Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.17 No.4 (December 2016) 57- 69 

ISSN: 1997-4884 

 
 
 
 
 

Experimental Work to Study the Behavior of Proppant Inside the Hydraulic 

Fractures and the Plugging Time 

 
Mohammed Abdul Ameer and Samera Hamed Allah  

Petroleum Engineering Department, College of Engineering, Baghdad University 
 

Abstract 

Experiments were conducted to study the behavior of the solid particles (proppant) 

inside the hydraulic fracture during the formation stimulation, and study the effect of 

the proppant concentration on the hydraulic fracturing process, which lead to bridge 

and screen-out conditions inside the fractures across the fracture width that restricts 

fracturing fluid to flow into the hydraulic fracture. The research also studies the effect 

of the ratio between the fracture size and the average particles diameter “proppant", 

on fracture bridging. In this study two ratios were considered β= 2 and 3 ,where β = D t  
/  D p  w h e r e:  D t =  h yd r a u l i c f r act u r e s i z e ( w i d t h )  an d  Dp=Average particles 

diameter. 

This work presents experimental work to study the behavior of these particles 

(proppant) inside the hydraulic fractures by measuring the plugging time for different 

particles concentration for different conditions. The experimental data recorded for 

different particle concentration and one flowing forces (gravity) inside the hydraulic 

fracture. Most recorded experimental data obtained were analyzed by using SPSS 

software. 

 

Introduction  

Hydraulic fracturing is a well 

stimulation method where a fluid is 

pumped into the rock to create 

fractures.  These fractures are intended 

to function as high-conductivity fluid 

pathways enabling increased well 

productivity [1]. 

The main goal of the hydraulic fracture 

treatment is to create a highly 

conductive flow path for hydrocarbon 

production. 

Hydraulic fracturing is a technique 

used to stimulate the productivity of a 

well [2]. Thus the effective 

permeability of a reservoir remains 

unchanged by this process. That mean 

increasing the  wellbore radius and 

increase its productivity, because a 

long contact surface between the well 

and the reservoir is created. 

Hydraulic fracturing is a technique in 

petroleum sciences. First applied of 

Hydraulic fracturing was at 1947 

(Hugoton gas field, Kansas) as a new 

technique to overcome the skin 

damage. Hydraulic fracturing is used 

mainly in reservoir stimulation, control 

of sand production, and other purposes. 

it has been used to extract gas and oil 

from shales and other tight reserves 

economically. 

The well treatment by hydraulic 

fracturing job states that the fracture is 

approximately perpendicular to the 

University of Baghdad 
College of Engineering 

Iraqi Journal of Chemical and 
Petroleum Engineering 

 



Experimental Work to Study the Behavior of Proppant Inside the Hydraulic Fractures and the 

Plugging Time 

  

 

58                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

axis of the least stress. Deepest 

reservoirs, the minimum stress is 

horizontal [3 and 9]. 

"A screenout is a blockage caused by 

Bridging, accumulation, clumping or 

lodging of the proppant across the 

fracture width that restricts fluid flow 

into the hydraulic fracture" [4]. 

The stimulation treatment (hydraulic 

fracturing job), ends when the 

engineers have completed their 

planned pumping schedule or when a 

sudden rise in pressure indicating that 

there is a  screenout has taken place 

[4]. 

There is problems, that called 

screenout, can occur during the 

fracturing job. Screen-outs as defined 

above happen when a continued 

injection of fluid into the fracture 

requires pressure above the safe 

limitations of the wellbore and surface 

equipment. This condition happened 

because of high fluid leakage, high  

concentration of proppants, and an 

insufficient pad size that blocks the 

flow of proppants. As a result of that, 

pressure rapidly builds up to high 

value. Screen-out can cause stopping a 

fracturing job or operation and need to 

clean the wellbore before resuming 

fracturing job [5]. 

During hydraulic fracturing job, 

engineers need to keep a constant rate 

for fracture fluid injection during the 

job. The volume injected includes the 

additional volume created during 

stimulation (hydraulic fracturing), and 

the fluid loss to the formation because 

of leak- off into the permeable wall of 

the fracture [6]. However, the rate of 

leak off during the growing hydraulic 

fracture tip is extremely high. 

Therefore, it is not possible to initiate a 

hydraulic fracture with proppant in the 

fracturing fluid because the high fluid 

loss would cause the solid particles 

(proppant), at the fracture tip to reach 

the consistency of a dry solid, that lead 

to bridge and screen-out conditions. 

