Wall Fracture Research Articles

Свободная кожная пластика как способ устранения рубцового выворота нижнего века (клинический случай)

Abstract. Cicatricial eyelids deformations associated with fractures of orbital walls may result in development of eyelids ectropion and lagophthalmos. Gaping of the eye slit results in secondary lesions of the cornea and a decrease of visual acuity which requires reconstructive plastic surgery with skin flaps transplantation. This report presents a case of cicatricial lower eyelid ectropion elimination after osteosynthesis with metal implant for a fracture of zygomatic orbital complex and lower orbital wall using full-thickness skin flap from preauricular face zone. The paper presents step-by-step description of the surgical technique as well as of the early and late post-op period. As the result of surgery, complete engraftment of the skin graft, elimination of ectropion, restoration of eyelids excursion and closing were achieved. Use of full-thickness skin autograft from preauricular face zone is an adequate choice in reconstructive surgery of the eyelids. The graft has high viability providing minimal risk of rejection. The technique is simple to perform and provides high functional and aesthetic results. Key words: cicatricial ectropion of the lower eyelid; full-thickness skin graft; reconstruction of the eyelids.

Analysis of Patients With Blowout Fracture Caused by Baseball Trauma

Abstract The purpose of this study was to investigate the characteristics of blowout fractures caused by baseball trauma. The authors reviewed 337 cases of blowout fracture surgeries and included 330 eyes of 330 patients who underwent blowout fracture reconstruction between January 2017 and December 2020, in the Department of Ophthalmology at Korea university Hospital. Medical records including patient demography, trauma etiology, accompanied ocular disease, and preoperative computed tomography images were evaluated. Patients were categorized into 2 groups: a group with blowout fracture caused by baseball trauma and another group with trauma due to other causes. Two-wall blowout fracture (orbital floor fracture and medial wall fracture) was most common (63.16%) in the baseball group, followed by medial wall fracture (21.05%). In contrast, orbital floor fracture accounted for the largest proportion (42.11%) among other causes, and 2-wall blowout fracture accounted for the second largest proportion (31.83%). The most common accompanied ocular disease was traumatic hyphema and traumatic iridocyclitis (36.84%) in the baseball blowout fracture group. in contrast, subconjunctival hemorrhage was the most common ocular disease in the other-causes group (16.08%). The frequency of traumatic hyphema and irido-cyclitis was significantly different among the 2 groups (P < 0.05). Distribution of blowout fracture sites and frequent ocular disease differed between baseball blowout fracture patients and other-cause blowout fracture patients.

Effects of Thermal Stress in Hot Dry Rock Fracturing

Summary China has rich geothermal hot dry rock (HDR) resources, but the development and usage of its thermal energy are still at an early stage. At present, few studies have investigated the variation law for fracturing pressure on the borehole wall and fracture wall under the influence of thermal stress. This study investigates the fracturing pressure around the borehole wall based on rock mechanics and thermal stress analysis. Two models were developed: one for borehole wall fracturing pressure with consideration for thermal stress and the other for temperature difference conditions related to the automatic opening of fractures. By analyzing the temperature variation in the fracture wall, the mechanism for the opening of branch fractures at the fracture wall was investigated based on rock mechanics, the theory of fracture extension in hydraulic fracturing, and the theory of thermal stresses. We developed a computational model for tensile or shear damage related to branch fractures in the fracture wall with consideration for thermal stress, as well as a model for temperature difference conditions for the automatic opening of branch fractures. The simulation results show that the fracturing pressure decreased significantly when thermal stress was considered. Under normal geostress and temperature conditions, large temperature difference conditions are needed for the HDR borehole wall to break naturally because of thermal stress alone. During fracture extension, branch fractures on the fracture wall are more likely to form because of thermal stress. Irrespective of the type of damage (tensile or shear), branch fractures on the fracture wall closer to the borehole required lower net fracturing pressure. The decline in the net fracturing pressure was greater in response to shear damage than to tensile damage. In a high-temperature thermal reservoir, when branch fractures in the fracture wall were subjected to the temperature difference conditions for automatic opening, shear damage was more likely to occur than tensile damage. From the results, the following conclusions were obtained: The developed mechanical model of fracture opening reflects the mechanism of fracturing at the borehole wall and the fracture wall during HDR fracturing, thereby revealing the mechanism of the formation of fracture networks under thermal stress. For HDR fracturing, thermal stress promotes the formation of branch fractures in the fracture wall and increases the occurrence of complex fractures in the near-well region. Under thermal stress, the main fractures are less likely to extend in the optimal direction but instead tend to develop into complex fractures, which is not conducive to fracture connectivity between wells.

