MAXIMIZING DRILLING PERFORMANCE THROUGH ENHANCED SOLID CONTROL SYSTEM
Sonny Irawan1, Imros Kinif2, Ridho Bayuaji2
1Department of Petroleum Engineering, Universiti Teknologi PETRONAS
2Department of Civil Engineering,Institut Teknologi Sepuluh Nopember, Surabaya, East Java, Indonesia Email: [email protected]
ABSTRACT
High solid content in drilling mud may affect its properties and result in uncertainties at downhole condition. It eventually contributes to poor rig operation performance and operating cost. This research focus on developing a solid control system that is suit for drilling 12.25-inch hole. The first part discussed on the effect of solid control system performance to mud properties Plastic Viscosity (PV), Yield Point (YP) and Low-Gravity Solid (LGS) while the second part of research discussed about the mud performance to Rate of Penetration (ROP), Equivalent Circulating Density (ECD) and drill string drag. The input parameters such PV, YP, LGS, ROP, LGS, ECD and drill string drag were gathered from two different set up of solid control systems that were used in Well A and Well B. The result was mainly based on the performance of old design and new design solid control system. Installation of mud flow distributor tank to channel the mud into respective shale shakers significantly enhanced the mud treatment capability and operational performance. Mud properties while drilling the 12.25-inch hole section; PV, YP and LGS values were improved by 14%, 17% and 25% respectively. The ROP improved by 25%, ECD margin by reducing additional pressure exerted using original mud from 4.9% to 2.9% and drill string drag friction factor (FF) concentrated within 0.2FF trend. Proper mud flow control and routing system at new develop design of solid control system effectively removed the solid in the drilling fluid. This improvement minimizes the tendency of frequent mud flow, screen mesh plugging and tool wear issue. Mud properties such PV, YP and LGS were maintained with an acceptable mud design envelope.
Keywords: PlasticViscosity (PV), LowgravitySolid (LGS), Rateofpenetration (ROP), Equivalent circulatingdensity (ECD), drillstringdrag.
INTRODUCTION
Effective performance of solid control equipment to remove drilled solids from drilling mud is a key factor to have good mud properties [1]. Solid and particles that are not removed during the mud circulation and remain in the system may reduce in size until it becomes difficult to remove using the mechanical solid control equipment (SCE). Mud properties must be maintained within the acceptable specification to allow efficient cuttings transport to surface [2]. This research focus on evaluating the performance of
two different solid control systems that were used to drill 12.25 inch wellbore section. Preliminary finding revealed that most of Non-Production Time (NPT) on the rig was always associated with mud performance and solid control equipment. Mud data and drilling parameters were carefully studied to understand the root cause of poor drilling performance. The condition of unequal flow distribution over the shale shakers resulted in screen mesh plugging, shakers overflow, cones plugged, and exhibit rope frequently seen at rig site. These contributed to increased solid content that eventually affected the properties of
Plastic Viscosity (PV), Yield Point (YP) and Low Gravity Solid (LGS.) Inability of the system to control these properties was the contributing factor for the poor Rate of Penetration (ROP), Equivalent Circulating Density (ECD) and high drill string drag. Therefore, the performance of drilling mud and role in this context was seen as vital for the whole drilling process.
Figure 1 shows the mud circulating system on a drilling rig and it allows the mud circulating down through the drill string, drill bit and up to the annulus [2]. Principal components of mud circulating system start from the mud pump unit by pumping the mud through the standpipe manifold, Kelly hose, swivel, down to drill string and bit [2]. As the mud passes the bit, the mud containing drill cuttings that generated during drilling then transported in the annulus to surface.
When the mud returns to surface, the contaminated mud with cuttings subsequently directed to solid control system to remove the solids particles before
Figure 1 Mud circulating layout on the rig [2]
the re-circulation. The solid control system sequence consists of shale shakers, desander and desilter and centrifuge.
