Analysis of wellbore stability considering the effects of bedding planes and anisotropic seepage during drilling horizontal wells in the laminated formation

2018 ◽  
Vol 170 ◽  
pp. 507-524 ◽  
Author(s):  
Jun Zhou ◽  
Shiming He ◽  
Ming Tang ◽  
Zhen Huang ◽  
Yulin Chen ◽  
...  
Keyword(s):  
Horizontal Wells ◽  
Wellbore Stability ◽  
Bedding Planes

Revealing Hidden Information: High-Resolution Logging-While-Drilling Slowness Measurements and Imaging Using Advanced Dual Ultrasonic Technology

2021 ◽  
Vol 62 (1) ◽  
pp. 89-108
Author(s):  
Matthew Blyth ◽  
◽  
Naoki Sakiyama ◽  
Hiroshi Hori ◽  
Hiroaki Yamamoto ◽  
...  
Keyword(s):  
High Resolution ◽  
Elastic Wave ◽  
Horizontal Wells ◽  
Wellbore Stability ◽  
Frequency Range ◽  
Ultrasonic Technology ◽  
Logging While Drilling ◽  
Pulse Echo ◽  
Depth Of Investigation ◽  
Wave Properties

A new logging-while-drilling (LWD) acoustic tool has been developed with novel ultrasonic pitch-catch and pulse-echo technologies. The tool enables both high-resolution slowness and reflectivity images, which cannot be addressed with conventional acoustic logging. Measuring formation elastic-wave properties in complex, finely layered formations is routinely attempted with sonic tools that measure slowness over a receiver array with a length of 2 ft or more depending upon the tool design. These apertures lead to processing results with similar vertical resolutions, obscuring the true slowness of any layering occurring at a finer scale. If any of these layers present significantly different elastic-wave properties than the surrounding rock, then they can play a major role in both wellbore stability and hydraulic fracturing but can be absent from geomechanical models built on routine sonic measurements. Conventional sonic tools operate in the 0.1- to 20-kHz frequency range and can deliver slowness information with approximately 1 ft or more depth of investigation. This is sufficient to investigate the far-field slowness values but makes it very challenging to evaluate the near-wellbore region where tectonic stress redistribution causes pronounced azimuthal slowness variation. This stress-induced slowness variation is important because it is also a key driver of wellbore geomechanics. Moreover, in the presence of highly laminated formations, there can be a significant azimuthal variation of slowness due to layering that is often beyond the resolution of conventional sonic tools due to their operating frequency. Finally, in horizontal wells, multiple layer slownesses are being measured simultaneously because of the depth of investigation of conventional sonic tools. This can cause significant interpretational challenges. To address these challenges, an entirely new design approach was needed. The novel pitch-catch technology operates over a wide frequency range centered at 250 kHz and contains an array of receivers having a 2-in. receiver aperture. The use of dual ultrasonic technology allows the measurement of high-resolution slowness data azimuthally as well as reflectivity and caliper images. The new LWD tool was run in both vertical and horizontal wells and directly compared with both wireline sonic and imaging tools. The inch-scale slownesses obtained show characteristic features that clearly correlate to the formation lithology and structure indicated by the images. These features are completely absent from the conventional sonic data due to its comparatively lower vertical resolution. Slowness images from the tool reflect the formation elastic-wave properties at a fine scale and show dips and lithological variations that are complementary to the data from the pulse-echo images. The physics of the measurement are discussed, along with its ability to measure near-wellbore slowness, elastic-wave properties, and stress variations. Additionally, the effect of the stress-induced, near-wellbore features seen in the slowness images and the pulse-echo images is discussed with the wireline dipole shear anisotropy processing.

