross (braided) fluvial system. At highstand, a meandering system might develop.

Abstract The challenge that we set in Chapter 2 — to maximize petroleum reserves and to develop our science with an eye toward achieving energy sustainability — can be addressed by applying the geoengineering skills discussed in Chapter 3 to the problem of breadth and integration. Geologic media are hierarchical and have multiple-length scales, so our examples cover scales increasing from pore to reservoir size. Ideally, a systematic geoengineering approach would set out to include all those scales in a new project. At this stage of development for the geoengineering method, studies have focused on individual parts of the problem. However, this work intends to show what might be achieved across all scale sizes, and in so doing, it aims to encourage a more systematic and complete approach to reservoir modeling. Numerical or digital pore-scale studies have become the norm in certain laboratories, and they allow pore-scale modeling of pore-scale physics designed to predict effective properties at the millimeter scale. Such studies tend to address the specific challenges of two-phase or three-phase flow. However, technology now being developed (the numerical approach to petrophysics often is referred to as “digital petrophysics”) will allow us to predict petrophysical and rock-physics properties to supplement and extend the range of limited numbers of measurements. Those modeled measurements are effectively at a fundamental scale because the models tend to be stationary — they are above the microscopic-macroscopic threshold (Figure 1 of Chapter 4 ) but within a lamina. Geologists define laminae as being texturally uniform, so this scale applies to the smallest representative elementary volume in a reservoir. The technology used in such studies combines high-resolution X-ray imaging, geostatistics, and pore-network modeling (Figure 1 ).

Abstract Much work is yet to be done. We need to extend the petroleum-geoengineering workflow to include characteristics of fault patterns, fault properties, and stress sensitivity, and we must model the geophysical response to production so we can improve our predictions of reservoir performance. Certain aspects of reservoir engineering need to be addressed in reservoir-specific challenges — such as the effect of solution seams on vertical permeability ( Mohammed et al., 2002 ). Teamwork also must be taught, trained for, and evaluated ( Corbett et al., 2002 ). Petroleum-geoengineering students welcome the link between outcrop analogues and reservoir performance in the field. The petroleum-geoengineering philosophy can be applied in training geologic modelers (O. Dubrule, personal communication, 2004). Petrophysical studies can be considered to be petroleum-geoengineering studies also ( Worthington, 2005 ; Corbett et al., 2005 ). In recent years, senior industry figures (J. Spath, personal communication, 2005) have questioned whether the time is right for engineering geologists or geologic engineers in the petroleum industry. Geologists have worked for many years with the type concept, using it to make sense of complex and often incomplete data sets. Lithotype, stratotype, and nomentype refer, respectively, to type sections of a lithology, a stratigraphic interval, and a type specimen (of a fossil species). These are published reference specimens — well-visited outcrops or museum specimens — against which new, unidentified examples are compared. In the work in hand, the idea of a reference catalog has been extended to petrophysics (petrotype) and to engineering (geotype) for use in permeability prediction and well-test diagnosis.

Abstract World oil reserves are estimated variously as being between 1850 and 3012 gigabarrels (Gb), or 10 9 barrels — that is, 1.8 trillion to 3.0 trillion barrels — according to the U. S. Geological Survey (USGS), as quoted in Deffeyes (2001). Deffeyes (2001) projects 2000 Gb from current production figures (Table 1 ). Peak oil production will occur between 2006 and 2021, according to the Association for the Study of Peak Oil and Gas ( ASPO, 2002 ), at which time it is expected that approximately half the world’s “easy-to-produce” oil will have been produced. Other estimates by the USGS have shown total world hydrocarbon reserves to be as high as 7000 Gb. Can improvements in recovery factor help delay the decline of oil production? Few publicly available data exist for oil-production decline rates, but such declines are thought to be generally rapid once the peak has been reached ( Simmons, 2004 ). It is harder to find figures for global recovery factors. Manoelle Lepoutre of Total reported a global recovery factor of 30% to 40% (M. Lepoutre, personal communication, 2006); Usman Ahmed of Schlumberger reported 37% ( Ahmed, 2004 ). Leif Meling of Statoil, in a paper presented at the World Petroleum Congress ( Meling, 2004 ), gave a present average field recovery of 29% and stated that with improved oil recovery, that figure might rise to 38%, thereby giving a growth of 600 Gb in reserves (based on a statistical analysis of 8600 oil fields). The 9% improvement in recovery factors is certainly a prize worth going after.

Abstract Petroleum geoengineering is defined as the systematic measurement, interpretation, and modeling of geologic media for the purpose of engineering the earth’s subsurface to exploit petroleum reservoirs optimally. In preparation for an engineering decision and ultimately for an engineering implementation, the petroleum-geoengineering workflow (Figure 1 ) proceeds from a geologic model to the use of petrophysical measurements in a numerical model that simulates outcomes. Petroleum geoengineering addresses several challenges. In applying this approach, the linkages among reservoir descriptions — both static and dynamic — with feedback loops ensures that the appropriate data are collected and are used in building the model. The ultimate intended use will influence the type of data acquired, and the engineering validation of the geologic model will improve geologic understanding. Measurement of reservoir parameters is a joint geoscience and engineering challenge because reservoir heterogeneity is nested inherently at various scales (Figure 2 ), and sampling strategies must distinguish cross-scaling relationships from upscaling issues. Systematically upscaling laboratory measurements to in situ pressure interference and well tests helps geoscientists to address the missing scales of data in petroleum-engineering studies. Sampling strategies should consider the concept of sample sufficiency to account adequately for the natural heterogeneity of many reservoirs. Compared with siliciclastics, carbonates are more variable and have less apparent intervals of homogeneity for the engineer to exploit. The nested scales of heterogeneity, often subseismic in scale but generally larger than core-plug scale, are considered to be the missing scales in reservoir descriptions (Figure 2 ). At such scales, a more systematic approach to modeling and measurement is required. Such modeling and measuring use samples taken at representative volumes. The models then employ different techniques to upscale for model validation, which is done by using measurements acquired systematically at large scales.

Abstract Petroleum Geoengineering: Integration of Static and Dynamic Models (SEG Distinguished Instructor Series No. 12) explores improved linkage among techniques used at various scales to describe and model petroleum reservoirs. The book, which accompanies the 2009 SEG/EAGE Distinguished Instructor Short Course, is aimed at a broad range of geoscientists and engineers working in the petroleum industry. The ultimate objectives are to enable technical staff members to maximize the recovery of hydrocarbons. The impact of petrophysical heterogeneity at various scales on the recovery of oil and gas provides the focus for the book. The integrated nature of the book makes it suitable for people from all subsurface disciplines (geology, geophysics, petrophysics, geomodeling, and reservoir and petroleum engineering). Petroleum Geoengineering is also very suitable for directing teams of subsurface staff members. (DISC on DVD, 758A, is also available.)