B-6/9, SVS-82 reservoir is located in Blocks IX and X in Maraven's concession area in Lake Maracaibo Basin in Western Venezuela. The field has been on production for more than 30 years and the recovery to date has been 45% of the OOIP (930 MMSTB). Its remaining reserves are confined between a gas front formed by the re-injection of the produced gas and a water front created by a strong aquifer in a relatively small area towards the top of a monoclinal structure. Though the reservoir is fairly well depleted, a prudent and comprehensive reservoir management program implemented during the past three years has substantially improved the production from this reservoir and consequently, the reserves have increased. This was accomplished by using new and existing technologies, such as, integrated reservoir characterization, 3-D Seismic, non-conventional simulation techniques, well workovers highly deviated wells and infill drilling. Prompt implementation of the exploitation policy has increased the reservoir production from 6 MSTB/D to 22 MSTB/D.
An integrated reservoir characterization study covering 3-D seismic, geology and geophysics, sedimentology, petrophysics and engineering has helped delineate the new reservoir limits and identified additional reserves and drilling prospects. A finely layered 3-D, 3-Phase reservoir simulation model was developed for a partial area of the field where most of the remaining reserves were confined between the advancing water and gas fronts. The Enumeration technique of reservoir initialization allowed a quick start of the forecast cases to investigate the productivity of the high angle wells and various combinations of infill drilling scenarios. The optimum number of infill wells — 20, was determined by economic factors.
B-6/9, SVS-82 is one of Maraven's largest light oil reservoirs, located in blocks IX and X in Maracaibo Lake, Venezuela (Fig. 1). Production started in 1965 and in 1974, a gas injection project was initiated mainly for the purposes for storage and conservation. After 31 years of production, 45% of the OOIP (417 MMSTB) has been produced. The drainage strategy implemented in this reservoir has caused the remaining reserves (80 MMSTB) to be confined updip between the advancing gas and water fronts in a relatively small area towards the northern part of the reservoir.
In 1993, the Ministry of Energy and Mines (M.E.M) restricted the production from the reservoir. High GOR wells >2500 SCF/B) had to be closed thereby reducing the reservoir oil rate to 6 MSTB/D. Production of high volumes of gas did not conform with the current reservoir drainage strategy (gas injection). Since it would be difficult to achieve the expected ultimate recovery for this reservoir under these conditions, a complete re-engineering of the project was initiated. Figure 2 shows a schematic of the reservoir management program that has been underway since 1993.
