Capturing and Preserving Sandbody Connectivity for Reservoir Simulation: Insights from Studies in the Dacion Field, Eastern Venezuela

Abstract

A critical part of the redevelopment plan for Dacion Field is to optimize depletion of the middle sands. To help develop a strategy for this, four geological models were built, upscaled, and numerically simulated. The models were constructed for the L2U-M2 and the P1-R0 intervals in both East Dacion and West Dacion. The deterministic framework for each geological model was built using a 3D seismic survey and wireline log correlations. Several techniques were used to distribute model properties including object modeling for facies bodies, sequential Gaussian simulation for porosity, a poroperm cross-plot for permeability and height vs. saturation curves for water saturations. Multiple realizations were generated for each of the four models and streamline modeling was used to identify key realizations with differing amounts of heterogeneity. These were then scaled-up and numerically simulated. The realization achieving the closest match to overall reservoir performance was chosen for detailed well history matching. The detailed history matches were optimized by modifying permeability/transmissibility values and relative permeability curves. Subsequent forecast runs identified 54 new well locations and showed that incremental recoveries of 6 to 18 percent of OOIP are possible through a combination of infill drilling, water injection, and the commingling of production. The simulations proved very useful for developing strategies to optimize production, but recent drilling indicates that the models were not very successful in predicting the performance of new wells on an individual well basis. The key reasons for this arethe distribution and connectivity of sand bodies in the models are different than those in the reservoirs, andthe data and analysis tools used in the modeling work need improvement. Introduction The Dacion Field is located in the Oficina Basin of Eastern Venezuela and consists of two separate accumulations: East and West Dacion (Figure 1). Dacion Field is part of the Dacion Block which also contains Levas, Ganso, and a number of smaller accumulations. Dacion Field originally contained about 1,700 MMBO of oil-in-place and began production more than 50 years ago. Production peaked at 45,000 BOPD in 1958, but by early 1998 rates had fallen to less than 8,000 BOPD with a cumulative production of 260 MMBO. In April, 1998, Lasmo Venezuela (ENI) and PDVSA began a redevelopment project in Dacion as part of the third Venezuelan licensing round. Infill drilling and workovers were initiated along with the installation of new facilities capable of handling 70,000 BOPD. The primary objective of the project is to increase production and reserves from thick, areally extensive sandstones which were previously shut-in at water cuts of 60–70%. A secondary objective is to increase oil production from thinner, more discontinuous sandstones through a combination of drilling, recompletions, and waterflooding.