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Various physico-chemical processes are affecting Alkali Polymer (AP) Flooding. Core floods can be performed to determine ranges for the parameters used in numerical models describing these processes. Because the parameters are uncertain, prior parameter ranges are introduced and the data is conditioned to observed data. It is challenging to determine posterior distributions of the various parameters as they need to be consistent with the different sets of data that are observed (e.g. pressures, oil and water production, chemical concentration at the outlet).
Here, we are applying Machine Learning in a Bayesian Framework to condition parameter ranges to a multitude of observed data.
To generate the response of the parameters, we used a numerical model and applied Latin Hypercube Sampling (2000 simulation runs) from the prior parameter ranges.
To ensure that sufficient parameter combinations of the model comply with various observed data, Machine Learning can be applied. After defining multiple Objective Functions (OF) covering the different observed data (here six different Objective Functions), we used the Random Forest algorithm to generate statistical models for each of the Objective Functions.
Next, parameter combinations which lead to results that are outside of the acceptance limit of the first Objective Function are rejected. Then, resampling is performed and the next Objective Function is applied until the last Objective Function is reached. To account for parameter interactions, the resulting parameter distributions are tested for the limits of all the Objective Functions.
The results show that posterior parameter distributions can be efficiently conditioned to the various sets of observed data. Insensitive parameter ranges are not modified as they are not influenced by the information from the observed data. This is crucial as insensitive parameters in history could become sensitive in the forecast if the production mechanism is changed.
The workflow introduced here can be applied for conditioning parameter ranges of field (re-)development projects to various observed data as well.
Neubauer, Elisabeth (OMV Exploration & Production GmbH) | Hincapie, Rafael E. (OMV Exploration & Production GmbH) | Borovina, Ante (OMV Exploration & Production GmbH) | Biernat, Magdalena (OMV Exploration & Production GmbH) | Clemens, Torsten (OMV Exploration & Production GmbH) | Ahmad, Yusra Khan (Nissan Chemical America Corporation)
This work examines the potential use of two different nanoparticle solutions for EOR applications. Combining the evaluation of fluid-fluid interactions and spontaneous imbibition experiments, we present a systematic workflow. The goal of the study was to enable the generation of predictive scenarios regarding the application of Nano-EOR in OMV's assets. Therefore, influence of high and low TAN crude oil, core mineralogy, composition of the nanofluid on wettability alteration and recovery were studied. Nanomaterials used in this work employ inorganic nano-sized particles in a colloidal particle dispersion. We evaluated two types; one utilizes surface-modified silicon dioxide nanoparticles, while the other employs a synergistic blend of solvent, surfactants and surface-modified silicon-dioxide nanoparticles. IFT experiments were performed using a spinning-drop tensiometer and results were compared at ~180 min of observation. Amott-Harvey experiments enabled investigating wettability alteration considering effects of crude-oil composition and core mineralogy (~5 and ~10% clay content).
Interfacial tension reduction was observed for both nanofluids. The blend yielded slightly lower values (~0.5- 0.6 mN/m) compared to the nanoparticles-only fluid (~0.8 mN/m), which is most likely related to the surfactant contained in the formulation. Amott-Harvey spontaneous imbibition experiments depicted clear wettability alterations for both nanofluids. Cores with ~5% clay content exhibited a water-wettish behavior, and additional recoveries using the nanofluids were up to 10%. In the cores containing ~10% clay, the nanoparticle-only fluid spontaneously imbibes to the rock matrix and quickly displaces large amounts of oil (~70% independently of the oil type that was used). Contrary, the blend yields higher recovery from the 10% clay cores, with the high TAN oil than with low TAN oil (57 ± 3 vs. 45 ± 1%). However, in 5% clay cores, faster imbibition was observed when the blend was used, which can be explained by a higher capillary pressure. A special case was observed in cores with 10% clay content (Keuper), where the baseline experiments using brine exhibited a high standard deviation. We attribute this behavior to the large mineralogical heterogeneity of the Keuper cores and the heterogeneous distribution of clays and mineralogical impurities. Both the blend and the surface-modified nanoparticles managed to restore a water-wet state, and additional promising recoveries were up to 65% in the case of strong oil-wetness.
Nano-EOR is an embryonic technology; hence, literature data is scarce on how oil composition and reservoir mineralogy could influence its use to obtain additional recovery and maximize benefits. Our systematic workflow, helps understanding the parameters that require detailed evaluation in order to forecast recoveries for field tests. The experimental synergies provide a good approach to evaluate fluid-fluid and rock-fluid interaction.
Injection of chemicals into sandstones could lead to wettability alteration, where oil characteristics such as the TAN (Total Acid Number) may determine the wetting-state of the reservoir. By combining the spontaneous imbibition principle (Amott-Harvey method) and interfacial tension indexers’ evaluations, we propose a workflow and a comprehensive assessment to evaluate wettability alteration and IFT when injecting chemical EOR agents. The study focused on examining the effect of alkaline and polymer solutions (alone) and alkali-polymer.
