1.1 obtained throughout the experiments were analysed and

1.1           IntroductionThe planned procedures listed in the methodology section in thisproposal were successfully completed. Citrus Sinensis are prepared and used asLost Circulation Material additives. Different concentration and sizes of thisadditive were tested for compatibility of this additives to prevent lostcirculation from occurring and how percent of it can be prevented.

Followingsection complying with the standard stipulated in API RP 13B-2; RecommendedPractice Standard Procedure for Field Testing Oil-Based Drilling Fluids. Thedata obtained throughout the experiments were analysed and interpreted.Summaries of results are generally presented in figures. Typical graph relatingto the experiments will be provided in this chapter, while all tables of rawdata and complete results relating to the experiments conducted are shown inAppendices. 1.

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2           MudData AnalysisTable 4.1 and Table 4.2 provide the dataobtained for all mud systems in this paper.

The results were taken before thesamples undergo Before Hot Rolled (BHR) and After Hot Rolled (AHR) for the mudrheological properties while HPHT filtration test and Sand Bed Test will beonly performed after the samples have been undergo AHR. The drilling fluidsamples were left for 16 hours in the oven at 150 ºF.  1.2.1      Rheological PropertiesThe rheological properties for bothparticle sizes were calculated in the Table 4.1 and Table 4.

2. The graphicaldata were shown as in Figure 1. The results were taken before the samplesundergo Before Hot Rolled (BHR) and After Hot Rolled (AHR) for the mudrheological properties. Table 4.

1Experimental dataresult for fine size of CS PROPERTIES BASE 3 g 6 g 9 g AMOUNT BHR AHR BHR AHR BHR AHR BHR AHR 600 rpm 59 65 65 84 71 89 65 93 300 rpm 40 45 45 55 49 58 48 61 200 rpm 34 39 44 53 39 54 55 63 100 rpm 29 30 35 40 28 42 37 43 6 20 25 25 30 15 22 18 23 3 15 18 20 27 14 19 18 20 PV 19 20 20 29 22 31 17 32 YP 21 25 25 26 27 27 31 29 GS 10 sec 14 15 16 16 16 17 17 19 GS 10 mins 18 18 17 19 18 20 19 21  Table4.2Experimental dataresult for coarse size of CS PROPERTIES BASE 3 g 6 g 9 g AMOUNT BHR AHR BHR AHR BHR AHR BHR AHR 600 rpm 59 65 68 77 80 90 87 93 300 rpm 40 45 49 56 62 64 65 66 200 rpm 34 36 43 48 55 57 53 59 100 rpm 29 30 37 44 40 45 44 52 6 20 25 18 19 19 20 19 20 3 15 18 15 18 14 15 15 17 PV 19 20 19 21 18 26 22 27 YP 21 25 30 35 44 38 43 39 GS 10 sec 16 15 15 17 18 19 18 20 GS 10 mins 18 18 17 20 20 22 19 24  1.2.1.1  Plastic ViscosityParticle size and concentration of CitrusSinensis additives of lost circulation material determine the total mass ofdrilling fluid. From the Figure 4.1 shown below, it can be observed the plasticviscosity containing fine size is greater than plastic viscosity with coarsesize. Reducing the particle size of Citrus Sinensis will cause increase in thefluid viscosity, as the percentage by volume of solids in the mud increasing,in this case, it affects plastic viscosity as been investigated by Ogbeide, P.

O. et al. (2016).

From the Figure 4.1, itwas found that addition of Citrus Sinensis as lost circulation materials hasimproved the rheological properties. It is identified that a relatively lowplastic viscosity is often necessary for having a greater efficiency duringdrilling operation as theviscosity of the drilling fluid increases when it is exposed to subsurfacecuttings (Jamal, J.

A., et al., 2007). However, a high viscous mud may not bereally in demand when lost circulation material; in this case Citrus Sinensisis added. Figure 4.

1 PlasticViscosity versus Concentration of CS 1.2.1.2  Yield PointFigure 4.

2 shows the graphical data ofyield point and concentrations versus Citrus Sinensis. Yield point is definedas the ability of drilling fluid in bringing up the cuttings into the surface(Ramezani, H. et l., 2015). Addition of Citrus Sinensis increases the yieldpoint of the drilling fluid which is similar to trend of its plastic viscositygraph that have been discussed earlier.  Figure 4.

2 Yield Point versus Concentration ofCS From the figure above, YPof fine particle size increased from 25 lb/100 ft2 to 29 lb/100 ft2with increasing Citrus Sinensis concentration while YP of coarse particle sizeincreased significantly from 25 lb/100 ft2 to 39 lb/100 ft2.As discussed in literature review part, high yield point will increase theability of drilling fluid to lift cuttings (Rabbani A et al., 2017). Hence,adding Citrus Sinensis to the drilling fluid may improves the ability ofliftings subsurface cuttings compared to only adding barite into the formation.This also has been proven in Nayberg L.

et al.’s (2012) research that yieldpoint increases with increasing particle volume fraction which will occurredwhen the applied stress is adequate to cause the network to break up. Besides,the Citrus Sinensis were dispersed in synthetic based mud due to the absorptionof water into it and from time to time it becomes agglomerated. This phenomenonwas proven by Saikaew W.

et al. (2010) that it will increase the viscosity ofdrilling fluid. 1.2.1.3  Gel StrengthFigure 4.

3 and Figure 4.4 shows gelstrength comparisons for 10 seconds and 10 minutes, respectively for bothcases; fine and coarse sizes. Gel strength is defined as the measurement ofshear stress at low shear rate under static condition for a certain period oftime, in this case 10 seconds and 10 minutes.From both figures, gelstrength obtained increased as the concentration of Citrus Sinensis isincreased. The coarse particle size shows a slightly greater value compared tofine particle size. These both graph shows the typical yield point graph interm of their trend. Figure 4.3 Gel Strength 10 seconds Figure 4.

