Advanced Drilling Engineering collaboration, teamwork and innovation between ConocoPhillips and contractors has produced a step-change in drilling performance on a number of our wells in the UK sector of the North Sea.

Coiled Tubing Underbalanced Drilling

A well on ConocoPhillips’ Vulcan field was drilled, tested and completed in the Rotliegendes reservoir in an underbalanced condition using coiled tubing. This technique showed improved deliverability from the poorer quality sands, indicating significant potential for the use of underbalanced drilling in future low permeability gas reservoirs. 

Extended Reach Drilling

With a total length of 7 kilometres and targeting a reservoir at a 5 kilometre step-out from the existing platform, one of the wells on ConocoPhillips’ Boulton field is pushing the limits of extended reach drilling in the Southern North Sea. The field’s proven casing and completion design that is standard in Carboniferous wells is also being challenged to alleviate rig and logistical issues resulting from such a long well.

Drilling Riser System

A unique 24-inch by 19-inch, 10,000 psi working pressure drilling riser system, designed to withstand 100 year North Sea storm environments is currently being developed and will shortly be used by ConocoPhillips in the Central North Sea. This system will allow the drilling and completion of conventional subsea wells from a jack-up drilling rig using regular surface blow out preventers (BOPs).

Geobaric Thermal Volume Analysis (GTVA)

GTVA is being deployed at MacCulloch using gas logs, drilling parameters, and log analysis to estimate formation pressure. With this advanced mud logging technology, real-time mud weight adjustments and optimisation is possible. For known fields, it also eliminates the need to run formation pressure test tools in the well. 

GeoSteering

A new innovative geosteering tool was used to drill the reservoir section of the BritSats Callanish well, which allowed the wellpath to be optimised to avoid encroaching shale beds. This tool had only once previously been run in the North Sea and had never before been used by ConocoPhillips. The use resulted in a horizontal reservoir section being drilled, with in excess of 4,000 feet of clean sand. Sand screens were subsequently run over the area with no issues. 

HP/HT Drilling

Special drilling tools have been built to support ConocoPhillips work at Jasmine in high pressure/high temperature (HP/HT) conditions. The temperature here is too high for standard drilling tools and it pushes modified tools near their design limit. Modified tools are temperature qualified, which allows them to be used in elevated temperatures. However, drilling friction in HP/HT causes operating temperatures to encroach pre-established limits. This means that circulation is needed to cool the tools to working range when drilling and continual monitoring of the tool temperature is needed. This can be a costly delay in the current North Sea drilling market. The new Solar suite of instruments continually operate without the need for cooling and circulation, allowing ConocoPhillips to realise full value from this new technology.

Managed Pressure Drilling (MPD)

This system is being used on one of ConocoPhillips’ Jade wells in the Central North Sea to provide an enhanced mud weight window between the pore pressure and fracture gradient. MPD reduces the risk of mud losses into the depleted reservoir zones. Pressure generated by fluid friction in the annulus is lot when mud pumps are shut down. The MPD system is activated during drill pipe connections to replace this pressure and maintain a constant pressure in the drill bit. The system works by creating a flow path across the surface of the well. Choking the flow provides a surface back-pressure, which ensures the well maintains a constant bottom-hole pressure greater than the pore pressure of the well. 

Motor Driven Rotary Steerable System

Rhea was the first well in the Southern North Sea area to use this technology. The system drilled the Zechstein sequence and achieved a significant increase in rate of penetration (ROP) compared to offset wells through the salts and anhydrite rafts. It was also the first well in this area to use a logging while drilling (LWD) formation pressure tester, which identified depleted sandstone within the 8.5-inch reservoir section requiring remedial action prior to completing the well.

The Finlaggan and the associated Enochdhu wells form a pair of deviated exploration wells in the Britannia Satellites area. They were drilled in an 8-1/2 inch hole from the same casing using a specially-designed motor and rotary steerable system to unlock drilling efficiency and allow use of more aggressive bit designs. It was the first time this technology was used in the North Sea and for ConocoPhillips worldwide. In this instance it significantly reduced shock and vibrations resulting in smoother, more efficient drilling.
 

Multi-Lateral Drilling

ConocoPhillips’ Hyperion well was the first multi-lateral well to be drilled in the Southern North Sea. It successfully drilled two legs, achieving two of the longest 6-inch horizontal sections ever drilled in this area. 

Quadrupole Mode Sonic Tool (QBAT)

This tool is being used to evaluate 4-D seismic and future well placements at MacCulloch. Based on offset wells, it is possible that the shear slowness will be greater than 400 usec/ft, which is at the limit for slow shear measurement with a conventional BAT (pseudo-dipole) tool. MacCulloch’s Sele Formation has an unusually slow shear and to date this data has not been captured in any of its wells. QBAT will now permit this measurement.