Sourceless Porosity-Density and Geomechanics with Logging-While-Drilling Tools in Carbonate Sequences

Chen, Chao; El-Aziz, Sabry Abd; Abdulkarim, Anar; Aki, Ahmet

doi:10.2118/185978-ms

Cited by 5 publications

References 2 publications

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An Integrated Approach for Comprehensive Formation Evaluation in Mixed Lithologies using Source-Less Logging While Drilling and Advanced Cutting Analysis: A Case History

Taher

Aki

Zeriek

2017

Day 4 Thu, November 16, 2017

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Accurate formation evaluation relies heavily on the quantification of rock matrix constituents. Rock mineralogy identification is commonly based on wireline spectroscopy measurements. Logging while drilling (LWD) techniques traditionally rely on density and neutron data to derive lithology. Historically, density and neutron tools that contain radioactive chemical sources were also the primary sensors used to determine porosity within the reservoir, which is a fundamental petrophysical attribute necessary to accurately quantify reserves. Although the potential irradiation and contamination risks associated with radioactive sources have always been known, the industry is now focusing toward reducing or eliminating their use, where possible. The alternative source-less sensors for density and neutron tools, such as acoustic and nuclear magnetic resonance (NMR) measurements, were commonly used for porosity calculations. However, calculated porosities from acoustic measurements could contain significant errors arising from the uncertainty associated with the mineralogical composition. In addition, NMR porosity values can contain errors as a result of the effect of density and the hydrogen index of the hydrocarbons in place. Advanced cutting analysis (ACA), either by X-ray fluorescence (XRF) and/or X-ray diffraction (XRD), provides an independent lithology from downhole tools. The lithology, matrix density, and slownesses computed from the minerals or directly measured by the XRD can, in turn, be used as input data for porosity calculations from sonic and/or NMR data. This helps to provide more accurate porosity measurements, as compared to the traditional calculated porosities, without using density and neutron tools. In addition, scanning electron microscopy (SEM) helps to enable the use of wellsite mineralogy, porosity, grain size distribution, and grain density from cuttings to calibrate the measurements from LWD acoustic and NMR tools. This paper presents a comprehensive, cost effective method for multimineral formation evaluation using a combination of LWD and advanced mud logging, without the use of radioactive sources. A practical workflow with limitations is also presented.

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An Integrated Approach for Comprehensive Formation Evaluation in Mixed Lithologies using Source-Less Logging While Drilling and Advanced Cutting Analysis: A Case History

Taher

Aki

Zeriek

2017

Day 4 Thu, November 16, 2017

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Application of Sourceless Solutions for Geosteering and Formation Evaluation with Logging While Drilling Technologies: Case Study from Kuwait Reservoir

Padhy

Gezeery

Rashidi

et al. 2019

Day 2 Wed, April 24, 2019

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An emerging technology called sourceless well placement and logging (without using traditional chemical radioactive sources) has intensified in recent years because of various factors, such as drilling risk reduction and cost optimization, as well as evolving government regulatory and health, safety, and environment (HSE) requirements. Established technologies, such as acoustic sensors, have been tested during pilot projects in several Middle Eastern development environments to evaluate the viability of replacing conventional density-neutron sensors. Current developments and integrated workflows are encouraging for the provision of sourceless well placement, porosity, and petrophysical and geomechanical evaluations for some of the mature reservoirs. These developments include a substantial number of case histories already established in clastic and carbonate depositional environments for the previous five years. The current well was planned through carbonate and clastic sequence as part of a geological section deemed important from a borehole stability point of view. Borehole deterioration and significant variations in pore pressure were also considered to increase the potential risk for the drillstring sticking. Conventional porosity tools used during a logging while drilling (LWD) bottomhole assembly (BHA) with radioactive sources exacerbate the potential risk at an environmental-hazard level. Additionally, retrievable-based sources can be problematic during extraction in high-angle wells. LWD azimuthal-acoustic tools free of radioactive sources were run for porosity measurements, pressure prediction, geomechanics, and possible anisotropy using a centralized four-axis acoustic caliper. A comprehensive petrophysical interpretation was also performed as part of the horizontal build section using acoustic porosities in comparison to its nuclear counterparts acquired in different modes. Permeability was deduced from acoustic and high-resolution microimaging data. This paper discusses the planning, design, and use of acoustic tools as part of the BHA and the viability, integrity, limitations, and reliability of logged data and interpreted results. The integration of petrophysical data with cutting analysis is investigated to optimize real-time drilling operations and petrophysical data acquisition requirements for improvement of future developments and overall reservoir management strategies.

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Reduced Well Construction Time with Accurate Geostopping in Harsh Drilling Conditions: Case Study from Kuwait

Saleh

Al-Khudari

Al-Najdi

et al. 2021

Day 2 Wed, May 26, 2021

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Traditionally, 12.25-in. hole sections in the Jurassic formations were planned to be drilled with mud weight (MW) of 20 ppg and solids content of 45%. The planned drilling would use a rotary assembly from the Hith formation, crossing several zones in which mud losses or gains were likely. The casing would then be set in the thin shale base of the Gotnia formation. A minor inaccuracy in casing setting depth could often lead to well-control issues. Pore pressure drops severely below the shale base and requires a MW of 15 ppg. Passing this shale base can lead to severe losses and potential abandonment of the well. An anhydrite marker is located approximately 50 ft above the shale base. To reduce risk, the operator would normally drill to this marker at a rate of penetration (ROP) of 20-30 ft/hr, then decrease the ROP to 2 ft/hr. While slowly drilling the last part of the section, penetration would be stopped every few feet to circulate bottoms-up to receive samples confirming the shale base; this process requires an additional 24 hours of rig time. After reaching the casing point, the operator would pull out of the hole to pick up logging-while-drilling (LWD) tools to perform a wiping run. This logging, however, is frequently cancelled because of wellbore stability issues, resulting in the loss of important formation-evaluation data across this interval. A new solution has been developed, comprising drilling with a rotary assembly to the final anhydrite marker, then pulling the string out of hole to pick up LWD triple-combo and sonic tools, with a conventional gamma ray sensor placed only 6 ft from the bit. The remaining part of the section would then be drilled at 7-10 ft/hr until the gamma-ray tool detected the shale base, thereby determining the casing depth. In addition, it was planned to re-log the previously drilled interval. This solution prevented the well from potential abandonment and reduced drilling time. It also secured critical formation evaluation data for exploration and future field development. The engineered drilling solution was tried for the first time in these formation sequences within a harsh drilling and logging environment. The option of rotary steerable services with an at-bit GR sensor was not considered because of the high cost.

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Sourceless Porosity-Density and Geomechanics with Logging-While-Drilling Tools in Carbonate Sequences

Cited by 5 publications

References 2 publications

An Integrated Approach for Comprehensive Formation Evaluation in Mixed Lithologies using Source-Less Logging While Drilling and Advanced Cutting Analysis: A Case History

An Integrated Approach for Comprehensive Formation Evaluation in Mixed Lithologies using Source-Less Logging While Drilling and Advanced Cutting Analysis: A Case History

Application of Sourceless Solutions for Geosteering and Formation Evaluation with Logging While Drilling Technologies: Case Study from Kuwait Reservoir

Reduced Well Construction Time with Accurate Geostopping in Harsh Drilling Conditions: Case Study from Kuwait

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