Coupled electrohydrodynamic transport in rough fractures: a generalized lubrication theory

Fractures provide pathways for fluids and solutes through crystalline rocks and low permeability materials, thus playing a key role in many subsurface processes and applications. In small aperture fractures, solute transport is strongly impacted by the coupling of electrical double layers at mineral–fluid interfaces to bulk ion transport. Yet, most models of flow and transport in fractures ignore these effects. Solving such coupled electrohydrodynamics in realistic three-dimensional (3-D) fracture geometries poses computational challenges which have so far limited our understanding of those electro-osmotic effects’ impact. Starting from the Poisson–Nernst–Planck–Navier–Stokes (PNPNS) equations and using a combination of rescaling, asymptotic analysis and the Leibniz rule, we derive a set of nonlinearly coupled conservation equations for the local fluxes of fluid mass, solute mass and electrical charges. Their solution yields the fluid pressure, solute concentration and electrical potential fields. The model is validated by comparing its predictions to the solutions of the PNPNS equations in 3-D rough fractures. Application of the model to realistic rough fracture geometries evidences several phenomena hitherto not reported in the literature, including: (i) a dependence of the permeability and electrical conductivity on the fracture walls’ charge density, (ii) local (sometimes global) flow reversal, and (iii) spatial heterogeneities in the concentration field without any imposed concentration gradient. This new theoretical framework will allow systematically addressing large statistics of fracture geometry realizations of given stochastic parameters, to infer the impact of the geometry and various hydrodynamic and electrical parameters on the coupled transport of fluid and ions in rough fractures.

Incorporating injection stage into DFIT analysis for permeability estimation, and its significance

Diagnostic fracture injection tests (DFIT) have been broadly used in unconventional reservoirs to derive properties such as initial formation pressure, formation permeability, and closure pressure. DFIT involve pumping a small volume of untreated fluid into the formation to form a small crack. Formation permeability is usually obtained by modeling fluid leakoff during well shut-in. Prevailing studies assume constant fluid pressure boundary conditions on the fracture walls, constant leakoff coefficient, or both. However, the results deduced from these assumptions can introduce tremendous errors because the fluid pressure inside the fracture dissipates fast as fluid leaks off. Therefore, this study proposes a material balance approach to analyze DFIT data and obtain formation permeability. The proposed analysis incorporates fluid leakoff during both injection and well shut-in periods. According to the material balance relationship, volume of water injected during hydraulic fracturing should be equal to the summation of leakoff volume during hydraulic fracturing, leakoff volume during shut-in period and residual fracture volume. Thus, we propose leakoff models for both fracture propagation and shut-in periods. These models are then validated through a few synthetic cases. The model accounting for leakoff during fracture propagation is modified to more accurately calculate the leakoff volume. The model for the shut-in period is solved using the Fourier transform and the eigenfunction expansion method. The results suggest that the proposed DFIT analysis approach can provide a good estimation of the formation permeability. The proposed solution can be used in the field even when pressure data contain significant levels of noise. We showed that more accuracy can be achieved using this method compared to available solutions in the literature.

