Frakturirana ležišta oduvijek su bila zanimljiva istraživačima zbog njihove složenosti i važnosti za naftnu industriju te postoji više metoda razvijenih posebno za proučavanje ovoga tipa ležišta. ...Svrha je ovoga istraživanja modeliranje frakturiranoga ležišta na temelju geomehaničke obnove. Istraživanjem je obuhvaćeno ležište Arab unutar strukture koja se sastoji od sedam slojeva vapnenca i dolomita razdvojenih tankim slojem anhidrita. Prvo su osim podataka o intenzitetu, kutu nagiba i azimutu fraktura određene magnitude i smjerovi djelovanja naprezanja u stijeni korištenjem karotažnih podataka, poput fotoelektričnoga apsorpcijskog faktora, gustoće dobivene zvučnom karotažom, šupljikavosti dobivene neutronskom karotažom te podataka s dipolnoga akustičnog skenera, mikroelektričnoga skenera i modularnoga dinamičkog uređaja za ispitivanje stijene. Zatim su interpretirani seizmički podatci te odabrani odgovarajući seizmički atributi. Jedan od izdvojenih atributa bilo je obilježje seizmičkoga atributa koji se koristi za identificiranje velikih fraktura i rasjeda. Upotrebom tih podataka moguće je identificirati različite frakture i rasjede u područjima udaljenim od samih bušotina. Nakon toga je rekonstruiran i početni model ležišta te je dobiveno stanje naprezanja i raspodjela pukotina u stijeni na temelju odnosa između naprezanja, deformacije i elastičnih svojstava postojeće stijene. Model je u konačnici potvrđen uporabom podataka o azimutu i intenzitetu pukotina izmjerenih u testnoj bušotini. Dobiveni rezultati upućuju na dobru povezanost između modela diskretne mreže fraktura koja se koristi geomehaničkom rekonstrukcijom sa stvarnim uvjetima u ležištu. Također je poboljšana i prostorna raspodjela pukotina u usporedbi s determinističko-stohastičkom diskretnom mrežom. Obnovljeni (restaurirani) model poboljšao je i prostornu raspodjelu te doveo do boljega donošenja odluka kod bušenja, projektiranja bušotine te simulacija toka fluida.
Quadrant geometry with permeability and wettability contrast occurs in different events, such as faults, wellbore damage, and perforation zones. In these events, understanding the dynamics of ...immiscible fluid displacement is vital for enhanced oil recovery. Fluid flow studies showed that viscous fingering occurs due to viscous instabilities that depend on the mobility of fluids and capillary forces. Besides, the porous domain heterogeneity is also effective on the formation of fingering. So, the purpose of the current research is to numerically investigate the effect of heterogeneity in wettability and permeability, and flow properties in Saffmann-Taylor instabilities. Numerical simulations with different flow rates in the permeability contrast model illustrated the nodal crossflow, growth of viscous fingering in the nodal part, and bypass flow in the second zone. In the wettability contrast model, a capillary fingering pattern is observed and fluid patches are isolated because of capillary force and the end effects are trapped within the quadrant. Moreover, the consequences of wettability on apparent wettability that alters the fluid-front pattern and displacement efficiency are shown.
Geometrija kvadranta s razlikama u propusnosti i močivosti pojavljuje se kod rasjeda, oštećenja pribušotinske zone ili u zonama perforacija. Kod takvih pojava razumijevanje dinamike istiskivanja ...nemješivoga fluida bitno je za povećanje iscrpka nafte. Studije protjecanja fluida pokazale su kako se viskozno probijanje događa zbog nestabilne viskoznosti fluida, a koja ovisi o mobilnosti i kapilarnim silama. Osim toga, heterogenost šupljikavosti također utječe na probijanje fluida. Stoga je cilj bio numerički istražiti utjecaj heterogenosti močivosti i propusnosti te svojstava protoka na Saffmann-Taylorovu nestabilnost. Numeričke simulacije s različitim protjecanjima i propusnostima prikazale su križni protok i porast viskoznoga probijanja u čvorištu modela te zaobilazni protok u susjednoj zoni. Kod modela s različitom močivošću uočen je oblik kapilarnoga probijanja i sloj izoliranoga fluida, ovisno o kapilarnoj sili i obliku pojave unutar kvadranta. Na kraju je opisan utjecaj prividne na ukupnu močivost te je prikazana posljedica močivosti na prividnu močivost kao silu koja utječe na oblik fronte fluida i efikasnost istiskivanja.
