scholarly journals Experimental Study on Fracturing Fracture Deformation Mechanism of Shale Reservoir

2022 ◽  
Vol 9 ◽  
Author(s):  
Zuping Xiang ◽  
Yangyang Ding ◽  
Xiang Ao ◽  
Zhicong Zhong ◽  
Zhijun Li ◽  
...  
Keyword(s):  
Particle Size ◽  
Fracture Surface ◽  
Deformation Mechanism ◽  
Large Scale ◽  
Main Mechanism ◽  
Rock Surface ◽  
Fracture Conductivity ◽  
Fracture Width ◽  
Fracture Deformation ◽  
Sensitivity Factors

After large-scale sand fracturing of horizontal wells in shale gas reservoir, fracturing fractures will deform in the production process. However, fracture deformation will lead to the decrease in fracture conductivity and then cause the decrease of gas well productivity. Therefore, in order to evaluate the fracturing fracture deformation mechanism of shale reservoirs, the shale proppant-supported fracture deformation evaluation experiments were carried out under different proppant types, particle sizes, sanding concentrations, and closure pressure conditions, respectively, and the variation curves of fracture width was calculated by a stereomicroscope under different experimental conditions. Then based on the experimental results, the fracture sensitivity factors and fracture deformation mechanism were analyzed, and the deformation mechanisms of fracturing fractures affected by proppant embedding and crushing were studied emphatically. The analysis results of fracture sensitivity factors indicate that the larger the particle size and hardness of proppant, the lower the sand concentration, proppant embedded on the shale rock surface. Moreover, the deeper the proppant is embedded, the faster the fracture conductivity decreases. In addition, the greater the closure pressure, the more serious is the proppant embedment, and the faster the fracture width decreases. The analysis results of fracture deformation mechanism show that, on the on hand, under variable closure pressure, the proppant with larger hardness and larger particle size is used for fracturing, and the proppant embedded in the fracture surface is the main cause of fracture deformation. However, if only the sand concentration of the proppant in the fracture is changed, the fracture deformation is jointly dominated by the embedding and crushing of the proppant. On the other hand, under constant closure pressure, the main mechanism of fracture deformation is that the proppant is embedded into the fracture surface when the closure pressure is low, but if the closure pressure is high, the main mechanism of fracture deformation is the crushing and compaction of proppant.

Wellbore Strengthening Design Criteria and Enhanced Fracture Gradient for Widening Stable Mud Weight Window and Enabling Safe and Efficient Drilling in Depleted Reservoirs

2021 ◽  
Author(s):  
Chee Phuat Tan ◽  
Wan Nur Safawati Wan Mohd Zainudin ◽  
M Solehuddin Razak ◽  
Siti Shahara Zakaria ◽  
Thanavathy Patma Nesan ◽  
...  
Keyword(s):  
Particle Size ◽  
Ct Scan ◽  
Design Criteria ◽  
Drilling Mud ◽  
Fracture Width ◽  
Wellbore Strengthening ◽  
Fracture Gradient ◽  
Mud Loss ◽  
Gradient Enhancement ◽  
Compound Particle

Abstract Drilling in permeable formations, especially depleted reservoirs, can particularly benefit from simultaneous wellbore shielding and strengthening functionalities of drilling mud compounds. The ability to generate simultaneous wellbore shielding and strengthening in reservoirs has potential to widen stable mud weight windows to drill such reservoirs without the need to switch from wellbore strengthening compound to wellbore shielding compound, and vice-versa. Wellbore shielding and strengthening experiments were conducted on three outcrop sandstones with three mud compounds. The wellbore shielding stage was conducted by increasing the confining and borehole pressures in 4-5 steps until both reached target pressures. CT scan images demonstrate consistency of the filtration rates with observed CT scanned mud cakes which are dependent on the sandstone pore size and mud compound particle size distributions. In wellbore strengthening stage, the borehole pressure was increased until fracture was initiated, which was detected via borehole pressure trend and CT scan imaging. The fractures generated were observed to be plugged by mud filter solids which are visible in the CT scan images. The extent of observed fracture solid plugging varies with rock elastic properties, fracture width and mud compound particle size distribution. Based on the laboratory test data, fracture gradient enhancement concept was developed for the mud compounds. In addition, the data obtained and observations from the tests were used to develop optimal empirical design criteria and guidelines to achieve dual wellbore strengthening and shielding performance of the mud compounds. The design criteria were validated on a well which was treated with one of the mud compounds based on its mud loss events during drilling and running casing.

scholarly journals Effects of CO<sub>2</sub> on particle size distribution and phytoplankton abundance during a mesocosm bloom experiment (PeECE II)