Experimental Study on Proppant Transport within Complex Fractures

Summary The process of proppant filling within complex fractures is a key factor that determines the effects of volumetric fracturing operation in shale. To address the need of simulating proppant transport within the complex fractures, a large size visual simulation equipment of particle transport within complex fractures was built. The equipment considers roughness and fluid leakoff on the fracture wall and includes branched fractures of different angles. We ensured that the fluid flow and proppant flow were similar to those in the actual fracture and carried out experiments to obtain the influence of operation parameters and fracture parameters on proppant transport, also including injection of special proppants and channel fracturing. Then, we quantified proppant placement through standardized processing of dune shape pictures. The results show that under the influence of perforation, the near-wellbore dune is distributed in a slope shape, and an increase in the perforation density causes dune migration toward the wellbore and proppant accumulation to a certain height within the wellbore. The carrier fluid flow velocity change from 1.0 to 1.5 m/s within the fracture has the greatest effect on the dune equilibrium height (DEH). The dune height only varies slightly after the proppant concentration reaches 12%. Small size proppants have better transport capacity in the slickwater, and the large size proppants are likely to settle down. Combination injection of increasing proppant size improves the filling effect of complex fractures significantly. Pulse injection and stopping pump during fracturing operation have little effect on the transport of conventional proppants. Nevertheless, stopping pump leads to a significant increase in the dune height of the lower density proppants. An increase in the flow rate within the branched fracture leads to the transition in the dune shape from triangle to trapezoid and rectangle. The dune height within the major fracture determines those within the branched fracture, and the proppant volume flowing into the branched fracture determines the dune length. Proppant accumulation within the branched fracture enhances the difficulty in the diversion of carrier fluid to the branched fracture. The proppant tumble area increases within the inclined fracture, which is conductive to proppant transport. The proppants form the dune through bridging within the horizontal fracture, and the dune is less stable than that within the vertical fracture. A reduction in the proppant density and size leads to a significant increase in the proppant transport distance, and the convection effect by concentration difference of the ultralow-density (ULD) proppant is of great significance for propping of the microfractures. In channel fracturing, the proppant and fiber agglomerates are formed at the fracture point with the relatively large fluid leakoff and wall roughness, and the agglomerates grow laterally against the fracture fluid flow direction. A reasonable increase in the injection rate enhances the connectivity between the channels within the fracture. This study provides guidance for the optimization of volumetric fracturing parameters.

The Kocher-Langenbeck approach combined with robot-aided percutaneous anterior column screw fixation for transverse-oriented acetabular fractures: a retrospective study

ObjectiveTransverse-oriented acetabular fractures (TOAFs), including transverse, transverse with posterior wall and T-shaped fractures, are always challenging for double-column reduction and fixation with minimally invasive method. The purpose of this study is to compare the therapeutic effects of robot-aided percutaneous anterior column screw fixation versus minimally invasive anterior plate fixation for TOAFs based on the Kocher-Langenbeck (K-L) approach.MethodsPatients suffering TOAFs that were fixed by robot-aided percutaneous anterior column screw fixation or minimally invasive anterior plate fixation associated with posterior fixation via the K-L approach were divided into two groups: group A (screw fixation) and group B (plate fixation). Surgical time, blood loss, incision length for anterior fixation and complications were recorded. Fracture reduction quality was evaluated using criteria described by Matta. Fracture healing was assessed on the series of pelvic radiographs at each follow-up. Functional outcomes were investigated using the modified Postel Merle D’Aubigne score at the final follow-up.ResultsTwenty-nine patients with TOAFs, including 12 patients in group A and 17 patients in group B, were evaluated for study eligibility. The mean surgical time of anterior fracture fixation was 18.7 ± 4.6 min in group A and 33.4 ± 5.0 min in group B (P < 0.001). The amount of intraoperative blood loss was 615.6 ± 178.7 ml in group A and 719.3 ± 199.0 ml in group B (P < 0.001). Incision length for anterior fixation was 9.0 ± 1.8 mm in group A and 81.2 ± 7.3 mm in group B (P < 0.001). The complications related to the surgery of anterior column only occurred in group B (lateral femoral cutaneous nerve palsy in 1 patient and groin discomfort in 1 patient). No significant differences in reduction quality, hospital stay, fracture healing time and functional results were noted between the two groups.ConclusionThe K-L approach combined with robot-aided anterior column screw fixation is a safe and effective option for TOAFs. Compared with minimally invasive anterior plate fixation, robot-aided screw fixation has obvious advantages on surgical time, blood loss, and invasiveness. The K-L approach combined with minimally invasive anterior plate fixation can also be a reliable alternative for TOAFs, with the similar reduction quality and functional results.

