Repeatedly Increased Efficiency and Success Rate From a New Solids-Cleanout Process Using Coiled Tubing: A Review of Recent Achievements From More Than 100 Operations
- Manfred Sach (BJ Services Company) | Jeff Li (BJ Services Company)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- August 2008
- Document Type
- Journal Paper
- 379 - 391
- 2008. Society of Petroleum Engineers
- 2.5.2 Fracturing Materials (Fluids, Proppant), 2.4.3 Sand/Solids Control, 2.2.2 Perforating, 2.4.5 Gravel pack design & evaluation, 5.3.2 Multiphase Flow, 4.1.2 Separation and Treating, 1.7.7 Cuttings Transport, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 2.5.4 Multistage Fracturing, 1.10 Drilling Equipment, 1.6.1 Drilling Operation Management, 3 Production and Well Operations, 4.1.5 Processing Equipment, 1.6 Drilling Operations, 2 Well Completion, 4.3.4 Scale
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Solids cleanouts using coiled tubing (CT) remain a major part of total activity in the CT industry. Because of the multitude of parameters that influence solids transport, it can be very challenging to design and execute solids cleanouts successfully with CT in highly deviated, larger wellbores with 7-in. production tubing, or even larger tubulars, installed.
Numerous papers have been written about the development of wiper-trip cleanout technology and associated engineering design tools, but this paper is focused instead on important practical issues that directly impact the effective implementation of wiper-trip technology in the field. This paper presents the results and lessons learned based on a database that was compiled from more than 100 solids cleanout operations using wiper-trip methodologies. Results will be presented showing how the wiper trip cleanout methodology has improved cleanout efficiency and success rate. Examples are presented showing how the effectiveness of cleanout bottomhole assemblies (BHAs) involving positive-displacement motors (PDMs) and mills has been improved, while simultaneously reducing stress on surface equipment during the operation. Circulation rates higher than specified maximum rates for the PDM are being used without danger of damaging the PDM, while reducing the total volume pumped through the PDM during the cleanout by 80-90%. Larger outer diameter (OD) items in the BHA are kept clean of solids while wiper tripping, reducing the risk of stuck CT and protecting sensitive completion components from undesirable interactions with the PDM/mill BHA. Multiple wiper trips can be performed in one run without the use of drop balls, while having the ability to use selected functions of critical BHA components and full-size drifting of the wellbore for subsequent operations. Field-proven procedures are explained, allowing solids loading in the annulus to be controlled and reduced when necessary, and allowing estimates of solids volumes during the cleanout to be established, on the basis of feedback from the cleanout BHA before any solids have actually reached surface.
It is well known that many CT operations start with a cleanout before being able to conduct other work in the wellbore. A review of all CT operations performed in the Norwegian sector of the North Sea since 2001 shows that 74% of the CT operations involve cleanouts of solids from the wellbore. This is reason enough to concentrate on performing repeatedly successful cleanouts, so that the process is economical and allows subsequent operations in the wellbore to continue as planned.
Solids transport is affected by many variables, and the complexity of the phenomena presents challenges to the field engineer who is trying to determine how the parameters affect solids transport even as one, or more than one, of the variables is changing during an operation. Most of the previous solids-transport studies in the oil industry focused mainly on finding the minimum critical velocity in the wellbore annulus for conventional rotary drilling with mud fluids. The studies lack information related to the prediction of the equilibrium solids-bed height during tripping in, the wiper-trip speed during tripping out, and the prediction of the hole-cleaning time. In field operations, people often use outdated "rules of thumb" (i.e., 2-hole-volume circulation to clean the well, annular fluid velocity two times the solids-settling velocity, or performing cleanout stages of a certain length).
In our previous studies (Li and Walker 2001; Walker and Li 2001, 1991; Li et al. 2002; Li et al. 2005; Li and Wilde 2005), a comprehensive experimental test of solids transport for both the stationary circulation and the wiper trip was conducted. The effect of multiphase flow, rate of penetration (ROP), deviation angle, circulation fluid properties, particle density and size, fluid rheology, pipe eccentricity, wiper-trip speed and nozzle type on solids transport was investigated.
On the basis of comprehensive research (Li and Walker 2001; Walker and Li 2000, 2001; Li et al. 2002; Li et al. 2005; Li and Wilde 2005), an effective solids-cleanout methodology/process using CT (see Fig. 1) has been developed, patented (Walker et al. 2005), and proved by field operations (Engel and Rae 2002; Ovesen et al. 2003; Hobbs and Liles 2002; Gilmore et al. 2005; Nasr-El-Din et al. 2006; Li et al. 2006). The developed solids-cleanout methodology/process includes a specialized downhole cleanout tool and a solids-transport simulator for CT in vertical, deviated, and horizontal well conditions. Empirical formulas are applied to predict surface and downhole pressures, fluid velocities, and solids transport effectiveness. The simulator is a powerful analytical tool that can characterize wellbore hydraulics and solids transport considering downhole conditions, especially when applying the concept of removing solids from wellbores by use of wiper tripping. Its use has resulted in better-designed and -performed cleanouts (Engel and Rae 2002; Ovesen et al. 2003; Hobbs and Liles 2002; Gilmore et al. 2005; Nasr-El-Din et al. 2006; Li et al. 2006).
