Riser Volume Control Using Slip Joint Compensation
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Solution Overview
Problem
Conventional drilling systems face challenges in accurately measuring fluid volume in risers due to fluctuations caused by telescopic joints, leading to inaccuracies in flow measurements and difficulties in detecting kicks and losses, especially in harsh weather conditions.
Innovation Solution
A section of the riser with an increased diameter is introduced below the bell nipple, equipped with sensors to measure slip joint position and fluid flow, allowing for continuous volume calculations and accurate fluid level adjustments, using a pump to maintain a stable reference point despite joint movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the outlet pipe diameter is increased to accommodate highest expected flow, then the flow capacity is sufficient, but the measurement accuracy deteriorates when flow is less
Solution Approach 1:
The riser is segmented into two distinct sections: a lower section with standard diameter for high-flow capacity, and an upper enlarged diameter section for accurate measurement. This segmentation allows each section to optimize for its specific function without compromise.
Solution Approach 2:
The riser transitions from uniform diameter to having different diameters in different locations. The upper portion has enlarged diameter specifically where measurement and control functions are needed, while the lower portion maintains standard diameter for flow capacity.
2Adaptability or versatility
If the slip joint is used to accommodate vessel movement, then the adaptability to harsh weather is improved, but the measurement reliability deteriorates due to constant volume changes
Solution Approach 1:
The measurement and control function is extracted from the lower riser section near the slip joint and relocated to the upper enlarged diameter section. This separates the measurement function from the sources of disturbance (slip joint motion, vessel movement).
Solution Approach 2:
The enlarged diameter section acts as an intermediary zone between the lower riser (subject to slip joint motion) and the outlet pipe (where measurement is needed). It provides a stable measurement environment despite disturbances from below.
3Ease of operation
If the riser volume changes due to slip joint extension and retraction, then the ease of operation in moving conditions is improved, but the detection precision of kicks and losses deteriorates
Solution Approach 1:
The system preliminarily compensates for slip joint volume changes by using sensors to detect joint position and calculating the corresponding volume change. This preliminary calculation allows the system to distinguish between volume changes due to joint motion and those due to actual kicks or losses.
Solution Approach 2:
The system implements feedback by continuously monitoring fluid level in the enlarged diameter section, comparing it against expected levels based on slip joint position, and using this information to detect actual kicks or losses. The feedback loop enables real-time correction and accurate detection.
Data Source
AI summary
The invention relates to an arrangement and methods to control volume of fluids in a well system having a riser (7) extending from a well to a rig. The riser (7) has an increased diameter section (1) situated below the upper end of the riser (7) and above any slip joint (12) in the riser. The arrangement further comprises a sensor (5) to continuously measure the position of the slip joint (12). the increased diameter section (1) is coupled to an outlet (19) that is in fluid communication with a fluid return system (18), and the arrangement further comprises a return pump (2) coupled between the outlet (19) and the mud return system (18). The outlet (19) is arranged at a lower level than the mud return system (18). Level sensors (22) measure the level of liquid within the increased diameter section (1).