Оптимизация хирургического лечения переломов нижней стенки глазницы у детей с использованием комбинированного доступа

Purpose.. To optimize surgical treatment of fractures of the lower orbital wall in children using combined access. Material and methods. The analysis of the results of surgical treatment of fractures of the lower wall of the orbit in 63 children using combined access performed at the Morozovskaya Children’s hospital in the period from 2018-to 2021 was carried out. Results. The use of the combined approach in surgical treatment of fractures of the lower wall of the orbit in children, including transconjunctival and transnasal access under endoscopic control with installation of a sinus catheter and a membrane of highly purified xenocollagen type 1, makes surgical intervention less traumatic, improves the postoperative period, allows to achieve complete restoration of the eyeball motility and no signs of diplopia. Conclusion. The method makes it possible to restore the integrity of the lower wall of the eye cavity in children aged from one to 18 years without violating the physiological growth of the facial skeleton. Key words: fracture of the lower orbital cavity wall, combined access, endoscopic control

Current Review of Analgesia and Regional Anesthesia Practices for Rib Fracture and Chest Wall Trauma

Current Review of Analgesia and Regional Anesthesia Practices for Rib Fracture and Chest Wall Trauma

DEVELOPMENT OF FIBROUS CALCITE VEINS RELATED TO HYDROCARBON GENERATION AND OVERPRESSURING IN ORGANIC‐RICH SHALE SOURCE ROCKS: THE VACA MUERTA FORMATION, NEUQUÉN BASIN, ARGENTINA

Fibrous calcite bed‐parallel veins (BPVs) are a typical feature of the Upper Jurassic – Lower Cretaceous Vaca Muerta Formation in the subsurface of the Neuquén Basin (Argentina). The formation is considered to be the main source rock in the basin as well as an important unconventional play. This study examines the growth of BPVs through an analysis of core from three wells located along a transect extending for some 150 km from the NE Platform near the basin margin in the east to the Agrio fold‐and‐thrust belt at the Andean deformation front in the west. The main objective is to integrate fluid inclusion data with the palaeothermal and palaeopresure evolution obtained from a regional‐scale 2D basin and petroleum systems model to examine the timing of fracture development and its relationship with hydrocarbon generation in the Vaca Muerta Formation through time.The apertures of BPVs were measured in more than 360 m of core from three wells (wells A, D and E). This data was combined with optical petrography to investigate the number of calcite cementation events, and the temperature of cement precipitation based on fluid inclusion data. The organic geochemical and mineralogical characteristics of the Vaca Muerta source rock were also analysed. The integrated results were incorporated into a poro‐elastic basin model to investigate the impact of horizontal shortening due to Andean compression on pore pressure development and fracturing in the Vaca Muerta Formation. This framework allowed the timing of BPV formation to be determined together with possible mechanisms governing overpressure conditions through time.Near the Andean deformation front in the west of the modelled section where the Vaca Muerta Formation is in the wet gas window (well D) and dry gas window (well A), BPVs are characterized by two or more generations of calcite fibres indicating multiple growth phases. Calcite which precipitated during cementation event 1 (E1) in the internal zones of BPVs consists of crystals oriented perpendicular to fracture walls, indicating perpendicular vein opening. Calcite precipitated during cementation event 2 (E2) in the outer zones of BPVs includes curved and oblique crystals. During this phase, shear occurred between the opening vein walls as a result of horizontal shortening. Cementation event 3 (E3) is characterized by an equant mosaic of calcite crystals which preserve intracrystalline porosity. E1cements formed between 110 and 90 Ma with trapping temperatures of ∼112 °C (upper Vaca Muerta, well A) and ∼125 °C (lower Vaca Muerta, well D). Fracturing resulted from disequilibrium compaction and from volumetric expansion due to primary cracking of kerogen within the oil window. E2 cements record a trapping temperature of ∼159 °C and formed between 70 and 55 Ma (lower Vaca Muerta, well D) during maximum burial of the Vaca Muerta Formation, synchronous with the secondary cracking of retained liquid hydrocarbons and the beginning of Andean compression. E3 cements (upper Vaca Muerta, well A) have a trapping temperature of ∼162 °C, and formed between 65 Ma and 53 Ma synchronous with the generation of thermogenic gas.By contrast, in the east of the modelled section in the less deformed foreland area of the Neuquén Basin where the Vaca Muerta Formation is in the early oil window (well E), BPVs are composed of a single generation of calcite fibres (E1)with a trapping temperature of ∼118 °C. The E1 cement is characterized by calcite crystals which are oriented perpendicular to fracture walls with no evidence of shearing. According to model simulations, cementation here occurred between 64 Ma and 53 Ma during maximum burial and was related to overpressures which resulted from both disequilibrium compaction and primary transformation of kerogen into oil.The data presented suggests that in some intervals of the Vaca Muerta Formation, a slight increase in TOC content is accompanied by an increase in vein thickness, with the highest number of cementation events occurring towards the Andean deformation front in the west of the study area compared to the foreland in the east.