2008 ◽  
Vol 5 (2) ◽  
pp. 509-521 ◽  
Author(s):  
A. Engel ◽  
K. G. Schulz ◽  
U. Riebesell ◽  
R. Bellerby ◽  
B. Delille ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Large Scale ◽  
Phytoplankton Community ◽  
Co2 Enrichment ◽  
Suspended Particles ◽  
Phytoplankton Abundance ◽  
General Importance ◽  
Co2 Treatment

Abstract. The influence of seawater carbon dioxide (CO2) concentration on the size distribution of suspended particles (2–60 μm) and on phytoplankton abundance was investigated during a mesocosm experiment at the large scale facility (LFS) in Bergen, Norway, in the frame of the Pelagic Ecosystem CO2 Enrichment study (PeECE II). In nine outdoor enclosures the partial pressure of CO2 in seawater was modified by an aeration system to simulate past (~190 μatm CO2), present (~370 μatm CO2) and future (~700 μatm CO2) CO2 conditions in triplicates. Due to the initial addition of inorganic nutrients, phytoplankton blooms developed in all mesocosms and were monitored over a period of 19 days. Seawater samples were collected daily for analysing the abundance of suspended particles and phytoplankton with the Coulter Counter and with Flow Cytometry, respectively. During the bloom period, the abundance of small particles (<4 μm) significantly increased at past, and decreased at future CO2 levels. At that time, a direct relationship between the total-surface-to-total-volume ratio of suspended particles and DIC concentration was determined for all mesocosms. Significant changes with respect to the CO2 treatment were also observed in the phytoplankton community structure. While some populations such as diatoms seemed to be insensitive to the CO2 treatment, others like Micromonas spp. increased with CO2, or showed maximum abundance at present day CO2 (i.e. Emiliania huxleyi). The strongest response to CO2 was observed in the abundance of small autotrophic nano-plankton that strongly increased during the bloom in the past CO2 mesocosms. Together, changes in particle size distribution and phytoplankton community indicate a complex interplay between the ability of the cells to physiologically respond to changes in CO2 and size selection. Size of cells is of general importance for a variety of processes in marine systems such as diffusion-limited uptake of substrates, resource allocation, predator-prey interaction, and gravitational settling. The observed changes in particle size distribution are therefore discussed with respect to biogeochemical cycling and ecosystem functioning.

scholarly journals OPTIMISATION OF HYDRAULIC FRACTURING DESIGN IN LOWER OLIGOCENE RESERVOIR, KINH NGU TRANG OILFIELD

2018 ◽  
Vol 18 (3) ◽  
pp. 323-337
Author(s):  
Nguyen Huu Truong
Keyword(s):  
Hydraulic Fracturing ◽  
Complex Structure ◽  
Power Requirement ◽  
Fracture Conductivity ◽  
Fracture Width ◽  
The North ◽  
Fracture Closure ◽  
Average Water ◽  
White Tiger ◽  
Fracture Height

Kinh Ngu Trang oilfield is of the block 09-2/09 offshore Vietnam, which is located in the Cuu Long basin, the distance from that field to Port of Vung Tau is around 140 km and it is about 14 km from the north of Rang Dong oilfield of the block 15.2, and around 50 km from the east of White Tiger in the block 09.1. That block accounts for total area of 992 km2 with the average water depth of around 50 m to 70 m. The characteristic of Oligocene E reservoir is tight oil in sandstone, very complicated with complex structure. Therefore, the big challenges in this reservoir are the low permeability and the low porosity of around 0.2 md to less than 1 md and 1% to less than 13%, respectively, leading to very low fracture conductivity among the fractures. Through the Minifrac test for reservoir with reservoir depth from 3,501 mMD to 3,525 mMD, the total leak-off coefficient and fracture closure pressure were determined as 0.005 ft/min0.5 and 9,100 psi, respectively. To create new fracture dimensions, hydraulic fracturing stimulation has been used to stimulate this reservoir, including proppant selection and fluid selection, pump power requirement. In this article, the authors present optimisation of hydraulic fracturing design using unified fracture design, the results show that optimum fracture dimensions include fracture half-length, fracture width and fracture height of 216 m, 0.34 inches and 31 m, respectively when using proppant mass of 150,000 lbs of 20/40 ISP Carbolite Ceramic proppant.

