Studying the Effects of Different Polymers on Rheological Properties of Water Base Muds

This research is focusing on finding more effective polymers that leads to enhance the rheological properties of Water Base Muds. The experiments are done for different types of mud for all substances which are Polyacrylamide, Xanthan gum, CMC (Carboxyl Methyl Cellulose). This study shows the effect of add polymer to red bentonite mud, effect of add polymer to Iraqi bentonite mud, the effect of add bentonite to polymer mud. The mud properties of Iraqi bentonite blank are enhanced after adding the polymers to the blank mix, CMC gives the highest value of plastic viscosity and Gel strength than others; X-anthan gives the highest value of yield point and gel strength than others. For the red bentonite mud, Polyacrylamide has the highest shear stress and yield point than the others polymers, but Xanthan has the highest effect on plastic viscosity than other polymers. All polymers reduce filtration loss. The polymer solution mud failed to suspend the barite so we cannot use it as drilling fluid even so this mud has good Rheological properties (PV and YP). The maximum amount of each polymer is founded for the studied clay types.                                                            
 


INTRODUCTION
Rheology is the learning of the twist and movement issues.Revision of rheology is significant because it permits the drilling fluid to be explicitly analyzed in expressions of fluid current profile, viscosity, pressure losses, hole cleaning capability, equivalent circulating density and the well bore hydraulics.Rheological properties of a mud are those properties which define the flow features of a mud under several flow circumstances.In a mud circulating structure, flow happens at a variation of amounts in conduits of dissimilar sizes and forms, Ogbeide, and Igbinere, 2016.In order to recognize or guess the effects of that flow, we need to distinguish the flow performance of the mud at the numerous topics of interest in the circulating system.To shorten the measurement way, we create only a restricted number of measurements.When a mud flows, it employs a frictional dragtermed shear stress on the surface of the channel.The amount of the shear stress is governed by the frictional drag between neighboring "layers" of nearby layers along the wall of conduit Winson, 1956.The variance in velocities between adjacent layers is titled shear rate.We are involved at effect of the flow at the wall anywhere both shear rate and shear stress are full Bourgoyne, 1986.To competition the supplies of dissimilar depth intervals, the properties of drilling mud are adapted by using many additives for the drilling mud Dhiman, 2012.

2.1Mud Density
The density is measured to governor subsurface pressures and for stabilizing the wellbore pressure.Drilling fluid density usually measured by using mud balance.The mud balance adjusted with fresh water and must provide reading of 8.3 lb/gal.The mud density check conducted via mud balance, Darely, 1988.

2.2Measuring (PH)
PH Meter: is one of many electrical devices using a glass electrode for measuring the potential variance and point out directly by dial reading the PH. of the mud.The PH meter is considering the best exact way of assessing PH Amoco, 2009.

Drilling Fluid Rheology Check (Mud Viscosity, Mud Yield Point Mud Gel Strength):-
The viscometer is used for measuring the values of shear rate/shear stress of a mud sample from which the Bingham Plastic factors, PV and YP, are calculated easily.This device is likewise used for measuring thixotropic belongings "gel strengths".The viscosity knows as the confrontation of the fluid to movement and is also stately as the relationship of shearing stress and rate of shearing strain, Amoco, 2009 The Plastic Viscosity (PV) and Yield Point are calculated from the 600-RPM and 300-RPM dial readings as follows and as in Eq. ( 1) and Eq. ( 2) Amoco, 2009:

MATERIALS 3.1 Commercial Bentonites and Iraqi Bentonite:
Those clays used in drilling fluids are naturally occurring clays and are founded in a lot of zones of the world.They enclose the clay mineral and could have addition minerals for example quartz, mica, feldspar and calcite.Red bentonite is consisting of three layers swelling clays.Red bentonite is furthermost major form is calcium, but also there is sodium.This clay has the capacity to hydrate in the existence of water; these bentonites are used to viscosify the muds.Sodium bentonite is found absolutely in the northwestern zone of the United States, is the maximum commonly desirable bentonite because its hydration capability is considerably better than that of calcium bentonite.It can be say that the term of premium bentonite is known to sodium bentonite.Because of the operating need of using bentonite differs from one place to another through the globe, API recognized specifications for covering sodium and calcium bentonites, Rabia, 2010 and as shown in Fig. 1.A rock sample of Iraqi bentonite was sourced and collected from west of Iraq, Anbar, Trefawi.

X-anthan C35H49O29
Xanthan is a biopolymer, is a produce from the act of bacteria (Xanthomonas Campestris) on sugar.This polymer is used in at a differen range of brines and salinity ranks.Xanthan reduce thermally at temperatures of above 225°F.Xanthum gum is the lone polymer that is responsible for thixotropy, in other words creation of gel structures.This polymer is an exceptional additive for enhancing the drilling mud.Its exclusive high viscosity at little shear could support little concentration of mud for hang solids.Even at extraordinary temperature and great concentration solution of acid, alkali, salt, Xanthan gum still could keep those properties.This is exclusively of Significant at offshore drilling and other harsh circumstances .Xanthan gum is suitable for the tertiary oil retrieval and improved oil recovery through oil production.Its strong heat struggle belongings create it be a dependable moving agent and mobile governor manager Rabia, 1985.Fig. 3 illustrated the Molecular structure of Xanthan. .

Polyacrylamide ("PAM") (C3H5NO):
Polyacrylamide is a water-soluble polymer formed from acrylamide (a compound with the molecular formula C3H5NO) subunits and as shown in .

