Where does energy in U.S come from? [Guest Article]

From burning firewood to using electricity from renewable sources, the home energy landscape has drastically changed over the last 150 years. This article and infographic explore the history of energy use and what the sustainable future may look like.

We no longer have to gather firewood for our wood-burning stoves to keep us warm at night, but there are a variety of energy sources used in each home. Most homes in the U.S. run on either electricity or natural gas, or a combination of both, but homeowners may also employ solar panels or even residential wind-powered solutions too. 

Looking at the charts below, you can see that energy consumption has grown significantly each year and in 2018, it hit an all-time high. However, you’ll notice some changes in the way we use each energy source. Coal is the only energy source below that has suffered a decline and renewable energy has recently surpassed nuclear energy. As new technologies are developed, we are finding new ways to meet the increased energy demand. The future of energy consumption will look very different than it does today.

Where does energy in US come from?

By no surprise, oil has been the largest and most popular source of energy. Since the 1950s, oil and natural gas were used to heat homes. Now in 2020, you know that petroleum is used for many other reasons and industries, from powering our cars to packaging products in plastic. 

Although coal was another popular source of energy, it has been on the decline for the last few decades. It’s less efficient than other sources and negatively impacts the environment. To answer that problem, the U.S. has been investing in renewable energy sources. Wind, solar, and geothermal energy are proving to be great resources for a clean future.

Are renewables the future?

Although only 11% of U.S. energy production comes from renewable sources, it is expected to grow. Solar, wind, and geothermal technology energy are three of the top sources for renewable energy. Among those, wind is the fastest growing and judging from the production map, it has wide geographic potential as well. Geothermal energy, which uses underground temperatures to transfer energy, is becoming a popular alternative for home heating and cooling. Of course, residential solar panels are gaining wide adoption as well. As renewable energy options become more available, the energy consumption landscape is likely to move toward a more sustainable future. 

This infographic from The Zebra walks through the history of energy use, where energy is produced, and what the future of energy may look like.

Author bio: Amanda Tallent is a writer who covers everything from business to lifestyle. She creates content to help people live more informed and confident lives. 

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1. Name: Sedimentology and Stratigraphy by Gary Nichols 
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2. Name: Physical Geology- Earth Revealed. 9th Edition by C.C. Plummer   
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Different shale distributions in low resistivity log response.

                   First, we will start with a small introduction about the resistivity logs                                           

Resistivity log

Technique : produce a current in the adjacent formation and measure the response of the formation to that current.

Resistivity logs are used to:

• determine hydrocarbon-bearing versus water bearing zones

• indicate permeable zones

• determine porosity

By far the most important use of resistivity logs is the determination of hydrocarbon-bearing versus water-bearing zones. Because the rock’s matrix or grains are non-conductive and any hydrocarbons in the pores are also non-conductive, the ability of the rock to transmit a current is almost entirely a function of water in the pores. As the hydrocarbon saturation of the pores increases (as the water saturation decreases), the formation’s resistivity increases. As the salinity of the water in the pores decreases , the rock’s resistivity also increases.

Resistivity tools principle : there are two types of resistivity tool , The dual lateral log ( DLL ) and the induction log ( DIL ) both types measures the resistivity in three zones simultaneously.

LLD looks deep into reservoir

LLS Looks shallow into the reservoir

MSFL reads the resistivity close to the wellbore.

Low Resistivity response :

High deep resistivity means : HCs or Tight streak  { low porosity }

Low deep resistivity means : Shale or wet sand.

Shale: Shale is defined as a fine-grained, indurated detrital sedimentary rock formed by the consolidation (by compression or cementation) of clay, silt, or mud.

It is characterized by a finely stratified structure of laminae ranging from 0.1 to 0.4 mm thick. Shale contains an appreciable content of clay minerals or derivatives from clay minerals, with a high content of detrital quartz; containing at least 50% silt, with 35% clay or mica fraction, and 15% chemical or authigenic materials

In petrophysical analysis, shale volume is one of the key answers used later to correct porosity and water saturation for the effects of clay bound water, (CBW).

Shale distribution in shaly sand :

 
Shale can be distributed in several different ways, as shown below.

Laminated shale is a special case in petrophysical analysis. Standard models for porosity and saturation do not work.

Dispersed shale is usually composed of from clay minerals that form in place after deposition due to chemical reactions between the rock minerals and the chemicals in the formation water.

Structural shale is usually deposited as particles, grains, or clasts during the initial depositional phase. For example, the flooding of a river valley can carry mud or shale from surrounding areas.

Different shale distributions have different effect on the sand reservoir.

In a sand reservoir contain structure shale : it will affect the reservoir porosity

In a sand reservoir contain laminae shale : it will affect only the net pay of the reservoir

In a sand reservoir contain : it will affect the porosity and permeability of the reservoir and also it will lead to a shortcut in the resistivity log response , which may result in a miss lead in the interpretation of the reservoir porosity and saturation  , it could be interpreted as sand bearing water instead of a sand contain dispersed shale.

So, the question here is how to differentiate between them and to avoid this wrong interpretation ?!

Let’s assume that you have a 100% clean sand reservoir. So the total porosity of this reservoir is 30% and the sand grains will represent 70% of the volume of the reservoir

Hint : Porosity of sandstone is 30 % and porosity of shale is 10%

Case 1 :

In the case of the presence of structure shale ,

So in this case shale grains will replace sand grains ( volume of 70% ) , the shale will bring its 10% porosity with it.

In other words , The porosity will be enhanced by 10% in the volume of 70% of the sand

So , the porosity will increase by 70/10 and the total porosity will be = 37 %

Case 2 :

In the case of the presence of laminae shale , in this case shale will replace the whole reservoir ( 100 & ) and also will bring its own 10% porosity.

In other words , the porosity will be reduced from 30% to 10%

Case 3 :

In the case of the presence of dispersed shale , in this case shale we will replace the porosity  volume it self ( 30 % ) and as usual it will bring its own porosity.

 
In other words , the porosity will be reduced into 3% ( 30 / 10 )Summarized figure for the different shale distributions in shaly sand reservoir and it’s effect on the reservoir porosity.

Shale distribution model proposed by Thomas and Stieber (Tyagi et al. 2009). Here Vshale is the volume of shale, φtotal is the total porosity, φmax is the maximum porosity, and φsh is the porosity in shale

Conclusion :

 So, we can differentiate between the three different types of shale distribution and according to the type we can make the right interpretation for the porosity and the saturation of the sand reservoir , also we will avoid the miss leading interpretation in the shortcut in the resistivity log.

Photo Credits: Ahmed Adel

Originally blog is written by Ahmed Adel