Practical petrophysics

Integrated Petrophysics for reservoir characterization
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Add to cart. Be the first to write a review About this product. About this product Product Information Practical Petrophysics looks at both the principles and practice of petrophysics in understanding petroleum reservoirs. It concentrates on the tools and techniques in everyday use, and addresses all types of reservoirs, including unconventionals.

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The book provides useful explanations on how to perform fit for purpose interpretations of petrophysical data, with emphasis on what the interpreter needs and what is practically possible with real data. Readers are not limited to static reservoir properties for input to volumetrics, as the book also includes applications such as reservoir performance, seismic attribute, geo-mechanics, source rock characterization, and more.

Principles and practice are given equal emphasis Simple models and concepts explain the underlying principles Extensive use of contemporary, real-life examples. Show More Show Less.

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Martin Kennedy Find more information about: Martin Kennedy. Illustrated Hardcover Science Fiction Books. In he left to work as an independent consultant and now supports a wide range of organisations working throughout the world. Overall a fantastic course.. Packaging should be the same as what is found in a retail store, unless the item is handmade or was packaged by the manufacturer in non-retail packaging, such as an unprinted box or plastic bag. About Martin Kennedy Martin Kennedy started his career as a wireline logging engineer with Schlumberger and has been involved in some aspect of petrophysics ever since. Any Condition Any Condition.

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Problems typically occur when they get applied outside these limits. The Archie equation epitomises the approach of combining models and experimental data and we will use it here to illustrate how petrophysics is applied to real-world problems and some of the pitfalls and misunderstandings that can occur. The equation quantifies what you might intuitively expect. All other things being equal, as porosity increases, resistivity decreases note that porosity has to be expressed as a fraction in Eq.

The first point tacitly acknowledges that the only part of the rock capable of conducting electricity is the brine. So, if a particular brine results in the rock having a resistivity R 0 say, then replacing it with a different brine that has double the resistivity of the original, causes the rock to have a resistivity of 2 R 0. The second point basically says as you increase the porosity, you are putting more brine into the rock and it will conduct better.

In other words its resistivity will drop. What is more difficult to predict is precisely how the resistivity will fall with increasing porosity. In fact, this can only be done analytically for very simple systems such as porosity consisting of parallel plane-sided fractures. But at this point experiment takes over and Archie measured the resistivities of hundreds of core plugs saturated with brine of known resistivity to find an equation linking resistivity and porosity.

This combination of a descriptive explanation of the physics combined with empirical observation is still the way most progress is made in petrophysics. The former can give some confidence in the empirical equations and they in turn allow the physics to be applied. But now consider the real — and rather unexceptional — data that is shown in Fig. This consists of porosities and resistivities measured on approximately 20 core plugs that have been saturated with brine with a resistivity of 1.

This data is the same type as generated by Archie, although, does not include any of his original measurements. Figure 1. See the text for an explanation of the various curves. The solid light grey line in Fig. It actually passes through a resistivity of 0.

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In terms of Eq. We could and often do avoid the contradiction by forcing the line to go through a resistivity of 1. But these advantages come at the price of a poorer fit to the data, we will consider whether that price is worth paying later. Sandstone will typically comprise at least 15 different minerals, but if we are using log analysis to solve the problem we are often limited to four or five components to describe the rock.

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This is because we rarely have more than a handful of truly independent log measurements available. In effect, to accurately describe most sandstones we have to solve for more unknowns than we have equations. Even if we did have a sufficient number of logs it is unlikely we could solve for every mineral because the logs have limited accuracy and some minerals have quite similar log responses. In any case, some of the minerals will only be present at trace levels. To make matters worse the relative amounts of the different minerals probably vary from place to place, even in a sand body that looks superficially uniform.

Fortunately, more often than not we do not need to know the relative amounts of every mineral that makes up the rock. So, to make progress, the rock is simplified to four or five key components. Two of these will almost certainly be the volume fractions of water and hydrocarbon which together give the porosity.