MUD TREATMENT PROCESS AND SOLID SEPARATION
Solid control equipment for mud treatment process used to control the build-up of solid in the mud while drilling. Figure 2 shows that each of mechanical equipment separate and work based on the solid particles sizes. The equipment connected in series and each stage of processing performance is partly dependent upon the previous equipment.
Should one piece of upstream equipment fail, the equipment downstream may soon lose efficiency or fail completely [3]. The equipment separates the solid particles in various sizes range from the liquid by screening, filtering or centrifuging.
Figure 2 Particle Diameter [4]
The circulated mud carries drilled cuttings to surface and bypassing the shale shaker unit constantly not recommended because it would overload the downstream equipment. Solids that remained in the mud system during the first circulation through the
surface equipment are always subject to mechanical degradation [4]. The smaller the particle, the greater the surface area may develop, and it is causing a greater effect to the mud system.
Mud return from well to Passum belly
Pump back to well
Sand Trap pit Passum Belly
Desander Desilter
Degaster Centrifuge
Shaker #1 Shaker #2 Shaker #3
Pit #1 Pit #2 Pit #3 Pit #4 Pit #5
Figure 3 Old design solid control system
DEVELOPMENT OF SOLID CONTROL EQUIPMENT The schematic in Figure 3 was a configuration of old design solid control system. The flow line of mud returns connected at the middle “Possum belly” tends to allow the mud flows that carrying drilled solids travelling on a straight path upon streaming into the
“Possum belly”. This design leads to the uneven of mud distribution across the shale shakers unit because middle shale shakers unit was seen overloaded while the adjacent shaker unit received less mud flow. The schematic in Figure 4 configuration was a new design solid control system. The contaminated mud with drilled solids from the well was initially contained into mud distributor tank and subsequently streaming to respective shale shakers unit through a pipe line. This system allowed the solids-containing drilling mud and divided equally between the desired numbers of shale shakers. The development was successfully reduced the overloading tendency to downstream equipment.
Mud return from well to Passum belly
Pump back to well
Sand Trap pit
Desander Desilter
Degaster Centrifuge
Shaker #1 Shaker #2 Shaker #3
Pit #1 Pit #2 Pit #3 Pit #4 Pit #5
Figure 4 New design solid control system
and re-drilling of solids as drilling fluid recycles itself through the mud system loop [1].
Effect of Solid particles on Mud weight (MW)
Density or MW measured and expressed in pounds per gallons (lb/gal), pound cubic feet (lb/ft3) and grams per cubic centimeter (g/cm2). It is an important property to maintain the well hydrostatic and prevent gas influx migration into the wellbore. Some of weight material such as barite and hematite added into the mud to increase the mud weight. Mud in the wellbore column must exert a greater pressure than the fluids in porous rocks that are penetrated by the bit [4]. The pressure exerted by the drilling mud at any depth or gradient of pressure is related to its density. Too dense or viscous mud may exert excessive pressure to the wellbore and causing loss of circulation.
Effect of Solid particles on well Bottom Hole Pressure High solids content ultimately can increase the density and viscosity of the mud. Hence, it exposes the well
Mud circulation without any reduction in solid concentration may thickening the fluid viscosity and develops resistance to flow character of the mud. This brings to the changes in its density, rheology and other properties. Utmost advantage is to remove as much solids as practical to reduce down time resulting from plug flow lines, fluid end repair, drill string erosion
to high BHP and mud properties contamination.
Moreover, high horse power is also required to break up the gel and pump the mud for circulation. This not only trigger to hydraulic fracturing effect, but also induce the tendency of mud losses into the formation.
Under the primary well control requirement, the mud density must be formulated to compensate the desire
BHP either meet or exceed the pore pressure of the rock formation [6]. Failure to control the build of solid and regrinding the same drilled cutting may increase the mud surface area become very difficult to remove using mechanical solid control equipment. High solids are abrasive and can increase the filter cake thickness.
The higher of filter cake, the higher chances of drill string to get stuck due to differential sticking effect.
Thin and impermeable filter cake important to reduce contact area across the drill string.