An Integrated Experimental Method to Investigate Tool-Less Temporary-Plugging Multistage Acid Fracturing of Horizontal Well by Using Self-Degradable Diverters

SPE Journal ◽  
2020 ◽  
Vol 25 (03) ◽  
pp. 1204-1219 ◽  
Author(s):  
Lufeng Zhang ◽  
Fujian Zhou ◽  
Jianye Mou ◽  
Wei Feng ◽  
Zhun Li ◽  
...  
Keyword(s):  
Fracture Surface ◽  
Evaluation System ◽  
Horizontal Well ◽  
Single Type ◽  
Fracture Width ◽  
Acid Fracturing ◽  
Integrated Method ◽  
Tight Carbonate ◽  
Operation Cost ◽  
Insight Into

Summary Tool-less temporary-plugging multistage acid fracturing of horizontal well is a necessary technology to unlock the production potential and enable commercial productivity for tight carbonate reservoirs. However, this technique has not been investigated experimentally yet, and the plugging behavior of diverters within acid-etched fracture is still unclear. In this paper, we propose an integrated method to experimentally study tool-less multistage fracturing with diverters. First, we introduce an innovative 3D printing method to reproduce the roughness of acid-etched fracture surface and design an acid-etched fracture temporary plugging evaluation system to satisfy the requirements of temporary plugging experiments. Then, we conduct a series of plugging experiments to optimize the diverter's formula for creating a tight plugging zone within an acid-etched fracture under different fracture widths. On the basis of the description of the fracture surface, we further analyze the formation process and mechanism of temporary plugging. Finally, we further verify through laboratory experiments using a modified true tri-axial fracturing system the feasibility of using a single type of diverter and combined diverters to achieve tool-less temporary plugging staged fracturing of horizontal well. The experimental results show the following findings: (1) Pure fibers can realize temporary plugging at lower fracture width (≤2 mm). (2) To achieve temporary plugging, the diameter of particulates should not be less than half of the fracture width under the condition of larger fracture width (≥4 mm). (3) The fracture surface morphology affects the formation time of temporary plugging, but does not affect whether temporary plugging is formed or not. (4) Using a steel plate with a smooth fracture surface to conduct optimization experiments will increase the dosage of diverters, thus increasing the operation cost. (5) Pure particulates cannot achieve favorable plugging effect. This study provides an insight into multistage acid fracturing.

Modelling the influence of total suspended solids on E. coli removal in river water

2015 ◽  
Vol 73 (6) ◽  
pp. 1320-1332 ◽  
Author(s):  
Jueying Qian ◽  
Evelyn Walters ◽  
Peter Rutschmann ◽  
Michael Wagner ◽  
Harald Horn
Keyword(s):  
Particle Size ◽  
Large Scale ◽  
Suspended Solids ◽  
Total Suspended Solids ◽  
Sensitivity Coefficient ◽  
Fecal Indicator ◽  
E Coli ◽  
Size Classes ◽  
Sedimentation Process ◽  
Particle Size Classes

Following sewer overflows, fecal indicator bacteria enter surface waters and may experience different lysis or growth processes. A 1D mathematical model was developed to predict total suspended solids (TSS) and Escherichia coli concentrations based on field measurements in a large-scale flume system simulating a combined sewer overflow. The removal mechanisms of natural inactivation, UV inactivation, and sedimentation were modelled. For the sedimentation process, one, two or three particle size classes were incorporated separately into the model. Moreover, the UV sensitivity coefficient α and natural inactivation coefficient kd were both formulated as functions of TSS concentration. It was observed that the E. coli removal was predicted more accurately by incorporating two particle size classes. However, addition of a third particle size class only improved the model slightly. When α and kd were allowed to vary with the TSS concentration, the model was able to predict E. coli fate and transport at different TSS concentrations accurately and flexibly. A sensitivity analysis revealed that the mechanisms of UV and natural inactivation were more influential at low TSS concentrations, whereas the sedimentation process became more important at elevated TSS concentrations.

Microstructure Evolution in Samples Prepared by Filter Pressing and Sintering of Zirconia Nanopowder

2006 ◽  
Vol 45 ◽  
pp. 572-577
Author(s):  
Łukasz Zych ◽  
Krzysztof Haberko
Keyword(s):  
Particle Size ◽  
Fracture Surface ◽  
Relative Density ◽  
Detailed Analysis ◽  
Microstructure Evolution ◽  
Open Porosity ◽  
Porosity Evolution ◽  
Water Suspensions ◽  
Heat Treated ◽  
Different Temperatures

The aim of this work was the investigation of microstructure evolution during sintering of zirconia nanopowder. The powder containing 97 mol. % ZrO2 and 3 mol. %Y2O3, with particle size about 8 nm was prepared by the hydrothermal method. The flocculated and dispersed water suspensions of the powder were filter pressed under 5 MPa, which led to green bodies of relative density about 40%. Samples prepared from the suspensions showed distinct differences in densification behaviour. The observation of the microstructure evolution (i.e. density, fracture surface) in samples heat-treated at different temperatures, and detailed analysis of open porosity evolution were performed.

scholarly journals Estimating Unpropped-Fracture Conductivity and Fracture Compliance From Diagnostic Fracture-Injection Tests