For that, using some volume of clean 

fluid (a pad), must be pumped before 

any proppant is pumped [4]. 

By using the down hole microseismic 

to indicate and control possible hazard 

during hydraulic fracturing job, i.e. 

fracture breakthrough to the over and 

underlying formation, screenout risk 

during pumping, etc. [7];  

The concentrated proppant slurry cause 

plugging of the hydraulic fracture, and 

preventing additional growth of the 

hydraulic fracture length. Additional 

pumping of the proppant with the fluid 

slurry into the formation after the 

screenout happen causes the hydraulic 

fracture to balloon. For that the 

fracture going to grow in Width rather 

than length, and large concentrations 

of proppant per surface area will be 

occur in the fracture [8]. 

 

Experimental Work 

 

Set the Apparatus to Measure the 

Plugging Time by using Gravity 

Force for β= 3 

Set the apparatus as shown in Figure 1, 

using viscose fluid (water + 1.0% 

Xanthan) which prepare by mixing 

fresh water + Xanthan for about 30 

min and then used, to carry and 

suspend the particles uniformly inside 

the cylinder, the particles represent the 

solid particles (ceramic proppant) from 

different sources in oil and gas 

industry.  

Gravity was used to force the viscose 

fluid with the particles, the carrier fluid 

with proppant through the tube Figure 

1 which represent the pore throat or 

hydraulic fracture were called without 

shift as a shape name need  to study.  

Filling the cylinder with the suspension 

about 450 cc + 27.6 solid% by volume, 

open the bottom valve of the cylinder 

to allow flow through the fracture. 

During the suspension flow through 

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Mohammed Abdul Ameer and Samera Hamed Allah   

 

-Available online at: www.iasj.net                    IJCPE Vol.17 No.4 (December 2016)                      59 
 

the fracture, digital camera recorded 

the cumulative weight “gm “in the 

graduate cylinder set above digital 

scale, recording the cumulative weight 

vs. time. This type of experiment is 

made for 27.6 solids % by volume, for 

β= 3 (the ratio between the pore throat 

pipe   “fracture size” and the average 

particles diameter “proppant").  

 

Set the Apparatus to Measure the 

Plugging Time by using Gravity 

Force for β= 3 Run No. 2  

The second run of experimental is the 

same as the first one of experiment 

using gravity force to force the fluid to 

flow through the fracture, for same 

particles concentration and  for same 

β= 3 again. During the run the 

experiment for the second time, there 

is no difference between the first and 

second run of experiments in 

experiment conditions, For the above 

two runs of experimental, were done at 

the same time for same concentration 

and same conditions, noticed that the 

plugging time “sec” was different and 

when the experiment was repeated for 

the third time, also was not similar to 

the previous two experiments. After 

that repeat the experiments for about 

more than 10 times for each 

concentration to get normal 

distribution for the plugging time 

frequency.  

For that it is decided to repeat the  

experiment for about 10 times to check  

the plugging time if it is the same or 

not for each run, but noticed that the 

plugging time is not the same for the 

same conditions for each run. Figures 

2, 3, 4 and 5 represent the relation 

between the plugging time (sec) and 

the cumulative weight (gm), for 

different concentration and β= 3, 

Figures 6, 7, 8 and 9 illustrate the 

normal distribution for different 

concentration. 

 

 
Fig. 1: the shape of the apparatus that used to represent inside the hydraulic fracture ,fracture shape 

without shift 

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Experimental Work to Study the Behavior of Proppant Inside the Hydraulic Fractures and the 

Plugging Time 

  

 

60                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

 
Fig. 2: Relation between the cumulative weight “gm” and the Plugging time “sec”, fluid flow by 

gravity force for β=3, concentration 27.6 % by Volume 

 

 
Fig. 3: Relation between the cumulative weight “gm” and the Plugging time “sec”, fluid flow by 

gravity force for β=3, concentration 33.3 % by Volume 

 

 
Fig. 4: Relation between the cumulative weight “gm” and the Plugging time “sec”, fluid flow by 

gravity force for β=3, concentration 38.9 % by Volume 

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Fig. 5: Relation between the cumulative weight “gm” and the Plugging time “sec”, fluid flow by 

gravity force for β=3, concentration 44.12 % by Volume 
 

 
Fig. 6: Normal distribution chart for plugging time “sec” vs. frequency of 27.6 % particles 

concentration by Volume, β=3 
 

    
Fig. 7: Normal distribution chart for plugging time “sec” vs. frequency of 33.3 % particles 

concentration by Volume, β=3 

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Experimental Work to Study the Behavior of Proppant Inside the Hydraulic Fractures and the 