Effect of Solid particles on Plastic Viscosity (PV) Plastic Viscosity (PV) is a function of solids concentration, size and shape of the solid particles and viscosity of liquid phase [3]. It is regarded as a guide to solid control for field application [5]. PV increases if the volume percent of solid increases, or if the volume percent remains constant and the size of the particles decreases. Decreasing particle size may increase the surface area that lead to fractional drag problem. This plastic viscosity is sensitive to the concentration of solid and depends largely on the bulk volume of solids in the mud [6]. A low PV implies lower ECD exerted at bottom while high PV trigger to an increase of ECD because high pumping pressure is needed to break the gel. A YP/PV ratio is a significant indicator of drilling fluid condition, low ratio indicates a smaller tendency for gas cutting, swabbing pressure and greater settling velocity of cuttings whereas high ratios indicate coagulation and flocculation [7]. Removal of drilled solids from a drilling fluid will decrease plastic viscosity and if this solid remain in the fluids, it will grind into smaller and more numerous particles which increases plastic viscosity and decreases drilling performance [8].
Effect of Solid on YP
Yield Point (YP) is the initial resistance of the fluids to flow caused by the electrochemical forces between the particles. It is also expected to be a function of the solid concentration of the solids and those factors, such as surface charges and potential, which affect the inter-particle forces [9]. The YP and gel strength should be low enough to allow sand and shale cuttings to settle out and entrained gas to escape, minimize swabbing effect during pulling the string
out of hole and permit the circulation to be started at low pump pressure [10]. Efficient elimination of drilled solids right after the fluid leaves the annulus was the best solution to avoid drilling fluid-cutting interaction that subsequently can increase the fluid density [11].
Changes in the PV of drilling mud can cause small changes in YP. Therefore, it is always important to keep the viscosity of a mud from getting too low. The mud should have minimum viscosity properties to lift the cuttings from the bottom of the hole to surface.
The mud must capable to keep the weighting material and drilled cuttings in suspension while circulating or stop pumping. Normal reaction in the event of poor cutting transport is to increase the YP of the mud.
However, significant increase in YP may result poor performance of finest mesh at shaker screen [12].
Effect of Solid on ROP
Rheological and filtration properties become difficult to control when the concentration of drilled solid becomes excessive [1]. High particulate solids in the mud reduce ROP because of increase in mud density and viscosity. The higher the mud density, the greater the differential pressure exerts. ROP decreases when differential pressure increases. Lower mud density may decrease the dynamic chip hold down and permitting faster RPM. Low viscosity mud promotes fast penetration because of good scavenging of drilled cuttings. Despite applying more WOB and RPM can comfortably achieve the desire ROP but drilling with the contaminated mud properties decrease in ROP for a long run [4]. Darley and Gray cited low concentration of non-colloidal drilled solid below 4% capable to maintain ROP at high level [6,4] Mud properties such as PV and Yield stress/gel strength showed that although these properties have effects on ROP, but not very significant, only annular pressure losses seemed to drastically affect the ROP which is directly related to ECD [5].
Effect of Solid on Drag and ECD
The fluid rheology plays an important role for solid transport and optimize the hole cleaning [13]. The best way to pick solid is with a low viscosity fluid in turbulent flow. Hole cleaning can be optimized by the use drilling mud with low gel strength and with low
viscosity within the shear rates exposed to the annular flow [13]. In situations where ECD is not a limiting factor, high – viscosity fluids with high YP/PV ratios are preferred. Under situations where ECD is a limiting factor, the use of thin fluids in turbulent flow should be considered. The driller must ensure the ECD as well as its static density is within the safe limit. ECD is the effective density of a moving fluid and slightly more
than the static density because of the friction pressure drop in the annulus. ECD depends on the pump rates and fluid viscosity. Therefore, maintain ECD within limits means keeping viscosity low. The main cause of elevated viscosity is low gravity solid (LGS) increased.
Close monitoring of solid control equipment must be performed to ensure LGS are kept to a minimum [14].
