TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractBauxite ceramics are a high strength proppant, which is often used for fracturing stimulation in deep and hot wells. Due to its higher specific gravity (3.5 -3.6), it is very challenging to design and execute the post-fracturing proppant cleanout with coiled tubing (CT) successfully in the highly deviated large wellbore.In a sand cleanout with CT the solids are moved by two modes of transport: circulation and wiper trip, in which the localized fluidization is caused by jet turbulence. The jetting turbulence is produced by the down hole wash tool, and as the CT is pulled from the hole it fluidizes and propels the solids in the direction of the wellhead. Some of these solids may stay in suspension and be circulated out of the well depending on the flow velocities, hole geometry and fluid choice. The remainder will tend to fall out of the flow channel downstream from the wash tool. These solids will be continually refluidised by the movement of the wash tool. The speed with which the wash tool can be pulled out of the hole is a complex function of the choice of fluid, flow velocities, hole geometry, hole deviation and the physical properties of the particles. When conditions result in complete removal of the solids, the corresponding maximum value of the CT speed is defined as the optimum wiper trip speed.In this study, the solids transport test results with bauxite in a full scale flow loop are summarized and four case histories performed on both subsea and land wells are presented. The engineering, implementation and challenge of CT post-fracturing sand cleanout for each individual field case are discussed. The paper also describes how to use a customized down hole switchable wash nozzle and a sophisticated solids transport computer modeling software to optimize the post-fracturing sand cleanout process with 100 % removal efficiency.
It is acknowledged that in many reservoirs, perforating in under-balanced conditions can bring significant and obvious production benefits. Under-balanced perforating in vertical or "near" vertical wells may be performed with wire-line, whilst perforating in highly deviated or horizontal wells through the completion tubing normally requires intervention with either a wire-line tractor, hydraulic work-over unit unit, or Coiled Tubing. Consideration of all parameters surrounding the choice of what method should be used to transport the guns into long reach horizontal wells will quite often direct the operator to choose Coiled Tubing as the optimum conveyance tool. Achieving true under-balanced perforation of a long reservoir section(s) utilising coiled tubing in an offshore environment presents a collection of technical, logistical and financial challenges. Three North Sea case histories of such operations are illustrated. These examples demonstrate how gun lengths of over 2,800 ft and 24,500 lb in weight can be deployed to a measured depth of 17,800 ft through a challenging well profile. Particular attention is paid to equipment challenges and selection, the use of friction reducers and techniques employed to maximise the operating window, hence achieving the operator's desired results and realise the benefits associated with under-balanced perforating. Introduction With the advancement of smart completion design and wire-line tractors the necessity to perforate using coiled tubing seems to have declined. However, there are still occasions when reservoir characteristics, interval length or economics deem that the alternatives are either less practical or not possible. Highly deviated or horizontal wells requiring under-balanced perforating, the inclusion of a cemented liner in completion design for subsequent isolation work, or a significant perforation interval will invariably require coiled tubing conveyance. Illustrated are three examples where coiled tubing perforating has been successfully performed for Talisman Energy (U.K.) Limited within the U.K. sector of the North Sea from the Clyde and Tartan platforms. Operators Perspective Clyde development well A35/01 is a long horizontal well. Two methods of perforating were considered for the projected 2,000 ft interval. The perforating strategy of ‘shoot and pull’ prior to running the completion, versus under-balanced coiled tubing perforating through the completion in a single run was evaluated. Significantly, the operator had previous experience of both methods and was aware of key issues such as initial production rates, associated time, cost and logistical implications. A significant factor in determining the perforating methodology was that access to the reservoir interval was required during the life of the well for production logging, water shut off operations, etc. This precluded the option of leaving the guns in the well.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractBauxite ceramics are a high strength proppant, which is often used for fracturing stimulation in deep and hot wells. Due to its higher specific gravity (3.5 -3.6), it is very challenging to design and execute the post-fracturing proppant cleanout with coiled tubing (CT) successfully in the highly deviated large wellbore.In a sand cleanout with CT the solids are moved by two modes of transport: circulation and wiper trip, in which the localized fluidization is caused by jet turbulence. The jetting turbulence is produced by the down hole wash tool, and as the CT is pulled from the hole it fluidizes and propels the solids in the direction of the wellhead. Some of these solids may stay in suspension and be circulated out of the well depending on the flow velocities, hole geometry and fluid choice. The remainder will tend to fall out of the flow channel downstream from the wash tool. These solids will be continually refluidised by the movement of the wash tool. The speed with which the wash tool can be pulled out of the hole is a complex function of the choice of fluid, flow velocities, hole geometry, hole deviation and the physical properties of the particles. When conditions result in complete removal of the solids, the corresponding maximum value of the CT speed is defined as the optimum wiper trip speed.In this study, the solids transport test results with bauxite in a full scale flow loop are summarized and four case histories performed on both subsea and land wells are presented. The engineering, implementation and challenge of CT post-fracturing sand cleanout for each individual field case are discussed. The paper also describes how to use a customized down hole switchable wash nozzle and a sophisticated solids transport computer modeling software to optimize the post-fracturing sand cleanout process with 100 % removal efficiency.
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