On average, 30% of drilling nonproductive time (NPT) in deviated offshore and onshore wells can be attributed to downhole tool failures related to ferrous and non-ferrous debris generated while drilling.

Although not as critical in vertical wellbores, debris control and containment have reached critical mass with the escalation of deeper wells with complex geometries, typically employing electronic-imbued intelligent BHAs under aggressive drilling parameters. Debris trapped in the circulating fluid can severely damage rotary steerable systems (RSS) and other debris-susceptible BHA components, while metal fragments entrained in the reused drilling fluid compromise the reliability of MWD and LWD measurements. With poorly designed surface ditch magnets and downhole filtering devices, the only recourse seems to be a trip to replace inoperative components.

The increasing costs associated with drilling debris prompted M-I SWACO, a Schlumberger company, to transfer lessons and technologies developed over 25 years of experience in pre-completion wellbore cleaning to the drilling environment. The emerging while-drilling debris management strategy capitalizes on proven technologies, employed individually or together to extract debris from the drilling path. Preventing debris ingress into BHA components, therefore, reduces trips and keeps the bit on bottom longer, while simplifying the mud-to-completion fluid displacement.

Field-proven technologies

A key element of the distinctively seamless approach, the MAGNOGARD* openhole magnet is ideally suited for hard and abrasive rock applications with aggressive drilling parameters. The tool is engineered to rotate and reciprocate in the open hole where it captures broken bit teeth and other metallic debris.

To illustrate, in a Texas horizontal drilling program, iron particles generated while drilling the abrasive formation had compromised the reliability of the RSS and MWD tools. In a subsequent well, the operator incorporated the MAGNOGARD magnet in the BHA where it recovered 33 lbm of ferrous material before it could damage the critical downhole tools.

The MUDGARD workstring filter efficiently captures debris without eroding. (Image courtesy of M-I SWACO)

The complementary MUDGARD* workstring filter is installed directly above the BHA to capture all fluid-borne debris before it can irreparably damage complex BHA components. In comparative analysis, the productive life of the internal filter is shown to be no less than 10 times greater than that of a conventional downhole filter.

The efficiency of the MUDGARD filter was demonstrated in multiple slimhole horizontal wells onshore Argentina where the drilling fluid had become contaminated with various debris, including O-ring and drive belt fragments, drill solids and fibrous material. After the workstring filter was installed, circulation testing showed no impairment of the MWD signal while pumping through the tool, which when pulled recovered 0.965 lbm of debris, enabling the operator to drill to programmed depth in a single run. On subsequent runs, the filter captured 0.21—3.30 lbm of the BHA-damaging debris. After more than 1,500 hours of circulating 13.0 lbm/gal through an individual MUDGARD tool, there was no apparent erosion of the filter screen.

Oftentimes, drilling deviated wells requires operators to boost annular velocities to better promote debris removal. For those applications, the drillstring can be augmented with the newest generation WELL COMMANDER* ball-activated drilling circulation valve. Likewise positioned above the BHA components, the valve when opened creates an alternate flow path to prevent hazards, such as the buildup of cuttings beds during the drilling operation.

The capacity of the technology to evacuate cuttings in complex wellbores was exemplified in its application in the 80-degree inclination of a 12 1/4-in. interval of an offshore Sakhalin Island well, where the operator required a valve that would enable the fluid stream to bypass equipment downhole. Several weighted, high-viscosity sweep pills were pumped through the ports of the drilling circulating valve at high rates to facilitate hole cleaning and debris removal. Once the valve was in service, the operator observed a more than 150% increase in the cuttings volume at surface.

For more information about the drilling debris management solutions, visit the Schlumberger booth 2415 or www.slb.com/debris.

*Mark of M-I SWACO, a Schlumberger company