Seepage loss remedy
A new lost circulation material (LCM) to help remedy the problem of seepage losses in depleted sands has been designed. It is a resilient, angular, dual-composition carbon-based LCM that allows tightly packed particles, under compression in pores and microfractures, to expand or contract without being dislodged by changes in differential pressure.
Halliburton Energy Services through its Baroid Drilling Fluids product service line developed the Steelseal Fine LCM product. The product has the ability to seal porous and microfractured formations and can help control seepage losses and serve as a bridging agent in depleted sands. With an 80-micron or smaller size, this material can penetrate into microfractured zones effectively.
Halliburton says the material is environmentally safe and easier to mix than traditional LCMs and will not increase or alter rheological properties. Combined with regular LCM, it can help control potentially severe losses and has the flexibility to be effective in synthetic, oil-based, and water-based fluids by using concentrations up to 110 lb/bbl without plugging drilling equipment.
The Spir-o-mizer centralizer is a cementing tool developed by Downhole Products PLC in Aberdeen, Scotland. The centralizer is said to be ideal for use when hole cleaning and cement placement are critical and torque and drag are not major issues. The spiral blade design enhan-ces fluid swirl in the annulus between the well bore and casing. As a result, drill cutting and filter cake removal is enhanced for improved cement bonding. In addition, the 360° cement coverage creates the mechanical seal required to isolate annular fluid and gas migration. The solid cast steel centralizer is manufactured utilizing new, innovative technology adapted from the motor industry.
Another centralizer, Econ-o-lizer, is a positive rigid tool made of solid steel. It was designed to replace the "bow spring" style that has been in use for more than 70 years. It is best suited for use on less demanding exploration and production wells with limited deviation. With "zero running force," significantly faster well bore running times have been recorded staying on the pipe without distorting or breaking up.
A new record in extended reach drilling has been set on the ChevronTexaco-operated Captain field in block 13/22a in the North Sea through the application of Weatherford's roller tool technology and torque and drag modeling.
The roller tools have been used in the difficulties associated with drilling and completing high-angle wells, by reducing friction and extending the reach of the completion to distances of around 16,000 ft. The tools are being used on a series of 16 wells drilled by the semisubmersible drilling rig Sedco 704 from a template in the Captain field. As the reservoir is at a vertical depth of less than 3,000 ft, the horizontal drilling and completion operations are among the most challenging and ambitious undertaken from a template and are at the limits of available technology.
The latest and most challenging of the wells to date was 13/22a-B10y, where previous roller tool experience and front-end engineering gave the asset team confidence that the well targets could be achieved. A 15,000-ft well may not sound especially long, but with a TVD of only 2,800 ft and a horizontal section over 11,000 ft, the engineering difficulties become apparent. At 4.6:1, this is the largest aspect ratio ever achieved from a subsea development and a semisubmersible rig.
The Spir-o-mizer centralizer is a cementing tool.
The sand screens were landed out with 65 Klb remaining above block weight and the possibility remains to extend the reach of the drilling and completion process to new levels within the appropriate geological constraints.
Dynamic modeling is also playing a key role in this well program. Real time information supplied from drilling operations, and historic data from file, is being put into torque and drag modeling software. The analysis provides the knowledge on how best to drill and complete the wells and which tools to use.
Fiber optic well surveillance
The Sensa fiber-optic distributed temperature sensor (DTS) measurement systems in gravel pack wells have been deployed, extending innovative measurement technology to reservoir situations requiring sand control. This Schlumberger system has successfully completed a full stack-up test on the Genesis rig in Sugar Land, Texas. In addition to the standard Sensa deployment hardware, the integrated system consisted of a customized Quantum multiport packer with a downhole wet connect and a lower turnaround sub. Allpac screens were used, with .25-in. capillary tube placed alongside the screens to provide a conduit for the optical fiber sensor. The fiber was installed using a proprietary fiber-pumping technique through the upper completion and into the lower sand control completion via the downhole hydraulic wetconnect.
With its roots in fiber optic technology, the system is a breakthrough in providing real-time distributed measurements along the complete wellbore. The system enables continuous temperature and position measurements over long distances using an optical fiber cable as the sensing element. It can also be applied through a wide range of downhole conditions extending the measurement envelope beyond that associated with more conventional gauges. The chemically inert, corrosion-resistant system can be used safely in hazardous environments and requires no electrical current in the monitored areas. Also, because optical fibers are immune to electromagnetic interference (EMI) radiation, they can be used in intense EMI applications such as power cable monitoring.
Optical fibers employ distributed sensing to measure temperatures, a technique in which one sensor collects data that is spatially distributed over thousands of individual measurement points. In conventional sensing, an individual sensor such as thermocouple or platinum resistance probe is needed for each measurement point. Distributed sensing presents several distinct advantages over conventional sensing in situations that require temperature profiles over long distances or large areas.
Data acquisition is faster and more cost effective because only a single data processor is required. Also, many measurement points are addressed simultaneously by a sensing cable that is rugged, low maintenance, and easy to install, simplifying and facilitating the acquisition of accurate, high-resolution temperature measurements.
The use of optical fibers as the sensing element has been proven in the field as a reliable, cost-effective medium for transmitting temperature data. The system was applied in a novel intelligent completions experiment that also included provisions for sand control. Owned and operated by Team Energy LLC, the test well, located in Posey County, Indiana, was completed using a three-zone gravel pack. The DTS system's optical fiber was installed inside a stainless steel capillary tube attached to the gravel pack screens. The temperature data was acquired with 1-20 minute time integration intervals and corresponding 0.5° and 0.2° C resolutions. The spatial resolution was 1 m.
This system can interface with a variety of monitoring and control systems. In addition to the fiber-optic system, Team Energy's test well included three sophisticated all-electric flow control devices - the only such devices installed outside of one at BP's Wytch Farm field, UK. This field test further proved that deploying fiber-optic temperature acquisition systems in gravel pack wells is now possible, even in more complex completion scenarios.
The systems have also been tested and applied in thermal recovery projects to measure reservoir temperatures and identify steam fronts for monitoring steam injection response, evaluating heavy oil recovery processes and, in some instances, constructing conceptual geological models when integrating acquired data with log data. For comparison purposes, some of the tests also included conventional temperature acquisition procedures. In such tests, the acquired temperature data showed agreement with conventional wireline measurements.