SPE-175165-MS

Utilization of an Innovative Tool to Improve Hole Cleaning Efficiency inExtended Reach Wells in Saudi Arabia

Mike Okot, Marlio Campos, German Muñoz, and Alawi G. Alalsayednassir, Saudi Aramco; Matt Weber, Frank’sInternational, LLC; Zahid Muneer, Schlumberger

Copyright 2015, Society of Petroleum Engineers

This paper was prepared for presentation at the SPE Kuwait Oil & Gas Show and Conference held in Mishref, Kuwait, 11–14 October 2015.

This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contentsof the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflectany position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the writtenconsent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations maynot be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.

Abstract

Saudi Aramco operates one of the largest offshore oilfield developments in the world. This field is madeup of 41 kilometers of causeway, 3 kilometers of bridges, 27 drilling islands, 13 offshore platforms, and16 onshore drill sites. The magnitude of the field has pushed cutting edge technology and processes to theforefront of the industry. This new development has driven achievements in multilateral and extendedreach directional wells. One challenge the operator faces is to maintain proper hole cleaning in extended8½ in. tangent sections at a 85-87° inclinations, which are drilled in excess of 10,000 ft.

Historically, drilling very long tangent sections required the use of several tandem sweep pills, wipertrips, and reaming/back reaming to maintain hole quality and efficiently remove cuttings bed from thewellbore. The negative effects of poor hole cleaning can lead to tight intervals, increased torque and drag,and eventually stuck pipe.

In an effort to drill efficiently, utilization of a new technology to increase the cutting removal was trialtested on well A1 from an onshore location of the field. The ERD well, A1, was drilled to a total depthof 30,480 ft MD (8,650 ft TVD) into a stratigraphic environment composed of limestone, shale, andsiltstone. The objective of the trial test for the tool was to improve the drilling efficiency. To obtain thebest possible hole cleaning, a simulation was performed by placing the tools every three stands along thetangent section in the 8½ in. hole section.

The goal of the trial test was to achieve the following:

● Enhance hole cleaning by removal of cuttings bed.● Reduce the frequency/number of tandem sweep pills.● Reduce the frequency/number of wiper trips.● Reduce torque and drag and compare it with the offset wells.● Reduce drilling cost.

A service company installed a cuttings flow-meter system at the shakers, which was used to evaluatethe hole cleaning efficiency and performance of the hole cleaning tools. This paper will demonstrate thesystematic methodology, which Saudi Aramco and the service company used to approach the utilizationof the hole cleaning tools to achieve a clean hole in well A1.

IntroductionHole cleaning in directional wells is one of the main limiting factors in today’s extended reach drillingcampaigns. As the industry continues to push the limits of extended reach wells, the much focus is spenton hole cleaning and cuttings removal. Previous studies have focused around critical mud flow rates andquantitative models to predict cuttings transport. A previous paper(1) calculated the rheology factor (RF)and angle factor (AF) and combined them with the mud weight (MW) to form the Transport Index (TI):

The RF can be found from the PV and YP and the AF looks at the effect of the hole angle. At a givenrate of penetration (ROP), increasing this TI will reduce the critical flow rate (CFR) and therefore improvehole cleaning. Advanced hydraulic programs have now become an industry standard to predict andoptimize mud velocities for optimal hole cleaning. This paper is focused on the mechanical agitation ofcuttings so that they may be reintroduced into the section annulus with critical mud flow to improve thetransport through the long horizontal section.

The analysis presented describes the setup, monitoring, and results of Frank’s cutting bed impeller(CBI™) tool performance in well A1, and provides a comparison to the well B1 offset.

Well A1 resumed drilling from a pre-set 95⁄8 in. casing point in December 2013 in the Manifa field. Thewell was drilled from surface to a 30,480 ft measured depth and into a stratigraphic environmentcomposed of limestone, sandstone, and siltstone (Buwaib, Yamama, Upper, and Lower Ratawi forma-tions-represented in Figure 1). The objective was to hold vertical from surface to 1,535 ft, build-up to 85°from 1,535 ft to 11,659 ft and hold a 85-90° inclination to total depth. The section and plan views can beseen in Figure 2 and Figure 3, respectively.