Figure 5 New design solid control system
RESEARCH METHODOLOGY
The Figure 5 showed the process optimization of solid control system. The treatment process started from the mud return from the well until the clean mud recirculated back into the well. Mud properties collected in the “active tank” and drilling parameters gathered from the downhole acquisition tool to evaluate the performance. Under this system development and performance evaluation, two wells drilled named as well A and well B. Well A was drilled with old design solid control system while well B drilled with new design mud treatment. Mud samples collected and measured to evaluate the properties were while the drilling parameters taken from downhole acquisition tool.
Mud return flow contain at mud distributor
The contaminated mud with drilled solids from the well was contained in mud distributor tank and subsequently stream to respective shale shakers unit through pipe manifold. The design allowed better control of mud streaming to shale shaker unit.
Mud treatment process at solid control system equipment
Mud streaming from the distributor tank initially treated at shale shaker unit. Large drilled cuttings entrained from the well were separated from the mud by vibrating screen while the cleaned mud flow back into the next pit. The cleaned and treated mud at shale shaker subsequently pumped to desander unit to separate the sand solid particles from the mud.
The cleaned mud discharged back to the system and contained at next pit. By using different pump and manifold, the treated mud pumped to desilter unit to remove the silt solid particles. The treated mud then discharged at the next pit. Final step of mud treatment was to remove the ultrafine sit solid particles whereby the mud treated at centrifuged unit and discharged into the next pit “active pit.
Measuring mud properties
The mud samplings collected at active pit because it representing the final mud properties condition before it pumped back into the well. A total of 40 mud
samples were collected to measure the properties of PV, YP, MW and LGS.
Drilling real time parameters
The real time parameters such as ECD and ROP reading were real time obtained from downhole acquisition tool PWD (Pressure While Drilling) and MWD (Measuring While Drilling). The drag data was obtained after making up the drill pipe connection by taking Pick Up (P/U) and Slack off (S/O) weight at off bottom condition
RESULT AND DISCUSSION
Field data obtained from onshore drilling operation in Borneo Block from two different nearby wells with similar formation lithology. The old design solid control system mud treatment was used during drilling the 12.25 inch section in Well A. Realizing the poor drilling performance and high number of Non-production time (NPT) on mud related at Well A. The mud system was developed by installing the mud flow distributor with piping manifold to control the mud stream into respective shale shakers. This new design was used on the entire 12.25 section for mud treatment during drilling Well B. A total of 40 mud samples were collected and measured to evaluate the properties of PV, YP and LGS. The results correlated with drilling parameters to investigate the performance of the mud on ROP, ECD and drill string drag.
Performance of solid control system on plastic viscosity (PV)
Figure 6 shows the PV reading of old design and new design solid control system. As drilling the well deeper in Well A, more cuttings generated and transported to surface. Mixture of drilled cuttings with the mud subsequently increased the mud weight and thereby changed plastic viscosity reading. Increased of plastic viscosity was proportionally subjected to increase of solid content in the mud. The average PV reading throughout drilling operation using old design solid control system was 33.7%. The result of high PV reading was contributed by frequent mesh screen plugging,
inability to reach the desire working pressure in desander and desilter, pressure loss due to vibration on flexible transfer hose and solid recirculation.
Drilling the Well B with new design mud processing treatment showed an improvement because the average PV reading maintained at 29% throughout the section. The PV properties improvement was 14%.
This statement justified that efficient solid separation system should work in peak performance and no overloading.
0 50 45 40 35 30 25 20 15 10 5 0
5 10 15 20
Data Point
Well A Well B
PV
25 30 35 40 45
Figure 6 PV vs data points
to middle shale shakers unit while the adjacent shaker unit received less mud flow. The situation getting worse when running the mud pump with high flowrate because the “Possum belly” fully occupied with mud and failed to handle the flow distribution.