Fluid Inclusion, Isotopic, and Elemental Geochemistry Studies of Cave-Filling Calcite in the Lower–Middle Ordovician Yingshan Formation of Tahe Oilfield, NW China: Implication for Karstification in Non-exposed Limestone

Improving the recognition of paleo-fluid circulation history is of great significance to reconstruct pore evolution during carbonate diagenesis. Integrated petrography, fluid inclusion, isotopic and elemental geochemistry (laser ablation inductively coupled plasma mass spectrometry) studies, calcites generated in paleocaves, and fractures were investigated. This study aims to reveal the paleo-fluid origin and karstification event within the nonexposed limestone of the Lower–Middle Ordovician Yingshan Formation in the Tarim Basin. The only generation of blocky calcite growing along the karst paleocave and fracture walls [cave-filling calcite (CFC)] crosscuts burial stylolites. The secondary fluid inclusions obtained from CFC are characterized by the coexistence of liquid-only and liquid-dominated aqueous inclusions with low salinities values (0–2.4 wt%), suggesting that the CFC has experienced a low-temperature environment (&amp;lt;50°C). The depleted δ18O values (−15.32‰ to 12.45‰), seawater-like yttrium and rare earth element patterns, and low ΣREE (&amp;lt;0.65 ppm) have recorded the major episode of meteoric water leaching the Yingshan limestone. This view was further confirmed by the calculated δ18Owater values of parent fluids (−14.3‰ to 2.2‰). The relatively higher 87Sr/86Sr ratios (0.70942–0.70994) are interpreted as the result of meteoric water interacting with the overlying Silurian detrital rock when percolated downward. The geochemical evidence recorded by CFC indicates that the karstification event for Yingshan nonexposed limestone possibly took place in the Early Hercynian period during the late Devonian. Therefore, meteoric water percolating downward along the fractures penetrating insoluble strata and/or migrating laterally along the permeable strata is deemed responsible for the karstification event, although the overlying thick insoluble strata in the coverage area.

Asymptotic series solution for plane poroelastic model with non-penetrating crack driven by hydraulic fracture

A new class of coupled poroelastic problems describing fluid-driven cracks (called fractures) subjected to non-penetration conditions between opposite crack faces (fracture walls) is considered in the incremental form. The nonlinear crack problem for a plane isotropic setting in a two-phase medium is expressed in polar coordinates as a variational inequality with respect to the solid phase displacement and the pore pressure. Applying nonlinear methods, the asymptotic theory and Fourier analysis, a semi-analytic solution given as the power series in the sector of angle 2π is proven using rigorous expansions with respect to the distance to the crack-tip. Here no logarithmic terms occur in the asymptotic expansion. Consequently, a square-root singularity for the poroelastic medium with a non-penetrating crack is derived, and the integral formulas for calculating the corresponding stress intensity factors are obtained.

