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Collaborating Authors
Rospo Mare Integrated Reservoir Study Italy, Adriatic Sea: An Innovative Approach of Karst System Modeling and History Match
Bellentani, G.. (Edison) | Godi, A.. (Edison) | Siliprandi, F.. (Edison) | Terdich, P.. (Edison) | Famy, C.. (Beicip-Franlab) | Fournier, F.. (Beicip-Franlab) | Jumeaucourt, C.. (Beicip-Franlab) | Leandri, P.. (Beicip-Franlab) | Le Maux, T.. (Beicip-Franlab)
Abstract Rospo Mare is a heavy oil fractured karstic carbonate reservoir producing since the 80's. Reservoir pressure is constant due to a strong aquifer tilted toward north east. The producing wells are systematically operated at critical rate to prevent water production (no water treatment installation). The paper is focused on the modeling of the fractures and the karst system in conjunction with an innovative history match approach used to match the forced anhydrous oil production and to represent the complex water position and behavior through time. As the main fracturing phase of Rospo Mare reservoir occurred before the karstification phase, the dissolution of the carbonates was guided by the existing fracture network. The karst system and the fracture network were modeled together thanks to a fracture model that includes several enlarged fracture sets and lineaments. The fracture modeling was also guided by the relative compactness of the matrix facies distribution. Because of limited data for fracture characterization, the dynamic characteristics of fractures, particularly the aperture of enlarged fractures, were fully considered as history match parameters. The history match approach consisted in using both the historical oil production and the prediction period to make sure that the wells were producing at their critical rate and ensure a realistic displacement of water at both field and well levels. This unusual strategy was necessary because of lack of data to constrain history match (no water and gas production, no pressure variation). Therefore the history match was performed by taking into account the prediction period through a do nothing case scenario. Based on the assumption of critical rate, a decline of the oil production rate is expected during the prediction period. This allowed assessing the vicinity of water at wells: both the rise of the water table and the coning effect at wells. The matched model successfully honors the water displacement and position at key wells including the last two side tracks drilled in 2012. The model allows a good representation of the reservoir physical behavior and provides a useful tool for piloting the field and assisting future decisions.
- Europe > Italy (0.83)
- North America > United States > Texas (0.46)
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Geological Subdiscipline (1.00)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation > History matching (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Best available copy Abstract Rospo Mare field is located in the Adriatic sea (Italy) 20 km off the Abruzzes coast, at a mean water depth of 80 meters. The joint venture ELF-AGIPstarted its development in 1982 with a pilot. For years now, this field is producing heavy oil from three platforms and twenty eight wells (two verticalsand twenty six horizontals). It is then one of the longest production history with horizontal wells actually available in the world. The challenges for the development of Rospo Mare field have been numerous and various in their nature as described as follows:โthe reservoir is a karst, essentially conductive, which is extremely different from a conventional reservoir. This is one of the reasons why a development with horizontal wells has been decided in order to increase the drainage area by intercepting as many fractures as possible with a limited number of wells. Also, such a reservoir cannot be simulated with the usual techniques. Therefore, several approaches as well as in the petrophysical parameters determination than in the reservoir simulation techniques, have been attempted to better describe the sweeping mechanism during the production period, โthe oil is very viscous (437 cPo at reservoir conditions) and heavy (0.962g/cm3 at reservoir conditions), which obliges to take care of the thermal and friction problems in the well during the production. This aspect may be crucial in some conditions as described in this paper, โthe water/oil contact is tilted,, and a strong hydrodynamism has been identified (no pressure decline). However, the inlets and outlets of the system were totally unknown. A new approach has been recently conducted using a finegridded model to better determine this system, and then to simulate the evolution of the water/oil contact during the production. It has also allowed to localize the oil actually remaining in place, and then to study the influence of several future production scenarii on the evolution of the water/oil contact, โfor not trapping oil in the reservoir and not to separate the water at surface because of the weak difference between the oil and water densities at these conditions, it has been decided to produce each well of Rospo Mare at its critical rate. The use of horizontal wells has allowed to increase the potential values of these critical rates in comparison with the ones which would have been obtained with vertical wells. In addition, with such a production philosophy, it has been shown theoretically that the critical rate can be written as a parabolic function of the cumulative production. This model, based on the stability of the water cone under the well during the production at its critical rate, has allowed to match the production historyand then to extrapolate it for the next years, โthe oil is also undersaturated with a very low saturation pressure (5.4bar for a reservoir pressure of 130.4 bar) and a GOR of 2.1 m3/m3. As a consequence, the well head flowing pressure is less than 10 bar and very sensitive at water presence. It has been shown that, due to the nature of the reservoir, the surface pressure can be restored removing the water present inside the well by injecting one well volume of oil. The aim of this paper is then to summarize the main steps of this long understanding process of the Rospo Mare behavior, and to highlight the innovative solutions developed in each area. Also, it is shown how all of these aspects are integrated in the daily regulation of the production in order to optimize the final recovery. Introduction In 1975, the vertical well Rospo Mare 1, at a mean water depth of 80 m in the Adriatic sea, discovered an oil accumulation at 1350 m/SL in a karsticalbian to cenomanian reservoir. From 1976 to 1979, three other appraisal wells were drilled. One of them (Nasello Mare 1) enabled to determine the Northern limit of the reservoir. The two others wells (Rospo Mare 2 and 3), located in the center of the field were favorable. At that time, the problem was to determine whether it was possible to extract this heavy oil from the reservoir, raise it to the surface and bring it to the refinery. Favoured by the high crude prices of this period, it has been decided in 1980 to go forward with a production pilot. The objective was to understand the production mechanism and to identity the best development scenario for Rospo Mare. P. 473
