Malave, Alida (PDVSA Oil & Gas) | Carpio, Gelson (PDVSA Gas & Oil) | Bolivar, Manuel (Petroleos de Venezuela S.A.) | Khan Torres, Karem Alejandra (Petroleos de Venezuela S.A.) | Bello, Joaquin Antonio (Petroleos de Venezuela S.A.)
The object of this work was Muri Field, which is located in eastern part of Venezuela. The expectations for this field were high at the beginning of the study. Firstly, the high oil quality of 30 °API; secondly, this field is located near another one under enhanced oil recovery processes with high production rate; and finally, the field has been inactive since 1.994.
This paper presents the use and results of a detailed Reservoir Characterization Model in the evaluation of opportunities for the drilling of new production wells. Applying conventional petroleum engineering methods, numerical simulation, and teamwork carried out the study.
Muri Field had a structural model generated from a 2D seismic interpretation. This model presented high simplicity and little coherence with the actual well information; being necessary to update it. This reservoir study considers a new structural model, based on a 3D seismic interpretation with a structural frame fitting actual data allowing optimizing the exploitation plans. The use of numerical simulation allowed strengthening the conventional reservoir engineering analyses and enhancing the production expectations for the area. The results are based on teamwork and the application of the available technology.
This new engineering study enabled to better evaluate the vertical communication in the field as well as the unification of four different reservoirs; all of them located in the geological formation with higher potential. As a consequence the official field limits were extended, and a lateral communication was established with a large producing field in north of Monagas State. The most relevant results were a two (2) fold increase in recoverable reserves and the evaluation of new exploitation scenarios. The locations of new producer wells were defined taking into account the new boundary area between Muri and the surrounding fields, to improve the final recovery.
Rodriguez, Fernancelys Del Carmen (PDVSA Gas & Oil) | Lopez G., Leonardo (Petroleos de Venezuela S.A.) | Bello, Joaquin Antonio (Petroleos de Venezuela S.A.) | Skoreyko, Fraser A. (Computer Modelling Group Inc)
The Carito-Mulata field is located in eastern Venezuela. This field is ranked as a giant oil producer because of its 240,000 STB/D current oil production and its 6.5 MMMSTB original oil in place. It is possible to observe a significant compositional gradient from seventy-five fluid samples taken at different depths, over a column of fluids of approximately 4000 feet thick. This complex system changes from a gas condensate at the top to an under saturated black oil down the flank. The depth of the Gas-oil contact is estimated at 14,040 feet.
The Carito-Mulata field has been operated and characterized traditionally in four blocks (Central, West, North and South). The fundamental goal of this study is to establish a compositional model that can represent areally and vertically the complex fluid system using an Equation of State (EOS), which represents a big challenge considering the huge number of laboratory experiments. This EOS will be used for EOR simulations under gas and nitrogen injection processes.
The Peng-Robinson EOS was used to match the PVT experiments. Included in the matching parameters was the variation of the saturation pressure of the gas condensate due to nitrogen injection. A swelling test using black oil crude with the injection of gas condensate was also fitted, as well as stacked core miscible experiments of gas condensate displaced by nitrogen injection. Finally, a set of PVT tables were generated for the compositional numerical reservoir simulator.
The most important result that has been obtained of this project is to prove that a single Equation of State can model the complex thermodynamic behavior of three areas that were previously modeled as isolated. Considering that the field could be under nitrogen or natural gas injection, the Equation of State generated in this study will allow the numerical simulation to predict the impact of these processes on the ultimate hydrocarbon recovery.
The Carito-Mulata field is located in the Eastern Basin of Venezuela, about 50 km west from city of Maturín, Monagas state. It is defined an asymmetrical anticline witch is characterized by a production of fluids whose composition varies with depth, from the condensate gas, at the crestal part of the structure, to under-saturated black oil in deep areas.
The field is situated in the northern part of Monagas State, between the El Furrial and Santa Barbara oilfields. Its production started in 1988 with the MUC-1E well. The reservoirs present a considerable level of heterogeneity as a result of a combination of complex geological events, including compressional tectonics, faulting and a diversity of sedimentary environments.
At the present time, the central and western blocks of the field are subject to natural gas injection, the northern block undergoes water injection while the southern one flows naturally.
Despite of the good definition of the fluid distribution throughout the field, the actual compositional modeling was still carried out in an isolated way previous to this study.
In order to create an integrated simulation model taking into account the observed communication between blocks, it is indispensable to have a correct areal and vertical fluid characterization based on revision and validation of the available laboratory data. These include PVT studies, production data, RFT logs, etc. In case of EOR process modeling, it is necessary to also consider the special fluid tests (swelling test and displacement measures on cores) which permit the evaluation of the injected gas effect on the original fluid properties in the reservoir, particularly at the saturation pressure.
The compositional modeling which is the subject of the present paper was aimed at reproducing the fluid behavior under reservoir and surface conditions through the equation of state (EOS) and experimental data. The objective is optimizing the field exploitation strategies considering the injection of nitrogen or natural gas.
El Furrial field is located in the Eastern part of Venezuela. The OOIP is about 7,500 MMSTB and the current daily production is 400 MSTBD. Due to the rapid pressure decline and the risks of asphaltene deposition, Enhanced Oil Recovery (EOR) processes have been implemented by water injection at the flank areas since 1992 and gas injection at the top of the structure since 1998.
Technical economical feasibility of infill drilling has been evaluated prior to considering the implementation of the full-field Water Alternating Gas (WAG) process. The main goal is to speeding-up of the recovery associated with the current EOR schemes. The applied methodology is based on maximization of the Net Present Value (NPV) under various schemes of production including new infill drilling.
The combination of numerical simulation results and economical analysis have led to a particular configuration of infill locations that will allow the extension of the current production plateau from 2007 to 2010. Incremental recovery after 20 years are as much as 250 MMSTB and the NPV could be increased more than 5000 MMUS$. Additionally, areal and vertical gas and water sweep efficiency is expected to improve with the optimization of the new well locations and the use of selective completions. This production plan would allow maximizing the efficiency of the current EOR schemes before implementing a WAG process.