Plugging Time 

  

 

62                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

 
Fig. 8: Normal distribution chart for plugging time “sec” vs. frequency of 38.9 % particles 

concentration by Volume, β=3 

 

 
Fig. 9: Normal distribution chart for plugging time “sec” vs. frequency of 44.1 % particles 

concentration by Volume, β=3  

 

Set the Apparatus to Measure the 

Plugging Time by using Gravity 

Force for β= 2 

Set the apparatus as shown in Figure 1, 

using viscose fluid (water + 1.0% 

Xanthan ) which prepare by mixing 

fresh water + Xanthan for about 30 

min and then used, to carry and 

suspend the particles uniformly inside 

the cylinder, the particles are represent 

the solid particles from different 

sources in oil and gas industry, 

effectively.  

To force the viscose fluid with the 

particles to flow, gravity was used to 

flow through the fracture, Figure 1 

which represent the pore throat or 

hydraulic fracture. Fill the cylinder 

with the suspension about 450 cc + 

solid % by volume; open the bottom 

valve of the cylinder to allow flow 

through the fracture. During the 

suspension flow through the fracture, 

digital camera was recorded the 

cumulative weight “gm“ in the 

graduate cylinder, recording the 

cumulative weight "gm" vs. time "sec". 

This type of experiment is made for 

different particles concentration (16.8, 

21.66, 24 and 29.6) solids % by 

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volume, for β= 2, Figures 10, 11, 12 

and 13 represent the experiments, 

Figures 14, 15, 16 and 17 represent the 

normal distribution for different 

concentration. 

 

 
Fig. 10: Relation between the cumulative weight “gm” and the plugging time “sec”, fluid flow by 

gravity force for β=2, concentration 16.8 % by Volume 
 

 
Fig. 11: Relation between the cumulative weight “gm” and the plugging time “sec”, fluid flow by 

gravity force for β=2, concentration 21.66 % by Volume 
 

 
Fig. 12: Relation between the cumulative weight “gm” and the plugging time “sec”, fluid flow by 

gravity force for β=2, concentration 24 % by Volume 

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Experimental Work to Study the Behavior of Proppant Inside the Hydraulic Fractures and the 

Plugging Time 

  

 

64                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

 
Fig. 13: Relation between the cumulative weight “gm” and the plugging time “sec”, fluid flow by 

gravity force for β=2, concentration 29.6 % by Volume 
 

 
Fig. 14: Normal distribution chart for plugging time “sec” vs. frequency of 16.8 % particles 

concentration by Volume, β=2 
 

 
Fig. 15: Normal distribution chart for plugging time “sec” vs. frequency of 21.66 % particles 

concentration by Volume, β=2 

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-Available online at: www.iasj.net                    IJCPE Vol.17 No.4 (December 2016)                      65 
 

 
Fig. 16: Normal distribution chart for plugging time “sec” vs. frequency of 24 % particles 

concentration by Volume, β=2 

 

 
Fig. 17: Normal distribution chart for plugging time “sec” vs. frequency of 29.6 % particles 

concentration by Volume, β=2 

 

Material Used in this Work 

The apparatus designed to meet the 

fracture or pore throat by using 

irregular tube representing the pore 

throat or hydraulic fracture, and the 

particles represent the solid particles 

from different sources including water 

flooding, drilling fluid, perforation, 

work over, and fracture fluid (viscose 

fluid) as shown in Figure 1. 

 

Material for Measuring Plugging 

Time by Gravity Force 

Carrier fluid used was prepared form 

fresh water 450 cc + Xanthan (1.0 %) 

+ Carbo prop ( 20/40 ), ceramic 

proppant, specific gravity =2.76 

gm/cm
3
, as solid particles. Using 1.0 % 

Xanthan to get suitable viscosity to 

carry the particles through the pipe and 

suspend the particles uniformly inside 

the cylinder , as shown in Figure 1, and 

the force to let the viscose fluid to flow 

was gravity. The ratio between the 

fracture diameter to average particles 

diameter was β =3 and 2. 

 

 

 

 

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Experimental Work to Study the Behavior of Proppant Inside the Hydraulic Fractures and the 

Plugging Time 

  

 

66                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

Experimental Results 

 

Plugging Time by Gravity Force 

Repeated for about 10 Times 

These experiments done for the same 

concentration and conditions for β=3, 

repeated for 10 time  to get the 

plugging time (screen out).  