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Geological Subdiscipline (1.00)
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (0.91)
Abstract Kharyaga Object 2 is an oil bearing reservoir with a gross thickness of 160-250m deposited on a rimmed shelf system. Two domains can be distinguished: the platform margin (the barrier domain), highly fractured and karstified, and the platform interior (the back-barrier domain), almost fault and fracture-free, non-karstified, and which shows a matricial behavior. Both domains are developed. As per current vision, flow behavior in the barrier part is mainly controlled by different dissolution features and a complex secondary porosity network. Field development started in 1999 and significant amounts of data were acquired (extensive use of down-hole gauges โ MDT โ PLT, well tests, interference tests, etc.). Integration of new data into the dynamic model required a rigorous history match process and an efficient workflow with a permanent link to the geological vision. A progressive match by steps (conductivity ร static pressure ร watercut ร vertical inflow performance ร well interference) helped to avoid being overwhelmed by the amount of data to be matched. This elaborated matching scheme permitted, as a result, to distinguish and reveal the impact of all types of heterogeneities on the matching process (matrix, karst or fracture dominated) and calibrate a complex representation with a dual medium (matrix and secondary media, the latter merging various types of karst, faults and fractures). Representing properly the field complexity required a significant number of cells, as well as the use of specific mechanisms (imbibition with hysteresis and gravity drainage). To simulate such sophisticated representations in a reasonable time, a new powerful software and high computational power were required. As a result of the smart use of acquired data for the calibration of the dynamic model, a powerful tool for reliable production forecast and business management was developed.
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Geological Subdiscipline > Geomorphology (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
Copyright 2012, Society of Petroleum Engineers This paper was prepared for presentation at the SPE Russian Oil & Gas Exploration & Production Technical Conference and Exhibition held in Moscow, Russia, 16-18 October 2012. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright. Abstract This paper presents the successive modeling solutions used to estimate the performance under primary and secondary recovery of the Kharyaga field. Kharyaga object 2 is characterized by different zones of heterogeneities and reservoir type: while platform margin is fractured and karstified, no karstic features are identified in the platform interior, transition zones seems the most complex.
- Europe > Russia > Northwestern Federal District > Nenets Autonomous Okrug (0.91)
- Europe > Russia > Central Federal District > Moscow Oblast > Moscow (0.24)
- Geology > Structural Geology (1.00)
- Geology > Geological Subdiscipline (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.93)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (0.68)
- North America > United States > New Mexico > San Juan Basin > Media Field (0.99)
- North America > United States > New Mexico > Permian Basin > Double Field (0.99)
- Europe > Russia > Northwestern Federal District > Nenets Autonomous Okrug > Timan-Pechora Basin > Pechora-Kolva Basin > Kharyaga Licence > Kharyaginskoye Field (0.99)
- (4 more...)
Abstract Kharyaga Upper Devonian oil reservoir, developed through water injection, is part of a highly heterogeneous carbonate platform. Three sedimentary domains can be identified from South to North: a microbial reef-flat, back-barrier grainy shoals and a non-reservoir lagoon. Static and dynamic data gathered since production start-up revealed that the barrier is extensively fractured and karstified and shows a dual permeability behavior. Understanding the distribution of the dual medium is key to successful development of such a complex reservoir. To capture the relative weight on the flow network of each type of heterogeneity, a new workflow to characterize the dual medium has been developed, including the following steps: karst facies identification from cores and borehole images, comparison of the karst facies over a detailed flow analysis including detailed PLT interpretation; analysis of the facies spatial distribution using various diagenetic scenarios. As a result a new integrated vision of the reservoir and flow system has been consolidated and 3 main emersions followed by a hydrothermal phase have been identified. Each individual emersion generated a complex karst system composed of several components linked to the paleo-topography. Representing properly such a heterogeneous system was coped with by iterating in order to match the dynamic data. A two-stage modeling workflow was used: (1) fast iteration process using a dedicated stochastic tool which generates karst conduits, constrained by infiltration zone, paleo-water-table and paleo-topography; (2) once the right inputs are captured, the forward modeling workflow simulated the process of dissolution and generated at very fine scale a more complex and more consistent system. Finally, this work allowed to model different representations of this complex reservoir capturing the range of remaining subsurface uncertainties and consistent with the integrated interpretation of static and dynamic data. It allows to highlight and evaluate quantitatively the stakes of current and potential new development.
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.48)
- Geology > Geological Subdiscipline > Environmental Geology > Hydrogeology (0.36)
- Geology > Sedimentary Geology > Depositional Environment > Marine Environment (0.34)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (0.88)
- Europe > United Kingdom > North Sea > Central North Sea > South Viking Graben > Block 16/18a > Alpha Field (0.99)
- Europe > United Kingdom > North Sea > Central North Sea > South Viking Graben > Block 15/8 > Alpha Field (0.99)
- Europe > Russia > Northwestern Federal District > Northwestern Federal District > Nenets Autonomous Okrug > Timan-Pechora Basin (0.99)
- (4 more...)