Chapter%201 - Petrophysics MSc Course Notes Introduction 1....

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Petrophysics MSc Course Notes Introduction Dr. Paul Glover Page 1 1. INTRODUCTION TO PETROPHYSICS AND FORMATION EVALUATION 1.1 Introduction The search or economic accumulations of oil and gas starts with the recognition of likely geological provinces, progresses to seismic surveying, and the drilling of one or more wild-cat wells. If one is lucky, these wells may encounter oil, and if that is the case, measurements made down the hole with wireline tools are used to assess whether sufficient oil is present, and whether it can be produced. Clearly, the evaluation of sub-surface formations requires the combined efforts of geologists, petrophysicists, drilling engineers and even geophysicists. However, it is the geologist and petrophysicist that has the most influence. The geologist is interested in the lithology, stratigraphy and depositional environment of the sub- surface strata penetrated by the drilling bit. The exploration geologist uses wireline tool responses in a number of wells to create a large scale image of the sub-surface geology by correlating wireline responses that are characteristic of a given formation or horizon between formations. This picture is very useful when carrying out initial reservoir modelling and in the decision where to drill new wells. Later the production geologist carries out much the same process with much more well information, and adds any extra information that has been gathered to produce a detailed geological model of the reservoir and related sub-surface formations. This model will be the basis of reservoir modelling, and all major reservoir management decisions from primary drainage through to enhanced oil recovery and shut-down. The petrophysicist’s job is to use all available information to analyze the physical and chemical properties of the rocks in the sub-surface, and their component minerals, with particular emphasis given to the amount and distribution of those fluid minerals that we know of as water, oil, and gas. The petrophysicist will use extensively wireline log data and data from experiments done on cores extracted from the well, and will occasionally use other sources of information such as engineering and production logs, as well as mud logging data. Initially, it is the aim of the petrophysicist to differentiate between oil, gas and water bearing formations, estimate the porosity of the formations and the approximate amount of hydrocarbons present in each formation. Ultimately, the petrophysicist also uses laboratory data to estimate how easy it will be to extract the hydrocarbons in place, and to design reservoir management strategies to optimize long term oil recovery. There is a large database of information available to both the geologist and the petrophysicist, and as time passes the amount and variety of information increases. Table 1.1 summarizes a few of the main measurement that a geologist or petrophysicist will have access to, arranged in approximate chronological order. It is the responsibility of the wellsite geologist or engineer to ensure that all this
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This note was uploaded on 10/30/2011 for the course PETROLEUM Short cour taught by Professor Dr.paulglover during the Winter '11 term at University of Aberdeen.

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Chapter%201 - Petrophysics MSc Course Notes Introduction 1....

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