The Effect of Cementation on the Mechanical Properties of Sandstones

2006 ◽  
Vol 9 (04) ◽  
pp. 308-316 ◽  
Author(s):  
Ashraf M. Al-Tahini ◽  
Carl H. Sondergeld ◽  
Chandra S. Rai
Keyword(s):  
Mechanical Properties ◽  
Saudi Arabia ◽  
Hydraulic Fracture ◽  
Gas Production ◽  
Wellbore Stability ◽  
Minor Role ◽  
Complex Nature ◽  
Thin Sections ◽  
Geomechanical Properties ◽  
A Minor

Summary The variability in mechanical properties measured on sands from the Jauf and Unayzah formations of Saudi Arabia is observed to be dependent upon cementation. Understanding the role of cementation in controlling the mechanical properties can improve the design of hydraulic-fracture treatments and, hence, improve reservoir performance. Strength measurements from triaxial-testing data and examination of core in thin sections were used to relate the detailed microstructure and cementation to the variation of mechanical properties. Strength and elastic moduli were determined for 65 samples cored from five different wells. Forty-seven samples were analyzed in thin sections and point counted to determine and quantify cementation. Cements in these two formations have variable composition and habits; both affect the mechanical properties and strength. It is not sufficient to know that cements exist; it is also necessary to know where the cement occurs. Pure quartz over growths play a major role in increasing strength, while clay coatings play a minor role. Simple linear correlations were found relating cement concentrations to strength. Introduction The Jauf and Unayzah reservoirs (Ghawar field, Saudi Arabia) are deep sequences of thin sandstones and shales saturated with condensate-rich gas. These reservoir rocks display a wide variation in both permeability and porosity (Fig. 1) (Al-Qahtani and Buhidma 2001). Hydraulic fracturing has been introduced to enhance productivity in the Jauf sandstones within the Ghawar reservoir. The complex nature of tectonic stresses, geomechanical properties, and geology leads to problems of sand production and wellbore stability in the Unayzah and Jauf formations. Such problems make the development of these reservoirs challenging. The variations of mechanical properties such as Young's modulus (E), Poisson's ratio, (u), and unconfined compressive strength (UCS) have a direct impact on hydraulic-fracture design. The variation of these properties affects fracture propagation and geometry and, consequently, gas production.

Effect of cementation on ultrasonic velocities in sandstones

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. E53-E58 ◽  
Author(s):  
Ashraf M. Al-Tahini ◽  
Carl H. Sondergeld ◽  
Chandra S. Rai
Keyword(s):  
Saudi Arabia ◽  
Microstructural Analysis ◽  
Acoustic Velocity ◽  
Minor Role ◽  
Point Counting ◽  
Ultrasonic Velocities ◽  
Thin Sections ◽  
Acoustic Velocities ◽  
A Minor

We determine the acoustic velocities for samples cored from the Jauf and Unayzah sandstone formations of Saudi Arabia. We use microstructural analysis including thin sections and point counting to quantify cementation. Velocities in these formations are strongly controlled by the combination of porosity and cementation. Consequently, rocks of similar porosity but with different cementation materials display different velocities. The objective of this study is to understand the effect of cementation on the acoustic velocity. Cements in these two formations have variable compositions and properties. Pure quartz overgrowth plays a major role in increasing velocities while clay and clay coatings play a minor role. We found that clay coatings inhibit the quartz overgrowth cement leading to a decrease in velocities. Understanding the influence of various cementation types on velocity, and thus elastic properties in sandstone cores, enables an understanding of the variation of sonic velocities and moduli across these formations. The uniqueness of this study is that we emphasize the quantification of the role of cement and not just mineral volume.

scholarly journals Functionally Distinct Tendons From Elastin Haploinsufficient Mice Exhibit Mild Stiffening and Tendon-Specific Structural Alteration

