Fully Integrated Hydrocarbon Reservoir Studies: Myth or Reality?

Abstract: Problem statement: In the petroleum industry and especially during reservoir studies, data coming from different disciplines must be combined in order to generate a model that is representative of the reservoir being studied and can be used for defining the most viable development strategy of the field from both an economic and technical standpoint. Each of these disciplines represents an independent piece of a puzzle that is solved by professionals from various scientific fields who have different educational backgrounds. Integration among geophysics, geology, fluid dynamics and geomechanics is truly essential, but requires specific approaches and procedures for generating and calibrating a reservoir model capable of dealing with all and each of these aspects. Approach: Independent workflows were examined for each of the disciplines involved so as to highlight unavoidable interdependencies between static, dynamic and geomechanical models, even when the goal is to tackle each issue separately. Then, the traditional working method was compared to the integrated approach that supports the generation and calibration of models based on data and interpretation results from all the disciplines involved in the entire project. Results: The Construction of a reservoir model should be regarded as a dynamic process, subject to repeated updates as new data is made available and by frequent modifications when inconsistencies are found between the understanding that different specialists have of the same system. This approach has exhibited great advantages in terms of improvement in the quality and flexibility of the model, reduction of working time and generation of a single final model that can be adapted or used for any kind of simulation problem. Conclusion: An integrated approach is necessary for reservoir modeling purposes. Modern reservoir studies should be designed accordingly to permit the full integration of static, dynamic and geomechanical data into a single reservoir model. Integration is always beneficial, even though there still remains a misconception that it is not needed at all times. For this reason, it is recommended that an effort is made to set up a model capable to handle all aspects of a reservoir study each time a new field study is undertaken, even when it is not envisioned that all aspects might be of interest in the futur

ENVIRONMENTAL SUSTAINABILITY OF OIL INDUSTRY

Similarly 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

Fully Integrated Hydrocarbon Reservoir Studies: Myth or Reality?

Abstract: Problem statement: In the petroleum industry and especially during reservoir studies, data coming from different disciplines must be combined in order to generate a model that is representative of the reservoir being studied and can be used for defining the most viable development strategy of the field from both an economic and technical standpoint. Each of these disciplines represents an independent piece of a puzzle that is solved by professionals from various scientific fields who have different educational backgrounds. Integration among geophysics, geology, fluid dynamics and geomechanics is truly essential, but requires specific approaches and procedures for generating and calibrating a reservoir model capable of dealing with all and each of these aspects. Approach: Independent workflows were examined for each of the disciplines involved so as to highlight unavoidable interdependencies between static, dynamic and geomechanical models, even when the goal is to tackle each issue separately. Then, the traditional working method was compared to the integrated approach that supports the generation and calibration of models based on data and interpretation results from all the disciplines involved in the entire project. Results: The Construction of a reservoir model should be regarded as a dynamic process, subject to repeated updates as new data is made available and by frequent modifications when inconsistencies are found between the understanding that different specialists have of the same system. This approach has exhibited great advantages in terms of improvement in the quality and flexibility of the model, reduction of working time and generation of a single final model that can be adapted or used for any kind of simulation problem. Conclusion: An integrated approach is necessary for reservoir modeling purposes. Modern reservoir studies should be designed accordingly to permit the full integration of static, dynamic and geomechanical data into a single reservoir model. Integration is always beneficial, even though there still remains a misconception that it is not needed at all times. For this reason, it is recommended that an effort is made to set up a model capable to handle all aspects of a reservoir study each time a new field study is undertaken, even when it is not envisioned that all aspects might be of interest in the future

Preliminary investigation on the geological potential for underground hydrogen storage (uhs) in saline formations in italy