Middle shaker overloaded with cutting with frequent overflow. As an option to minimize the surface losses, the shale shaker unit was bypassed and changed the screen mesh. However, bypassing the unit significantly overloaded the downstream mechanical equipment
Performance of solid control system on yield point (YP)
Figure 7 shows the YP for old design and new design solid control system. While drilling well A with old design solid control system, the YP gradually increased because solid in the drilling mud was not properly discarded and solid still remained in the system after complete circulation. Mud flows that carrying drilled solids from the well travelling on a straight path flow line upon streaming into the “Possum belly”. This result the mud flow and distribution was only concentrated
and changing the mesh to a coarser type eventually lead to poor solid removal. Vibration of mud transfer hose was also main contributor of poor mud properties because desander, desilter and centrifuge unable to achieve the desire separation pressure. The average YP reading throughout drilling operation using old design solid control system was 26.3%. Drilling the Well B with new design mud processing treatment showed that the YP maintained at 21.8% average reading. This brought a 17% of improvement on the YP properties during drilling the section. Reduction of YP within the specification contribute to low pressure loss while the
mud circulation. Replacement of flexibly mud transfer hose from the suction and discharge into desander and desilter with rigid piping significantly reduce the pressure losses due to vibration. Good control of YP reduces the chances of pressure spike that can break the formation and potential of lost in circulation.
35 30 25 20 15 10 5 0
Data Point
Well A Well B
YP
0 5 10 15 20 25 30 35 40 45
Figure 7 YP vs data points
Performance of solid control system on low-gravity solid (LGS)
Figure 7 shows the LGS for old design and new design solid control system. Using the old design solid control system for mud treatment while drilling Well A.
Shale shakers was frequently overflow and bypassed in order to prevent massive surface loss of expensive fluids. This drastically increase the LGS content in the mud system. Furthermore, the desander and desilter were also unable to work at desire pressure because mud transfer hose detached whenever the pressures regulated to optimum working pressure. This situation eventually result more cutting accumulated and plugged the cones. Realized the increase in LGS,
the screens were changed to furnish the excessive overload. However, such option allowed smaller solids particles seeped back into the mud tank. It also known high solid can abrasive and degrade down the drilling equipment through silt size. The smaller the particles the more pronounced the effect on the
mud properties because smaller particles are more difficult to remove or control its effect on the fluid.
Re-circulating of mud that contained drilled solid may gradually deteriorate mud properties. The average LGS reading using old design solid control system was 11.6% and 8.7% while drilling the Well B with new design solid control system. This brought a 25% of improvement on the LGS properties during drilling the section in Well B.
16 14 12 10 8 6 4 2 0
Data Point
LGS (%) Old LGS (%) New
LGS (%)
0 5 10 15 20 25 30 35 40 45
Figure 8 LGS vs Data points
Performance of solid control system on mud weight (MV) and equivalent circulating density (ECD)
Well A was drilled using old design solid control system mud treatment as shown in Figure 9. The section drilled from 760m MDRT to 2163m MDRT and MW gradually increased from 10ppg – 11.6ppg mud to maintain the hydrostatic pressure. Early tabulated data on the top section demonstrated a good ECD trend with no significant pressure spike. As drilling the well deeper in Well A, ECD spike increased up to 12.4ppg at depth 1124m MDRT. One reason of high ECD was because of drilled solids still remain in the well after several circulations due to poor solid removal at surface solid control system. This not only thickening the mud viscosity but also piled up of cutting in the annulus creating tight tolerances between hole and drill string geometries. The mud properties those pumped back to wellbore still contaminated with solid.
Despite managed to resume the drilling operation but the entire progress became slow because more
circulations performed for hole cleaning. Furthermore, the flowrate reduced to minimize the ECD effect. Drill string drag was high because solids accumulated increased the surface contact area between pipe and wellbore. Therefore, several wiper trips to previous casing shoe and performed until the hole confirmed clean. The ROP and drill string rotation also controlled to reduce the impact of high ECD. The average ECD additive factor was 0.6 ppg which equivalent to 4.9
% additional pressure exerted in the wellbore from original MW during mud circulation.