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Jeremy D. Eekhoff ◽  
Fei Fang ◽  
Lindsey G. Kahan ◽  
Gabriela Espinosa ◽  
Austin J. Cocciolone ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Fiber ◽  
Mechanical Effect ◽  
Elastic Fibers ◽  
Minor Role ◽  
Tendon Mechanics ◽  
Different Types ◽  
A Minor ◽  
Collagen Alignment

Elastic fibers are present in low quantities in tendon, where they are located both within fascicles near tenocytes and more broadly in the interfascicular matrix (IFM). While elastic fibers have long been known to be significant in the mechanics of elastin-rich tissue (i.e., vasculature, skin, lungs), recent studies have suggested a mechanical role for elastic fibers in tendons that is dependent on specific tendon function. However, the exact contribution of elastin to properties of different types of tendons (e.g., positional, energy-storing) remains unknown. Therefore, this study purposed to evaluate the role of elastin in the mechanical properties and collagen alignment of functionally distinct supraspinatus tendons (SSTs) and Achilles tendons (ATs) from elastin haploinsufficient (HET) and wild type (WT) mice. Despite the significant decrease in elastin in HET tendons, a slight increase in linear stiffness of both tendons was the only significant mechanical effect of elastin haploinsufficiency. Additionally, there were significant changes in collagen nanostructure and subtle alteration to collagen alignment in the AT but not the SST. Hence, elastin may play only a minor role in tendon mechanical properties. Alternatively, larger changes to tendon mechanics may have been mitigated by developmental compensation of HET tendons and/or the role of elastic fibers may be less prominent in smaller mouse tendons compared to the larger bovine and human tendons evaluated in previous studies. Further research will be necessary to fully elucidate the influence of various elastic fiber components on structure–function relationships in functionally distinct tendons.

scholarly journals Material constituents and mechanical properties and macro-micro-failure modes of tight gas reservoirs

2020 ◽  
Vol 38 (6) ◽  
pp. 2631-2648
Author(s):  
Zhaoyi Liu ◽  
Ligang Zhang ◽  
GR Liu ◽  
Wei Li ◽  
Shibin Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Gas Production ◽  
Wellbore Stability ◽  
Porous Polymer ◽  
Tight Gas ◽  
Tensile Shear ◽  
Gas Reservoirs ◽  
Tight Gas Reservoirs ◽  
Triaxial Compressive Strength

In this work, a series of intensive laboratory tests are conducted to measure the material constituents, mechanical properties, and to examine macro-micro-failure modes of various types of rocks from tight gas reservoirs in the Da Qing oilfield in China. A set of key parameters are experimentally determined, including porosity, mineralogical compositions, microstructure, Young’s modulus, Poisson’s ratio, triaxial compressive strength, as well as macro- and micro-morphology failure modes. The relationships of these parameters are systematically analyzed, and the effects of the material constituents and microstructure characteristics such as cementation type, porosity, and mineral composition on rock mechanical properties are revealed as well as the patterns of micro- and macro-failures in types of rocks are investigated. The result shows that the micro-failure mainly exhibits features of transgranular and intergranular porous polymer fracture, and the macro-failure modes are mainly three types: shear-dominated, mixed shear–tensile and mixed tensile–shear. The mixed tensile–shear failure has mainly tensile fractures with branch fractures crossing each other, which forms a complex system fracture network. These findings are of importance for “sweet pot” evaluations, wellbore stability analysis, and hydraulic fracturing design for oil and gas production in tight gas reservoirs.

scholarly journals Multiscale Mechanical Evaluation of Human Supraspinatus Tendon Under Shear Loading After Glycosaminoglycan Reduction

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Fei Fang ◽  
Spencer P. Lake
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Core Protein ◽  
Supraspinatus Tendon ◽  
Shear Loading ◽  
Minor Role ◽  
Shear Stresses ◽  
Stress Ratios ◽  
Injured Tendon ◽  
A Minor