In the last years, energy transition from fossil fuels to renewable resources has been largely acknowledged as a necessity to reduce emissions of greenhouse gases in the atmosphere. Hydrogen, the simplest element on Earth, can play an important role in this transition. It is not as an energy source but rather as an energy carrier: in layman’s terms, electricity is converted in chemical energy, which can then be converted again in electricity or in green methane, if combined with carbon dioxide. Because hydrogen can be obtained from the excess of electricity produced from power plants or from renewable energy sources, such as solar panels or wind mills, it is a clean and sustainable form of energy, to be stored and used when needed. As a consequence, a key issue is hydrogen storage. Large metallic containers are typically used to this end but their capacity is limited. Given the increasing hydrogen production and perspective large use, the only viable alternative is underground storage in geological formations, which can be depleted hydrocarbon reservoirs, deep saline aquifers, or cavities in salt domes. Underground hydrogen storage (UHS) is already in use in various countries and mostly in salt caverns artificially made by circulation of fresh water. In the Italian territory there are several areas where saline deposits are both observable as outcrops or detected deep in the subsoil. Their thickness and their geological, petrophysical and mechanical characteristics vary from one area to another depending on the depositional conditions, which favored the formation of different sedimentary facies. These characteristics have a strong impact on the decision to convert a saline dome into a hydrogen storage and, therefore, they should be thoroughly investigated. The aim of this work is to map the salt formations mapped on the Italian territory and to preliminarily assess their potential on the basis of the geological characteristics for a possible future use as underground hydrogen storages

Global Energy Demand and Its Geopolitical and Socioeconomic Implications: Which Role Would Shale Resources Have?

This paper discusses the geopolitical and socioeconomic implications the development of shale gas (& oil) has had in the US. The approach has been that of placing shale gas under erasure (or sous rature). In other words, the assumption that shale is currently both present/absent was made to answer the question of whether it can actually be considered as a resource. Moreover, the success of the “shale revolution” in the US has not only had an impact on the International Oil & Gas, Petrochemical, natural resource and renewable markets, but it has also triggered certain geopolitical events which are modifying the role played by nations globally. Finally, it is suggested that under the prevailing circumstances these unconventional resources appear to still be more of a challenge than part of the solution to the ever growing energy demand, and production of goods associated with societal needs/aspirations worldwide

Pressure detrending in harmonic pulse test interpretation: When, why and how

In reservoir engineering, one of the main sources of information for the characterization of reservoir and well parameters is well testing. An alternative to the standard drawdown/buildup test is Harmonic Pulse Testing (HPT) because it can provide well performance and reservoir behavior monitoring without having to interrupt field production, which is appealing from an economic standpoint. Recorded pressure analysis is performed in the frequency domain by adopting a derivative approach similar to conventional well testing. To this end, pressure and rate data must be decomposed into harmonic components. Test interpretability can be significantly improved if pressure data are detrended prior to interpretation, filtering out non periodic events such as discontinuous production from neighboring wells and flow regime variations that did not respect the designed test periodicity. Therefore, detrending offers the possibility of overcoming the limitation of HPT applicability due to the difficulty of imposing a regularly pulsing rate for the whole test duration (typically lasting several days). This makes HPT attractive for well performance monitoring, especially in gas reservoirs converted to underground gas storage. In this paper, different detrending methodologies are discussed and applied to synthetic and real data. Results show that, if a proper detrending strategy is adopted, information provided by HPT interpretation can be maximized and/or improved

Application of A* algorithm for tortuosity and effective porosity estimation of 2D rock images

Characterization and understanding of fluid flow phenomena in un-derground porous media at the micro and macro scales is fundamental in reser-voir engineering for the definition of the optimal reservoir exploitation strategy. Laboratory analyses on rock cores provide fundamental macroscale parameters such as porosity, absolute and relative permeability and capillary pressure curves. In turn, macroscale parameters as well as flow behavior, are strongly af-fected by the micro geometrical features of the rock, such as pore structure, tor-tuosity and pore size distribution. Therefore, a thorough comprehension of sin-gle and multiphase flow phenomena requires analyses, observations and charac-terization at the micro scale. In this paper we focus on the analysis of a 2D bina-ry image of a real rock thin section to characterize the pore network geometry and to estimate tortuosity, effective porosity and pore size distribution. To this end, a geometrical analysis of the pore structure, based on the identification and characterization of the set of the shortest geometrical pathways between inlets and outlets pairs, is implemented. The geometrical analysis is based on the A* path-finding algorithm derived from graph theory. The results provided by the geometrical analysis are validated against hydrodynamic numerical simulation via the Lattice Boltzmann Method (LBM), which is well suited for simulating fluid flow at the pore-scale in complex geometries. The selected rock for this analysis is Berea sandstone, which is recognized as a standard rock for various applications such as core analysis and flooding experiment. Results show that the path-finding approach provides reasonable and reliable estimates of tortuos-ity and can be successfully applied for analyzing the distribution of effective pore radius, as well as for estimating the effective porosity