500 700 900 1100 1300 1500 1700 1900 2100 2300
MW & ECD
ECD (Well A) MW (Well A)
Section Depth (MD)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
Figure 9 Section Depth vs MW & ECD (Old Design)
500 700 900 1100 1300 1500 1700 1900 2100 2300
MW & ECD
ECD (Well B) MW (Well B)
Section Depth (MD)
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
Figure 10 Section Depth vs MW & ECD (New Design)
Well B was drilled using a new design of solid control mud treatment system as shown in Figure 10. The section drilled from 750m MDRT to 2200m MDRT. The MW used to drill this section was 10.0ppg to 11.9ppg and gradually increased to maintain the hydrostatic pressure. The tabulated data from downhole acquisition tool shows that there was no severed ECD increase until reaching section TD at 2150m MDRT.
A slight increase of ECD was observed at 1935m MDRT with 12.32ppg to 12.5ppg but the impact was still far below the formation fracture gradient. Good control of mud flow at surface and no shale shaker unit by-pass allowed each of solid control equipment operating in peak performance. The desander and desilter operating pressures regulated at optimum pressure. Increase in ECD occurred because more cutting bed accumulated on the low side of drill string.
Due to gravity effect at deviated hole, heavier cuttings and mud along the lower side of the hole moved at lower rate than the clean mud on the upper side..
The average ECD additive factor was 0.3 ppg which equivalent to 2.9 % additional pressure exerted in the wellbore from original MW during mud circulation.
500 700 900 1100 1300 1500 1700 1900 2100 2300
Instantaneous ROP
ROP (Well A)
ROP (Well B)
Section Depth (MD)
0 20 40 60 80 100
Figure 11 Section Depth vs ROP
Performance of solid control system on rate penetration (ROP)
The ROP tabulation in Figure 11 was seen concentrated at ranges between 40m/hr to 60 m/hr while drilling Well A using old design solid control mud treatment system. The reason of ROP remain within this range was because of the ECD surge close to formation fracture gradient whenever any attempted to push for high ROP, stick slip and downhole vibration.
Poor solid separation at surface by mechanical solid control equipment allowed the recirculating of solid back into the wellbore. This condition contributing to high of drilled solids in the mud system thereby thickening the mud in the wellbore. The shaker screen mesh was changed to accommodate the mud flow characteristic but it was only reducing the potential of shale shaker overflow. In a long term run, it eventually allowed more solids back into the system. The more solids remained in the mud system and recirculated in the annulus, the more differential pressure acting on the formation. This indirectly lead to slower drilling ROP because of Chip down hole effect. Instantaneous
maximum ROP achieved using old design system was 62m/hr with 48.78m/hr on average. Drilling the Well B using new design of mud solid control system, the maximum instantaneous ROP registered at 77m/
hr with 61m/hr in average. This brought a significant improvement to the performance of ROP by 25%. In the standpoint of mud performance, this quantify that good control of mud flow between equipment at surface allowed each of the separation unit work in peak performance. Less drilled solid in the mud system attribute to a better control in mud viscosity.
Performance of old design of solid control system on hole cleaning and drag
The friction factor (FF) in the broomstick plot as shown in Figure 12 used to measure the hole cleaning performance. This tabulation generated to measure the drag force due to contact of drill string with the formation. In a practical viewpoint at rigite, this drag force known as the difference between free rotating weight and the force required to move the string up and down in the hole. Furthermore, it was also a
measure of hole cleaning performance in a particular section. Higher drag force indicates more drilled solid accumulated in the annulus that restricted the string movement. The data of the tabulation was taken from the hookload gauge reading by picking up (P/U) and slacking off (S/O) the drill string prior to continue drilling after the drill pipe connection.
Free rotating weight under this analysis represented by green curve. Drilling the Well A using old design mud treatment system, more solids were not properly separated from the mud because of shale shakers bypassed and changing the screen with coarser mesh.
Solids were eventually increased the mud viscosity and altered the mud properties. Changing the screens made to minimize frequent overflow and overloading.