Using the SPSS software to get the 

confidence interval for plugging time 

for each concentration, we can get 

normal distribution for plugging time. 

Figure 2 illustrates the relation 

between the plugging time and the 

cumulative weight for solid 

concentration 27.6% by volume 

particles concentration, Figure 3 for 

33.3% by volume particles 

concentration, Figure 4 for 38.9% by 

volume particles concentration, and 

Figure 5 for 44.1% by volume particles 

concentration. 

We can notice from these figures that for 

the same condition and for the same 

concentration the plugging time was 

different for each run of the experiments. 

The force used to force the fluid to flow 

was by gravity. 

 

Plugging Time by Gravity Force 

After the experiments were done for 

about 10 times, for β=3 and the same 

condition but different concentration 

and for fracture shape (without shift) 

Figure 1, to get the plugging time by 

taking the average value for plugging 

time for different concentration.  

Figures 2, 3, 4 and 5 illustrate the 

results for the fracture shape without 

shift for β=3 for various particles 

concentration by volume percent, and 

Figures 6, 7, 8 and 9 illustrate the 

normal distribution for the results for 

β=3 for various particles concentration 

% by volume.  

For β=2 for the same fracture shape for 

different particles concentration we 

can see the results in Figures 10, 11, 12 

and 13 without shift represent the 

results for the relation between the 

plugging time (sec) vs cumulative 

weight (gm), and Figures 14, 15, 16 

and 17 illustrate the normal 

distribution for different particles 

concentration solid % by volume.  

 

Analysis of the Data 

 

Data Results from Plugging Time 

Measurement by using Gravity 

Force and β=3 

We can see in Figures 2 through 5 

which represent the relation between 

the Plugging time (sec) vs Cumulative 

weight (gm), that the plugging time 

represented by the sharp deflection in 

the curve for each of the 

concentrations (27.6, 33.3,38.9 and 

44.12) % by volume. These plugging 

time correlated with the concentration 

% by volume and get the correlation 

for different concentration % by 

volume, as shown before, using the 

gravity force to allow the suspension to 

flow through the fracture  Equation 1 

and Figure 18, and the R
2
 =0.9808, 

exponential relation between the 

concentration and the plugging time 

for  β=2 

 

y= 2 0 3 . 3 5  e
- 0 . 0 7 5 x          

         … ( 1 )  

 

W h er e :  y=  p l u g g i n g  t i m e “s e c” ,  

x =co n c en t r at i o n  o f  t h e p ar t i c l e s  

i n  t h e s u s p e n s i o n  %  b y v o l u m e .  

 

Data Results for Plugging Time 

Measurement by using Gravity 

Force Repeated for each 

Concentration when β=2 

Using the SPSS software to analyze 

the results gotten for the different runs 

of experiments. The experiments were 

repeated because of the results of the 

plugging times were varied when the 

experiments were repeated for the 

same concentration and same 

conditions, because the plugging times 

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-Available online at: www.iasj.net                    IJCPE Vol.17 No.4 (December 2016)                      67 
 

depend on the probability of the 

particles to be in the same place at the 

same time. For that the experiments 

were repeated for about 10 times to get 

normal distribution for the frequency 

of the time vs. the plugging times 

"sec", Figures 6, 7, 8 and 9 represents 

the normal distribution of 27.6, 33.3, 

38.9 and 44.12% by volume particles 

concentration. Analyzing these data by 

SPSS getting 95% the confidence 

interval of plugging times Table 1, we 

can see from Table 1 that the plugging 

time for 27.6% by volume of particles 

concentration, the plugging time 

between 24.95 – 28.29 sec, that what 

we call it confidence interval of the 

plugging times with 95% correct and 

5% error.  

Table 1 represent the results from 

analyzed data, for 33.3, 38.9 and 44.12 

respectively,  using the SPSS software 

to get the confidence interval and the 

mean value of plugging time for each 

concentration with 95% correct and 

5% error. 
 

Table 1: represent confidence interval for 

different β and concentration % by volume 

Plugging time (sec) 

conditions 

95% Confidence 

Interval for Mean 

Β concentration 
Lower 

Bound 

Upper 

Bound 

3 27.6 24.9567 28.2933 

3 33.3 13.2721 18.3643 

3 38.9 9.5041 17.3848 

3 44.12 5.0021 8.9979 
 

T h e m e an  v al u e o f  t h e p l u g g i n g  

t i m es  “s e c” f r o m  t h e r e s u l t s  

i l l u s t r a t e d  i n  Fi g u r e 1 0  

r e p r es en t s  t h e r el at i o n  b et w e en  

t h e s o l i d s  co n c en t r at i o n  %  b y 

v o l u m e a n d  t h e p l u g gi n g t i m e  

f o r  β =3 .  

