Permeability Calculations From Clustering Electrofacies Technique for the Petrophysical Evaluation in La Peña and Tundy Oil Fields

Abstract

Abstract A relatively new technique has been applied for the purpose of providing more accurate Permeability information and identify rocks types with good fluid flow characteristics from wireline logs data. The study for which this technique was applied included wells drilled over the last 30 years up to present. When you have a wide range of logging tools and differences in logs scales or presentations it becomes really difficult to identify the existing facies on a depositional cycle just by following the shape of the log curves. Even when you count with a consistent or homogeneous log set of curves, the task of identifying the different facies is often difficult. The technique used applies the clustering K-Means2 algorithm based on wireline logs characteristics to identify the different Electrofacies. The Electrofacies found were very useful to determine rock types with identifiable fluid flow characteristics. Porosity/Permeabilty relationships were then assigned to the various Electrofacies and used to calculate permeabilties during the log analysis. The method was applied for 79 wells from La Peña Field and for the 9 wells from the Tundy field and proved to be very successful in dealing with a wide heterogeneous range of wireline log types when working on a multiwell field petrophysical analysis. The application of this technique is very simple if we look at the existing pattern recognition software designed to identify facies that include the complicated stochastic algorithms which usually requires the operation of skilled users in order to obtain impressive results. This paper presents a description of the clustering K-Means2 algorithm used for the Electrofacies calculations and also shows the permeabilities results obtained in the petrophysical analysis for each of the Facies. Finally some examples of the petrophysical evaluation and the calculated Electrofacies will also be visualized graphically and discussed here. Introduction The La Peña oilfield was discovered by the Bolivian Gulf Oil Company in the sixties decade (1965) and the structure is about 8 Km. long from north to south and 2 Km wide from east to west. The La peña field has been producing oil for 35 years and the Oil Cummulative Production is 35.5 MMBBLS. from La Peña and Bolivar sandstones. The related but hydraulically isolated Tundy oilfield was discovered in 1992 for the State Bolivian Oil Company Y.P.F.B. and is located to the north of La Peña field. To the present the Oil Cummulative Production is over 2 MMBLS. only from the La Peña sandstone. A total number of 82 wells in the La Peña field and 11 wells in the Tundy field were drilled but only 13 wells are producers, 10 from the La peña sand and 1 from the Bolivar sandstone. The La Peña and Tundy oilfields are located east of Santa Cruz de la Sierra - Boliva and are on the eastern side of the Andes orogenic influence (Fig. 1). The producing horizons mainly belong to the Carboniferous San Telmo (La Peña sandstone) and Escarpment (Bolivar sandstone) formations (Fig 2). This sedimentary deposits are lithologically complex and considered to have been deposited mainly in fluvial environments. Permeability data is not often an available data for each well and in continuous depth intervals. The main objective of this study was to obtain permeability data as accurate as possible to have the most reasonable idea of the flow characteristics around the entire fields to be used later in simulation study.