1,720,999 research outputs found
Approaches to geomechanical modeling in reservoir engineering
No full textHistorically, much of reservoir simulation has accounted for rock mechanics only by simple use of a constant compressibility. In reality, in many reservoirs fluid flow is intimately coupled with rock mechanics. Therefore, rigorous reservoir simulation should include simultaneous solution of multiphase flow and stresses, and account for the appropriate dependencies between these two processes. The technical literature shows several theoretic approaches to model reservoir behaviour considering different degrees of coupling between rock deformation and fluid flow: from partially coupled to fully coupled methods. Even if these couplings physically exist to some extent in all reservoirs, the need for using more complex, fully coupled geomechanical modeling is generally acknowledged limited to the cases of compacting reservoirs or high-pressure injection operations.
The rock stress-strain conditions must be assessed when conceiving gas storage in aquifers or in other potential new unconventional sites due both to their technical characteristics and to the increasing environmental and public acceptance constraints. Additionally, in the case of underground gas storage the system integrity includes the absence of leakage through the cap rocks over the entire life of the storage and under the alternate injection and withdrawal cycles and, therefore, often requires geomechanical studies
Development of a fully coupled approach for evaluation of wellbore stability in hydrocarbon reservoirs
No full textProblem statement: When a well is drilled in a hydrocarbon reservoir, the original thermodynamic conditions are altered, the natural stresses are redistributed and a stress concentration occurs around the hole. The alteration of the original equilibrium can lead to wellbore damage, sometimes to its complete collapse. Loss of time associated with stability problems is estimated to account for 12-15% of drilling costs world-wide. Approach: The adoption of a reliable modeling approach to predict instability due to time-dependent alteration of natural equilibrium is fundamental for the optimization of drilling plans, completion design and production activities. Results: In this study the possibility of investigating instability phenomena in terms of both stress-strain and thermodynamic formation behavior through a fully coupled thermo-porous-elastic-plastic approach is demonstrated. According to the fully coupled approach, porous flow, temperature development and stress-strain calculations are performed together: the whole system is discretised on one grid domain and solved simultaneously for both the thermodynamic and the geomechanical variables. For the plastic analysis implementation, an iteratively coupled approach was adopted inside the fully coupled routine: the model basic equations (porous flow and rock deformation) and the plastic behavior equations were solved separately and sequentially at each non-linear iteration. The iterative coupling approach corresponds to an implicit treatment of the plastic variables, essential to preserve the stability of the elasto-plastic solution. The key points of the model analytical formulation, of the numerical formalization as well as of the implementation of the adopted solutions to make the thermo-porouselastic-plastic model applicable to assess wellbore stability are presented. Conclusion: The proposed model was first validated and then applied to several synthetic and real cases. In this study the effectiveness of the developed model to investigate the potential impact of instability phenomena on the well drilling design is demonstrated also by discussing the results from a case history
ENVIRONMENTAL SUSTAINABILITY OF OIL INDUSTRY
Full text linkSimilarly to most industrial activities, the oil industry can affect the environment at several stages. The greatest impact is the release of waste into the environment in concentrations that are not natural. Virtually in all cases, the adverse impact can be minimized or eliminated through the implementation of a proper waste management plan. Over the past few years the oil industry has placed greater emphasis on minimizing the environmental impact of its operations in all the main phases of a hydrocarbon reservoir life: from appraisal to field development, from production and recovery to reservoir decommissioning. As a consequence, the oil industry is facing important technical challenges, approaching with great interest and expectation new emerging technologies, such as nanotechnologies and alternative solutions, like CO2 underground storage. This study provides an overview of the most interesting solutions that have been proposed and critically highlights their potential benefits and drawbacks. The following paper focuses on some of the new approaches that have already changed the routine operation workflow, while others are currently being tested and may yet require further improvement
Stability modelling applied to wellbore design
No full textWhen a well is drilled in a hydrocarbon reservoir, the thermodynamic equilibrium of virgin rocks is altered, the natural stresses are redistributed, and a stress concentration occurs around the hole. The alteration of original equilibrium can lead to wellbore yield, evidenced as shear banding and dilatation, circumferential crack, and microfissuring process. Borehole instability represents the main cause for loss of drilling fluids and consequent potential kick problems, and can be so severe to determine the wellbore abandonment. Loss of time associated with stability problems is estimated to account for between 12 and 15% of drilling cost world-wide. Physical and mechanical processes occurring within and around the borehole because of interaction between drilling fluids and rocks can degrade the stability of the wellbore especially in shale intervals, which can make up over 75% of drilled formations. In fact, due to their fine-grained nature and low permeability, in association with high porosity and high fluid saturation, shale minerals are particularly sensitive to time-dependent stability degrade. In order to accurately analyse the complex behaviour of shale minerals, the effects of mechanical deformation, hydraulic diffusion and temperature gradient, as well as their combination must be taken into account. The classic poro-elastic theory, which allows consideration of the coupled phenomena of time-dependent pore fluid diffusion and formation stress variation, fails to capture the effects of temperature gradient and plastic deformation, particularly remarkable in the shale behaviour analysis. So a thermo-poro-mechanical approach, coupling constitutive equations with thermal and hydraulic laws, is necessary to perform accurate time-dependent analyses of stress, pore pressure and temperature distribution around the wellbore in shale formations. This paper presents the analytic formulation of a thermo-poro-mechanical model, in which the basic Desai's model is used to describe the rock plastic behaviour for a mono-dimensional, axisymmetric problem in plane state of strain. With the aid of an in-house software, the proposed model was first validated, also by comparison with the output of a well-known geomechanical numerical simulator available on the market, and then applied to several real and synthetic cases. Based on the results of one of the examined case history, the paper shows how the borehole stability modelling approach is fundamental to systematically take into consideration the stress variations around the hole and the associated rock deformation and pore pressure changes during drilling. The prediction of natural equilibrium time-dependent alterations allows drilling engineers to improve the design phase, to take decisions on critical effects potentially occurring during drilling as well as to optimize completion (e.g. casing placement and/or cementing) of a well