Harmonic pulse testing for gas well deliverability assessment

Harmonic Pulse Testing was introduced in the early 1970’s as a special case of pulse testing. It is characterized by a periodic variation of production/injection rate. Subsequent developments proved that it could provide the same information as a conventional well test (permeability and skin, heterogeneity) in addition to those given by a pulse test (areal connectivity within the reservoir) if proper interpretation models were adopted. Consequently, it can be considered as a promising methodology to test a well during ongoing field operations without stopping production and thus it is very attractive for monitoring well performance, especially of gas storage wells. Initially applied to oil wells, Harmonic Pulse Testing has recently been extended to gas wells for which the assumption of Darcy flow regime is no longer valid because of inertial phenomena and/or turbulence. Harmonic Pulse Testing for gas wells comprises three or more consecutive sequences of pulses characterized by increasing average rate, similar to a Flow After Flow test. The interpretation of a single-well Harmonic Pulse test is based on the derivative approach in the frequency domain to obtain kh and the skin components (mechanical skin and D factor). The possibility of assessing well deliverability from a multi-sequence pulse test was analysed in the research work presented in this paper. Different Pulse test configurations were considered and compared with the well-established Flow After Flow test in terms of deliverability estimate. To this end synthetic well test data were generated and sensitivity to test design, well parameters and reservoir interference were carried out. Results show that multi-sequence pulse tests can be used to obtain the well deliverability of a gas well with the advantage that both the tested well and the neighboring wells needn’t be shut-in prior to or during the test

Prove di Pozzo non Convenzionali a Basso Impatto Ambientale

Le prove di produzione eseguite su pozzi a olio o a gas consentono di caratterizzare alcuni parametri chiave per la descrizione del comportamento fluido-dinamico di pozzo e di giacimento. Le prove di produzione di tipo convenzionale vengono eseguite erogando una o più portate costanti, registrate in superficie, e misurando la corrispondente evoluzione della pressione nel tempo a fondo pozzo. Durante la fase esplorativa e di delimitazione del giacimento, specialmente in ambienti off-shore, i fluidi prodotti durante la prova vengono generalmente bruciati in fiaccola. Nell’ottica di una maggiore tutela e sicurezza dell’ambiente, una delle alternative più promettenti è rappresentata dalle prove di iniezione che consistono nell’iniettare un fluido, liquido o gassoso, in giacimento e registrare la risposta dinamica del sistema. Tali prove consentono pertanto di evitare l’erogazione di fluidi in superficie e quindi l’emissione di gas esausti in atmosfera a seguito della combustione in fiaccola nonché qualsiasi rischio di sversamento nel caso di miscele di idrocarburi liquidi o di fuga nel caso di miscele di idrocarburi gassosi. Gli studi sinora condotti hanno riguardato sia gli aspetti teorici, soprattutto allo scopo di poter progettare e interpretare correttamente questo tipo di prove, sia l’analisi di alcune applicazioni reali ai fini di validare le potenzialità delle prove di iniezione come efficace alternativa alle prove di produzione tradizionali. Lo studio fa parte del programma di ricerca del polo SEADOG (Safety & Environmental Analysis Division for Oil & Gas), nato nell’ambito della collaborazione tra il Politecnico di Torino e la Divisione DGS del MISE sul tema della sicurezza off-shore

2D Microfluidic Devices for Pore-Scale Phenomena Investigation: A Review

Underground porous media are complex multiphase systems, where the behavior at the macro-scale is affected by physical phenomena occurring at the pore(micro)-scale. The understanding of pore-scale fluid flow, transport properties, and chemical reactions is fundamental to reducing the uncertainties associated with the dynamic behavior, volume capacity, and injection/withdrawal efficiency of reservoirs and groundwater systems. Lately, laboratory technologies were found to be growing along with new computational tools, for the analysis and characterization of porous media. In this context, a significant contribution is given by microfluidics, which provides synthetic tools, often referred to as micromodels or microfluidic devices, able to mimic porous media networks and offer direct visualization of fluid dynamics. This work aimed to provide a review of the design, materials, and fabrication techniques of 2D micromodels applied to the investigation of multiphase flow in underground porous media. The first part of the article describes the main aspects related to the geometrical characterization of the porous media that lead to the design of micromodels. Materials and fabrication processes to manufacture microfluidic devices are then described, and relevant applications in the field are presented. In conclusion, the strengths and limitations of this approach are discussed, and future perspectives are suggested