In this plot, the hook load readings when P/U the drill string tabulated between 0.2FF to 0.3FF. The P/U FF plot was exceeding 0.3FF at depth around 1550m MDRT and 1900m MDRT. The reasons of this condition was due more drilled cuttings bed accumulated in the hole that increased the drill string contact with the wellbore. The parameters including flowrate, ROP and RPM were controlled to prevent high ECD that can lead to loss circulation. Therefore, frequent
0 50 100 150Hook Load lbs200
250 300 350
S/O P/U
0
500
1000
1500
2000
2500
Measure Depth (m)
Actual Slack Off Actual Rotating Slack Off Weight 0.2FF Slack Off Weight 0.3FF Slack Off Weight 0.4FF Slack Off Weight 0.5FF
Actual Pick up No Pump Rotating Weight Pick up Weight 0.2FF Pick up Weight 0.3FF Pick up Weight 0.4FF Pick up Weight 0.5FF
Figure 12 Drill string drag vs Depth (Old Design)
mud circulation for hole cleaning was performed to remove the cuttings from the well which also slow down the operational progress. The S/O weight of the drill string in this chart tabulated between 0.2FF to 0.3FF exceeding the 0.3FF at 1600m MDRT and 1900m MDRT. Accumulated cutting in annulus restricted the drill string to move down. Therefore, extra cumulative axial force was required to free the drill string. Failure to effectively transports the cuttings to surface result in a number of drilling problems including: excessive overpull on trips, high rotary torque, stuck pipe, hole- pack off, excessive ECDs and cutting accumulation.
Performance of new design of solid control system on hole cleaning and drag
Realizing multiples of problems encountered and operation intervened due to poor surface equipment performance at well A as shown in Figure 13. The 12.25 inch section in well B was drilled with new design mud treatment system. Under the new design solid control system, mud distributor tank allowed the mud flows from the distributed evenly at respective
shaker shakers through pipe manifold. Good control mud at shale shaker unit not only reducing the potential of screen overloading or damage but it provides proper mud intake volume into downstream solid control equipment. The desander, desilter and centrifuge were operated at recommended pressure because no significant vibration exerted in the piping for mud transfer. In operation performance point of view, the cutting transport was even better because the flowrate regulated as per recommendation, string rotated at higher RPM to assist for hole cleaning and ECD far below the fracture gradient. The hook load readings during P/U the drill string tabulated just across the 0.2FF. The hole was considerably clean because no excessive tight spots and drill string drag was observed. Furthermore, there was no multiples wiper trip required for hole cleaning as drilled cutting effective transported to surface during drilling operation. The S/O weight of the drill string in this chart tabulated across 0.2FF and significant restriction due to drilled cutting pile up in the annulus. Less axial force was required to move the drill string as there was no severe contact of drilled cuttings with the string.
Hook Load lbs
0 50 100 150 200 250 300 350
S/O P/U
Measure Depth (m)
Actual Slack Off Actual Rotating Slack Off Weight 0.2FF Slack Off Weight 0.3FF Slack Off Weight 0.4FF Slack Off Weight 0.5FF
Actual Pick up No Pump Rotating Weight Pick up Weight 0.2FF Pick up Weight 0.3FF Pick up Weight 0.4FF Pick up Weight 0.5FF
0
500
1000
1500
2000
2500
Figure 13 Drill string drag vs Depth (New Design)
CONCLUSION
A new solid control system was developed with detailed studies on the effect of drilled solids to mud properties and drilling performance. The following conclusion can be drawn from this investigation and as an improvement of the rig solid control system.
1. The installation of mud distributor tank offers flow stability and control of mud return from the well.
This effectively removes the solids from the mud, minimize the tendency of frequent mud flow and screened mesh plugging.
2. Comparing the old design while drilling 12.25-inch hole section, the new design improved the mud properties of PV by 14%, YP by 17% and LGS by 25%.
3. New design improved the ROP by 25% while drilling the 12.25-inch hole section .
4. New design improved average ECD margin by reducing additional pressure exerted using original mud from 4.9% to 2.9% at 12.25 inch. High ECD margin not recommended because it can break the weak formation.