The evaluation focused on comparing the effects of chemical agent injection on wettability and IFT due to: core ageing (non-aged, water-wet and aged, neutral to oil-wet); brine composition (no divalent and with divalent ions); core mineralogy (~2.5% and ~10% Clay) and crude-oil type (Low and high TAN). Amott experiments were performed on cleaned water-wet core plugs as well as on samples with restored oil-wet state. IFT experiments were compared for a duration of 300 minutes.
Data was gathered from 48 Amott imbibition experiments with duplicates. IFT and baselines were defined in each case for brine, polymer and alkali on every set of experiments. When focusing on the TAN and aging effects it was observed that in all cases, the early time production is slower and final oil recovery is larger comparing to non-aged core plugs. This data confirms the change of rock surface wettability towards more oil-wet state after ageing and reverse wettability alteration due to chemical injection. Furthermore, application of alkali with high-TAN oil resulted in a low equilibrium IFT. In contrast, alkali alone fails to mobilize trapped low-TAN oil, but causes wettability alteration and neutral-wet state of the aged core plugs. Looking into brine composition, the presence of divalent ions promotes water-wetness of the non- aged core plugs and oil-wetness of the aged core plugs. Divalent ions act as bridges between mineral surface and polar compound of the in-situ created surfactant, hence accelerating wettability alteration. Finally, concerning mineralogy effects, high clay content core plugs are more oil-wet even without ageing. After ageing, a strongly oil-wet behaviour is exhibited. Alkali-polymer is efficient in wettability alteration of oil-wet core plugs towards water-wet state.
Three main points are addressed in the paper: A comprehensive methodology to evaluate wettability and IFT changes for different oil and mineralogy types is presented In particular, for alkali injection, substantial wettability change effects are observed. For high TAN number oils, wettability and IFT effects can be quantified using the methodology and applied for screening of chemical agents for various rock types.
A comprehensive methodology to evaluate wettability and IFT changes for different oil and mineralogy types is presented
In particular, for alkali injection, substantial wettability change effects are observed.
For high TAN number oils, wettability and IFT effects can be quantified using the methodology and applied for screening of chemical agents for various rock types.
Langbauer, Clemens (Montanuniversitaet Leoben) | Hartl, Manuel (Montanuniversitaet Leoben) | Gall, Sergej (OMV Austria Exploration & Production GmbH) | Volker, Lukas (OMV Austria Exploration & Production GmbH) | Decker, Christian (OMV Austria Exploration & Production GmbH) | Koller, Lukas (OMV Austria Exploration & Production GmbH) | Hönig, Stefan (OMV Austria Exploration & Production GmbH)
Tense economic situations push the demand for low-cost oil production, which is especially challenging for production in mature oil fields. Therefore, an increase in the meantime between failure and the limitation of equipment damage is essential. A significant number of wells in mature fields are suffering under sand by-production. The objective of this paper is to show the development process and the testing procedure of an in-house-built, effective downhole desander for sucker rod pumps on the basis of a sophisticated analytical design model.
In weak reservoir zones, often the strategy to prevent equipment damage due to sand by-production is the sand exclusion method using a gravel pack. Nevertheless, a certain amount of small sand grains still enter the wellbore and may damage the sucker rod pumping system over time. In early 2018, various types and sizes of downhole desander configurations were tested at the pump testing facility (PTF) at the University of Leoben (Montanuniversitaet Leoben). In a period of about 4 months, testing took place under near field conditions to find the optimum and most efficient design. The design optimization was focused on the geometry of the swirl vanes and the sand separation distance at the sucker rod pump intake. An analytical model provided the basis for geometric optimization. Concurrently, field tests of the in-house downhole desander were performed in the Vienna Basin that confirmed the findings of the tests at the PTF.
The test results have shown that the downhole desander design and the pumping speed are the most influencing parameters on sand separation efficiency. Poor design in combination with a wrongly selected pumping speed can reduce the sand separation efficiency to lower than 50%, while if all parameters are chosen correctly, the sand separation efficiency can be 95% or higher. The grain size distribution is the additional parameter that enables a decision and ranks the performance. The sensitivity analysis, performed for several downhole desander types, has shown the high dependency of the sand separation efficiency on the major desander design parameters. Proper selection of the components and operating parameters will contribute to an increase in the meantime between failures.
This paper will present the testing configurations, the development of the high-efficiency in-house downhole desander, and the sensitivity analysis performed on the design.
A 1 km long excavated section of the Semmering Base Tunnel has been analysed. With a few exceptions, two distinct and continuous features of the system behaviour can be observed: (1) the displacements of the sidewalls are larger than of the crown and of the shoulder points; (2) the displacements of the right sidewall are larger than those of the left sidewall. As the rock mass in this section comprises different types of rock and the rock mass structure varies too, the anisotropic displacement pattern must have its origin not only in the geology but also in the excavation geometry and in the boundary conditions. To identify the main reasons for the anisotropic behaviour, construction details, primary boundary conditions and the rock mass are analysed (from preliminary investigations / design, and as met during construction). Factors which do not cause such anisotropic behaviour are excluded. Results from numerical simulations validate hypotheses introduced to explain the anisotropic displacements. Including the geological and geotechnical site observations in the study of the displacement pattern, the cause for anisotropic displacements and for any deviation from the normal behaviour could be found. The anisotropy origins from the orientation of the foliation and from the primary stress state with the major horizontal stress pointing either to the left or the right side of the tunnel. Deviations are mostly caused by geological inhomogeneities and structural features.