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Figure 1—Stratigraphic Chart

Figure 2—Section View Well A1

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The challenges were to hole clean while drilling the long 8½ in. tangent section from 11,659 ft to24,160 ft to address these challenges, Frank’s recommended the utilization of 47 tools of 5 in. SeriesCBI’s at a frequency of one tool per three stands on the 5 in. drill pipe with 4½ in. IF connections. SeeTable 1 for the full bottom-hole assembly (BHA), Figures 4 and 5 for side forces experienced, and Tables2 and 3 and Figures 6 and 7 for CBI placement information.

End of Run:The 8½ in. tangent section was drilled with 5 bit runs and Schlumberger PowerDrive assemblies. The

interval was drilled smoothly without any hole cleaning issues (no tight hole or stuck pipe). The primaryhole cleaning was achieved during drilling and no secondary hole cleaning was required.

The placement of 47-5 in. Series CBI’s in the drill string provided reduction in torque and drag, reducedthe chances of getting stuck due to pack off and ensured cleaner and more stable hole conditions.

Context

● Saudi Aramco – Saudi Arabia – NBR-115 rig – well A1● 8 ½ in. Section: From 10,828 ft to 24,160 ft● Profile: Tangent section [85-87° inclination]● Driving System: Rotary Steerable System – Schlumberger Xceed 675● Frank’s CBI: 5 in. series

➢ No. of tools used: 47➢ Connection: 4 ½ in. IF➢ Placement at TD: 11,828-23,013 ft

Objectives

● Install Frank’s CBI’s every three stands to enhance hole cleaning and ensure cleaner and morestable hole conditions

Figure 3—Plan View Well A1

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● Reduce frequency of HI Vis pill or wiper trips to save drilling cost● Reduce torque and drag while in drilling and tripping mode

BHA Description

Table 1—BHA Description Well A1

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CBI Placement / InclinationStart of Run:

Table 2—Start of Run

Figure 4—Side Force

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End of Run:

Table 3—End of Run

Figure 5—Side Force

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At a total depth of 24,160 ft, the Frank’s CBIs were covering the 8½ in. OH tangent section from11,828 ft to 23,013 ft MD.

CBI Placement/Well ProfileStart of Run:

Figure 6—Start of Run

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End of Run:

Torque and Drag Analysis

Off Bottom Torque Chart

Figure 8 shows that from 10,828 ft to 14,000 ft, the off-bottom drilling torque progressively increasedfrom 7,000 ft-lb to 10,000 ft-lb with an open hole friction factor of 0.22. From 14,000 ft to 17,000 ft, theoff-bottom drilling torque remained constant at 10,000 ft-lb, and the open hole friction factor droppedfrom 0.22 to 0.14. From 17,000 ft to 19,000 ft, the off-bottom drilling torque increased from 10,000 ft-lbto 13,000 ft-lb, with an open hole friction factor of 0.16. From 19,000 ft to 24,160 ft, the off-bottomdrilling torque slighly increased from 13,000 ft-lb to 14,000 ft-lb, and the open hole friction factor droppedfrom 0.16 to 0.12.

Figure 7—End of Run

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The 47 CBIs installed on the 5 in. drill pipe contributed to the low rotational open hole friction factorexperienced while rotating off-bottom. The open hole friction factor decreased from 0.22 at the beginningof the run to 0.12 at total depth. Non rotating drill pipe protector (NRDPPs) were also installed on the 5in. drill pipe throughout the cased hole, and contributed to the low rotational friction factor encounteredduring this run.

On-bottom Torque ChartFigure 9 shows that from 10,828 ft to 14,400 ft, the on-bottom drilling torque progressively increased from11,000 ft-lb to 14,000 ft-lb, and the open hole friction factor was 0.18. From 14,400 ft to 18,800 ft, theon-bottom drilling torque slightly increased from 14,000 ft-lb to 15,000 ft-lb, and the open hole frictionfactor dropped from 0.18 to 0.12. From 18,800 ft to 19,600 ft, the on-bottom drilling torque increased from15,000 ft-lb to 18,000 ft-lb, and the open hole friction factor increased from 0.12 to 0.16. From 19,600

Figure 8—Off-bottom Torque Chart

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ft to TD, the on-bottom drilling torque slightly increased from 18,000 ft-lb to 19,000 ft-lb, and the openhole friction factor decreased from 0.16 to 0.12.

