Modeling of Azimuthal Gamma Ray Tools for Use in Geosteering Unconventional Reservoirs

Wang, Haijing; Stockhausen, Edward J.; Wyatt, D.F.; Gulick, Dean

doi:10.15530/urtec-2018-2898135

Cited by 3 publications

(4 citation statements)

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“…This provides foundational insights for subsequent trajectory refinements, significantly minimizing the risk of deviating from the target formation, especially in thin layers or smallscale structures. 28,30 The azimuthal GR can be used in realtime to determine the angle between the formation and the wellbore trajectory, and this calculation model can be represented using trigonometric relationships (Figure 10).…”

Section: Precise Control Of Horizontal Trajectorymentioning

confidence: 99%

“…In response to challenges arising from narrow target windows in horizontal sections, the development of small-scale structures, and the presence of numerous small faults that make it very easy to deviate from the target window, it is not just essential to promptly adjust the geosteering model using well-seismic data, but it is also vital to leverage azimuthal GR and GR imaging data provided by near-bit or rotary steerable tools, as well as distinctive points on the GR curve of the layers above and below the target window, to determine the orientation and trajection within the target formation in the horizontal section. , Through the trajectory optimization technique, the trajectory can be adjusted in advance to an appropriate orientation within the target window. This avoids frequent, excessive, and untimely adjustments to drill out of the target formation.…”

Section: Key Technologies Of Geosteering In the Study Areamentioning

confidence: 99%

“…The azimuthal GR curve from near-bit or rotary steerable tools serves multiple purposes. Not only can it identify the lithology of the encountered formation and verify if the trajectory lands within the target formation, but it also accurately pinpoints the trajectory’s location within the target, its intersection pattern, and how it exits the target formation. ,− Specifically, the relative variations in the up GR (GR U ) and down GR (GR D ) values at a given measurement point can determine the relationship between the well inclination and the formation’s apparent dip angle and the bit’s relative position in the formation. For instance, when the formation’s GR shape displays a peak and GR U < GR D , the trajectory is ascending relative to the formation, indicating an upcut.…”

Section: Key Technologies Of Geosteering In the Study Areamentioning

confidence: 99%

“…Such proactive adjustments ensure that the drilling trajectory remains optimally positioned within the reservoir. This provides foundational insights for subsequent trajectory refinements, significantly minimizing the risk of deviating from the target formation, especially in thin layers or small-scale structures. , The azimuthal GR can be used in real-time to determine the angle between the formation and the wellbore trajectory, and this calculation model can be represented using trigonometric relationships (Figure ). The adjacent side represents the amplitude of the sinusoidal curve aligned with the well tracjectory direction on the imaging, while the opposite side accounts for the wellbore diameter plus twice the tool’s investigation depth.…”

Section: Key Technologies Of Geosteering In the Study Areamentioning

confidence: 99%

See 3 more Smart Citations

Study on Key Technologies of Geosteering for Shale Gas Horizontal Wells in the Complex Structural Area of Block H in Western Hubei-Eastern Chongqing

Shi,

Feng,

Zhao

et al. 2024

ACS Omega

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Block H, located in western Hubei-eastern Chongqing, remains at a low exploration degree. Characterized by its complex structural attributes, the area presents adverse conditions such as a thin thickness of high-quality shale reservoir, rapid lateral formation occurrence, and poor stratigraphic correlation, challenging conventional geosteering methods. The primary shale gas reservoir in Block H corresponds to the Upper Permian Wujiaping Formation. To ensure that the shale gas horizontal wells in this block effectively penetrate high-quality gas reservoirs, this study delves into the geological characteristics of this stratigraphic unit, identifies principal challenges faced by current geosteering techniques, and introduces a tailored technical solution. This solution encompasses the application of real-time 3D geological modeling to track while drilling, identification of steering marker layers, optimization of steerable tools, and optimization of the steering trajectory while drilling. In the technology of optimization of the steering trajectory while drilling, a trajectory control calculation model based on the average angle technique was established for the first time. Additionally, a sectional control chart for marker layers and well inclination under different deflecting constraints was established. These methods have solved the problems of large error in target prediction and poor trajectory control effects by using the equal thickness method alone. The findings from this study can significantly enhance target prediction and trajectory control accuracy in complex structural areas, offering pivotal insights for the proficient development of analogous shale gas reservoirs in the future.

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Section: Precise Control Of Horizontal Trajectorymentioning

confidence: 99%

Section: Key Technologies Of Geosteering In the Study Areamentioning

confidence: 99%

Section: Key Technologies Of Geosteering In the Study Areamentioning

confidence: 99%

Section: Key Technologies Of Geosteering In the Study Areamentioning

confidence: 99%

See 2 more Smart Citations

Study on Key Technologies of Geosteering for Shale Gas Horizontal Wells in the Complex Structural Area of Block H in Western Hubei-Eastern Chongqing

Shi,

Feng,

Zhao

et al. 2024

ACS Omega

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A Method for Calculating More Accurate Stratigraphic Positioning of Horizontal Wells Using Continuous Inclination and Azimuthal Gamma Ray Images Even While Sliding