SPE Journal ◽  
2018 ◽  
Vol 23 (05) ◽  
pp. 1648-1668 ◽  
Author(s):  
HanYi Wang ◽  
Mukul M. Sharma
Keyword(s):  
Earth Science ◽  
Mathematical Framework ◽  
Field Scale ◽  
Time Data ◽  
Fracture Conductivity ◽  
Reliable Technique ◽  
Fracture Width ◽  
In Situ Conditions ◽  
Fracture Closure

Summary A new method is proposed to estimate the compliance and conductivity of induced unpropped fractures as a function of the effective stress acting on the fracture from diagnostic-fracture-injection-test (DFIT) data. A hydraulic-fracture resistance to displacement and closure is described by its compliance (or stiffness). Fracture compliance is closely related to the elastic, failure, and hydraulic properties of the rock. Quantifying fracture compliance and fracture conductivity under in-situ conditions is crucial in many Earth-science and engineering applications but is very difficult to achieve. Even though laboratory experiments are used often to measure fracture compliance and conductivity, the measurement results are influenced strongly by how the fracture is created, the specific rock sample obtained, and the degree to which it is preserved. As such, the results may not be representative of field-scale fractures. During the past 2 decades, the DFIT has evolved into a commonly used and reliable technique to obtain in-situ stresses, fluid-leakoff parameters, and formation permeability. The pressure-decline response across the entire duration of a DFIT reflects the process of fracture closure and reservoir-flow capacity. As such, it is possible to use these data to quantify changes in fracture conductivity as a function of stress. In this paper, we present a single, coherent mathematical framework to accomplish this. We show how each factor affects the pressure-decline response, and the effects of previously overlooked coupled mechanisms are examined and discussed. Synthetic and field-case studies are presented to illustrate the method. Most importantly, a new specialized plot (normalized system-stiffness plot) is proposed, which not only provides clear evidence of the existence of a residual fracture width as a fracture is closing during a DFIT, but also allows us to estimate fracture-compliance (or stiffness) evolution, and infer unpropped fracture conductivity using only DFIT pressure and time data alone. It is recommended that the normalized system-stiffness plot (NS plot) be used as a standard practice to complement the G-function or square-root-of-time plot and log-log plot because it provides very valuable information on fracture-closure behavior and the properties of fracture-surface roughness at a field-scale, information that cannot be obtained by any other means.

The Effects of Particle Size-Matching Filling of Spherical Silica on the Flowability of Epoxy Molding Compounds for Large-Scale Integrated Circuits Packaging

2011 ◽  
Vol 194-196 ◽  
pp. 1524-1528 ◽  
Author(s):  
Ming Shan Yang ◽  
Lin Kai Li ◽  
Yang Liu
Keyword(s):  
Particle Size ◽  
Integrated Circuits ◽  
Large Scale ◽  
Simulation Software ◽  
Classical Particle ◽  
Matlab Simulation ◽  
Molding Compounds ◽  
Particle Accumulation ◽  
Spherical Silica ◽  
Twin Roll

By means of matching filling of five kinds of spherical silica with the particle size of 2μm, 3μm, 5μm, 10μm, 20μm respectively, the epoxy molding compounds(EMC) for integrated circuits(IC) were manufactured. Using classical particle accumulation theory, the particle distribution according with Dinger-Funk-Alfred equation was calculated by Matlab simulation software, and then the optimal particle size formulations were obtained. Adding the mixed silica according to the above optimal formulations into epoxy resin, the EMCs were manufactured by twin-roll compounding at 95~105°С . The melt viscosities of varied EMCs were measured by Rotating Rheometer. The results showed that the matching filling of different silica with different particle size can improve the flowability of EMC greatly.

Catalytic action of goethite in the oxidation of 2-chlorophenols with hydrogen peroxide

2007 ◽  
Vol 55 (12) ◽  
pp. 101-106 ◽  
Author(s):  
Y.-T. Lin ◽  
M.-C. Lu
Keyword(s):  
Hydrogen Peroxide ◽  
Particle Size ◽  
Catalytic Oxidation ◽  
Organic Compounds ◽  
Oxidation Rate ◽  
Catalytic Action ◽  
Main Mechanism ◽  
Ferrous Ions

The use of goethite and hydrogen peroxide was recently found to effectively oxidise organic compounds. This research was to investigate the effect of adsorption, pH, Fe2 +  and Fe3 +  on 2-CP oxidation. Results indicated that 2-CP can be decomposed with hydrogen peroxide catalysed by goethite and the oxidation rate increased with decreasing goethite particle size. The optimum oxidation rate was observed at the pH below 3.0.Addition of Fe2 +  and Fe3 +  can enhance the catalytic oxidation rate of 2-CP very efficiently. The main mechanism of goethite catalysing hydrogen peroxide to oxidise 2-CP may be due to the catalysis of ferrous ions and goethite surface.

Sign in / Sign up

Export Citation Format

Share Document