1Structure Contour MapStructure Contour MapTop of Reservoir SandstoneTop of Reservoir Sandstone

Contour Interval: 50 ftContour Interval: 50 ft

2Question

How much (volume of ) sand do we have?

3IntroductionIntroduction

Determining the size of an area is a common problem in GRV determination.

Areas are calculated by using one of two methods. Field measurementsMap measurements

4Introduction--cont.Introduction--cont.

Common techniques for determining area (on map) are: Coordinate squares Division into simple figures Digitizing coordinates Planimeter

5Coordinate SquaresCoordinate Squares This method overlays a map with a grid that has a

known size.

Knowing the size of the grid and the scale of the map, the area can be determined by counting squares. Whole and partial squares are counted.

6Coordinate SquaresCoordinate Squares This method

overlays a map with a grid that has a known size.

Knowing the size of the grid and the scale of the map, the area can be determined by counting squares. Whole and partial

squares are counted.

When the map scale is expressed as a ratio, the area is determined by:

Area (ft2) = Grid size (in) x Map scale (in)12

2

Example 1/2 inch grid is used and the map cale is 1:1,000, then each square would be equivalent to:

Area (ft2) = Grid size (in) x Map scale (in)12

2

= 0.5 x 1,00012

2

= 1,736 ft2

7Coordinate Squares--cont.Coordinate Squares--cont.

If the map scale is expressed in in/ft then each grid area is:

Area (ft2)=Grid size x map scale( )2

Example: a 1/2 inch grid is overlaid on a map with a scale of 1 in = 500 ft. The area of each grid is:

Area (ft2) = Grid size x map scale( )2=(0.50 in x 500)2

= 62,500 ft2

8Coordinate SquaresCoordinate SquaresExampleExample

Determine the area for the illustration.

The first step is to draw a grid on a clear material and lay it over the map.

The area is determined by counting the grids.

9Coordinate SquaresCoordinate SquaresExample--cont.Example--cont.

Whole squares are counted and then partial squares are estimated.

63 + 12 = 75 squares

Area ft2

square = Square size x Map scale

12

2

= 0.25 x 100012

2

= 434 ft2/square

Area (ac) =434 ft

2

square x 75 square

43560 ft2

ac= 32552.08 ft

2

435600.75 ac

Convert to Acre

10

Digitizing CoordinatesDigitizing Coordinates

This method requires a machine called a digitizer.

The operator moves a special mouse or pen around the map and activates the mouse at each desired location.

Computer records x - y coordinates.

11

PlanimeterPlanimeter

A Planimeter is a device the determines area by tracing the boundary on a map.

Two types: Mechanical Electronic

http://www.nas.com/~kunkel/java/planimtr.htm http://persweb.wabash.edu/facstaff/footer/planimeter/Polar&Linear.htm#How%20they%20work

12

How Polar Planimeters are How Polar Planimeters are UsedUsed

planimeters are used by moving the tracer point around the boundary of the region being measured.

As the tracer point moves the wheel partially rolls and partially slides on the paper, recording its motion perpendicular to the tracer arm.

when the tracer point returns to the point where it started, the net roll of the wheel is proportional to the area of the region.

If a scale attached to the wheel is calibrated appropriately, the area can

be read from the scale.

13

Part II

Volume

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

Rock VolumeRock Volume

Contour Height above OWC

Area (ac)

4400 350

4450 300

4500 250

4550 200

4600 150

4650 100

4700 50

4750 (OWC)

0 11910 Area

Hei

gh

t

above

OW

C

Contour Height above OWC

Area (ac)

4400 350

4450 300

4500 250

4550 200

4600 150

4650 100

4700 50

4750 (OWC)

0 11910

34

Gross Rock VolumeGross Rock Volume

GRV 1.39 x 106 ac-ft 10787 x 106 bbls 1726 x 106 m3

07758

o

GRV NTG SOIPB

=

Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34