Effect Of Adding Red Bentonite To Polymer Mud (Low Solid Mud)
The word of low solid mud is not applied for every specific configuration.Somewhat it has been practical to the number of composition which used chemical and mechanical ways to keep the lowest practical solid content.Wheless, 1990 determined from his clarifications and observations of the drilling periods on field improvement wells in Ark-La-Tex area that buildup of drilling solids in the drilling fluid slow down the rate of penetration.Tow mixture are used as low solid mud; the first mixture consists of 1gm polyacrylamide, with 2, 4 and 6gm of bentonite as shown in Fig. 9.In addition, the second mixture consists of 1gm xanthan, with 2, 4 and 6gm of bentonite as shown in Fig. 10.Addition of bentonite to polymer leads to increase shear stress, Pv and reduce filtration.The experimental work shows that the polyacrylamide has not ability to suspend barite particles therefore adding bentonite is necessary to suspend the barite particles and the lowest weight of bentonite that lead to suspend barite is 6gm.The filter cake thickness is 1mm for the first mixture.While with xanthan gum the bentonite is more stable with a lowest percent than with polyacrylamide.In other words adding 2gm of bentonite lead to increase in PV, YP, and Gel and reduce filtration.The mud cake thickness for the second mixture is 1.5 when 6gm of bentonite is added.

5.3Effect of Adding Polymer to the Red Bentonite Mud (Polymer Mud):
The mixture consists of 350cc of water, 22.5 gm.bentonite, and additives and as shown in Figs.11, 12, 13, 14 and 15, and illustrated in Tabel.1 .The used polymers are CMC, Xanthan and Polyacrylamide.From our results, it can be notice that adding polymer to red bentonite mud lead to increase PV, YP, and Gel and decrease filtration loss.The effect differs among polymers where polyacrylamide has the highest shear stress and Yp than the others polymers, but Xanthan has the highest effect on PV than other polymers.All polymers reduce filtration loss.CMC and Xanthan increase gel strength more than polyacrylamide, which show the lowest effect on gel strength so it can use as visosifier.Also, the limit of add polymers can be determine by add more solid by weight (S%), until viscometer reading get out of scale reading such as polyacrylamide and xanthan.where they gives out of scale reading when 4gm of each one is added to blank mix as shown in the below tables; while CMC is 5gm to give out of scale reading.So the maximum amount of polyacrylamide and xanthan is 3gm for 350 cc of water and 22.5 gm.Of red bentonite and the maximum amount of CMC is 4gm for350 cc of water and 22.5 gm. .

Effect of Polymers Additives on Iraqi Bentonite Mud:
The mixture consists of 350cc of water, 22.5gm of Iraqi bentonite and polymers additives.The polymers can used to enhance the rheological properties of Iraqi bentonite mud.The three used polymers are (CMC, polyacrylamide, Xanthan gum).The blank mix show very low values of shear stress, gel, PV,YP ,it cannot be used it in drilling process.But after adding the polymers to the blank mix all the mud properties is enhanced.We found that there are increase in the values of shear rate and PV, YP and Gel but with different values depend on the polymer type and solids by weight (S %), and as shown in Fig. 16, Fig. 17

CONCLUSIONS:
1-The results show that for polymer solution, The PV in 2gm additives is largest for Xanthan Gum and also less YP, when reach to 6gm additives the polyacrylamide has largest PV and lowest YP, Xanthan gum And CMC vice versa.
2-the polymer has not ability to suspend barite particles therefore bentonite add is necessary to suspend the barite particles and the lowest weight of bentonite that lead to suspend barite is 6gm .
3-For the red bentonite, Polyacrylamide has the highest shear stress and Y p than the others polymers, but Xanthan has the highest effect on PV and gel strength than other polymers.4-The mud properties of Iraqi bentonite blank are enhanced after adding the polymers to the blank mix.X-anthan gives the highest value of yp than others; CMC gives the highest value of PV and Gel strength than others.5-The results show that adding the polymers lead to increase the value of PH.
6-The experimental work shows that for each studied polymer there is a maximum amount should be don't exceed it, because if we exceed that maximum amount the viscometer dial will give us scale out also the mud sample will be more thick and sticky.
Fig.4 .This polymer is the most frequently used for rising the viscosity of water or drilling fluid (creating a thicker solution) or for inspiring the flocculation of atoms existing in the water.Polyacrylamide is synthetic chemical which could be tailored to appropriate

Figure 7 .
Figure 7.Shear rate vs. Shear stress for Polymer mud 6 gm of CMC, X-anthan and poly.

Figure 9 .
Figure 9. Shear rate .vs.Shear stress for Add Red Bentonite to polyacrylamide.

Figure 11 .
Figure 11 .Shear rate .vs. shear stress Effect of add (1gm) of polymer on the red bentonite mud.

Figure 12 .
Figure 12.Shear rate .vs. shear stress Effect of add (2gm) of polymer on the red bentonite mud.

Figure 13 .
Figure 13.Shear rate .vs. shear stress Effect of add (3gm) of polymer on the red bentonite mud.
, Fig.18and Fig.19.Polyacrylamide gives the highest value of PV than others; CMC gives the highest value of YP and Gel strength than others.The maximum S% that the mud mix can be accepted until gives out of scale reading is: polyacrylamide 9gm, CMC 8gm and Xanthan gum 7gm.It can be say that we can use any of these polymers to enhance the rheological and filtration of Iraqi bentonite mud.

Figure 18 .
Figure 18.Shear rate vs shear stress Effect of Poly.Additives on Iraqi bentonite mud.

Figure 19 .Figure 20 .
Figure 19.PV vs %S and YP vs%S Effect of Polymer additives on Iraqi bentonit mud.

Figure 21 .
Figure 21.The effect of polymer on PH. of Iraqi bentonite(polymer mud).