Coreflood Effluent and Shale Surface Chemistries in Predicting Interaction between Shale, Brine, and Reactive Fluid

Summary Field and laboratory observations to date indicate that the efficiency of hydraulic fracturing, as it relates to hydrocarbon recovery, depends significantly on geochemical alterations to rock surfaces that diminish accessibility by partial or total plugging of the pore and fracture networks. This is caused by mineral scale deposition, such as coating of fracture surfaces with precipitates, particle migration, and/or crack closure, because of dissolution under stress. In reactive flow-through experiments, mineral reactions in response to acidic fluid injection significantly reduced system porosity and core permeability. The present study focuses on changes to fluid chemistry and shale surfaces (inlet and fracture walls) resulting from shale-fluid interactions and integrates these findings for an improved estimate of transport-related consequences. The pre- and post-reaction shale surfaces were examined by spatially resolved scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis. Importantly, inductively coupled plasma-mass spectrometry/optical emission spectroscopy (ICP-MS/OES) was utilized to probe the chemical evolution of the coreflood effluents. The three study cores selected from the Marcellus formation represent different mineralogies and structural features. In flow-through experiments, laboratory-generated brine and HCl-based fracture fluid (pH = 2) were injected sequentially under effective stress (up to 500 psi) at reservoir temperature (80°C). SEM-EDS results confirmed by the ICP concentration trends showed significant Fe hydroxide precipitates in the clay- and pyrite-rich outcrop sample because of partial oxidation of Fe-bearing phases in the case of intrusion of low salinity water-based fluids. Porosity reduction in the Marcellus Shale Energy and Environmental Laboratory (MSEEL) carbonate-rich sample is related to compaction of cores under stress because of matrix softening with substantial dissolution, and pore filling by hydroxides, as well as secondary barite and salts. Despite the same fluid compositions and experimental conditions used for both MSEEL samples, barite precipitation was much more intense in the MSEEL clay-rich sample because of its greater sorption capacity and additional sulfate source as well as its fissile nature with multiple lengthwise cracks. ICP tests revealed time-resolved concentration behavior in produced brine and reactive fluids that in turn complemented the pre/post-reaction SEM-EDS observations. The greatest release of metal ions into brine was in clay-rich systems indicating the importance of chemical compatibility between in-situ shale and nonequilibrated injection solutions. A thorough examination of surface and effluent data pointed to the substantial influence of formation brine in the shales, mixing of brine with fracture fluid during flow, and shale mineralogy on mineral dissolution and scale formation that significantly affect flow efficiency.

A comprehensive study of the effect of Brinkman flow on the performance of hydraulically fractured wells

The most recent study shows that a rigorous Darcy flow does not exist in hydraulic fractures due to the effect of viscous shear from fracture walls, and the Brinkman equation can be a more accurate method to characterize the fracture flow (Teng et al., 2020). For Darcy flow, the fracture permeability is equivalent to the proppant-pack permeability, whereas, for the Brinkman flow, the fracture permeability is related to the fracture width as well as to the proppant-pack properties. In this work, the authors conducted a comprehensive study of the effect of Brinkman flow on the performance of fractured wells by use of a proposed semi-analytical model. In addition to the Brinkman flow, this proposed semi-analytical model also can account for the geomechanical effect to describe the stress-dependent proppant-pack properties and fracture width. The calculated results in this work show that the fracture permeability is lower than the proppant-pack permeability ascribing to the effect of Brinkman flow. As the production proceeds, the Brinkman flow will play a more important role in influencing the fluid transport within propped fractures. The effect of Brinkman flow on the well performance is significant only if the geomechanical effect is considered. If the fracture volume is sufficiently large or the proppant-pack permeability is sufficiently high, a longer fracture can be more favorable for improving the well productivity. If the Darcy parameter (defined in Eq. (22)) of the hydraulic fracture is less than 0.001, the long-term cumulative production of the fractured wells will not be influenced by the Brinkman flow. If the Darcy parameter is larger than 0.001, the effect of Brinkman flow cannot be neglected unless the Darcy-flow dimensionless conductivity is sufficiently large.

