Multiple Advanced Logging-While-Drilling Technologies Optimized for Drilling and Well Placement

Gravem, Trond; Thorsen, Arve K.; Helgesen, Tron Bjelland; Waldron, Glen; Lofts, Jeremy

doi:10.4043/18037-ms

Cited by 2 publications

(1 citation statement)

References 5 publications

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“…By design, the BHA configuration on the A-8 exploration well was able to deliver functionality throughout the sequence of operations from the beginning of the borehole section to the end. Typically, the BHA must drill out cement, drill ahead, under-ream, deliver a smooth and gauge borehole, provide vital directional measurements, and provide essential formation evaluation to facilitate decision making while drilling [Gravem 2006]. In extended reach wells, tripping in and out leads to a variety of potential problems, including borehole cleaning and borehole stability.…”

Section: Bha Designmentioning

confidence: 99%

Combining Seismic Models with Realtime LWD Measurements to Reduce Geologic Uncertainty: A Case Study of the Mars A-8 Extended Reach Well

et al. 2010

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In January of 2008, Shell began drilling an extended reach exploration well from the Mars tension leg platform (TLP). This was an ambitious undertaking with targets nearly 20,000 ft (6,096 m) away in an unexplored fault block. Because of the high inclination of the borehole and the shallow depth of the objective sands, any geological uncertainty in the targets jeopardized the success of the project.While surface seismic is used to evaluate potential targets, it lacks the resolution needed to reliably place those targets. Different seismic processing techniques are available, but the validation of each model requires additional information. True vertical depth (TVD) and true vertical thickness (TVT) synthetic ties created from realtime logging data can improve that resolution. By employing a method that uses TVT, the synthetic ties better match the seismic model allowing for updates to the well path and precise placement inside the target. Multiple velocity models are also incorporated to obtain better time-to-depth relationships and to better predict pore pressure anomalies.In extended reach wells, small issues in the beginning can escalate into more serious problems at total depth. The well path, dogleg severity, and casing shoe placements must be optimized, leaving room for the possibility of changes due to unexpected events. Bottom hole assembly (BHA) design is also a key success factor. Acquiring the needed information in realtime to update the seismic model, while also factoring in tool reliability and planning for shoe-to-shoe performance, is critical. Further, at these high angles, it is important to drill a smooth and continuous borehole to reduce torque and allow for better casing runs. This paper describes how the geological, mechanical, and economical uncertainties were identified and minimized through well planning and the use of realtime data. Specifically, this paper addresses those uncertainties, associated risks, and the methods to minimize them in the A-8 well.The authors examine the pre-well work undertaken with the seismic data and how the BHA and well plan were designed to allow for possible changes. In addition, they will discuss how all the data were used to continually update the model and reduce geologic uncertainty as the targets were approached. Answers were provided in time to update the well path, increasing the chances for success, and ultimately meeting the well objectives.

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Section: Bha Designmentioning

confidence: 99%

Combining Seismic Models with Realtime LWD Measurements to Reduce Geologic Uncertainty: A Case Study of the Mars A-8 Extended Reach Well

et al. 2010

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Challenges in Identifying and Quantifying Hydrocarbons in Thinly Bedded, Laminated, and Low-Resistivity Pay Zones

Okowi

Ishola

Onuoha³

et al. 2014

All Days

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Borehole images acquired in low-resistivity formations can help in the analysis of structural dip, fracture systems, depositional environments, borehole stability, and net-pay identification in thinly bedded sequences.Net-sand analysis from these resistivity borehole images-in conjunction with results from a multicomponent induction logging service-helps to determine an accurate net-pay, even in thinly bedded intervals.Laminated formations frequently exhibit electrical anisotropy where resistivity measured perpendicular to the bedding (Rv) is significantly higher than resistivity measured parallel to the bedding (Rh). This occurs when high-resistivity sand layers are interspersed with low-resistivity shale layers.Analysis based on conventional resistivity tools will often bypass pay zones in thinly bedded sand-shale sequences. Average resistivity over these tools' vertical resolution can be misleadingly low and computed water saturation pessimistically high. This is a major cause of "low-resistivity pay" in thinly bedded laminated formations.The multicomponent induction logging service is designed to efficiently and economically identify and quantify hydrocarbons in laminated, low-resistivity pay zones. It enables the determination of Rh and Rv. These resistivity measurements, when utilized with the laminated sand-shale analysis and stable tensor petrophysical model, enable the determination of the true formation resistivities and water saturations, and thus lead to accurate identification, and quantification of hydrocarbons-in-place (OIP).In the Niger Delta where a comparison was made between the Water Saturation computed from Conventional and Multi-Component Resistivity, there was a 30% reduction in the computed Water Saturation, which gave a substantial increase in the computed OIP.

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Multiple Advanced Logging-While-Drilling Technologies Optimized for Drilling and Well Placement

Cited by 2 publications

References 5 publications

Combining Seismic Models with Realtime LWD Measurements to Reduce Geologic Uncertainty: A Case Study of the Mars A-8 Extended Reach Well

Combining Seismic Models with Realtime LWD Measurements to Reduce Geologic Uncertainty: A Case Study of the Mars A-8 Extended Reach Well

Challenges in Identifying and Quantifying Hydrocarbons in Thinly Bedded, Laminated, and Low-Resistivity Pay Zones

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