Drilling & Production

Shell and Schlumberger have completed the first successful run of a slimhole rotary steerable system in the Shell Brent Delta field.

Frank Hartley, Houston

Slimhole rotary steerable system

Shell and Schlumberger have completed the first successful run of a slimhole rotary steerable system in the Shell Brent Delta field. The Schlumberger PowerDrive Xtra 4 3/4-in. rotary steerable system drilled 2,377 ft in 43.5 hours with an average rate of penetration of 67 ft/hr during its first field test for Shell Expro in the North Sea. It is the first known rotary steerable system to drill this size of hole section. The test saved 8.42 days, compared to a typical 6 1/8-in. section.

The system includes a steering unit with a Vision telemetry system for transmitting data and a specially designed RS223 PDC bit. The well required 3D steerability to intersect multiple targets. The job was completed in a single run instead.

Reducing trouble time

A new applied drilling technology system has been developed from a variety of downhole and surface sensors and specialized software applications created by Halliburton's Sperry-Sun with technology sharing from Baroid, Security, and GeoMechanics International. The system focuses on reducing drilling trouble time and optimizing drilling practices using critical data interpretation.

The team also has created a system that focuses on three areas of expertise critical to a successful and efficient drilling process - wellbore integrity, hydraulics management, and drillstring integrity. This goal was achieved with a proven philosophy of modeling, measuring, and optimizing by personnel whose expertise enables operators to make better decisions.

By optimizing the drilling process in real time while enhancing rig safety and achieving all well construction objectives, the system improves the overall well construction cycle and reduces costs.

Wellbore instability has historically accounted for a significant percentage of non-productive drilling time. Wellbore integrity is achieved with comprehensive modeling and robust collaborative real-time monitoring of pore pressure and fracture gradients. Wellbore stability parameters are then integrated with a geo-mechanical earth model, incorporating such logging while drilling measurements as sonic, density, and resistivity. Wellbore stability solutions, such as optimal mud weights, casing seats, and wellpaths, are determined using real-time comprehensive 3D effective stress software model that comprehends earth-stress anisotropy.

Hydraulics management is particularly beneficial in deepwater drilling and other situations where there are tight operating pressure windows. It focuses on the need to optimize hole-cleaning and hydraulics forces under static and dynamic drilling operations. The system combines downhole annular and bore pressure measurements from Sperry-Sun's PWD tool with unique surface monitoring techniques and Baroid's DrillAhead forward modeling hydraulics software.

The drillstring integrity portion of the system focuses on the prevention or reduction of destructive downhole mechanical forces. The system utilizes downhole measurements from drillstring dynamics sensor and surface measurements, as well as torsional vibration detection and analysis of vibration modes to identify and adjust for destructive drillstring energies.

Long-term zonal isolation

A new approach to oil- and gas-well cementing that goes beyond maximizing compressive strength, the FlexSTONE slurry can be adapted to match dynamic conditions of pressure, temperature, and formation stress over the life of the well. This cementing technology, developed by Schlumberger Oilfield Services, has been successfully used in Gulf of Mexico and North Sea wells and on projects in Algeria, Canada, Oman, and onshore the United States.

This technology provides both flexibility and expansion of the set cement. Traditionally, compressive strength was the only mechanical property of set cement considered for oil and gas well cement systems, and the degree of zonal isolation could only be monitored during and immediately after logging. By looking beyond the bond log, set cement properties can be matched from drilling, to production, to abandonment, to ensure that problems with zonal isolation are avoided long after the logging truck has left the wellsite.

To maintain zonal isolation over the life of a well, the cement sheath around the casing must be able to adjust to changing wellbore rock properties and predicted temperature and pressure conditions. Zonal isolation is key to eliminating problems with lost production due to crossflow, surface breaching of formation fluids and gases, corrosion of casing, and associated remedial repair efforts.

Nonmineral-based particles in an optimized distribution to produce set cement with variable mechanical properties are used in this technology. Using the stress analysis model software system, the wellbore can be evaluated for future problems of zonal isolation caused by imposed stresses. Set-cement properties of this advanced slurry can be engineered to match formation properties and future well conditions.

Expandable sand screen completion

Halliburton Energy Services recently completed four PoroFlex expandable sand screen completion system jobs in three production wells on opposite sides of the world. The company expanded each planned interval according to completion procedure.

The installations confirmed results seen in the development and test program of the technology. They highlighted four major design benefits of the system:

  • Superior collapse resistance and broader remedial completion options through the use of perforated solid base pipe
  • Saving rig time by faster make-up with threaded connections and flexibility to rotate during installation
  • Highest, long-term sand control reliability provided with the only diffusion-bonded laminate expandable filtration media available and with premium one-piece screen construction
  • Lowering risk by reducing the pipe weight required to expand the screen through the ability to use hydraulic expansion that also allows expansion in wellbores where it is not possible to apply set-down weight at the expansion face.

Two of the installations took place at the Breton Sound block 51 No. 1 well in the Gulf of Mexico for Amerada Hess in cased hole. The others took place in open hole for Repsol YPF Maxus, Southeast Sumatra, offshore Indonesia. The success of the first installation prompted Repsol to schedule another installation.

The design features of the system will aid in a majority of production scenarios, in which collapse resistance, long-term reliability, and the ability to rotate and wash the screen to bottom are critical.

A system for standards and H2S service for 8.5-in. open-hole or cased-hole screens is being developed, including corrosion resistant alloy base pipe.

Low-dosage hydrate inhibitors

A new low-dosage hydrate inhibitor has been developed to help deepwater operations inhibit hydrate plugging, reduce costs, and increase hydrocarbon recovery. In field applications, the low-dosage HI-M-PACT inhibitors by Baker Petrolite have achieved significant total cost savings in production systems designed for conventional methanol treatment.

Hydrates are ice-like crystalline structures that form in deepwater systems through the combination of light hydrocarbons and water under low seabed temperatures and high reservoir pressures. Hydrate plugs have formed as long as 2,000 ft and have blocked pipelines as large as 40 in. in diameter. The cost of remediating hydrate plugging can be extremely high in subsea lines that stretch as long as 60 mi.

Based on anti-agglomerant technology, these low-dosage inhibitors disperse hydrates into the liquid hydrocarbons. Dosage rates are typically 1/40th that of conventional inhibitors. With this anti-agglomerant inhibitor, total costs for existing production systems are expected to be cut by as much as 50%. The savings are expected in the design of new production systems through reduction.

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