TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractSand cleanouts using Coiled Tubing (CT) have been performed for as long as CT has been in service and still account for a large percentage of applications today. For larger, deviated wellbores, sand cleanouts become increasingly difficult, even with larger sizes of CT. Sand settling to the low side of the wellbore results in the formation of solids beds. In combination with the eccentric annular flow path created with the CT, substantial amounts of sand can easily be left behind. Current approaches to eliminate the solids bed involve using higher flow rates, or exotic and costly fluids, neither of which ensures complete solids removal in every case. These methods also typically spend a great deal of time circulating, after having reached the desired cleanout depth.Using a specially developed cleanout tool and a computer simulator for solids transport provides an opportunity to optimize the operation for the removal of solids to near 100% efficiency, with all fluidizable solids being removed. Simplified operational procedures allow for making a more qualitative decision about the cleanout efficiency. This new, patented process is called "Tornado TM ".In this paper, results from two case histories performed on subsea wells in the Norwegian sector of the North Sea are presented. Both operations were performed from semisubmersible rigs, with one representing the first use of 60.325 mm (2 3/8") CT from a floating platform in the Norwegian sector of the North Sea.The process of removing the majority of sand from the wellbore with only one wiper trip will be explained, as well as a comparison of sand removal predictions from the computer simulator to actual conditions observed.To-date, 3 cleanouts utilizing CT and the Tornado cleanout process have been performed inside 177.8 mm (7") and 244.5 mm (9 5/8") wellbores in the Norwegian sector of the North Sea. No indications of increased CT pickup weights or stuck CT were experienced while following the job program and established best practice guidelines for sand cleanouts. This indicates the Tornado cleanout tool's reverse jetting action and circulating procedure does not increase the risk of stuck CT, while offering the advantages of a slick bottom hole assembly in larger, deviated wellbores. Centralizers are sometimes used to assist the cleanout process by disturbing the velocity profile around the bottom hole assembly. However, they also increase the risk of stuck CT and should be avoided.

Summary 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. Background 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.

Solids-cleanouts using Coiled Tubing (CT) remain a major part of total activity in the CT industry. Due to the multitude of parameters that influence solids-transport, it can be very challenging to design and successfully execute solids- cleanouts with CT in highly deviated, larger wellbores with e.g. 7″ 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 instead focused 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, which 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-bottom hole assemblies (BHA's) 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 of using 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, as well as estimates of solids- volumes during the cleanout to be established, based on feedback from the cleanout BHA before any solids have actually reached surface. Background It is a known fact 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 are changing during an operation. Most of the previous solids- transport studies in the oil industry mainly focused 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's 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 volumes circulation to clean the well, annular fluid velocity two times of the solids-settling velocity or performing cleanout stages of a certain length. In our previous studies1–6, a comprehensive experimental test of solids-transport for both the stationary circulation and the wiper trip was conducted. The effect of multi-phase 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.

No abstract

A newly-developed 3 ½-in. coiled tubing telemetry (CTT) system has been used for the real-time operational optimization of such coiled tubing (CT) applications as milling, cleanout, logging, and perforation, in an offshore multi-well campaign in Norway. The CTT system consists of surface hardware and software, a dual-purpose wire inside the carrying CT, and the multi-function bottom hole assembly (BHA). The wire transmits electrical power from surface to the downhole sensors located in the BHA and the downhole data from these sensors to surface. The BHA, designed in one of three sizes (i.e., 2 ⅛-, 2 ⅞-, and 3 ½-in.), contains a casing collar locator (CCL) and two pressure and temperature transducers that are capable to measure downhole data inside and outside the BHA. One of the main advantages of the CTT system is its versatility. For instance, switching between applications is as simple as only changing a certain part of the BHA. This reduces the need to rig-up and rig-down and leads to operational time and cost savings to operators. Another main advantage stems from its real-time downhole data certainty, as the CT field crew can immediately make decisions based on dynamic downhole events. A few papers have been published recently regarding a similar 2 ⅛ and 2 ⅞-in. CTT systems (SPE-174850, IPTC-18294, SPE-179101, and SPE-183026). In this paper, several case studies are presented for the 3 ½-in. CTT system for the first time. For instance, in the first well, the CTT system helped remove approximately 26,500 lb of scale through a complex wiper trip schedule, effectively preparing the well for re-completion by the main rig. In the second well, the CTT system helped pull all shallow and deep plugs and perforate three intervals in one run. In the third well, the CTT system helped clean out the well, set a plug, and re-perforate it. In addition to successfully performing all these operations, several other benefits resulted due to the real-time downhole data monitoring provided by the CTT system. For instance, the fluid friction reducer (used for reducing the fluid frictional pressure drop) was effectively used at volumes of 70-75% lower than those recommended when the CTT system is not used. Also, all these operations were performed without the need to mobilize most of the wireline and tractor equipment and crew, saving an estimated time per well of six days of wireline logistics and work. The paper briefly describes the 3 ½-in. CTT system and discusses the data acquired during these field operations. The system performance and operational benefits confirmed are presented. These findings outline the versatility of the 3 ½-in. CTT system, the predictability of successful operations resulting from using this system, and the cost and time savings to operators.