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

coping with uncertainties through an automated workflow for 3d reservoir modelling of carbonate reservoirs

Abstract Reliable 3D modelling of underground hydrocarbon reservoirs is a challenging task due to the complexity of the underground geological formations and to the availability of different types of data that are typically affected by uncertainties. In the case of geologically complex depositional environments, such as fractured hydrocarbon reservoirs, the uncertainties involved in the modelling process demand accurate analysis and quantification in order to provide a reliable confidence range of volumetric estimations. In the present work, we used a 3D model of a fractured carbonate reservoir and populated it with different lithological and petrophysical properties. The available dataset also included a discrete fracture network (DFN) property that was used to model the fracture distribution. Uncertainties affecting lithological facies, their geometry and absolute positions (related to the fault system), fracture distribution and petrophysical properties were accounted for. We included all different types of uncertainties in an automated approach using tools available in today's modelling software packages and combining all the uncertain input parameters in a series of statistically representative geological realizations. In particular, we defined a specific workflow for the definition of the absolute permeability according to an equivalent, single porosity approach, taking into account the contribution of both the matrix and the fracture system. The results of the analyses were transferred into a 3D numerical fluid-dynamic simulator to evaluate the propagation of the uncertainties associated to the input data down to the final results, and to assess the dynamic response of the reservoir following a selected development plan. The "integrated approach" presented in this paper can be useful for all technicians involved in the construction and validation of 3D numerical models of hydrocarbon-bearing reservoirs and can potentially become part of the educational training for young geoscientists and engineers, since an integrated and well-constructed workflow is the backbone of any reservoir study

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

Fluid Production Dataset for the Assessment of the Anthropogenic Subsidence in the Po Plain Area (Northern Italy)

Fluid produced/injected volumes from/into underground natural formations and their spatial allocation play a key role in addressing the superposition of anthropogenic subsidence effects, but the definition of coherent datasets is usually very challenging. In this paper, the creation of a gas and water production dataset for the Po Plain area in northern Italy is presented, focusing on the Emilia-Romagna region (an industrialized, highly-populated area characterized by rapid subsidence). The produced volumes and their spatial/temporal allocation are gathered from different sources, analyzed, and organized via dedicated georeferenced maps. The geological framework of the Po Plain is delineated, with attention to the superficial aquifers. Reference ranges of petrophysical and pseudo-elastic parameters are reported for both aquifer and reservoir formations. Water extractions from the superficial unconsolidated sediments are widespread, both in space and time; instead, primary gas production and underground storage of natural gas, involving deeper formations, are spatially and temporally well constrained. Drastic increases in water production and high concentrations of gas production temporally coincided between the 1950s and 1970s. The ‘hotspots’ of the strongest superposition are recognized in Piacenza, Ferrara, Bologna, and Ravenna provinces. Qualitative and quantitative information represent a reference source for both Oil and Gas Societies and Regional/National authorities in addressing the subsidence analysis to plan the field production life and predict the environmental consequences

Coupling approach in shallow, unconfined aquifers in the Po Plain area: A preliminary study for future ground monitoring purposes.

The use of the coupling approach in analyzing the interaction between the flow field and the stress field in shallow, unconsolidated aquifers allows a better description of the involved phenomena. We perform our study on an area in the Po Plain (northern Italy) in the province of Bologna in Emilia-Romagna based on intended future studies on ground movements due to the superposition of shallow water production with deep underground gas storage. The static geological model of the alluvial sediments, locally exceeding 500 meters of thickness, is developed via a stochastic approach in order to manage the high degree of uncertainty in the system spatial continuity and heterogeneities. Corresponding water production data and piezometric measurements are collected for simulating the dynamic behavior of the shallow aquifer. The high uncertainty in water production data are managed considering a maximum and minimum scenarios on the basis of punctual well measurements and regional trend information. Correlation law between petrophysical parameters and deformation variables are derived for technical literature. The coupling technique is then applied and some sensitivity analysis are developed to assess the effects of the correlation laws. The results are finally compared with the output from the uncoupled techniques

Development of a petroleum knowledge tutorial system for university and corporate training