Consultant Petrophysicist, Perfect Petrophysics, London and Melbourne

The commonest models consist of four components: shale, matrix, water and hydrocarbon. The two fluids are self-explanatory although we will define them more carefully later in the book. For example, if a dense mineral is present in varying amounts we may wish to try and resolve it because it can have quite a significant effect on the interpretation.

The process of building a petrophysical model is illustrated in Fig. The real rock, in this case a sandstone, is shown by the thin section in Fig. The relative amounts of all the different minerals and the porosity is shown in Fig. This is ideally what our petrophysical interpretation would show. In this particular case there are only five minerals plus whatever is in the pore space. Three of the minerals only comprise a few volume per cent of the total and in practice log analysis is unlikely to be able to determine them separately.

Because the matrix is mainly quartz it would have similar properties to pure quartz and in fact could conceivably be given the properties of quartz. The end product is thus a three-component system shown in Fig. Notice that although in this case clay is only a minor component it is still being treated as a separate component. At the end of the day any interpretation has to be a compromise between the maximum number of components that can be resolved with the available data and the minimum number of components to adequately describe the rock.

Practical petrophysics

In most oilfield applications it is the porosity that needs to be most accurate and the model should be chosen to ensure that occurs. In reality we are unlikely to be able to faithfully reproduce the volume fraction of each component at every point in the well. But the model should at least underestimate a volume fraction as often as it overestimates it and at any depth the departure from the true value should not be excessive.

More rigorously stated, it should accurately reproduce the mean and distribution in a particular interval. By re-arranging Eq. To do this we need to find the constants a and m we will assume we know R w. For the core plug data for Cretaceous sands shown in Fig. But close inspection of the plot shows that there is scatter in the data. It is tempting to dismiss this as experimental error, but in fact, most if not all, of the scatter is real. The difference between the measured porosity and the prediction from the line is an indication of how good this approximation is.

The fact that the line passes through the cloud of points shows that we would underestimate porosity as often as we overestimate it.

Finding composition from one or more physical properties is the most common application of petrophysics, but the reverse problem of predicting one or more of the physical properties knowing the composition is also important. This is required for properties that cannot be directly measured with logging tools.

A particular application is to calculate the density and acoustic properties of porous rocks filled with different mixtures of water, oil and gas. This allows geophysicists to predict how reliable seismic is for identifying hydrocarbon pools. It is also routinely used in log analysis to estimate the physical properties of the solid part of a rock — the matrix, which are an input to porosity calculations. The rocks that concern us typically consist of a large number of minerals plus some fluid in the pore space. These include the gases — air, nitrogen and helium and liquids such as chloroform, decane and mercury as well as water of course.

Carbonates are normally simpler than clastics but still consist of at least one solid mineral plus fluids.

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In some basins thick evaporate beds are encountered, in which a single mineral with very well-defined properties is present most commonly halite or anhydrite but occasionally something more exotic. The log analyst must deduce what these components are and in what proportion. In Table 1.

More extensive tables can be found in text books on mineralogy, the chart books published by logging companies and possibly the help files associated with log analysis software. Notes: Properties of the fluids depend to a varying degree on pressure, temperature and composition. Typical values are given in the table.

Some of the properties shown in Table 1. Rightly or wrongly the cross-sections are converted into quantities, which are more easily related to petrophysical properties. The best example is probably the so-called neutron porosity, which is the standard output from most modern neutron tools. The neutron porosity is computed from count-rates that are themselves determined by the nuclear properties of the formation, borehole and the tool itself.

One property that is almost always measured during logging but is not included in Table 1. This will be discussed at length when saturation is considered for now it will just be noted that all the minerals in Table 1. It is worth noting that there is some disagreement on the value a particular property has for a particular mineral. Often, the differences are too small to bother about but for clay minerals there can be substantial disagreements between different sources.

The reasons for this will be discussed in the sections on clay and shale volume.

Introduction to Porosity and Permeability concepts, Petrophysics Lecture 1

But as an example different contractor chart books give the density of dolomite as anything from 2.