Utilization of the 47 CBIs showed a great reduction in the rotational friction factors from 0.18 to 0.12while drilling the 8 ½ in. tangent section. A major reduction in the friction factor was also observed inthe last 5,000 ft of the run, when the majority of CBI tools covered the tangent section.

Tripping Load ChartThe 47 CBIs installed on the 5 in. drill pipe showed a substantial reduction in hook load (Figure 10). InTable 4, the last trips (#2 and #3) showed a 27.3% increase of slack-off weight and an 11% decrease ofpickup weight, when compared with the simulated hook load with FF � 0.15/0.20.

Figure 9—On-bottom Torque Chart

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Figure 10—Tripping Chart Load

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Hole Cleaning AnalysisSchlumberger–Geoservices installed a cuttings flowmeter (CFM) at the shaker to evaluate hole cleaningand monitoring the well using their CLEAR service. The CLEAR service monitors hole-cleaningeffectiveness and wellbore stability. The weight of cuttings reaching the surface was continuouslymeasured and analyzed coming off the shale shakers. By comparing measured and theoretical volumes,the service provides early detection of inadequate hole cleaning and excess returns caused by wellboreinstability (caving) and/or formation damage. Figure 11 shows the cumulative cuttings recovery for wellA1.

Table 4—Tripping Chart

Figure 11—Hole Cleaning Chart Showing Recovery % of Cuttings and Dry Volumes

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SummaryA cumulative depth of 13,332 ft was drilled in 8½ in. and a final trip at section TD was smooth onelevators, which indicated an excellent hole cleaning. Table 5 summarizes the hole cleaning status andrecovered volumes as recorded by the cuttings flowmeters.

Figure 12 shows smooth pull out at TD in open hole section, showed efficient hole cleaning and stablewellbore conditions.

Result

● Drilled 13,332 ft in 8½ in. section without any hole cleaning issues and no tight hole or stuck pipeevents were recorded.

● Drilled 5,490 ft and 3,895 ft in one run (POOH for BOP test and tool failures).● Primary hole cleaning was achieved during drilling – no secondary hole cleaning was required.● Excellent hole cleaning efficiency with a CFM recovery of 91.6%.

Table 5—Cuttings

Figure 12—Time Chart Showing the Hook Load and Block Position while Pulling Out in the Open Hole Section

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● All planned short trip/wiper trips were avoided due to optimum hole cleaning, although smoothtripping to the last casing shoe without pump or rotation was performed four times due to toolfailures and BOP test.

● Pill efficiency was monitored and optimized based on CFM data. Only one pill was pumped every4-5 stands drilled instead off every 45 ft or stand drilled.

● With the help of hole cleaning assurance, up to 1,100 ft were drilled without pumping any tandempill.

● Final trip at TD was smooth, which ensured a better hole cleaning and stable wellbore conditionprior to running 7in. liner.

Offset Well Comparison

Well A1 versus Well B1

Using almost the same drilling parameters, a significantly higher ROP and more consistent footage perday as noticed in well A1 due to better hole cleaning as compared to well B1 (Figure 13).

Drilling Parameters and RecoveryWell A1 and Well B1 have similar well profiles and architecture. The 8½ in. sections for both wells werea long slant of 85-88° inclination. Identical drilling practices were utilized for both wells (Table 6). Table7 and Figure 14 show a 91.6% cumulative recovery of well A1 was observed, while a cumulative recoveryof only 82% of well B1 was recorded. An enhancement of 11.7% of cumulative recovery attests to thegreat potential of the CBI tools to improve hole cleaning.

Figure 13—Comparison between Footage per Day and ROP on Well A1 and B1

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Table 6—Drilling Parameters

Table 7—Drilling Parameters - 2

Figure 14—CFM Recovery% as recorded on Well A1 & B1

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Pills Monitoring and OptimizationPills were monitored with the help of CFM data and based on their efficiency the frequency of pills wereoptimized. A major improvement in pills frequency and the total number of pills experienced in well A1,and a reduction of greater than 50% in pills frequency was achieved (Table 8).

Trips/Wiper TripsAll trips in well A1 were due to measurement while drilling (MWD) failure as seen in Table 9. Theprimary hole cleaning was achieved while drilling. No wiper trip or back ream was required due to theexcellent hole condition. In well B1, tight spots and high torque were observed, and several wiper tripswere necessary to clean the hole.