Praćenje kretanja granice dvaju fluida vrlo je važno kod protjecanja dviju faza u poroznoj heterogenoj sredini, osobito kod primjene metoda povećanja iscrpka nafte. S obzirom na viskoznost fluida i ...kapilarni broj moguća su tri različita oblika toka: stabilni te viskozno i kapilarno probijanje. Dodatno, granica fluida i koeficijent obuhvata ležišta istiskivanjem ovise i o heterogenosti porozne sredine. U ovome istraživanju heterogena porozna sredina predstavljena je (1) zonom normalnoga rasjeda ili unakrsne slojevitosti s heterogenom propusnošću i (2) frakturom ili diskontinuitetom između dviju poroznih sredina koja se sastoji od dvaju homogenih slojeva s vrlo niskom i vrlo visokom propusnošću, u kojoj je izvedeno nemješljivo zavodnjavanje kako bi se promatrao koeficijent obuhvata ležišta istiskivanjem i pratilo strujnice toka fluida. Razmatranjem eksperimentalnoga staklenog mikromodela i rezultata simulacije diskontinuiteta utvrđeno je da glavni tok fluida prati pukotinu. Nakon proboja fluid nastoji prodrijeti i kroz međuprostor sačinjen od finih i grubih čestica uokolo pukotine. Štoviše, povećanjem protoka s 1 na 200 ml/h, i kod eksperimentalnoga i kod simulacijskoga modela, došlo je do smanjenja koeficijenta obuhvata ležišta istiskivanjem do trenutka proboja s 14% na 7,3% odnosno s 15,6% na 10%. U zoni rasjeda uočena je ovisnost koeficijenta obuhvata ležišta istiskivanjem i strujnica utisnutoga fluida o upadnome kutu na površinu rasjeda i propusnosti slojeva. Prezentirani stakleni mikromodel i rešetkasti Boltzmannov model bili su u skladu s dinamikom fluida i oba se mogu koristiti za preciznu ocjenu koeficijenta obuhvata ležišta istiskivanjem i vizualizaciju preferiranoga puta kretanja fluida kroz područja unakrsne slojevitosti ili diskontinuiteta kod metoda povećanja iscrpka nafte.
Fractured reservoirs have always been of interest to many researchers because of their complexities and importance in the oil industry. The purpose of the current study is to model the fractured ...reservoir based on geomechanical restoration. Our target is the Arab Formation reservoir which is composed of seven limestone and dolomite layers, separated by thin anhydrite evaporate rock. First of all, in addition to the intensity, the dip, and the azimuth of the fractures, the magnitude and the direction of the stresses are determined using wireline data e.g. photoelectric absorption factor (PEF), sonic density, neutron porosity, a dipole shear sonic imager (DSI), a formation micro imager (FMI), and a modular formation dynamics tester (MDT). Then, the seismic data are interpreted and the appropriate seismic attributes are selected. One of our extracted attributes was the ant tracking attribute which is used for identifying large-scale fractures. Using this data, fractures and faults can be identified in the areas away from wells in different scales. Subsequently, the initial model of the reservoir is reconstructed. After that, the stress field and the distribution of fractures are obtained using the relationship between the stresses, the strains, and the elastic properties of the existing rocks. The model is finely approved using the azimuth and the intensity of fractures in the test well. Our findings showed that the discrete fracture network (DFN) model using geomechanical restoration was positively correlated with real reservoir conditions. Also, the spatial distribution of fractures was improved in comparison to the deterministic-stochastic DFN.
