# True-vertical-depth

**by [Matt Hall](https://github.com/kwinkunks)**

We have some well data. Some of the wells have deviated (non-vertical) sections. All well sections are straight; the corners are not rounded. Each well record is represented by 7 numbers:

     x   y   d  k   i  a    t
    123,654,24,450,12,254,1200
    
These numbers are (_x_, _y_) of the surface location, the elevation of the datum _d_, the kick-off point _k_ (from the datum), the inclination _i_ and azimuth _a_ of the deviated section, and the total depth _t_ (measured along the hole from the datum).

Some wells have an unknown datum, denoted by 'UNK'; you should ignore them.

We wish to know:

1. What is the highest datum?
2. What is the greatest offset distance reached, **to the nearest metre**? 
3. What is the greatest true vertical depth reached, **to the nearest metre**?
4. At a TVDSS of -2000 m, how many wells have **an absolute _y_-offset** of more than 100 m?

Note the following assumptions and definitions:

- *Measured depth* is measured along the well path, starting at the top, and is always positive.
- Elevations are positive above sea-level, and negative below sea-level.
- *True vertical depth sub-sea*, or TVDSS, is the vertical depth below mean sea level.
- The *offset distance* is the horizontal distance from the surface location to the bottomhole location.
- The section of the well above the *kick-off point* is vertical.
- A kick-off point of -999.25 indicates that there is no deviated section.
- The 'deviated' section of the well below the kick-off point is straight but inclined at _i_ degrees off the vertical.
- On a map, the deviated section of the well is oriented towards the direction _a_ degrees clockwise from North.

This diagram might help. Then again, it might not.

<img src="https://kata.scienxlab.org/static/tvd.svg">


## Example wells

Your questions relate to the collection of wells. In this example, we'll look at just one well:

    212,32,68,322,8,295,2630

- The datum of this well is **68** m above sea-level.
- The offset distance at the bottom of this well is about 321.21 m, or **321** to the nearest m.
- The TVDSS at the bottom of this well is -2539.54 m, or **-2540** to the nearest m.
- At a TVDSS of -2000 m, this well has a y-offset of 103.7 m and therefore would be counted for question 4.

Let's look at another well.

    416,232,89,-999.25,-999.25,-999.25,1989

- The datum of this well is **89** m above sea-level.
- The offset distance at the bottom of this well is **0** m; it is not deviated.
- The TVDSS at the bottom of this well is **-1900** m.
- This well does not reach -2000 m.


## A quick reminder how this works

This document is formatted in [Markdown](https://daringfireball.net/projects/markdown/).

You can retrieve your data, which is always a string, by choosing a **`<KEY>`** (also a string). This ensures that you have different data from other people, so be creative. 

```
url = 'https://kata.scienxlab.org/challenge/true-vertical-depth'
params = {
    'key': <KEY>  # Replace <KEY> with your own string.
}
r = requests.get(url, params)
r.text
```

To answer question 1, change the `params`:

```
params = {
    'key': <KEY>,   # Use the same key you used to get your input.
    'question': 1,
    'answer': 1234  # Your answer; can be a float, int, list or array;
                    # the challenge description will tell you which.
}
```

To get a hint for a question, provide the question number but no answer:

```
params = {
    'question': 1,
}
```

[Complete instructions at kata.scienxlab.org](https://kata.scienxlab.org/challenge)

[An example notebook to get you started](https://gist.github.com/kwinkunks/50f11dac6ab7ff8c3e6c7b34536501a2)

----

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