Revisiting reverse osmosis as a mechanism contributing to metal zoning in porphyry copper deposits

The Mid Permian San Pedro porphyry deposit in the San Rafael Massif (central-western Argentina) offers a valuable opportunity to contribute in the understanding of ore concentration mechanisms operating during the phyllic alteration stage. In this deposit, two generations of low-temperature D-veins (D1 and D2) formed during the phyllic alteration stage. The D2-type veins show an atypical Cu-Ag sulfide paragenesis consisting mainly of galena, chalcocite, native silver, chalcopyrite and bornite, which can not be explained using the traditional cooling model. Based on previous research and own data, we test Reverse Osmosis as a possible mechanism contributing to D2-vein ore deposition. Reverse Osmosis is a pressure-driven retention-selective membrane filtration process resulting in solute/ion retention on the high-pressure side of the membrane.D2-veins from San Pedro porphyry formed at 211°–176 °C during transient fluid overpressures produced by the hydrothermal sealing that followed the earlier D1-vein formation. Besides the temperature range and the declining orogeny, physico-chemical conditions were optimal for Reverse Osmosis to activate because the presence of a semi-permeable phyllic membrane and a transmembrane pressure gradient with hydrothermal fluid pressure exceeding the relatively low stress normal to the fracture walls (σn). This particular condition activated Reverse Osmosis, allowing to get similar membrane rejection values for Cu and Ag chloride complexes at lower fluid temperatures, causing the decrease of the osmotic differentiation performance, and the consequent coeval precipitation of Cu and Ag sulfide minerals.

Pressure transient response with random distributed fracture networks using a semi-analytical method for fractured horizontal wells in a rectangular closed reservoir

The focus of this paper is to establish a general model, which is capable of dynamic simulation of discrete fractures at any position and arbitrary distribution in rectangular closed reservoir. In this article, a semi-analytical model for fractured horizontal wells with random distributed fracture networks is proposed to facilitate pressure transient response using a double node method. A rectangular closed reservoir model and fracture network flow model are established respectively, and then coupled at the fracture wall. In order to deal with the flow distribution at the fracture intersection, a simple adaptive material balance method is proposed in this paper, which successfully solves the flow distribution at the intersection. Using advanced mathematical means, the model is successfully solved in Laplace space, and then the pressure response solution in real space is obtained by Stehfest numerical inversion method. The obtained solutions are verified and compared with the numerical simulation results. The calculation results show that the flow characteristics of the orthogonal fracture network can be roughly divided into six stages, namely, bi-linear flow, first linear flow, first radial flow, second linear flow, second radial flow and boundary dominated flow. However, these flow characteristics will deviate or even be missing, depending on the complexity of the fracture network. Finally, the effects of some important parameters (such as dimensionless fracture network conductivity, main fracture length, fracture network density, reservoir area and eccentric position) on pressure response and pressure field distribution are discussed in detail.

An experimental investigation on the influence of temporary plugging fibers and particles on the fracture conductivity

After temporary plugging and fracturing, some of the difficult-to-degrade temporary plugging agents (fibers and particles) in the fractures will affect the conductivity and ultimately affect the rate of oil production. However, the influence law and mechanism of the fibers and particles on the fracture conductivity are still unclear. In order to solve this problem, based on the FCS-842 fracture conductivity test system, the influence law and mechanism of fibers and particles on the fracture conductivity were investigated. The experimental results show that the larger particles support the fracture wall when particles are contained, resulting in higher conductivity. Further studies have found that high fibers content will lead to a significant decrease in the fracture conductivity under low closure pressure. However, high particles content means high fracture conductivity. The placement position of fibers and particles also affects the fracture conductivity. When the pressure is 10 MPa, the conductivity is maximum when the fibers and particles are placed at the fracture opening. Then, when the pressure increases, the conductivity drops sharply by about 88%. When the closure pressure is ≥ 20 MPa, the conductivity is the highest when the fibers and particles are placed at the fracture tip, followed by the middle of the fracture and the smallest at the fracture opening. After analysis, at the fracture opening, the high flow velocity forms a fiber “Barrier” in the fracture, which makes the conductivity decrease rapidly. In the middle of the fracture, the “Dot-net” structure composed of fibers and particles makes the fracture conductivity decrease, but the decrease amplitude and speed are small. At the fracture tip, the lower flow rate makes the fibers and particles form “Clusters”, and the large flow channel between the clusters makes the fracture conductivity higher than the former two. When the fibers and particles are evenly laid, the fibers are easy to form clusters with the particles to block the flow channel, reducing the fracture conductivity.

