Abstract

Operational execution of Fluid Sampling technologies in the logging-while-drilling (LWD) environment compared with Wireline requires a different set up and allows new operational capabilities for LWD. The objective of this paper is to identify what are the jobs operational risks, in order to select the best LWD technologies and operational approach to identify and mitigate these risks while drilling, resulting in the fastest and cleanest reservoir sample. LWD fluid sampling technology brings three new operational capabilities to this type of service: ability to select pad orientation; drilling fluid flow is required to keep the BHA energized and real time (RT) data telemetry and; capability of operating in HAHZ wellbores without additional risk. To take full advantage of these new capabilities, there must be a full understanding of the relationship between wellbore and formation, analyzing subjects such as filtrate invasion profile, borehole stability, sand production, petrophysics and LWD FE. The ability to choose pad direction, coupled with high end technologies, such as NMR and resistivity images generate important capabilities to be evaluated considering formation quality and borehole condition, allowing the selection, not only of the best depth to sample, considering petrophysical properties, but also the optimum pad direction, considering borehole conditions. Images allow the identification of drilling induced fractures, breakout, faults and thin bed, making it possible for RT interpretation for optimum pad direction, avoiding undesired features. Prior geomechanics study help identify issues that might come up during fluid sampling operation, such as breakout, sand production and borehole failure related to bedding plane. Technologies such as acoustic, NMR and images allow RT evaluation of these issues and the ability to select pad orientation and nonstop drilling fluid flowing may result in correcting these issues. Filtrate invasion profile generates complex geometries with lateral displacements and gravitational segregations. Prior study of invasion profile reservoir and drilling fluid properties, thin bed analysis and reservoir/non-reservoir interface analysis must be considered to achieve optimum operational time. This paper presents a technical and operational approach for LWD fluid sampling operations, regarding FE, geomechanics and fluid invasion profiles, which minimizes operational risk and optimizes sampling time.

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