Carrilero

Holmes

Hinz

et al. 2018

SPE Annual Technical Conference and Exhibition

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Geosteering long lateral wells in narrow target windows demands accurate stratigraphic positioning, true vertical depth (TVD) positioning, and apparent dip determinations. Using positive displacement motors with alternating slide and rotate drilling modes to control the well trajectory, along with standard 90-ft surveys and single-detector azimuthal gamma ray (GR) tools, have proven to be inadequate. To overcome these issues, a new method has been developed that combines continuous measurements and uses a four-detector azimuthal GR tool. The bottomhole assembly (BHA) used here is equipped with two inclinometer packages and a four-detector azimuthal GR logging-while-drilling (LWD) tool. A high-resolution survey is calculated using a combination of the two continuous inclination survey data sets for the deeper portion of the well and the stationary survey data from the shallow (low inclination) portion of the well, which provides a more accurate well path that better reflects the TVD positioning of the wellbore. The four-detector azimuthal GR tool is used to generate high-quality wellbore images, both while sliding and rotating. This enables more accurate structural dip angles to be determined from the continuous GR images. It also leads to better stratigraphic and structural positioning of the wellbore and a better understanding of changes in stratigraphy across the length the lateral section. Combining more accurate surveys with complete GR images and more accurate dip picking enables a better determination of the stratigraphic position of the wellbore and its path through stratigraphic layers. The wellbore can be divided into various up- and down-drilled sections that can be compared side-by-side using true vertical thickness (TVT) methods to show lateral continuity of the beds.

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Modeling and Inversion with Azimuthal Gamma Ray for a Better Geosteering Decision-Making

Wang

Crawford

Montgomery

2020

SPE Annual Technical Conference and Exhibition

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Azimuthal gamma ray (GR) logging-while-drilling (LWD) tools have demonstrated great value for geosteering applications in directional drilling. Their ability to indicate the relative stratigraphic position of the drilling assembly can determine whether the well should be steered up or steered down to stay in the target zone. However, this determination remains rather qualitative and largely depends on the user experience, especially when the quality and amount of real-time data is limited by intrinsic statistical noise, telemetry bandwidth, rate of penetration (ROP), and other drilling conditions. In addition, the commonly used geosteering modeling for azimuthal GR is geometry based only, without considering any measurement physics. Thus, a new forward-modeling and inversion method has been developed to provide an optimized pre-job planning and potentially quantitative real-time decision-making for more accurate geosteering with azimuthal GR. The geosteering question can be simplified mathematically to a prediction of separation between azimuthal GR curves when approaching or passing a bed boundary in a two-bed formation model. Separation will give an indication of a steering direction change, even in the simplest case of only up- and down-facing GR curves. In this study, a method was developed to solve this question in seconds with only two factors: measurement precision and front-to-back ratio. The theoretical up- and down-facing readings of an azimuthal GR tool can be forward-modeled accurately from this ratio for any bed boundary changes. Combined with measurement precision, the counting statistics effects can be added to the model to mimic the real-world log curves, and this for any pre-selected stratigraphic marker. The forward model results agree well with industrial standards of full Monte Carlo nuclear simulation and its deterministic nature allow it to run very fast. Thus, various scenarios can be evaluated quickly during either the pre-well phase or the operation. Detection limits achieved by any azimuthal GR tool in any given scenario can be statistically predicted for various confidence levels (e.g., 95% possibility of up/down curve separation). Thus, based on the detection limits, confidence level, and their variation with ROP, .etc. the drilling and geosteering plan can be optimized to reach the best ROP confidently without compromising the steering capability. Also in real time, when a potential separation of up- and down-facing azimuthal GR curves appear on the log, inversion of this model can be carried out to derive the possibility that this separation truly reflects formation changes to offer some quantitative insight to make steering decisions. Inversion of the modeling also has the potential to help recover the true API values of the formation beds and enhance the detection of the bed boundary positions. The novelty of this approach stems from the statistical nature of nuclear counting statistics and the derivation of front-to-back ratio. Front-to-back ratio, when properly defined, is a factor that fully represents the measurement physics of the tool. In addition to the aforementioned applications, an overall coverage chart can be recalculated as a quick look-up reference to measure the effectiveness of azimuthal GR. The chart reflects the detection limits that an azimuthal GR tool can resolve for geosteering in a 0–200-API sampling space at a certain confidence level. Overall, the paper includes a detailed description of the model and its inversion, applications, and example log demonstrations from early trials.

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Modeling of Azimuthal Gamma Ray Tools for Use in Geosteering Unconventional Reservoirs

Cited by 3 publications

References 0 publications

Study on Key Technologies of Geosteering for Shale Gas Horizontal Wells in the Complex Structural Area of Block H in Western Hubei-Eastern Chongqing

Study on Key Technologies of Geosteering for Shale Gas Horizontal Wells in the Complex Structural Area of Block H in Western Hubei-Eastern Chongqing

A Method for Calculating More Accurate Stratigraphic Positioning of Horizontal Wells Using Continuous Inclination and Azimuthal Gamma Ray Images Even While Sliding

Modeling and Inversion with Azimuthal Gamma Ray for a Better Geosteering Decision-Making

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