4 Gel Strength of 10 minutes Furthermore, the drillingfluid for both particle size showed comparatively higher gel strength value for10 minutes measurement after the addition of Citrus Sinensis in compared to thebase drilling fluid. This is however an impressive indicator to improvesuspension of drilling cuttings at static condition especially when theoperation is halted due to maintenance, but too high of gel strength will causecatastrophic problem (Nayberg, T.  M. etal., 1984). In fact, previous research of Wu B.

et al. (2006) states that the10 minutes gel strength will have higher gel strength as compared to 10seconds. This is because the particles will have more time to arrange and alignthemselves in an appropriate manner in which both repulsive and attractiveforces best satisfied. 1.

2.2      Mud Cake Thickness and FiltrateFigure 4.5 and Figure 4.6 shows arelationship graph between filtration loss and concentration of CitrusSinensis. An impressive result of fluid loss is shown in Figure 4.5 with bothparticle sizes show different trend. After the Citrus Sinensis were added,fluid loss was slightly larger than of the base fluid.Increasing Citrus Sinensisconcentrations in the formulation indeed helps reduce the amount of filtrateproduced, however, in this case, an optimum range of combination should beinvestigated for better formulation in order to have an extraordinary lowerfiltrate volume.

It is seen that at 6 g concentration of Citrus Sinensis, thefiltrate volume was decrease to 5.6 mL in compared to the based case. Figure 4.5 Filtration Loss However, increasing theconcentration of 9 g Citrus Sinensis has caused the fluid loss to be increaseback.

This indicated that increase the concentration of 9 g of Citrus Sinensisin synthetic based drilling fluid was not enough to plug the pores, in thiscase, filter paper. It is proven that the important factors in controlling thepermeability are the shape, the size and of course, the deformability of thesolids in the drilling fluid system (Windarto et al., 2011).

Particles of onemicron or smaller size will enhance the extraordinary and impressive mud cakecomposition as been demonstrates by Ibrahim N. et al. (2006) in his paper.

From the figure also, itcan be observed that for fine particle case, as the concentration of CitrusSinensis increases, the fluid loss is decreases. This encouraging result provesthat fine particle of Citrus Sinensis can be used as an alternative lostcirculation material with better formulation of drilling fluid. The theory alsoproves the fact that as the amount of lost circulation material additives isincreasing, the viscosity is increases, thus cause the water to be less filtered.The higher the viscosity of the drilling fluid, the better the formulation is,the most desirable of Citrus Sinensis can be as lost circulation materialadditive. Figure 4.

6 Mud Cake Thickness The thickness wasmeasured where it ranged from 1.75 in to 2.4 in. It can be observed from thefigure above that there is a decrease in the thickness of the filter cakeformed as the concentration of Citrus Sinensis in the drilling fluid increased.The synthetic based mud with 6 g concentration of Citrus Sinensis, has a smallvalue of thickness.

It was found in earliear research that the filter cakethickness is depend on the filter porosity and formation permeability (Jian H.et al., 2013). As expected, the newapproaches of nano-sized Tapioca starch brought by Mansoor Z. et al. (2016) hasbeen implemented in this paper where the sample with thicker filter cakeexperienced more severe change in the permeability due to greater cumulativevolume of filtration. In normal conditions, the thick filter cake will enhancethe chance of drilling problems such as stuck pipe.

Thus, based on this result,the lower the filtrate volume, the thinner the filter cake formed, indicatesthat good fluid loss control in drilling fluid, hence shows that CitrusSinensis has a potential to be an impressive fluid control additive not onlybeing as lost circulation material additives. 1.2.3      Sand Bed TestFrom the Figure 4.

7, sand bedtest data shows that 6 g concentration of Citrus Sinensis has an astonishingfilm-forming plugging ability. It can well prevent sandstone reservoir fromseepage and enhance the bearing capacity of the borehole wall. As it can beseen from the figure, the base sample, the drilling fluid enter the formationand within 5 minutes, it has already damaging the whole 10-cm formationthickness.  Figure 4.7 Sand Bed Test Adding more concentrationof this additive into the synthetic based mud can slow down the formationdamage as it can be observed for 9 g concentration of Citrus Sinensis. Thefirst minutes, the drilling fluid able to damage the formation around 2.3 cmwhile 6 g concentration of Citrus Sinensis damaging the formation around 2.

0 cmfor the first minute. If the mud cake permeability is low, then the filtrationvelocity is low as for 6 g and 9 g concentration of Citrus Sinensis. In actual conditions,Mansoor Z. et al. (2016) identifies two causes of formation damage by drillingmud are filtrate invasion and solid invasions.

In this case, using incompatiblefluid loss control additive such as improper particle size with drilling fluidwill enhance the formation damage and increase lost circulation (Fathi, B., etal., 2004). It can be observed from Figure 4.

7, the invasion velocity ofdrilling fluid filtrate for coarse particle size case is fast. The drillingfluid invasion is due to absence of filter cake that prevents solid particlesinvasion into the formation (Calcada, L. A.

et al, 2015). In this case, 6 g and9 g concentration of Citrus Sinensis of coarse size which is 6.00 mm are unableto form a filter cake in order to prevent the drilling fluid from damaging theformation. Hence, it can be observedthat 6 g of Citrus Sinensis is the optimum concentration and most suitable lostcirculation material additive since it able to slow down and prevent the formationfrom damage.