Abstract This paper presents the results of a Material Balance Study in the Mene Grande field, in the Lake of Maracaibo of the region of Venezuela. The study represents the continuation of ongoing subsurface evaluations, which have been the subject of previous publications. The identification and confirmation of the major drive mechanisms and source of water encroachment in the field has led to successful use of traditional Material Balance techniques, where different areas are selected in order to determine the viability ofinfill well locations. Prior to obtaining a clear understanding of the subsurface drive mechanisms, infill drilling was based on neighbor well production and reservoir thickness. The results of the infill locations based on this type of evaluation were highly variable and somewhat disappointing. Although simulation modeling was used initially, subsequent well results indicated large discrepancies between the static models and the actual field results. Once these discrepancies had been reconciled, a consistent understanding of the reservoir performance began to develop. This paper presents the results of applying material balance techniques to reservoir sectors incorporating entire production history and pressure of the neighboring wells to the future infill target. Each sector was matched to the observed pressure, which again showed signs of a secondary support mechanism developing from the reservoir mudstones. It is in fact this secondary pressure support, which allows for higher production from the recent infill wells. A comparison of the completed wells using this methodology and the wells that were located without it is shown indicating a clear and significant benefit to production rates. This methodology can be considered as a first step towards the construction of a full field 3D model. The proposed methodology is simple and easy to use. This case study clearly demonstrates, that subsurface success depends more on correct understanding of the reservoir rather than the degree of complexity with which it is modeled. Introduction Mene Grande was the very first oil field discovered in Venezuela in 1914, with the drilling of the Zumaque-1, which is still producing 20 bopd. The Field is situated approximately 120 km southeast of Maracaibo City on the eastern side of the Lake Maracaibo Basin (Fig. 1). The field extension is 123 km2 and 945 wells have been drilled to date since the field was discovered. The field comprises a heavy oil Miocene reservoir with overlying stratified tar sands within the 1200–1500ft thick Isnotu Formation. The Isnotu Formation is bounded above and below by unconformities and lies unconformably upon sands and muds of the Eocene Pauji Formation. The reservoir comprises unconsolidated fluvial channel sands and crevasse splays, bounded by poorly indurated muds and silts. This formation is a combination of three main levels, the "K" sands, the "KLM" clays and the "LM" sands. The overall net sand/gross percentage in the total reservoir is generally low to moderate varying between 10 and 35%. The oil found in the Miocene formation has an API varying between 12 and 20 and has a viscosity between 10–30 cp. Most wells are producing under artificial lift conditions (Rod Pump and PCP).