Proteoglycans (PGs) are broadly distributed within many soft tissues and, among other roles, often contribute to mechanical properties. Although PGs, consisting of a core protein and glycosaminoglycan (GAG) sidechains, were once hypothesized to regulate stress/strain transfer between collagen fibrils and help support load in tendon, several studies have reported no changes to tensile mechanics after GAG depletion. Since GAGs are known to help sustain nontensile loading in other tissues, we hypothesized that GAGs might help support shear loading in human supraspinatus tendon (SST), a commonly injured tendon which functions in a complex multiaxial loading environment. Therefore, the objective of this study was to determine whether GAGs contribute to the response of SST to shear, specifically in terms of multiscale mechanical properties and mechanisms of microscale matrix deformation. Results showed that chondroitinase ABC (ChABC) treatment digested GAGs in SST while not disrupting collagen fibers. Peak and equilibrium shear stresses decreased only slightly after ChABC treatment and were not significantly different from pretreatment values. Reduced stress ratios were computed and shown to be slightly greater after ChABC treatment compared to phosphate-buffered saline (PBS) incubation without enzyme, suggesting that these relatively small changes in stress values were not due strictly to tissue swelling. Microscale deformations were also not different after ChABC treatment. This study demonstrates that GAGs possibly play a minor role in contributing to the mechanical behavior of SST in shear, but are not a key tissue constituent to regulate shear mechanics.

Viscoelastic properties of the salts of some polymeric acids

1964 ◽  
Vol 282 (1388) ◽  
pp. 137-146 ◽  
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Properties ◽  
Elastic Moduli ◽  
Softening Temperature ◽  
Decomposition Temperature ◽  
Minor Role ◽  
Metallic Oxides ◽  
Metallic Salts ◽  
A New Technique ◽  
A Minor

The mechanical properties of rigid polyelectrolyte-type polymers have been measured. Polymers studied include polyacrylic acid, copolymers of styrene and methacrylic acid, and their salts. Some of the test specimens were fabricated by a new technique involving the reaction of polyacids with metallic oxides in the form of mixed powders in a mould at high temperatures and pressures. Metallic salts of homopolymeric acids have no measurable softening temperature below their decomposition temperature, and they are characterized by elastic moduli several times greater than the corresponding moduli of ordinary organic polymers. Evidence is presented which indicates that hydrogen bonding plays a minor role in determining the mechanical and rheological properties of these polymers.

Geomechanical Properties Estimation Utilizing Artificial Intelligence Prediction Tool

2021 ◽  
Author(s):  
Mohammed Alabbad ◽  
Mohammad Alqam ◽  
Hussain Aljeshi
Keyword(s):  
Mechanical Properties ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Significant Loss ◽  
Wellbore Stability ◽  
Rock Properties ◽  
Ann Model ◽  
Full Field ◽  
Geomechanical Properties ◽  
Rock Mechanical Properties

Abstract Drilling and fracturing are considered to be one of the major costs in the oil and gas industry. Cost may reach tens of millions of dollars and improper design may lead to significant loss of money and time. Reliable fracturing and drilling designs are governed with decent and representative rock mechanical properties. Such properties are measured mainly by analyzing multiple previously cored wells in the same formation. The nature of the conducted tests on the collected plugs are destructive and samples cannot be restored after performing the rock mechanical testing. This may disable further evaluation on the same plugs. This study aims to build an artificial neural network (ANN) model that is capable of predicting the main rock mechanical properties, such as Poisson's ratio and compressive strength from already available lab and field measurements. The log data will be combined together with preliminary lab rock properties to build a smart model capable of predicting advance rock mechanical properties. Hence, the model will provide initial rock mechanical properties that are estimated almost immediately and without undergoing costly and timely rock mechanical laboratory tests. The study will also give an advantage to performing preliminary estimates of such parameters without the need for destructive mechanical core testing. The ultimate goal is to draw a full field geomechanical mapping with this tool rather than having localized scattered data. The AI tool will be trained utilizing representative sets of rock mechanical data with multiple feed-forward backpropagation learning techniques. The study will help in localizing future well location and optimizing multi-stage fracturing designs. These produced data are needed for upstream applications such as wellbore stability, sanding tendency, hydraulic fracturing, and horizontal/multi-lateral drilling.