Fluid front tracking is important in two-phase/component fluid flow in porous media with different heterogeneities, especially in the improved recovery of oil. Three different flow patterns of ...stable, viscous fingering, and capillary fingering exist based on the fluids’ viscosity and capillary number (CA). In addition, fluid front and sweep efficiency are affected by the heterogeneity of the porous medium. In the current study, the heterogeneous porous media are: (1) normal fault zone or cross-bedding with heterogeneity in permeability, and (2) a fracture or discontinuity between two porous media consisting of two homogeneous layers with very low and high permeabilities, in which immiscible water flooding is performed for sweep efficiency and streamlines tracking purposes. By considering the experimental glass micromodel and the simulation results of discontinuity, a crack is the main fluid flow path. After the breakthrough, fluid inclines to penetrate the fine and coarse grains around the crack. Moreover, an increase in flow rate from 1 and 200 (ml/h) in both the experimental and simulation models causes a reduction in the sweep efficiency from 14% to 7.3% and 15.6% to 10% by the moment of breakthrough, respectively. In the fault zone, the sweep efficiency and the streamline of the injected fluid showed a dependency on the interface incident angle, and the layers’ permeability. The presented glass micromodel and Lattice Boltzmann Method were consistent with fluid dynamics, and both of them were suitable for a precise evaluation of sweep efficiency and visualization of preferential pathway of fluid flow through cross-bedding and discontinuity for enhanced oil recovery purposes.
Shear wave velocity is one of the essential parameters for describing hydrocarbon reservoirs that have several applications in petrophysical, geophysical, and geomechanical studies. Shear wave ...velocity usually does not exist in all wells, especially in old oil fields. In the current study, two equations of Carroll and Castagna have been modified, and linear and nonlinear multi-regressions were used to estimate shear wave velocity in an oil reservoir in southwestern Iran. Initially, compressional wave velocity and porosity were determined as the most effective wire-line logs on shear wave velocity by comparing their correlations. Then, two equations of Carroll and Castagna were modified. In addition, new equations based on porosity and compressional wave velocity for estimating the shear wave velocity were obtained. Shear wave velocity was estimated by new exponential equations in the wells of the current oil field with excellent goodness of fit by determination coefficients of 0.80 in the whole well, 0.72 in the Ghar-Shale-1, and 0.78 in Ghar-Shale-3 in X-07 well.
Layering detection is an important step in petroleum engineering. Time series of post-stack seismic data and wire-line log data belong to subsurface layering. They exhibit multifractal properties ...with complex patterns because of the heterogeneity and different genetic properties in the earth layers. In a multifractal configuration, any piece of a series has a distinct Hurst exponent that reflects its nature and can be used for zone detection. Time series are post-stack seismic traces and wire-line log data near the well-bores. Self-similar Autoregressive Exogenous (SAE) model is a modified method which can place self-similar post-stack seismic and wire-line log segments across layers with the same lithology. The results satisfy the capability of layering identification from seismic data by SAE model.
Mining wastes are a great source of pollutants. Open-pit backfill materials can be found as waste rock and as tailings. The aim of the current study was the investigation of the contaminant ...transportation pathways by groundwater flow from these waste materials through heterogeneous porous media. Numerical Lattice Boltzmann Method (LBM) was used for examining the effects of different factors on pollutant transportation through groundwater beneath the waste materials. Grain size, vertical and horizontal fracturing, and hydraulic pressure gradient were factors considered here. The results showed that contaminant transportation by the groundwater flow from the waste materials through porous media depends on primary and secondary matrix porosity of the open-pit material, heterogeneity in permeability of aquifer rock, and hydraulic head of groundwater.
Fluid flow in a dual permeable medium (DPM) is essential in solute transport in mining and aquifer studies. In this paper, water flushing into a contaminated DPM containing fine-grained lenses with ...different geometries was investigated with the Lattice Boltzmann Method (LBM). The LBM model used in this study was D2Q9 with a relaxation time of 1, a cohesion value of 3 for a fluid density of 1 (mu.Lu-3). The saturated fluid in the DPM was a contaminant that usually stays in low permeable lenses and after flushing, it is leaked into the porous medium by a second fluid (water). This phenomenon is predominant when the displacing fluid has a lower concentration than the contaminated fluid. Diffusion and advection are the main mechanisms that control fluid flow in the porous medium. The results of the simulations showed: (1) advection controlled solute transport through the flushing phase, and back-diffusion occurred after the change in phase; (2) the lenses’ geometry influenced the fluid flow pattern and the remediation process. As a result, aquifer remediation strategies based on the lenses’ geometry and their permeability can help us select the appropriate environmental protection.
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