Coiled Tubing Window Milling

Hearn, D.D.; Blount, C.G.; Kamlowsky, P. E.

doi:10.2118/35126-ms

Cited by 4 publications

(1 citation statement)

References 4 publications

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“…Cutting force of the bit head tooth surface is about 80% of total cutting force of the window bit. 25,26 Therefore, this article focuses on the cutting mechanical analysis by taking cylindrical cemented carbide teeth on the window bit head as an example.…”

Section: Working Mechanical Model Of the Window Bitmentioning

confidence: 99%

Research on cutting mechanics of window bit cutting teeth

Kong

Zheng

Zhang

et al. 2016

Advances in Mechanical Engineering

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According to structural characteristics of dual-effect strong side-cut window bit (hereinafter referred to as window bit) and the theory of metal cutting and the rule of teeth arrangement of window bit, a cutting mechanical model of window bit cutting teeth is established, window bit geometric equations deduced and the solution of the cutter cutting mechanical model completed; finally, the casing window experiment is conducted with the dual-effect strong side-cut window bit developed to verify the accuracy of the cutting mechanical calculation model and the simulation results. The results show that the variation tendency of the main cutting force of the bit and the experimental data are similar in the windowing process, the simulation results can accurately reflect the change rule of the main cutting force and the requirements of engineering applications are basically met. The research results of this article provide theoretical basis for the analysis and calculation of the cutting force of the window bit and can serve as a reference for the design of deep/ultra-deep well casing window bits and cutting mechanics research.

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Section: Working Mechanical Model Of the Window Bitmentioning

confidence: 99%

Research on cutting mechanics of window bit cutting teeth

Kong

Zheng

Zhang

et al. 2016

Advances in Mechanical Engineering

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Concentric String Windows: Development, Testing and Field Experience

Blount¹,

Gantt²,

Hearn³

et al. 2000

SPE Annual Technical Conference and Exhibition

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Re-entry sidetracking has become an important development tool in the oilfields of the North Slope of Alaska. To date, approximately 220 wells have been sidetracked through existing production tubing in Alaska with coiled tubing. The easier candidates are diminishing in number as this cost effective re-entry technique is more widely applied. Many of the recent candidate wells have required cutting a window through two concentric strings of tubulars. Some of the 2 string windows were performed without significant problems using proven window techniques including whipstock and cement window technology. However, difficulties were experienced when attempting to mill through concentric strings with large differences in size such as 3.5" tubing inside of 9–5/8" Casing. This paper details the design criteria, testing and field implementation of tools and techniques used to mediate the problem encountered in achieving consistent window success for these more challenging dual string windows. Introduction Horizontal sidetracks drilled using Coiled Tubing Drilling (CTD) techniques have become an integral part of the development drilling program on the North Slope of Alaska1,2,3. The primary objective of the CTD re-entry program is to convert noncompetitive, low rate slant hole completions into horizontal completions in order to enhance the production rate and to access additional drainage acreage. To date, over 220 CTD sidetracks have been drilled in Alaska with this system. The CTD sidetrack program began using 3" nominal OD directional drilling equipment ran through existing 4–1/2" and larger production tubing. However, it was estimated that the candidate population could be increased by over 30% if CTD operations through 3.5" tubing were possible4. In an effort to capture this additional market, the 3" BHA was downsized to 2–3/8" nominal OD. At present, more than 35 wells have been CT sidetracked through existing 3–1/2" production tubing using this 2–3/8" system. Windows were cut in most of the wells, either off of cement or from through-tubing whipstocks. These window cutting operations have good success rates with 1st try windows being achieved in approximately 80% of the wells. Recently, several of the candidate wells have required cutting windows through 2 strings of pipe. Initial window cutting work in the dual string wells was performed without significant problems. In these windows, the size difference between the 2 strings of pipe were not large compared to the mill size. However, a significant challenge was presented when one of the candidate wells required cutting through both 3–1/2" tubing and 9–5/8" casing using the 2–3/8" nominal drilling equipment. Results of the expensive failure are detailed in Well A overview below. An aggressive dual string window testing program was started to develop tools and techniques to increase the efficiency of concentric string window cutting. A typical candidate well for a concentric string window is shown in Figure 1. The development program involved full scale testing of new equipment including a low-side window whipstock and numerous window mills. A better understanding of the parameters that lead to a successful window were learned from the full scale testing. This knowledge was successfully applied in a CTD re-entry well to cut a window where previous attempts had all failed. The equipment and techniques are now considered to be standard tools in the concentric string drilling tool box. The knowledge learned from the recent testing also helps in understanding parameters affecting success in all windows.

