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.
Well integrity is very important for well operation in oil and gas industry. Advanced technologies and analyses have been developed to ensure well integrity. One of the most important analysis to be done is the evaluation of the cement bond which measures the presence and bonding of cement between casing and the formation in a particular depth or interval. This evaluation is critical for hydraulic isolation to withstand subsequent completion and production operation. Usually, Cement bond evaluation is done from wireline logging, with a tool that transmits acoustic waves and compute the acoustic energy propagating through the casing, the cement and the formation. The amplitude and the attenuation of the returned wave can be correlated with Bond Index (BI), due to the difference in acoustic impedance between casing and cement. Over years, different wireline technologies have been developed and matured for cement bond evaluation. Nowadays, it can be found scenarios where wireline operation is not feasible, such as in highly deviated wells or when a quick turnaround is needed. Acoustic technology in Logging While Drilling (LWD) has been developed to measure the compressional and shear slowness of the formation. These devices are able to transmit acoustic wave at different frequencies and receive them after propagation through a medium, applicable in cased hole condition. This paper presents a case study where the LWD Acoustic technology was successfully used to evaluate the cement bond in a high deviated well in Brazil and the results show the capabilities of the technology to generate a qualitative cement bond data quality. These results were successfully validated using sonic and ultrasonic wireline technologies. This comparison, between LWD acoustic and wireline results, is shown in this paper, including details of the methodology applied to the test, parameters considered and the data processing.
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