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Oil E&P Proof of Concept Project - Low Power Removal Of Well Cuttings
PROJECT OBJECTIVE : Investigate potential low power techniques for cuttings removal during
side-line drilling operations.
There were 3 important points to establish in this research project :
1) Determine the lowest average flushing velocity needed to
reliably transfer cuttings and measure pumping powers at the optimised
condition. This confirms the ability of the wireline power delivery system to provide sufficient continuous power, 2) Run an endurance test to confirm that operating
conditions do not precipitate system blockage, 3) Examine all equipment and
determine the various wear modes caused by operating with intentionally high cuttings
concentrations.
Responsibility for this Proof of Concept project was entrusted to Validata and subsequently all engineering operations were performed in-house.
These included definition of the experimental programme, design of the test
rig, sourcing specialist oil abstraction pumps, rig manufacture,
testing, data analysis and reporting. The design of the experiment was a
complex task; Silica sand was selected as a suitable alternative to well cuttings and necessitated a
study into sand pumping technology in order to specify
suitable fluid test velocities. This data then allowed prediction of rig pumping
pressures and powers requirements.
The rig was a closed loop system that continuously circulated a slurry of water and
sand. The slurry was maintained in a 1500 liter stirred vessel and it’s
composition at pump inlet was controlled by either manual addition or cyclonic
subtraction of a suitable fraction of sand from the vessel. The slurry was
pumped 1200 meters along a series of 5 experimental cuttings transportation
tubes, through a flow visualisation pipe, through a flow meter and back to the
reservoir. The visualisation pipe allowed observation of the sand particles as they
moved in the form of traveling dunes along the pipe floor. The minimum
acceptable mean fluid velocity within each tube was based upon identifying an
acceptable traveling dune structure that didn't cause pipe blockage. During
commercial oil abstraction pumps are expected to cope with a low level of sand
contamination however in these tests the concentration vastly and purposely
exceeded the norm and no pump manufacturer would guarantee their product’s
durability. A thorough selection process identified a “hardened” progressive cavity pump and a “hardened”
multistage centrifugal pump for the testing that would demonstrate their
performance under severely abrasive conditions.
Realistic hardware simulation required the insertion of a smaller diameter cable the
length of each transportation tube. This created an unusual crescent shaped
flow passage and a computational fluid dynamics model was used to predict
pressure drops along the length of each tube.
A LabView based system both controlled the flow rig
and continuously logged pump performance and the flow parameters of each
section of transportation tube. Fluid velocities were monitored by an electro-magnetic
flow meter and tube pressure drops were monitored by a series of differential
pressure transducers. The system accurately monitored both the effect of erosion on
reducing pump efficiency and changes in the resistance to flow caused by the build up of
sand within the tubes.
The project was a complete success. It demonstrated and quantified the low power transportation of a high concentration
cuttings / water slurry. The final project report provided all the data needed to calculate the
power requirements of a production system, it quantified pump efficiencies and
finally identified the wear characteristics of each pump type.
