Industry Article: Improved Understanding of Reservoir Potential through Fluid Composition

A new mapping-while-drilling service gives a full view of the reservoir in real time

Publication: OTC Show Daily
Publication Date: 05/01/2017

Understanding fluid properties at all stages of the life of a reservoir is key to estimating reserves, enhancing completions and achieving production goals. However, these datasets are traditionally available only after performing conventional formation sampling in a laboratory setting. In the ideal scenario, mapping the entire reservoir’s fluid characteristics—as opposed to obtaining individual samples of the reservoir fluids—would address this challenge by giving the ultimate reservoir insight in real time.

Introduced at OTC, the new SpectraSphere fluid mapping-while-drilling service provides critical data about fluid composition in real time. By delivering reliable characterization of fluid properties, the new service enables an improved understanding of the reservoir potential, which is essential for estimating well deliverability and producible reserves, optimizing well placement and completions, designing surface facilities and meeting production goals. The service's capability to deliver these data while drilling in real time contributes to reduction in overall well construction cost.

Improved Understanding of Reservoir Potential through Fluid Composition

By taking high-quality fluid samples and accurate pressure measurements while drilling, the SpectraSphere service enables real-time decisions that help improve geosteering outcomes, guide wells to the ideal trajectory and access more reserves. (Photo courtesy of Schlumberger)

Fluid-mapping service for characterization, production

The SpectraSphere comprises three modules: pretest probe, fluid mapping and sample carrier. The pretest probe module delivers accurate measurements of formation pressure and mobility to determine the best location in the reservoir to analyze the fluid.

Once at the select location in the reservoir, the downhole fluid analyzer—as a part of the fluid mapping module—uses spectrometer data obtained from the visible and near-infrared spectrum. Data are used from fluid composition analysis while drilling. The sample carrier module then acquires up to 12 PVT-grade fluid samples.

In exploration, the new fluid mapping-while-drilling service helps operators gain an early understanding of untapped reservoir potential and reduce exploration costs by acquiring laboratory-quality samples while drilling. In the appraisal and development phase, which can include highly deviated or extended-reach wells, the new service ensures optimal positioning of wells to mitigate wellbore risks, enable better completions, and, ultimately, more production from the field.

The service can be used with the GeoSphere reservoir mapping-while-drilling service to combine structural information with reservoir fluid data, resulting in a true reservoir structural and fluid map. Using deep directional electromagnetic measurements, the GeoSphere service reveals subsurface bedding and fluid contact details more than 30 m (100 ft) from the wellbore.

This combined reservoir-scale view of rock and fluid properties provides a new depth of investigation, enabling operators to optimize landing, maximize reservoir exposure and refine field development plans.

Case study: Gulf of Mexico

In the Gulf of Mexico, the SpectraSphere service was used to acquire and analyze samples in real time and measure formation pressure from the wildcat exploratory Mississippi Canyon well. The service was added to the downhole drilling assembly to collect reservoir representative samples while performing accurate downhole fluid analysis while drilling. Traditionally, sampling happens about a day after drilling, which often results in contamination of the reservoir by the drilling fluid filtrate.

The new service collected and analyzed six samples downhole in real time, setting an industry-first for the transmission of detailed in situ fluid properties. The service estimated contamination and time to clean up, performed fluid identification and typing, and measured the gas-oil ratio and fluid composition (C1 to C5, C6+ and CO2).

These results were verified 10 weeks later by laboratory results, which showed good agreement with field results on every measure. Contamination was estimated in real time to within +/- 2% of the laboratory-determined values. Pretests, pressure measurements and fluid gradients were also successfully taken during the operation. A total of 28 pretests were taken—17 while drilling and 11 while pulling out—that provided the operator a dull description of the reservoir pressure and fluid gradients.

By delivering laboratory-quality results while drilling, it was concluded that the SpectraSphere service is a reliable sampling service capable of gathering clean samples and good measurements while demonstrating a time savings of about 10 weeks.

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