A TEM study of the interface between organic matrix and aragonite in a biological hard tissue, nacre

1992 ◽  
Vol 50 (2) ◽  
pp. 1024-1025
Author(s):  
Jun Liu ◽  
Katie E. Gunnison ◽  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Mechanical Properties ◽  
Ion Beam ◽  
Laminated Composite ◽  
Organic Matrix ◽  
Pearl Oyster ◽  
Interfacial Structure ◽  
Interfacial Region ◽  
Thin Sections ◽  
Organic Layers ◽  
Transmission Electron

The interfacial structure between the organic and inorganic phases in biological hard tissues plays an important role in controlling the growth and the mechanical properties of these materials. The objective of this work was to investigate these interfaces in nacre by transmission electron microscopy. The nacreous section of several different seashells -- abalone, pearl oyster, and nautilus -- were studied. Nacre is a laminated composite material consisting of CaCO3 platelets (constituting > 90 vol.% of the overall composite) separated by a thin organic matrix. Nacre is of interest to biomimetics because of its highly ordered structure and a good combination of mechanical properties. In this study, electron transparent thin sections were prepared by a low-temperature ion-beam milling procedure and by ultramicrotomy. To reveal structures in the organic layers as well as in the interfacial region, samples were further subjected to chemical fixation and labeling, or chemical etching. All experiments were performed with a Philips 430T TEM/STEM at 300 keV with a liquid Nitrogen sample holder.

The Effect of Path Length and Display Size on Memory for Spatial Information

2012 ◽  
Vol 59 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Katherine Guérard ◽  
Sébastien Tremblay
Keyword(s):  
Path Length ◽  
Potential Role ◽  
Spatial Information ◽  
Recall Performance ◽  
Minor Role ◽  
Length Effect ◽  
Serial Memory ◽  
Fixed Reference ◽  
A Minor

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.

Use of Different Tissue Thromboplastins in the Control of Anticoagulant-Therapy

1958 ◽  
Vol 02 (05/06) ◽  
pp. 462-480 ◽  
Author(s):  
Marc Verstraete ◽  
Patricia A. Clark ◽  
Irving S. Wright
Keyword(s):  
Prothrombin Time ◽  
Anticoagulant Therapy ◽  
Factor Vii ◽  
Rabbit Brain ◽  
Minor Role ◽  
Rabbit Lung ◽  
Coagulation Mechanism ◽  
Time Test ◽  
The One ◽  
A Minor

SummaryAn analysis of the results of prothrombin time tests with different types of thromboplastins sheds some light on the problem why the administration of coumarin is difficult to standardize in different centers. Our present ideas on the subject, based on experimental data may be summarized as follows.Several factors of the clotting mechanism are influenced by coumarin derivatives. The action of some of these factors is by-passed in the 1-stage prothrombin time test. The decrease of the prothrombin and factor VII levels may be evaluated in the 1-stage prothrombin time determination (Quick-test). The prolongation of the prothrombin times are, however, predominantly due to the decrease of factor VII activity, the prothrombin content remaining around 50 per cent of normal during an adequate anticoagulant therapy. It is unlikely that this degree of depression of prothrombin is of major significance in interfering with the coagulation mechanism in the protection against thromboembolism. It may, however, play a minor role, which has yet to be evaluated quantitatively. An exact evaluation of factor VII is, therefore, important for the guidance of anticoagulant therapy and the method of choice is the one which is most sensitive to changes in factor VII concentration. The 1-stage prothrombin time test with a rabbit lung thromboplastin seems the most suitable method because rabbit brain preparations exhibit a factor VII-like activity that is not present in rabbit lung preparations.

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