The specialized downhole cleanout tool offers the option of using downhole-facing, high-energy jetting nozzles or a PDM, in order to ensure sufficient penetration energy required for harder solids depositions. Having penetrated the targeted solids, the specialized downhole cleanout tool allows the fluid pumped during the cleanout to be redirected to uphole-facing, low-energy nozzles, simultaneously stopping the fluid stream through the jetting nozzle or PDM. A surface indication of the specialized-downhole-cleanout tool position is provided for the CT operator.
|File Size||2 MB||Number of Pages||13|
Engel, S.P. and Rae, P. 2002. New Methods for Sand Cleanout inDeviated Wellbores Using Small Diameter Coiled Tubing. Paper SPE 77204presented at IADC/SPE Asia Pacific Drilling Technology, Jakarta, 8-11September. doi: 10.2118/77204-MS
Gilmore, T., Leonard, R., and Steinback, S. 2005. Software, Fluids and Downhole Toolsfor Successful Sand Cleanouts in Any Wellbore Geometry Using Small CoiledTubing. Paper SPE 97080 presented at the SPE Annual Technical Conferenceand Exhibition, Dallas, 9-12 October. doi: 10.2118/97080-MS
Hobbs, D. and Liles, C. 2002. Technique, nozzle enhance coiled tubingwiper-trip efficiency. Oil & Gas Journal 100 (13): 52-56.
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Li, J. and Wilde, G. 2005. Effect of Particle Density and Sizeon Solids Transport and Hole Cleaning with Coiled Tubing. Paper SPE 94187presented at the SPE/ICoTA Coiled Tubing Conference and Exhibition, TheWoodlands, Texas, USA, 12-13 April. doi: 10.2118/94187-MS
Li, J., Bayfield, I., and Paton, G. 2006. Effective Heavy Post-FracturingProppant Cleanout With Coiled Tubing: Experimental Study and Field CasingHistory. Paper SPE 101235 presented at the SPE Annual Technical Conferenceand Exhibition, San Antonio, Texas, USA, 24-27 September. doi:10.2118/101235-MS
Li, J., Walker, S., and Aitken, B. 2002. How to Efficiently Remove Sand FromDeviated Wellbores With a Solids Transport Simulator and a Coiled TubingCleanout Tool. Paper SPE 77527 presented at the SPE Annual TechnicalConference and Exhibition, San Antonio, Texas, USA, 29 September-2 October.doi: 10.2118/77527-MS
Li, J., Wilde, G., and Crabtree, A. 2005. Do Complex Super-Gel Liquids PerformBetter Than Simple Linear Liquids In Hole Cleaning With Coiled Tubing?Paper SPE 94185 presented at the SPE/ICoTA Coiled Tubing Conference andExhibition, TheWoodlands, Texas, USA, 12-13 April. doi: 10.2118/94185-MS
Nasr-El-Din, H.A., Al-Anazi, M.A., Balto, A., Proctor, R., and Saleh, R.M.2006. Challenging WellboreCleanouts with Coiled Tubing Made Easy with Computer Modeling Technology.Paper SPE 100129 presented at the SPE/ICoTA Coiled Tubing Conference andExhibition, The Woodlands, Texas, USA, 4-5 April. doi: 10.2118/100129-MS
Ovesen, M., Sach, M., Laun, L., Gill, G.E., and Juel, H. 2003. Efficient Sand Cleanouts in LargerWellbores Using Coiled Tubing: A New Approach Making an Old Problem Simple.Paper SPE 81727 presented at the SPE/ICoTA Coiled Tubing Conference andExhibition, Houston, Texas, USA, 8-9 April. doi: 10.2118/81727-MS
Walker, S. and Li, J. 2000. Effects of Particle Size, FluidRheology, and Pipe Eccentricity on Cuttings Transport. Paper SPE 60755presented at the SPE/ICoTA Coiled Tubing Roundtable, Houston, Texas, USA, 5-6April. doi: 10.2118/60755-MS
Walker, S. and Li, J. 2001. Coiled-Tubing Wiper Trip HoleCleaning in Highly Deviated Wellbores. Paper SPE 68435 presented at theSPE/ICoTA Coiled Tubing Roundtable, Houston, Texas, USA, 7-8 March. doi:10.2118/68435-MS
Walker, S.A., Li, J., and Wilde, G. 2005. Coiled Tubing Wellbore Cleanout.US Patent No. 6,982,008.