Iain Whyte and Brian Coll, M-I Swaco
A North Sea operator was planning to drill an extended-reach well on a platform where hole cleaning problems were expected during drilling, as was loss of circulation in and above the reservoir. Prior successful experience with a ball-activated drilling valve had led this operator to consider application of the M-I Swaco Well Commander valve.
TOOL FUNCTIONALITY
The valve assists in removing cuttings beds in high-angle/horizontal wells during drilling and, when opened, relieves circulating pressure above small-diameter tools in the bottomhole assembly (BHA) and in flow-restrictive equipment such as a mud motor, Fig. 1. After circulating and boosting annular velocities to remove cuttings beds, the tool is closed and drilling is resumed until the next time it is needed.
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Fig. 1. The ball-activated valve eases hole cleaning and other drilling applications.
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Valve applications include enhanced hole cleaning during hole-opening and under-reaming operations; spotting lost-circulation material (LCM) or kill-weight fluid; and conditioning or displacing wellbore fluids at high flowrates. In horizontal, underbalanced and managed pressure drilling applications, the tool allows spotting and removal of kill-weight fluid in the vertical section prior to commencement of the trip or additional drilling.
The valve’s ports can promote jetting of BOP cavities at high flowrates, when appropriately positioned. Finally, the valve can be used as a fill-and-drain sub in any drilling or displacement string to avoid swabbing or surging the open hole.
Restrictive BHAs can limit the flowrate and annular velocity, preventing effective hole cleaning while drilling or displacing wellbore fluids. These same BHAs can also limit the size and concentration of LCM or wellbore strengthening material (WSM) that can be placed in troublesome zones. The valve lets operators perform the necessary operations by providing a large flow-area bypass on demand through as many as seven open-and-close cycles in one trip.
The high flowrates achieved through the tool’s large ports save time and money in spotting effective LCM/WSM treatments or kill-weight fluids and reduce circulating time during displacements. The tool also helps avoid problems such as cuttings beds and pack-offs in extended-reach wells.
The tool allows small-diameter work strings to drain easily during a trip by bypassing restrictive BHA equipment, so a slug can work every time at any angle, thus avoiding drilling fluid spills and promoting a safer work environment. Pills can be spotted and circulation increased exactly where the operator wants, with no impact on the BHA, logging tools or the bit.
The ball-activated circulating valve is placed above sensitive BHA equipment such as MWD and LWD tools, core barrels and mud motors. It provides an alternate circulation path for boosting annular velocities during drilling or completion operations. This is typically done to prevent or remove cuttings-beds buildup, to enhance fluid displacement or to simplify reverse circulation. Placing the tool above other ball-drop tools, such as an under-reamer, can also be highly advantageous.
The valve can also be used to help fill or drain the drillstring during trips, in order to control surge and swab pressures and to enhance tripping operations by minimizing fluid discharge.
The tool can be run into or pulled out of the hole with the ports locked open or closed. The ports remain in the same position until the tool is activated by dropping a ball and pressuring up to shift the circulating port. The tool uses the same size operating ball to open and close the ports, with the capacity of the ball catcher (14 balls, or seven cycles) being the only limit. A smaller BHA-shutoff ball can be dropped to prevent fluid flow or solids deposition at the top of the BHA. This ball is expelled with the subsequent operating ball.
The operating balls and BHA-shutoff balls are collected in a ball-catcher assembly below the tool. This bypass ball catcher captures the balls to one side of the inside diameter to facilitate positioning of other ball-drop tools below it. This allows the smaller activation balls to pass through the valve and the bypass ball catcher.
Unique ball-seat technology allows same-size balls to open and close the tool, eliminating the risk of dropping the wrong size ball. No complicated ball/dart sequence or potentially problematic pump on/off hydraulic sequencing is required to open and close the tool. Additionally, high circulation rates will not cause the tool to function prematurely.
The valve is usually run in the hole in the closed position, and it remains inactive during normal drilling operations. When the need arises to open the circulating ports, an operating ball is dropped and pumped down to the valve. When the operating ball lands on the seat and pressure is applied, the tool is primed open. Increased pressure drives the ball through the ball seat, and a pressure drop is observed. The operating ball is expelled into the ball catcher, and the tool advances to the locked-open position.
With the circulating ports open, the pump rate can then be increased to circulate at higher annular velocities through the open ports. In this open position, there is still a small percentage of fluid circulating around the BHA, keeping it lubricated. In this position, the tool can be used to spot LCM or WSM. If these materials have the potential to damage any of the BHA components, flow to the bit can be isolated by dropping a smaller, differently colored BHA shutoff ball. This smaller-diameter shutoff ball can also be used to stop flow to the bit.
To close the tool and restore all the flow through the BHA again, another operating ball is dropped and pumped down to the ball seat. When the ball lands on this seat and pressure is applied, the tool is primed closed via an indexing system. Increased pressure drives the ball through the ball seat, and a pressure drop is observed. The operating ball and the BHA shutoff ball are both expelled into the ball catcher, and the valve returns to its original, closed position. The pressure is allowed to bleed off before continuing operations.
In managed pressure or underbalanced drilling operations, the tool can be opened to displace kill-weight fluid prior to tripping to simplify the operation. It can remain open while tripping out of the hole to avoid swabbing and permit tripping dry. It can also remain open while tripping into the hole to avoid surging and allow the pipe to readily fill. Once on bottom, an operating ball can be pumped to close the valve and commence operations. The open-and-close cycling can be repeated on a single trip until the maximum capacity of the ball catcher is reached. The ball catcher can be emptied on surface during each trip, and the balls (if still in good condition) can be reused on subsequent trips. The valve can be run on multiple trips before redress is required.
NORTH SEA FIELD EXPERIENCE
On an early application, one operator dropped a total of 28 activation balls over the course of five runs, including activation balls dropped at surface to function test the tool while running in hole. A total of 15 balls were dropped to the primary tool over two runs, and 13 were dropped to the backup tool over three subsequent runs.
Both tools were used principally to fill pipe while running in hole, to drain the string while pulling out of hole or for annulur velocity boosting when required. No major operational problems were recorded, and importantly, all of the shear pressures required to shear the balls through the unique ball seats were within the technical specification set out in the valve’s running procedure.
The valve showed itself to be a reliable and functional tool when utilized in the drilling environment with an average-weight drilling fluid. Almost three days were saved, and drilling fluid expenditures were also reduced significantly. 
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THE AUTHORS
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Iain Whyte is Senior Business Development Manager for M-I Swaco’s Specialized Tools department. He graduated with honors from the University of Glasgow in Scotland. Mr. Whyte began his career in the Middle East with NL Baroid and held management roles in Denmark and the UK before joining Anchor Drilling Fluids. In 1993 he joined Milchem Drilling Fluids in Aberdeen, which later became Baker Hughes Inteq. Mr. Whyte also worked for Tetra Technologies and as Director of Wellbore Productivity and Business Development Manager for SPS International in Aberdeen.
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Brian Coll is Business Development Manager for New Technologies within the M-I Swaco Specialized Tools department. He joined the oil industry in 1996, working as a Downhole Gyroscopic Survey Engineer for Gyrodata UK. Mr. Coll joined SPS International in 2006 prior to the merger with M-I Swaco. Based in Aberdeen, his responsibilities are global and he routinely works in the Americas, Continental Europe, Central Europe, Africa and the Far East.
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