Method for calculating the fracture porosity of tight-fracture reservoirs

Xu, Jingling; Zhang, Baoying; Qin, Yuxing; Cao, Gang; Zhang, Hui

doi:10.1190/geo2015-0434.1

Cited by 21 publications

(4 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The volume fraction of a fracture, also known as the fracture porosity, is a key parameter used in estimating the gas hydrate saturation of fracture-filling gas hydrate reservoirs. The dual laterolog resistivity model and density-velocity model are generally used to predict the fracture porosity of rocks (Xu et al, 2016). However, for fracture-filling gas hydrate reservoirs, velocity and resistivity are considered to be functions of rock composition, fracture porosity, and gas hydrate saturation.…”

Section: Fracture Porositymentioning

confidence: 99%

Evidence of Pore‐ and Fracture‐Filling Gas Hydrates from Geophysical Logs in Consolidated Rocks of the Muli Area, Qinghai–Tibetan Plateau Permafrost, China

Peng

Zou

et al. 2019

JGR Solid Earth

View full text Add to dashboard Cite

Natural gas hydrates were discovered in the Muli area of the Qinghai-Tibetan Plateau permafrost, which is an area of alpine permafrost in the midlatitudes. Resistivity models were employed to understand the distribution and accumulation mechanism of gas hydrates in the Muli area, as these models are suitable for use in detecting the presence and amount of pore-and fracture-filling gas hydrates in consolidated rocks, and geophysical logs were used to constrain gas hydrate saturation. The results show that resistivity logs are sensitive to gas hydrate saturation in consolidated rocks in the Muli area. Geophysical log analysis enabled the discovery of eleven pore-filling gas hydrate reservoirs (total thickness: 21.95 m) and nine fracture-filling gas hydrate reservoirs (total thickness: 90.55 m). It is hypothesized that gas accumulation is more likely to occur in fractures within mudstones due to good permeability and sealing properties and that fracture-filling gas hydrates are more likely to occur than pore-filling gas hydrates. Poor preservation conditions may thus be the key factor in the absence of gas hydrates in the eastern part of the study area. Evidence from geophysical logs shows that the upper boundary of the gas hydrate stability zone in the Muli area is at a depth of 133.25 m and that the lower boundary is deeper than 400 m. The results of this study are useful for further gas hydrate exploration in alpine permafrost at the midlatitudes.Key Points:• Resistivity logs are more sensitive to gas hydrate saturation than compressional-wave velocity logs in consolidated rocks of the Muli area • Resistivity models of pore-and fracture-filling gas hydrate reservoirs are used to detect gas hydrates in consolidated rocks • Gas hydrate accumulation in the Muli area is affected by faults, lithology, and the gas hydrate stability zoneSupporting Information:• Supporting Information S1

show abstract

Section: Fracture Porositymentioning

confidence: 99%

Evidence of Pore‐ and Fracture‐Filling Gas Hydrates from Geophysical Logs in Consolidated Rocks of the Muli Area, Qinghai–Tibetan Plateau Permafrost, China

Peng

Zou

et al. 2019

JGR Solid Earth

View full text Add to dashboard Cite

show abstract

“…Mechanical properties and reservoirs characterization of carbonate reservoirs have contributions from several factors, including mineralogy, microstructure, regional tectonic, depositional facies and alterations during diagenetic processes (Hensel, 1989; Jardine & Wilshart, 1982; Lucia & Conti, 1987; Sayers, 2008; Tucker, 2011; Xu et al., 2016). Fractures and cracks are the most compliant parts of porosity in carbonate rocks, which can significantly affect reservoir quality as well as reservoir elastic behaviour.…”