 

 
Fig. 18: The relation between the concentration % by volume  and the plugging time “sec”, the flow by 

gravity, β=3 , without shift 

 

Also using the SPSS software to 

analyze the results gotten for the 

different runs of experiments for β=2. 

The experiments were repeated 

because of the results of the plugging 

times were varied when the 

experiments were repeated for the 

same concentration and same 

conditions, the results with the set of 

conditions for β=2 because the 

plugging times depend on the 

probability of the particles to be in the 

same place at the same time. For that 

the experiments were repeated also for 

more than 10 times to get normal 

distribution for the frequency vs. the 

plugging times "sec", Figures 10 

through 13 represents the relation 

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Experimental Work to Study the Behavior of Proppant Inside the Hydraulic Fractures and the 

Plugging Time 

  

 

68                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

between the plugging time "sec" and 

the cumulative weight "gm" each 

figure represent the same condition 

repeated more than 10 times to get the 

confidence interval for the plugging 

time sec. Figures 14, 15, 16 and 17 

represents the normal distribution of 

16.8, 21.66, 24 and 29.5 solids % by 

volume particles concentration. 

Analyzing these data by SPSS getting 

95% the confidence interval of 

plugging times Table 2, we can see 

from Table 2 that the plugging time for 

16.8% by volume of particles 

concentration is (15.61 21.46) sec, that 

what we call it confidence interval of 

the plugging times with 95% correct 

and 5% error. 

The mean value of the plugging times 

“sec” from the results illustrated in 

Figure 19 represents the relation 

between the concentration % by 

volume and the plugging time for β=2. 

Table 2 represent the results from 

analyzed data, for 16.8, 21.66 , 24 and 

29.6% respectively,  using the SPSS 

software to get the confidence interval 

and the mean value of plugging time 

for each concentration with 95% 

correct and 5% error. 

 
Table 2: represents the confidence interval for 

different β and concentration % by volume 

Plugging time (sec) 

conditions 

95% Confidence 

Interval for Mean 

Β concentration 
Lower 

Bound 

Upper 

Bound 

2 16.8 15.6130 21.4639 

2 21.66 6.7128 10.6718 

2 24 6.3129 10.1871 

2 29.6 2.6488 5.3512 

 

Table 3 l i s t  t h e v a l u es  o f  R –

s q u ar e,  an d  t h e eq u at i o n s  f o r  

d i f f e r en t  co n d i t i o n s  ( p r o p p an t  

co n c en t r at i o n ,  p l u g g i n g t i m e  

( s ec )  an d  β ) . 

 

 
Fig. 19: The relation between the Concentration % by Volume and the plugging time “sec”, the flow by 

gravity, β=2 , without shift 
 

T a b l e  3 :  r e p r e s e n t  t h e  v a l u e s  o f  R  – s q u a r e  a n d  t h e  e q u a t i o n  

e x p e r i m e n t s  

N o .  

F r a c t u r e  

s h a p e  

β  

v a l u e  
R

2
 C o r r e l a t i o n  F i g u r e  N o .  

1  
W i t h o u t  

s h i f t  
3  0 . 9 8 0 8  y  =  2 0 3 . 3 5 e

- 0 . 0 7 5 x
 1 8  

2  
W i t h o u t  

s h i f t  
2  0 . 9 9 4 7  y  =  1 6 3 . 3 8 e

- 0 . 1 2 4  x
 1 9  

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C o n cl u s i o n  

The two Figures 18 and 19 above, 

illustrates that the region below the 

curve line that indicate the conditions 

for non-screen out whereas the region 

above the curve indicate the screen -

out region, because of that fracture 

engineer need to avoid the conditions 

above the curves and make an 

optimization between the fracture 

width, proppant concentration and the 

proppant size for success fracture job. 

 

References 

1. Yongping Li, Yonghui Wang, 
Xingsheng Cheng, Mingguang Che, 

Langfang Branch of RIPED, 

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118858 Copy right  2009, Society  

of   Petroleum  Engineers. 

2. Gidley, J.L., John L. Gidley and 
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Engineering, Volume 6, Number 4, 

November  1991. 

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Copyright © 2013 Schlumberger. 

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DETECTING SCREEN-OUT 

USINGA FRACTURING VALVE 

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