To evaluate observation results of accomplished projects is key for basic understanding in civil engineering. In tunnelling the engineers still have only an approximate idea about the conditions surrounding the opening even after the tunnel has been excavated. Thus, site observations can contain information helping in identifying the origin of events (i.e. rock falls) and to understand the ground- and system behaviour in general. As every tunnel with its unique distribution of boundary conditions is a prototype, from each case study valuable lessons can be learned for the safe construction of tunnels to be built. In this paper, the system behaviour (i.e. displacements of the shotcrete liner) recorded at the first kilometre of track 1 of the construction lot “SBT1.1”, part of the Semmering Base Tunnel in Austria, is evaluated. The Semmering Base Tunnel consists of two single track railway tunnels with a length of approx. 27.3 km. The construction of the most Eastern lot of which the tunnel section analysed in this study is part of, started in July 2015. With today, 10 August 2019, approx. 3.5 km of each of the 7 km long main tracks of lot “SBT1.1” are excavated. (ÖBB, 2019)
The drilling process is fundamentally controlled by the interaction of the bit with the rock which is characterized by its mechanical properties. The focus of various studies is directed mainly on the optimal design of drill bits and drilling operations related to the (expected) geological situation for a safe and efficient drilling process.
The question arises: "Is it possible to extract any rock properties information from drilling data?". In a previous paper the correlation of drilling properties with the lithology of penetrated formation was evaluated. A clear correlation could be demonstrated by applying different statistical methods.
Based on these results a simplified model for the rock destruction at the bit is developed and a "formation strength parameter S" is defined. As a cut-force parameter in the equation, weight on bit (WOB) is used primarily for vertical sections. For deviated or horizontal sections the differential pressure Delta-p is a more relevant parameter. A new parameter S is calculated as a function of drilling parameters only (RPM, WOB, Delta-p, Bit-size). This new parameter S is compared with existing parameters for rock characterization (Mechanical Specific Energy) and discussed herein.
For four wells this parameter S is plotted as function of the depth representing a first geomechanical model. The main results are:
Well A: Geomechanical characterization of different clastic and carbonate sections of a vertical well. Clastic (sandstone, shale) and carbonate (limestone, dolomite) are clearly separated. The carbonate section is detailed and subdivided in dense-hard and fissured-porous parts.
Well B: Calculations are made for vertical (based on WOB) and deviated/horizontal section (based on Delta-p) and compared; for the deviated/horizontal section the Delta-p version gives more reliable results.
Well C: For a specific section of this well after drilling a profile of Unconfined Compression Strength (UCS) with a standard well-logging algorithm was calculated. A comparison of the "during-drilling" derived geomechanical model in terms of S and the "post-drilling" derived in terms of UCS demonstrates similar tendencies and confirms the character of S as a geomechanical measure.
Well D: Data (WOB, ROP, RPM) for this example are logged as part of a test of the new PDS Digital Drilling technology (Powerline Drillstring Technology) in an igneous formation (phyllite). It demonstrates the ability to discriminate different geomechanical sections of one formation.
OMV's exploration efforts in Austria include the prospecting for new fields in units of the Alpine thrust belt below the Neogene Vienna Basin. Current exploration efforts are targeting the deep and underexplored parts of the Paleogene thrust belt with potentially large structural closures within the so-called Rhenodanubian Flysch units.
Interpretation of fold-thrust structures is primarily based on new 3D seismic reflection data, which images the Paleogene nappes buried below the Neogene Vienna Basin fill and is supplemented by well data. In order to improve the understanding of the structural architecture, the results are compared to the regional structural framework of the Eastern Alps and West Carpathians to the W and NE of the Vienna Basin, respectively.
Spatial seismic interpretation depicts the Rhenodanubian Flysch units being subject to three major phases of deformation during the Paleogene and Neogene:
Our interpretation depicts several large ∼NE-trending structural closures within the deeper parts of the N-vergent Paleogene nappe stack with structural closures of up to 1000 m and areas of up to 5km2. They include Paleogene turbidites, which are known dual porosity fractured reservoirs in producing fields within overlying nappes. The NE-trending structural closures result from both Paleogene N-directed thrusting and subsequent refolding of the N-vergent flysch nappes by Early Miocene NW-directed out-of-sequence thrusts. Comparison of data with the regional tectonic framework suggests that the NW-directed out-of sequence thrusts result from a local reorientation of thrusting and from basement buttressing during the Early Miocene, both being triggered by the shape and geometry of the underlying basement units.
Our results highlight the exploration potential in the deeper parts of the Alpine thrust belt with target depths exceeding 3 km. Due to the complex deformation, challenging reservoir types, high formation pressures and limited amount of data, the exploration of these deep targets translates to higher geological/technical risks and uncertainties, compared to shallower, more traditional plays. However, though very challenging, the deep opportunities have the potential for finding significant resources in an already hypermature hydrocarbon basin.