Section: Introductionmentioning

confidence: 99%

A novel approach for fracture porosity estimation of carbonate reservoirs

Sharifi

Moghaddas

Saberi³

et al. 2023

Geophysical Prospecting

View full text Add to dashboard Cite

The quality of carbonate reservoirs is linked to their rock properties and surrounding stress settings which can play a vital role in their production optimization and development programs. Imposing various stresses can increase porosity and permeability by creating joints and cracks across the rock mass. Therefore, developing methods to identify and accurately evaluate fractures in carbonate reservoirs is very significant in reservoir characterization. To deal with this necessity, we developed a fracture porosity estimation method using empirical and analytical solutions based on the wireline data considering stress conditions. The proposed methodology was applied to a carbonate reservoir as the case study. As fracture porosity is sensitive to stress, experimental tests were conducted on the core samples using triaxial hydrostatic tests. These tests are needed to simulate reservoir conditions to investigate the relationships between fracture volume fraction and the applied stress. A substantial porosity loss was observed during the hydrostatic test, which can be linked to the crack porosity closure. The reliability of our results was validated by thin section, computed tomography-scan images, velocity deviation method, elastic boundary laws, and image logs. Eventually, we introduced an equation to estimate in situ fracture porosity from the relationship between porosity and effective confining pressure. We verified the repeatability and generality of our proposed methodology using a blind well, and the results indicate a comparable level of accuracy. Our findings are applicable for estimating crack porosity for rock physics modelling purposes of detecting fracture zones in the absence of image logs and core data. Moreover, by calibrating and optimizing the constant parameters in our proposed relationship, one may further estimate crack density in any other given carbonate reservoirs.

show abstract

“…In recent years, the exploration results are remarkable for the weathered crusts of dolostone reservoirs on top of the Ordovician succession in the basin, indicating a huge potential in oil and gas exploration. Of these, the Daniudi Gas Field of the Ordos Basin is located on an ancient weathered crust slope, which has good reservoir development conditions (Han et al, 2019; Xu, Qiu, et al, 2016; Xu, Zhang, Qin, Cao, & Zhang, 2016). A decade of exploration in this area shows that the weathering crust gas layer from the Ordovician sediments of the Ma 5 member of the Majiagou Formation has favourable production conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Daniudi Gas Field of the Ordos Basin is located on an ancient weathered crust slope, which has good reservoir development conditions (Han et al, 2019;Xu, Qiu, et al, 2016;Xu, Zhang, Qin, Cao, & Zhang, 2016). A decade of exploration in this area shows that the weathering crust gas layer from the Ordovician sediments of the Ma 5 member of the Majiagou Formation has favourable production conditions.…”

mentioning

confidence: 99%

Characteristics, influencing factors, and prediction of fractures in weathered crust karst reservoirs: A case study of the Ordovician Majiagou Formation in the Daniudi Gas Field, Ordos Basin, China

Xie

Zhou

Zhang³

et al. 2020

Geological Journal

View full text Add to dashboard Cite

The study of fractures in karst reservoirs is a hot spot in the field of geosciences. In this article, we conducted a systematic study on the characteristics, influencing factors, and prediction methods of karst reservoir fractures of the Ordovician Majiagou Formation in the Daniudi Gas Field, China. Both weathering and tectonic fractures are mainly developed in the Ma 5 member of the Majiagou Formation. The former is categorized into surface weathering, steep wall tensile and karst collapse fractures, and the latter is made of tensile and shear fractures. The palaeo-temperatures of the fracture filling inclusions range from 90 to 140 C, peaking at 111-120 C, which are derived from oxygen isotopes of −7.9 to −17.5‰, with average −14.1‰ from the same filling inclusions. Integrations of regional tectonic activities, inclusion tests, and stable isotope analysis recognizes four formation periods of fractures since the Caledonian. The factors controlling the development degree of the karst reservoir fractures include lithology, petrophysical properties, rock layer thickness, structural deformation strength, and karst palaeomorphology. The buckling thin plate simulation results show a good positive correlation between the maximum principal stress and tensile fracture density. The same positive correlation is also observed between the shear stress and fracture density. The ancient karst landforms have strongly affected the distribution of weathering fractures. Surficial weathering fractures occur typically in the weathered residual monadnocks, while steep wall tension ruptures in areas near geomorphic steep ridges, and karst collapse fractures in karst residual monadnocks and karst pit areas.

show abstract

Method for calculating the fracture porosity of tight-fracture reservoirs

Cited by 21 publications

References 11 publications

Evidence of Pore‐ and Fracture‐Filling Gas Hydrates from Geophysical Logs in Consolidated Rocks of the Muli Area, Qinghai–Tibetan Plateau Permafrost, China

Evidence of Pore‐ and Fracture‐Filling Gas Hydrates from Geophysical Logs in Consolidated Rocks of the Muli Area, Qinghai–Tibetan Plateau Permafrost, China

A novel approach for fracture porosity estimation of carbonate reservoirs

Characteristics, influencing factors, and prediction of fractures in weathered crust karst reservoirs: A case study of the Ordovician Majiagou Formation in the Daniudi Gas Field, Ordos Basin, China

Contact Info

Product

Resources

About