Simulating the effect of subsurface stresses and transient pore pressure on wellbore stability in subsea horizontal wells

2019 ◽  
Vol 41 (16) ◽  
pp. 2028-2038
Author(s):  
Ubedullah Ansari ◽  
Cheng YuanFang ◽  
Li QingChao ◽  
Georgia George Mawaipopo ◽  
Jia Wei
Keyword(s):  
Pore Pressure ◽  
Horizontal Wells ◽  
Wellbore Stability

Application of Research of the Relationship between Ground Stress and Fractures in the Trajectory Optimization of Horizontal Wells

2013 ◽  
Vol 765-767 ◽  
pp. 300-306
Author(s):  
Hui Zhang ◽  
Fang Jun Ou ◽  
Guo Qing Yin ◽  
Jing Bing Yi ◽  
Fang Yuan ◽  
...  
Keyword(s):  
Stress State ◽  
Stress Field ◽  
Trajectory Optimization ◽  
Horizontal Wells ◽  
Wellbore Stability ◽  
Natural Fracture ◽  
Fracture System ◽  
Well Trajectory ◽  
The Stability ◽  
The Relationship

From the perspective of improving single well production and wellbore stability, stress field and natural fractures are the factors which have to be taken into account in the development of horizontal wells of the complex carbonate oil and gas fields in Kuqa piedmont and platform-basin transitional area. On the one hand, as the present stress field is the key factor to control fracture permeability, the trajectory of horizontal wells should pass through fracture system with good permeability as much as possible, being conducive to the effective stimulation of the reservoir. On the other hand, at the state of specific stress, the stability of well trajectory varies with directions. Therefore, before drilling horizontal wells, it is necessary to fully analyze the quantitative relationship between the present stress state and natural fracture occurrence and mechanical characteristics, etc., to optimize and determine a well trajectory conducive to high yield and wellbore stability. In this study, firstly, the fundamental principles for evaluating the present stress state and analyzing the relationship between the stress and fractures were described. Then based on the relationship between them, the occurrence and longitudinal positions of permeability fractures were analyzed. Apart from that, the stability index and fracture opening pressure distribution of wells in different directions at given stress state and fracture system were also analyzed. Finally, the optimization scheme for trajectory of horizontal wells under complex conditions was discussed with three aspects taken into account, i.e. best drilling in permeability fractures, wellbore stability and drilled reservoir stimulation.

Wellbore Stability Management in Weak Bedding Planes and Angle of Attack in Well Planing

2014 ◽  
Author(s):  
Paul Fekete ◽  
Adewale Dosunmu ◽  
Chimaroke Anyanwu ◽  
Samuel B. Odagme ◽  
Evelyn Ekeinde
Keyword(s):  
Angle Of Attack ◽  
Wellbore Stability ◽  
Bedding Planes

Wellbore Stability in Layered Rocks: A Comparative Study of Strength Criteria

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Xiangchao Shi ◽  
Xiao Zhuo ◽  
Yue Xiao ◽  
Boyun Guo ◽  
Cheng Zhu ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Good Choice ◽  
Wellbore Stability ◽  
Gas Field ◽  
Well Drilling ◽  
Shale Formations ◽  
Single Plane ◽  
Collapse Pressure ◽  
Bedding Planes ◽  
Laminated Structures

Abstract Wellbore instability is a critical issue restricting efficient well drilling and successful development of oil and gas field. Most instability problems originate from shale formations because of their distinct laminated structures that cause significant anisotropy and moderate to high clay contents that are prone to shrinkage and swelling. To account for these influences on the mechanical responses of shales, this study aims to identify an appropriate strength criterion for stability analyses. Two anisotropic criteria including single plane of weakness and the modified Hoek–Brown criteria were compared to evaluate their suitability in characterizing the anisotropic strength of layered rocks including shale, schist, and slate under different confining pressures. Comparative case studies indicated that the single plane of weakness criterion overestimates the strength of layered rocks at some orientation angles. The modified Hoek–Brown criterion can fit well with the experimental data of layered rocks. Moreover, wellbore stability analysis models for shale gas wells were built, respectively, for each criterion and applied to in situ scenarios. The single plane of weakness and modified Hoek–Brown criteria provide similar results of collapse pressure, and the shale failure is mainly determined by the bedding plane. This further validates that the modified Hoek–Brown criterion is a good choice for wellbore stability analysis in shale formations with bedding planes. This study shows the potential of using the modified Hoek–Brown criterion to enhance the safety and efficiency of well drilling and operation in shale formations.