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Improvements in Coiled-Tubing Window-Milling Operations Cut Costs and Increase Reliability, Prudhoe Bay, Alaska

Hupp¹,

Johnson

Wilson

et al. 2001

All Days

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The original through-tubing window milling procedure was designed to run through 4–1/2" tubing, milling a window in the 7" casing below the tubing tail. The window was milled off a pre-set mechanical whipstock that was set on electric line before the coiled tubing unit was moved over the well. It generally took 2 to 3 mill runs before an effective exit window was obtained in the 7" casing. The goal of the project was to obtain an effective one-trip window exit. The milling assembly had to reduce the torque and work effectively with minimal weight on bit to allow deployment on 1–3/4", 2" and 2–3/8" coiled tubing. By milling the window in one trip versus 2 trips, approximately 12 hrs of rig time could be saved. Introduction Coiled tubing (CT) sidetracks (see Fig. 1) currently account for 50–60% of the total sidetracks constructed on the North Slope of Alaska. Approximately 75% of the CT sidetrack operations are conducted utilizing a mechanical whipstock through 4–1/2" tubing (3.82" ID), exiting through the 7" or 5–1/2" liner. The window milling operation accounts for 10–20% of the time spent on CT drilling operations. Conventional carbide mills used initially were very aggressive, causing numerous drilling motor stalls as the milling process was initiated. Equipment failures (motor rotors, stators and drive shafts) were directly related to the aggressive carbide mills and the effects of sinusoidal buckling. Two-Assembly Window Milling Operations Previous to this project, the 3.80" exit windows were cut in using a process that employed two bottom-hole assemblies (BHA's). Based on the proposed directional drilling plan, the whipstock depth was selected to avoid casing collars, corroded casing and troublesome shale intervals. The mechanical whipstock was set at the predetermined depth using an electric line (0.625" OD, 7-conductor line) logging unit. In high angle wells, coiled tubing was used to deploy the whipstock.After the whipstock was set, the CT unit was moved over the well and the milling operation commenced. Bottom hole assembly #1 was made up to mill the 3.8" OD exit window:3.80" OD Baker Carbide Dimple Mill (See Fig. 2)2–7/8" positive displacement motor (pdm)3–1/8" drill collars or 2–3/8" tubing (60 ft)Circulation sub (ball drop)Disconnect sub (ball drop)Coiled tubing connector or crossover to drill pipe. Seawater with polymer sweeps was used in milling the landing profile and the exit window. BHA #1 was run in the well and milled the profile nipple inner diameter from 3.725" ID to 3.80" ID. (Landing nipples are positioned 30–60 ft below the production packer.) Minimal weight on the mill reduced the risk of backing off tailpipe. (See Fig. 1.) After milling through the landing nipple, the assembly was run in the well to the preset whipstock. The window milling operation started off the mechanical whipstock. Due to the aggressive nature of the carbide mill, starting the window was the most critical part of the milling operation. After numerous motor stalls, milling/drilling proceeded to approximately 6 feet below the casing exit point. The average rate of penetration (ROP) while milling the casing was 1–2 feet/hr. After no further milling progress could be made or after 6 ft of new formation had been drilled, BHA #1 was pulled from the well.

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Coiled Tubing Window Milling

Cited by 4 publications

References 4 publications

Research on cutting mechanics of window bit cutting teeth

Research on cutting mechanics of window bit cutting teeth

Concentric String Windows: Development, Testing and Field Experience

Improvements in Coiled-Tubing Window-Milling Operations Cut Costs and Increase Reliability, Prudhoe Bay, Alaska

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