5. The drill string drag effect to the hook load for P/U and S/O on old design were tabulated between 0.2FF to 0.3FF while drilling the section with new design were mostly tabulated at 0.2FF and less.
ACKNOWLEDGMENT
The authors wish to thank UTP for providing the resources and opportunity to conduct this research.
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AUTHORS' INFORMATION
Sonny Irawan is associate professor at Petroleum Engineering Department - Universiti Teknologi PETRONAS. He graduated with BSc. in Petroleum Engineering in 1991 from Universitas Pembangunan Nasional-Yogyakarta, Indonesia. In 1997, he earned his MSc. in Petroleum Engineering from ITB – Bandung, Indonesia and PhD in Petroleum Engineering from Universiti Teknologi Malaysia in 2006. Experienced as a Drilling and Production Engineer in PT. Caltex Pacific Indonesia (Now PT. Chevron Pacific Indonesia). His research interests are in the area of drilling and drilling fluid technology, formation damage, well completion and alternative energy (geothermal, shale gas and coal bed methane). His research efforts with his graduate students have produced more than 70 BSc, 6 PhD and 30 MS theses.
Imros Kinif currently works as a Drilling
& Workover Engineer for Kuwait Oil Company. He has been working in Oil and gas industry (Drilling, Workover &
Completion) for 10 years. Started his career in the oilfield with drilling services in Mud logging company (Geoservices Malaysia), drilling rig contractor (KST Drilling Technologies in Indonesia), drilling downhole tools engineering with Smith International (Schlumberger Malaysia) and drilling engineer (Petrofac). He holds a degree in Mechanical Engineering (UTP-2007), IWCF & IADC Certified and currently pursuing Msc in Petroleum Engineering (UTP). He researches interests are more on drilling optimization and developing tool/
equipment for enhancing drilling performance.
Ridho Bayuaji is Geopolymer and Green Material Researcher in Infrastructure Civil Engine ering D epar tment, Vocational Faculty, Institut Teknologi S e p uluh N o p e mb e r, Sur ab ay a , Indonesia. Bayuaji was born in Probolinggo, East Java on July 10th, 1973. He graduated with Bachelor of Civil Engineering, Institute of Technology Sepuluh Nopember (ITS) Surabaya in 1997; Master of Civil Engineering Gadjah Mada University, Yogyakarta in 2005 and obtained his Ph.D of Civil Engineering Department, University Technology PETRONAS Malaysia in 2010.
Prof Dr Abdul Ghani Md Rafek
Department of Geoscience, Universiti Teknologi PETORNAS, Malaysia Prof Dr Ariffin Samsuri
Faculty of Petroleum & Renewable Energy Engineering, Universiti Teknologi Malaysia, Malaysia Prof Dr S S Gokhale
Department of Aerospace Engineering, Indian Institute of Madras, Chennai, India Assoc Prof Ir Dr Mokhtar Awang
Department of Mechanical Engineering, Universiti Teknologi PETORNAS, Malaysia Assoc Prof Dr Lau Kok Keong
Department of Chemical Engineering, Universiti Teknologi PETORNAS, Malaysia Assoc Prof Dr Mohammed Shakir Nasif
Department of Mechanical Engineering, Universiti Teknologi PETORNAS, Malaysia Dr Ahmed K Hussien
Faculty of Mechanical Engineering, University of Babylon, Iraq Dr Ahmed Mohamed Ahmed Salim
Department of Geoscience, Universiti Teknologi PETORNAS, Malaysia Dr Haslinda Zabiri
Department of Chemical Engineering, Universiti Teknologi PETORNAS, Malaysia Dr Tituss Ntow Ofei
Department of Petroleum Engineering, Universiti Teknologi PETORNAS, Malaysia Dr Tuan Mohammad Yusoff Shah bin Tuan Ya
Department of Mechanical Engineering, Universiti Teknologi PETORNAS, Malaysia Mohd Aslam Yusof
Department of Petroleum Engineering, Universiti Teknologi PETORNAS, Malaysia REVIEWERS