INTERPRETATION OF LWD ACOUSTIC BOREHOLE IMAGE LOGS: CASE STUDIES FROM NORTH AMERICAN SHALE PLAYS

2021 ◽  
Author(s):  
Bo Gong ◽  
◽  
Ela Manuel ◽  
Youfang Liu ◽  
David Forand ◽  
...  
Keyword(s):  
Case Studies ◽  
Reservoir Characterization ◽  
Low Cost ◽  
Horizontal Wells ◽  
Drilling Fluids ◽  
Imaging Tool ◽  
Bedding Planes ◽  
Drilling Parameters ◽  
Acoustic Images ◽  
Formation Property

Logging-while-drilling (LWD) acoustic imaging technology emerged in the past few years as a low-cost solution to detect and characterize fractures in high-angle and horizontal wells. This type of imaging tool works in either water-based or oil-based drilling fluids, making it a competitive choice for logging unconventional shale wells, which are often drilled with oil-based mud. With high-resolution acoustic amplitude and travel-time images, fractures, bedding planes and other drilling-related features can be identified, providing new insights for reservoir characterization and wellbore geomechanics. The quality of LWD acoustic images however is directly affected by drilling parameters and borehole conditions, as the received signal is sensitive to formation property and wellbore changes at the same time. As a result, interpretation can be quite challenging, and caution needs to be taken to differentiate actual formation property changes from drilling-related features or image artifacts. This paper demonstrates the complexity of interpreting LWD acoustic images through multiple case studies. The examples were collected from vertical and horizontal wells in multiple shale plays in North America, with the images logged and processed by different service companies. Depending on the geology and borehole conditions, various features and artifacts were observed from the images, which can be used as a reference for geologists and petrophysicists. Images acquired with different drilling parameters were compared to show the effect of drilling conditions on image quality. Recommendations and best practices of using this new type of image log are also shared.

The Essence of Horizontal Drilling Challenges in Depleted Reservoirs

2021 ◽  
Author(s):  
Rida Mohamed Elgaddafi ◽  
Victor Soriano ◽  
Ramadan Ahmed ◽  
Samuel Osisanya
Keyword(s):  
Pore Pressure ◽  
Horizontal Well ◽  
New Technology ◽  
Horizontal Wells ◽  
Stability Loss ◽  
Wellbore Stability ◽  
Planning Stage ◽  
Horizontal Drilling ◽  
Infill Drilling ◽  
Drilling Operations

Abstract Horizontal well technology is one of the major improvements in reservoir stimulation. Planning and execution are the key elements to drill horizontal wells successfully, especially through depleted formations. As the reservoir has been producing for a long time, pore pressure declines, resulting in weakening hydrocarbon-bearing rocks. Drilling issues such as wellbore stability, loss circulation, differential sticking, formation damage remarkably influenced by the pore pressure decline, increasing the risk of losing part or even all the horizontal interval. This paper presents an extensive review of the potential issues and solutions associated with drilling horizontal wells in depleted reservoirs. After giving an overview of the depleted reservoir characteristics, the paper systematically addresses the major challenges that influence drilling operations in depleted reservoirs and suggests solutions to avoid uncontrolled risks. Then, the paper evaluates several real infill drilling operations through depleted reservoirs, which were drilled in different oilfields. The economic aspect associated with potential risks for drilling a horizontal well in depleted reservoirs is also discussed. The most updated research and development findings for infill drilling are summarized in the article. It is recommended to use wellbore strengthening techniques while drilling a horizontal well through highly depleted formations. This will allow using higher mud weight to control unstable shales while drilling through the production zone. Managed Pressure Drilling should be considered as the last option for highly depleted formations because it will require a greater level of investment which is not going to have a superior rate of return due to the lack of high deliverability of the reservoir. Using rotary steerable systems is favored to reduce risks related to drilling through depleted formations. Precise analysis of different drilling programs allows the drilling team to introduce new technology to reduce cost, improve drilling efficiency and maximize profit. It is the responsibility of the drilling engineer to evaluate different scenarios with all the precautions needed during the planning stage to avoid unexpected issues. The present market conditions and the advancement in technologies for drilling horizontal wells increase the feasibility of producing the depleted reservoirs economically. This paper highlights the challenges in drilling horizontal wells in highly depleted reservoirs and provides means for successfully drilling those wells to reduce risks while drilling

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