Green methodologies to test hydrocarbon reservoirs
Full text linkProblem statement: The definition and the economic viability of the best development strategy of a hydrocarbon reservoir mainly depend on the quantity and type of fluids and on the well productivity. Well testing, consisting in producing hydrocarbon to the surface while measuring the pressure variations induced in the reservoir, has been used for decades to determine the fluid nature and well potential. In exploration and appraisal scenarios the hydrocarbons produced during a test are flared, contributing to the emissions of greenhouse gases. Approach: Due to more stringent environmental regulations and a general need for reduced operating expenses, the current industry drivers in today's formation evaluation methodologies demand short, safe, cost-effective and environmentally friendly test procedures, especially when conventional tests are prohibitively expensive, logistically not feasible or no surface emissions are allowed. Different methods have been proposed or resuscitated in the last years, such as wireline formation tests, closed chamber tests, production/reinjection tests and injection tests, as viable alternatives to conventional well testing. Results: While various short-term tests, test procedures and interpretation methods are apparently available for conducting successful tests without hydrocarbon production at the surface, clarity is lacking for specific applications of these techniques. An attempt to clarify advantages and limitations of each methodology, particularly with respect to the main testing target is pursued in the study. Specific insight is provided on injection testing, which is one of the most promising methodology to replace traditional well testing in reservoir characterization, except for the possibility to sample the formation fluids. Conclusion/Recommendations: Not a single one method but a combination of more methodologies, in particular injection testing and wireline formation testing, is the most promising strategy to achieve all the targets of a conventional well testing with no surface hydrocarbon production, increased safety during operations and reduction of the testing costs
Application of a cluster analysis-based methodology on InSAR data to detect ground deformations in the Po plain (Northern Italy)
Full text linkThe Po Plain basin in the Emilia Romagna Region (Italy) has been historically affected by strong land movements ascribed to both anthropogenic and natural sources, as well as their superposition. The paper aims to the identification, geolocation and quantification of the main land movement phe-
nomena of the Region via the time-series decomposition and the clustering analysis on the vertical component of satellite DInSAR time-series. The results were interpreted on the basis of ancillary information, such as: land use maps, water production (in terms of wells positions and produced volumes) and position of underground gas storage sites. In particular, the analysis of the purely seasonal components allowed a straightforward correlation between the identified land movement phenomena and the gas storage operations or aquifer recharge/ground water productions seasonality
Cluster analysis applications for ground deformation monitoring due to fluid production/injection in underground geological formations, based on InSAR measurements
Full text linkUnderground storage of natural gas (UGS) represents a key tool worldwide used for giving real-time responses to energy demands, in areas lacking near gas reservoirs or with limited gas supply, becoming strategic against high future prices and temporary shortages (Verga, 2018). UGS involves the cyclical injection and withdrawn of gas into subsurface formations in response to the seasonal energy needs (storage during spring-summer months and production during autumn-winter months). Storage activities are expected to increase for meeting the SDGs (Fibbi et al., 2022) storing also H2 and CO2 as potential energy sources and potential solutions to fulfil the net-zero targets.
The InSAR satellite measurements have been successfully applied for monitoring the anthropogenic induced ground deformations (GD). The effects of UGS activity are characterized by a seasonal cyclical vertical oscillation behaviour (uplift during injection periods and subsidence during withdrawn). (Codegone et al., 2016). Whereas a more continuous behaviour in time for extended time-frame (i.e. trend) is typical of other anthropic-originated GD, like hydrocarbon production or aquifer withdrawn. However, interpreting large InSAR datasets can be difficult due to the volume of data generated, rising the need for a reliable, consistent, versatile and easy-to-deploy investigation approach. This works addresses both challenges studying two cases, one UGS site near Minerbio city, and one coastal zone near to Ravenna, both in the Po Plain area, part of the Emilia-Romagna region in northern Italy
Approccio integrato per l'analisi della subsidenza indotta dalla coltivazione dei giacimenti di idrocarburi
No full textLa variazione della quota altimetrica del piano campagna è imputabile a cause sia naturali sia antropiche. Queste ultime dipendono principalmente dall'emungimento degli acquiferi e dalla coltivazione dei giacimenti di idrocarburi. La verifica che la subsidenza potenzialmente indotta dall'estrazione di fluidi dal sottosuolo non abbia impatto sugli edifici e sulle infrastrutture esistenti nell'area di interesse deve essere condotta valutando sia l'estensione areale del cono di subsidenza sia gli spostamenti massimi. Nel presente articolo viene proposto un approccio numerico 3D per l'analisi dei fenomeni accoppiati fluidodinamici e tenso-deformativi che governano l'evoluzione della subsidenza. Tale approccio si basa sull'integrazione di tre modelli di riferimento: il modello geologico, quello fluido-dinamico e quello geomeccanico. L'approccio di analisi descritto è stato efficacemente adottato per valutare le variazioni altimetriche indotte sul piano campagna dalle attività di uno stoccaggio sotterraneo di gas naturale. L'abbondanza e la qualità delle informazioni disponibili ne facevano un caso studio ideale. L'analisi totalmente integrata ha consentito di ottenere un modello affidabile, come dimostrato dal fatto che il modello è in grado di riprodurre l'evoluzione delle variazioni altimetriche del piano campagna storicamente indotte dalle operazioni di stoccaggio, registrate nel tempo mediante acquisizioni satellitari (misure InSAR)
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