The increasingly rapid development of the disciplines of petroleum engineering and petroleum geology has led to new methodologies and interpretation techniques forming new knowledge that should be offered quickly and efficiently to modern engineers and geologists. This need is equally important for students as well as for young professionals. Access and training to all scientific information is necessary to ensure success in their future careers. Today, e-learning has become a common medium for the management and distribution of on-line educational content. Learning Management Systems (LMSs) were not only developed to handle a large variety of multimedia content that provides an organized knowledge repository used to accelerate access to information and skill acquisition; but, LMSs can also keep detailed statistics on the use of the available material offering a powerful training and educational tool. In this document, the Petroleum Knowledge Tutorial System, an LMS platform offering a variety of online educational and training options to petroleum engineers and geologists, is presented. It was created using Moodle, open-source software that can be used to create on-line courses. The platform covers fundamental educational concepts in a structured way. It follows an optimized "workflow" that can be applied not only to solve a specific exercise but also any similar problem encountered over the course of one's career. The platform was designed to offer a repository of learning material in various forms and to favor user-platform interactions. It can be used for training and evaluation purposes through exercises and problem solving that the user can perform online by using browsing software along with internet access. Special tools were created and implemented on the platform to assist the user in completing a variety of tasks including performing exercises involving calculations with given data and plots of points or lines on graphs without leaving the learning environment. Furthermore, videos with detailed explanations follow each learning module and provide the full solution to every exercise. The LMS automatically keeps a large statistical database including the users' access to activities on the platform that can be exported and further processed to improve the platform functionality and evaluate the users' performance

Gridding Effects on CO2 Trapping in Deep Saline Aquifers

Three-dimensional numerical models of potential underground storage and compositional simulation are a way to study the feasibility of storing carbon dioxide in the existing geological formations. However, the results of the simulations are affected by many numerical parameters, and we proved that the refinement of the model grid is one of them. In this study, the impact of grid discretization on CO2 trapping when the CO2 is injected into a deep saline aquifer was investigated. Initially, the well bottom-hole pressure profiles during the CO2 injection were simulated using four different grids. As expected, the results confirmed that the overpressure reached during injection is strongly affected by gridding, with coarse grids leading to non-representative values unless a suitable ramp-up CO2 injection strategy is adopted. Then, the same grids were used to simulate the storage behavior after CO2 injection so as to assess whether space discretization would also affect the simulation of the quantity of CO2 trapped by the different mechanisms. A comparison of the obtained results showed that there is also a significant impact of the model gridding on the simulated amount of CO2 permanently trapped in the aquifer by residual and solubility trapping, especially during the few hundred years following injection. Conversely, stratigraphic/hydrodynamic trapping, initially confining the CO2 underground due to an impermeable caprock, does not depend on gridding, whereas significant mineral trapping would typically occur over a geological timescale. The conclusions are that a fine discretization, which is acknowledged to be needed for a reliable description of the pressure evolution during injection, is also highly recommended to obtain representative results when simulating CO2 trapping in the subsurface. However, the expedients on CO2 injection allow one to perform reliable simulations even when coarse grids are adopted. Permanently trapped CO2 would not be correctly quantified with coarse grids, but a reliable assessment can be performed on a small, fine-grid model, with the results then extended to the large, coarse-grid model. The issue is particularly relevant because storage safety is strictly connected to CO2 permanent trapping over time

HOW TO APPROACH SUBSIDENCE EVALUATION FOR MARGINAL FIELDS: A CASE HISTORY

This paper presents the evaluation of the subsidence potentially induced by underground storage of natural gas in a marginal depleted field located in Southern Italy. The critical aspect of the study was the lack of data because economic and logistic reasons had restricted data acquisition at the regional scale to perform a geomechanical study. This limitation was overcome by accurately gathering the available data from public sources so that the geometry of a largescale 3D model could be defined and the formations properly characterized for rock deformation analysis. Well logs, seismic data and subsidence surveys at the regional scale, available in open databases and in the technical literature, were integrated with the available geological and fluid-flow information at the reservoir scale. First of all, a 3D geological model, at the regional scale, incorporating the existing model of the reservoir was developed to describe the key features of a large subsurface volume while preserving the detail of the storage reservoir. Then, a regional geomechanical model was set up for coupled mechanic and fluid-flow analyses. The stress and strain evolution and the associated subsidence induced in the reservoir and surrounding formations by historical primary production as well as future gas storage activities were investigated. Eventually, the obtained results were validated against the measurements of ground surface movements available from the technical literature for the area of interest, thus corroborating the choice of the most critical geomechanical parameters and relevant deformation properties of the rocks affecting subsidence

Source Process of Normal Earthquakes: the 3 February 2002, M6.3 Afyon, Turkey and the 7 September 1999, M5.9 Athens, Greece Earthquakes

The source process of two normal-fault earthquakes, the 3 February 2002, M6.3 Afyon, Turkey and the 7 September 1999, M5.9 Athens, Greece earthquakes are studied using regional, teleseismic and strong motion data. Detailed information derived from teleseismic waveform modeling and source time functions inversions are combined and used to forward model recorded strong ground motion. Both events presented evidence for emergence of strong directivity effects during their rupture, which greatly affected the distribution of strong ground motion. These results are indicative of the contribution of the source factor to the distribution of earthquake damage and consequently of its importance in engineering practice in the proximity of large faults, especially within urban areas