Table 8—Pills Monitoring

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Desired/Undesired PracticesMost effective drilling practices were followed in well A1, and as a result a significant higher performancewas noticed. Primary hole cleaning was achieved while drilling and therefore planned wiper trips wereavoided. Some undesired drilling practices were noticed in well B1 that affected the overall performance.Primary hole cleaning was compromised from the start of section and as a result few wiper trips andsecondary circulations were necessary to avoid hole cleaning issues (Table 10).

Table 9—Trips monitoring

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Well A1 versus Well C1

Tripping Load Comparison Well A1 and well C1 have similar well profiles and architecture. Theslackoff weight of well A1 had a tendency to increase and the pickup weight showed a decreasing trendin the last 5,000 ft of the run, while the slackoff weight of well C1 had a tendency to decrease and thepickup weight showed an increasing trend for the 8½ in. run, as evidenced in Table 15 and 16. Thepositive trend of the drag confirms the CBI’s cleaning effect in well A1.

Table 10—Desired and Undesired Practices

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Figure 15—Tripping Load Comparison of Well A1

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Conclusion

● The 8½ in. tangent section from 10,828 ft to 24,160 ft was drilled successfully with 5 bit runs. Allbits were POOH in excellent and re-runnable condition. The 47 CBIs installed in the drill stringmet and exceeded expectations. The CBIs efficaciously enhanced hole cleaning and ensured acleaner and more stable hole condition while drilling the 8½ in. tangent section of well A1.

● The 8½ in. section was successfully drilled without any hole cleaning issues (no tight hole or stuckpipe events were noticed). Primary hole cleaning was achieved during drilling and no secondaryhole cleaning was required.

● The CFM recovery of 91.6% showed excellent hole cleaning. All short/wiper trips were avoidedbased on hole cleaning assurance. Pills efficiency was also monitored and their frequency wasoptimized. As a result, above 50% of pills volume was saved as compared to drilling plan.

● The hole cleaning comparison between well A1 and well B1 revealed the effectiveness of the CBItools, with an 11.7% improvement of recovery and a 50% decrease of pills frequency; no wipertrip was performed.

● The 47 CBIs showed a substantial reduction in the rotational friction factor while rotatingoff/on-bottom. The open hole friction factor was reduced from 0.22 at the beginning of the run to0.12 at TD.

● The 47 CBIs showed a significant reduction in hook load. The last trips (#2 and #3) showed a27.3% increase of slack-off weight and an 11% decrease of pickup weight compared with thesimulated hook load with FF � 0.15/0.20.

● For well A1, the slackoff weight had a tendency to increase and the pickup weight had a decreasingtrend in the last 5,000 ft of the run. Alternatively, the slackoff weight of well C1 had a tendency

Figure 16—Tripping Load Comparison of Well C1

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to decrease and the pickup weight showed an increasing trend for the entire 8½ in. run. Thepositive trend of the drag confirmed the CBI’s cleaning effect in well A1.

Nomenclature

ERD Extended Reach DrillingMD Measured DepthTVD Total Vertical DepthCBI™ Cutting Bed ImpellerTI Transport IndexRF Rheology FactorsAF Angle FactorsMW Mud WeightCFR Critical Flow RateTD Target DepthHI Vis High ViscosityOH Open HoleBHA Bottom-hole AssemblyDP Drill PipeHWDP Heavy Weight Drill PipeCHFF Cased Hole Friction FactorOHFF Open Hole Friction FactorNRDPP Non-Rotating Drill Pipe ProtectorsCFM Cuttings FlowmeterPOOH Pull Out of HoleBOP Blowout PreventerROP Rate of PenetrationRPM Revolutions Per MinuteHC Hole Cleaning

AcknowledgmentsWe would like to thank the management of Saudi Aramco for the permission to publish this work. Thanksare also due to all the operations personnel of Saudi Aramco, Frank’s International, and Schlumbergerwho have provided considerable support throughout this work.

References:1. Luo, Y., Bern, P.A., Chambers, B.D., Kellingray, D.S.: �Simple Charts to Determine Hole

Cleaning Requirements in Deviated Wells,� paper IADC/SPE 27486, presented at the 1994IADC/SPE Drilling Conference, Dallas, Texas, February 15-18, 1994.

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