The grain size of the filter pack material is based on the t

The grain size of the filter pack material is based on the type of the formation opposite to the screen. For example, if the formation is fine sand, then the grain size distribution is determined. Generally, the filter pack material should have a mean grain size that is twice the mean grain size of the formation. Also, the screen-slot opening is typically selected to retain 90% of the filter pack.

(a) Attached excel (problem 2.xls), provide sieve no., sieve size (inches) and mass retained in each sieve (g) for filter pack materials. If the total mass of the sample is 500 g what is 10, 25, 50 and 75 percentile grain size for this sample. What is your estimated well screen diameter size for this filter pack material? What is the geometric mean of the grain size? Then what is the mean grain size of filter pack material?

(b) Suppose your aquifer thickness is 20 m and DNAPL was spilled in this aquifer 20 years ago. If the DANPL concentration occurs ~50 % thickness of the aquifer, then what is the bottom and top boundary of the well screen?

Total mass		500 g
Seive	Inches	Mass retained (g)
No. Seive 4	0.187	9.7
No. Seive 5	0.157	20
No. Seive 6	0.132	40
No. Seive 7	0.111	80
No. Seive 8	0.0937	100
No. Seive 10	0.0787	150
No. Seive 12	0.0661	200
No. Seive 14	0.0555	300
No. Seive 16	0.0469	425
No. Seive 17	0.0394	450
No. Seive 50	0.01	475
No. Seive 60	0.0009	499

Sizes of the sieves for

10% =0.116 inch

25% =0.0862 inch

50% =0.0608 inch

75% =0.0520 inch

Well screen diameter of the filter material= 0.0394 inch( where 90% of formation retained)

Geometric mean size grain=0.0608 inch

mean grain size of the filter material=0.1216inch(twise the mean size of formation)

S.no	sieve size(inches)	cumulative mass retaained(g)	cumulative %retained
4	0.187	9.7	1.94
5	0.157	20	4
6	0.132	40	8
7	0.111	80	16
8	0.0937	100	20
10	0.0787	150	30
12	0.0661	200	40
14	0.0555	300	60
16	0.0469	425	85
17	0.0394	450	90
50	0.01	475	95
60	0.0009	499	99.8

The grain size of the filter pack material is based on the type of the formation opposite to the screen. For example, if the formation is fine sand, then the gr

The grain size of the filter pack material is based on the t

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