In any drilling environment, the removal of drill cuttings from the wellbore is critical for avoiding problems such as bit balling, pack-off and stuck pipe. If left unchecked, these problems can lead to formation damage, loss of cir-
culation and nonproductive time, requiring the driller to pull the drillstring and clean out the well before drilling can continue.
The risks and costs associated with inadequate hole cleaning and wellbore instability are only increasing as operators continue drilling more complex boreholes, including extended-reach wells with long laterals, highly deviated wells,
and horizontal and multilateral wells. In deepwater wells, operators are looking to reduce rig time by optimizing their hole cleaning practices and off-bottom circulating time.
Monitoring drill cuttings at the surface is a popular method of determining hole cleaning efficiency and potential borehole stability issues. However, conventional monitoring methodologies are non- automated, imprecise and do not provide
real-time information that the driller requires to perform meaningful quality control and stay ahead of stabil- ity challenges downhole.
The CLEAR hole cleaning and wellbore risk reduction service, monitors hole cleaning effectiveness and wellbore stability, providing real- time data to help the drilling team continually improve drilling performance and reduce NPT. By
comparing measured and theoretical volumes, the service provides early detection of inadequate hole cleaning and of excess returns caused by wellbore instability (caving) or damage
Applications
Extended-reach drilling and highly deviated wells
Horizontal and multilateral wells
Deepwater wells
Benefits
Increase safety by monitoring wellbore stability with drilling practices based on cuttings flowmeter measurements and indicators
Drill faster by ensuring good wellbore cleaning and condition
Reduce NPT and stuck pipe risk by optimizing monitoring, analysis, and hole cleaning recommendations
Optimize pill program and identify best practices for future wells
Features
Digital measurements for improved cuttings evaluation accuracy
Real-time dashboard with a simple, intuitive interface
One-click report generation
Transparency in data delivery
Automatic alarm to signal when operational integrity of the equipment is compromised
Multiple sensors and digital signals
The CLEAR service has a cuttings flowmeter (CFM) and weighing tray, located at the end of each shale shaker, positioned to catch cuttings as they fall off the screen. The tray is locked in position for a fixed interval as determined by
Geoservices and the customer. Cuttings accumulate on the tray and are weighed with strain gauges.
Digital outputs are sent to the acquisition system, which performs the computations. At the end of the adjustable preset period, the tray swings down and discharges the wet cuttings. The tray then returns to a horizontal position for the
next measurement. The pneumatically controlled device is powered by the rig air supply, and the equipment does not obstruct access to the shale shakers.
The CLEAR service is compliant with the European Union’s Atmosphères Explosives (ATEX) directive as well as rated by the European Conformance (CE) and by the International Electrotechnical Commission Explosive Scheme (IECEx).
Real-time data dashboard
The comprehensive, real-time cuttings flow information provided by the CLEAR service is integrated with drilling parameters, cuttings geology, drilling fluid properties, and MLWD data. These results are visually displayed through the
CLEAR service dashboard accessible online whenever and wherever it’s needed—at the rigsite or at remote offices for analysis by well construction engineers. The accessibility and ease-of-use of the dashboard allows the drilling team to
more efficiently assess hole cleaning effectiveness and to minimize wellbore instability risks.
Flexible service delivery
Advanced services are available in addition to the CLEAR service dashboard and CFM equipment, providing next-level analysis through expert-level interpretation and evaluation of hole cleaning, lessons learned, and best practices for
future use. Automated solutions improve data integrity and quality control as well as reduce the workforce required on the rig. With multiple service delivery options, the CLEAR service provides the flexibility to choose which services
and deliverables are most appropriate for the operation.
Mud-effect correction
Because the coating of mud on cuttings can vary considerably, a correction factor called the equivalent dry cuttings ratio (EDCR) is applied to account for this variation. The wet cuttings weight is thus converted into an equivalent
volume of dry cuttings, which can be compared with the theoretical volume of formation drilled at any time.
The CLEAR service measures and records the following data:
cumulative wet weight of cuttings falling from the shakers
cumulative dry weight of cuttings
measured dry cuttings volume
theoretical dry cuttings volume
measured cuttings flow rate (dry flow)
theoretical cuttings flow rate (nominal flow) based on ROP
volume excess or deficit
percentage of cuttings recovery.
Optimizing drilling
The CLEAR service has been successfully deployed in a number of field scenarios. An operator in the Middle East deployed the service as part of an integrated drilling solution aimed at optimizing the drilling of a sidetrack in one run.
This would require reducing the flat time associated with stuck-pipe incidents and wiper trips while maximizing ROP and footage drilled.
Assuring wellbore stability
An operator in Southeast Asia deployed the hole cleaning service with an aim of mitigating anticipated wellbore instability challenges during a three-well extended-reach drilling operation. The operator needed to monitor and optimize its
hole cleaning strategy while drilling 121?4-in. by 131?2-in. sections at 70 degrees with an average departure greater than 1,524 m (5,000 ft).
The information provided by the CLEAR service indicated that the drilling fluid rheology was inefficient at lifting the cuttings to surface. The drilling team used this insight to raise the low-end fluid rheology, thus improving hole
cleaning and avoiding the need for unplanned circulation.
Using the new service, the drilling team was able to enhance its pill strategy. Fewer pills were deployed with no detrimental impact on hole cleaning, which increased the net ROP and decreased the time spent on mud treatment. The size,
frequency and type of pills used also were revised, which ultimately optimized efficiency and control time dedicated for a secondary hole clean- ing. High-viscosity pills were maintained for the larger outer-diameter (OD) slant hole, and
tandem pills were assessed and measured as having optimal performance in smaller ODs.
The solution led to an overall improvement in drilling performance and gave the operator greater confidence to drill faster. The average time spent per stand for circu- lating and pumping pills decreased by 11 minutes com- pared with
previous wellbores. In total, the systematic approach saved the operator 16 hours of rig time and $194,000 in direct costs.
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