Revision Hip Arthroplasty After Acetabular Cup Protrusion

Acetabular protrusion after total hip arthroplasty is considered to be produced by an acetabular defect resulting from the displacement of the acetabular cup medially. The most frequent cause, a fractured medial wall, can lead to important impediments in performing revision total hip arthroplasty (RTHA). When it comes to an anterior hip replacement that requires revision, it may need a different approach. This case suggests an intersting alternative in the management of these rare and problematic pathologies. We would like to present the case of an acetabular fracture with a protrusion at the level of the acetabulum in a 52-year-old patient following a falling trauma from the same level and which presented itself one year after the trauma. The surgical intervention consisted in extracting the acetabular cup and reaming the acetabular fossa, filling the remaining defect with bone graft and bone cement, and then applying a semi-retentive cemented cup. The recovery was complete and uneventful. Thus, although it is known that acetabular protrusion can occur in rarer cases in people with a total hip prosthesis, we want to increase attention to this complication. A thorough initial assessment must be performed to identify the patients who may require stabilization of the pelvic ring.

A dimensionally-reduced fracture flow model for poroelastic media with fluid entry resistance and fluid slip

We develop a model which couples the flow in a discrete fracture to a deformable porous medium. To account for the discrete representation of the fracture, a dimensionally-reduced fluid flow model is proposed. The fluid flow model incorporates both a reduced permeability of the fracture walls due to the skin effect, and a slip of fluid flowing along the permeable fracture walls. Biot's model for poroelastic media is coupled to a fracture flow model based on a thin-film approximation of the compressible Navier-Stokes equations. The fracture flow model incorporates a fluid entry resistance parameter to relate the leak-off through the fracture walls to a pressure jump across the fracture walls, and the Beavers-Joseph-Saffman slip rate coefficient to represent the fluid slip along the fracture walls. The numerical model is based on a thermodynamic framework in which all energy storage and dissipative mechanisms in the problem are identified, including the mechanisms related to the interface effects. The thermodynamic framework is employed to solve the nonlinear coupled problem up to a specified energy range through a Picard iteration technique and to study the model and its results. Studies are presented for a range of fluid entry resistance parameters and Beavers-Joseph-Saffman slip rate coefficients, showing the capability of the model to simulate skin and slip effects in a dimensionally-reduced fracture setting.

High temperature resistant polymer gel as lost circulation material for fractured formation during drilling

A cross-linked polymer gel system used for lost-circulation control during drilling with a high-temperature resistance of 160 °C was prepared from a formulation containing 1% of polymer ZB-1/ZB-2 (1:1 ratio), 0.2% of catechol, 0.4% of hexamethylenetetramine, and 0.3% of thiourea. The effects of time, temperature, and salinity on the gelation performance of polymer gel were analyzed. The results indicate that the gelation time of the polymer gel lost-circulation system at high temperature (160 ℃) is 6–20 h, with the maintenance of the storage modulus after gelation at greater than 60 Pa with the loss modulus retained at above 20 Pa. The polymer gel displayed excellent gel strength and viscoelasticity. The salinity has little influence on the viscoelasticity of the gel system, indicating that the gel system has excellent salt-resistance and is suitable for lost circulation control in the drilling process of high-temperature and high-salinity formations. The plugging performance of the polymer gel lost circulation material system on fractures with different widths and roughness was studied. The results show that the bearing resistance capacity of the gel gradually decreases as the fracture width increases, and the lost circulation control performance of the gel is significantly better on rough walls than on smooth walls. In addition, as the fracture width increases, the gel strength contributes to the bearing resistance capacity. This study indicates the excellent lost-circulation-control performance gained using the polymer gel LCM for fractures. To improve lost-circulation-control performance, the gel strength and the cementing force between the gel and the fractured wall must be improved.