(Photo: The EcoScope multifunction LWD service provides a full suite of measurements for productive drilling to put wells in the best place in less time.)
Schlumberger has been providing services to oil and gas companies offshore Newfoundland for over a decade. These services fall into three main groups: directional drilling (DD) for steering the drill bit through the rocks to the hydrocarbon reservoir, logging-while-drilling (LWD) for measuring properties of the reservoir quality and measurements-while-drilling (MWD) which provides a means to communicate with the DD and LWD equipment downhole.
In the 15 years since the first Hibernia gravity-based structure (GBS) well was drilled. Schlumberger drilling solutions extended the life of many projects, specifically because we penetrated deeper parts of the reservoir than initially planned.
In 2008, the latest generation of LWD technology, the EcoScope* multifunction logging-while-drilling service, was introduced into offshore Newfoundland.
The EcoScope service incorporates decades of Schlumberger experience in providing quality measurements for productive drilling. The EcoScope service integrates a full suite of formation evaluation, well placement, and drilling optimization measurements in a single collar to increase operational efficiency, reduce risk and increase confidence in data interpretation, and calculations of production and reserves. Designed around a pulsed neutron generator (PNG), the service uses technology developed by Schlumberger, Japan Oil, and the Gas and Metals National Corporation. In addition to the suite of resistivity, neutron porosity, and azimuthal gamma ray and density measurements, this service provides the only commercial LWD measurements of elemental capture spectroscopy and sigma. Drilling optimization measurements include annular pressure-whiledrilling (APWD), caliper and shock.
T he PNG used in the EcoScope service allows the generation of neutrons on demand. This design eliminates the need for an americium beryllium (AmBe) chemical source, substantially reducing risk during transportation and at the wellsite.
The EcoScope service integrates multiple LWD sensors in a single collar. This compact design reduces the amount of rathole that must be drilled to provide comprehensive formation evaluation measurements. Because there is only one collar, fl at time associated with making up and breaking down the BHA is reduced. Having fewer connections also enhances BHA reliability. The EcoScope service’s large memory capacity allows recording of the industry standard 6.5 data points/m at drilling speeds of up to 135 m/hr.
The service provides more downhole information from a single collar than any other LWD service. Dedicated internal diagnostic electronics record information used for EcoScope preventive maintenance, which can significantly extend drilling length between failures and reduce non-productive time on the rig.
In 2011, Schlumberger provided, for the fi rst time ever, the EcoScope spectroscopy service in offshore Newfoundland. The PNG generates more neutrons, with much higher energies, than a traditional AmBe chemical source. This provides deeper, more precise measurements and also enables the EcoScope service to acquire industry-first nuclear spectroscopy, density, and sigma measurements in addition to the formation evaluation suite of measurements. These nuclear measurements—made close to the bit— further reduce the uncertainty in data interpretation.
The spectroscopy measurement provides dry-weight elements, lithology and matrix properties. The first step involves spectral deconvolution of the composite gamma ray energy spectrum by using a set of elemental standards to produce relative elemental yields. The relative yields are then converted to dry-weight elemental concentration logs for the elements Si, Fe, Ca, S, Ti, and Gd using an oxides closure method. Matrix properties and quantitative dryweight lithologies are then calculated from the dry-weight elemental fractions using the SpectroLith* lithology processing of spectra from neutroninduced gamma ray spectroscopy tools empirical relationships derived from an extensive core chemistry and mineralogy database.
The ability to provide consistent nuclear MWD, exclusive of chemical sources, with no compromise on quality, historical comparability or workflow compatibility will be valuable to the offshore Newfoundland industry. Replacing the chemical neutron source with the PNG results in an 85% reduction in immediate surface exposure risk and a nearly 100% reduction in long-term contamination risk downhole. EcoScope empowers users to obtain the critical density and porosity measurements, in the form and quality they are used to, while taking advantage of technical innovations that makes the rig site safer and poses less environmental risk.
As the oil and gas industry matures in Newfoundland and Labrador, the requirements that operators have for the cutting-edge DD and LWD services is ever increasing, and Schlumberger looks forward to providing the very best technology available for many years to come.
For additional information, visit www.slb.com/ecoscope.
Japan Oil, Gas and Metals National Corporation (JOGMEC), formerly Japan National Oil Corporation (JNOC), and Schlumberger collaborated on a research project to develop LWD technology that reduces the need for traditional chemical sources. Designed around the pulsed neutron generator (PNG), EcoScope service uses technology that resulted from this collaboration. The PNG and the comprehensive suite of measurements in a single collar are key components of the EcoScope service that deliver gamechanging LWD technology.
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